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I have a 2010 E350 4matic that runs great except for this one issue. The car will run flawlessly for weeks but then out of the blue the temperature gauge will go up to 120. If I shut off the hvac that temperature quickly drops to the normal high 80 degree range.
The car has no water pump leaks or noises- the thermostat was replaced last year (slow to heat up). At first I assumed that the temperature spike was caused by air in the system. Burped the system several times with no real improvement. The car will run fine for days- the problem seems to occur after a 10+ mile drive (but not always) The temperature will slowly spike to almost 120. If I shut down the hvac system the temperature drops fairly quickly. If I do nothing the temperature will eventually return to the normal range. I dug out my icarsoft reader--no codes all systems 100% Using the live data feature on the icarsoft I have done the following” Start car drive the temperature will sometimes climb to 117 degree engine coolant temperature on the icarsoft (car gauge reads 110+) Turn off dash hvac, the temperature drops quickly to 90 Carsoft and about 93 gauge. Coolant fan runs on high with hvac on--runs low with hvac off. If I run car with hvac on but with the ac off the temperature goes to 117 Icarsoft--gauge 103. I then got my thermal laser reader-- with the inside gauge at 115 degrees the top hose to the t stat reads 63degrees--the lower hose to the radiator reads 60 If I shoot the thermostat housing I get a high 60 degree reading. The coolant water temperature off the carsoft reader is 119. Other readings without the thermal gun gauge icarsoft
90 110
96 112
94 113
I need help to solve this problem. Thermostat?? Replaced last with with a waler oem. I believe that the thermostat is mechanical and not electrical? Most thermostats fail in the open position. Does anyone know what the electrical connection does. Does it feed the gauge or ECM unit?? Water Pump?? No leaks or noises (car has 75K miles) Radiator?? Using the thermal gun found no hot spots most readings were under 20 degrees Temperature control sensor on rear of motor?? Not sure what this does or what it controls--any ideas? Dash gauge faulty?? Could it be bad? The temperature readings on the gauge and the icarsoft (ie car’s computer) are different. Could the temperature spike in the gauge be a bad dash gauge?
The radiator has no hot spots and appears to be working properly
The car appears to be not overheating using the thermal reader--based on the temperature of the hoses and thermostat housing.
Since the car is not throwing any codes and the problem does not always occur I am not sure that a dealer or indi would find and solve the problem.
Engine temperatures can't "out of blue" spikes.
So unless there is something you are not telling us, - you have electric problem with sensor.
What is iCarsoft showing when dash shows 120C ?
Your description is too chaotic and infra-red thermometer need some know-how where to point it.
When gauge is reading 115 the carsoft engine coolant reading was reading 119. The top and bottom radiator hoses were around 60 and the t stat housing below the hose was 62.
Any ideas as to where I should be taking infrared readings?
Agree with you that out of the blue spikes do no occur. The fact that if I hit the off vac button on the cabin controls the temperature quickly drops.
If it happens again I will try the old raise the heat settings to see if that has any effect.
Only 2 things can keep engine hot and radiator cold
1 closed thermostat
2 broken pump impeller.
The 320 engines for some years had plastic pump impellers with high failure ratio, not familiar with 350 thought.
When pump is usually hard to remove for inspection, I was able to remove thermostat and feel the impeller with finger.
Another easy test is drive with removed thermostat.
HVAC system has its own coolant loop and its own electric pump, so using it as engine cooler will work, but only to some degree.
I don't think a faulty thermostat or a defective water pump impeller would cause my problem. New oem thermostat impeller was installed 2 years ago. Most times they fail in the open position so the motor takes longer to heat P0124 code. Would like to know what the electrical portion of the theromostst does?
Believe the 350 did not have the plastic impeller water pump. I would think the pump works or not. Temperature spike occurs randomly.
Based on the gauge reading hot and the iCarsoft engine coolant temperature it would appear that the motor is running hot--however the infrared temperature readings would suggest something other. If the sensor is bad that controls the gauge and ecu both could have bad readings.
need someone in the community to advise me as to the possibility of the ending temperature sensor on the back near fire wall would cause this issue The fact that when I shut down the HVAC the temperature quickly returns to normal , to me suggests some type of sensor or control issue.
I don't think a faulty thermostat or a defective water pump impeller would cause my problem. New oem thermostat impeller was installed 2 years ago. Most times they fail in the open position.
Nope, thermostat can fail in CLOSED position or get sort of hampered for its movement because of scoring on the middle shaft and can never open 100%.
I seen it happened, on big MAN 10 cylinder diesel generator ( 500kva , 1,500 RPM) which has 3 similar thermostat in a row due to big size waterflow.
1 is the bad one, the other 2 okey, but temperature rise about 4C above normal.
I know this engine well, coz my friend's yacht uses the same engine in marine version at 820HP 2,300RPM.
True thermostats can fail in the closed position. Mine works fine mostnof the time. Never seen one open/close/open on a running vehicle. Temperature on dash gauge appears high but infrared gun reding at thermostat and motor block seem to indicate something else is going on.
I am not too familiar with the engine you have, but on most engines- thermostat removal for the inspection take about the same time what doing 2 forum replies....
The 350 has a thermostat housing that incorporates the thermostat. It is not like the older E320 that had the old fashion separate thermostat. On the 320 you could take out the thermostat--on the 350 that is not possible. I know I have both a 320 and a 350..
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Do you know the purpose of the electrical connection. Does that control the eco and or gauge or just used to produce the P0124 cel which indicated a slow thermostat
Agree with you that out of the blue spikes do no occur. The fact that if I hit the off vac button on the cabin controls the temperature quickly drops.
If it happens again I will try the old raise the heat settings to see if that has any effect.
Your symptoms indicate that you have marginal heat transfer in your radiator as turning the HVAC off helps to bring engine temperature down. HVAC here means A/C compressor and its loop.
The condenser of the A/C is mounted in front of the bottom part of the engine cooling system radiator in front of the car. The condenser takes very hot refrigerant gas from the compressor and cools it down condensing it in the liquid form that then runs in the evaporator where the liquid refrigerant evaporates taking heat from surroundings when it turns back to gas form.
The issue here is that the condenser is hot and is cooled with the same air flow that also cools the engine radiator so with the A/C compressor running the air that cools engine gets pre heated first at condenser and does not do as effective engine cooling as it does without running the A/C.
So, what does this mean? It can be limited coolant flow thru the radiator, which could be issue with the thermostat or the water pump. But, as you say the temperature comes down quickly when you turn the A/C off for me this could mean your radiator is not all the way full. If your radiator is filled only up to level of top of the condenser (give or take) all your engine cooling in the radiator would receive pre-heated air with A/C running and this would cause the higher than normal engine temperature. Then when A/C is off air is cool and does a good job for engine cooling.
As said it can be pump or thermostat but from your posts I understand both have been replaced within two years so not likely sources for the problems especially the pump impeller is not. Thermostat could be faulty though even a brand new one but I think you would have issues almost every time you drive if that is the case. You probably have more problems when outside temperature is higher meaning the A/C compressor is running. You can have the A/C button light on but this does not mean the A/C compressor is running at all times. It only means the compressor is available for the system to use when it needs it so you can have many driving days without the high engine temperature because the HVAC system is not needing the A/C compressor or needs it so little the engine cooling in front is not disturbed,
Raising the cabin temperature setting for sure will help as the heater core would do part of the engine cooling what the radiator in front is lacking.
I would carefully check the coolant level inside the radiator. Don't trust the small reservoir level. I have had a very bad experience with this with another car where car engine over heated badly because I lost almost all coolant but the reservoir was at the correct mark.
I don't know if your car has a cap on the radiator. That would be a very easy place to check the coolant level.
Will check water level in radiator. No cap on radiator only plastic resivour which appears to be full.
The thermostat was changed two years ago. The pump is original.
Do you know what the ets (engine temperature señor does? Does it communicate with the dash gauge? Reason I ask is that when the gauge reads hot the infrared heat gun on the stat housing and top/bottom hoses and radiator are much lower. Do these sensors fail?
Product Information Includes thermostat and thermostat housing seal
Most thermostats operate within a mechanically specified temperature range. However, this thermostat is controlled actively by an internal heating element which regulates engine temperature as needed based on engine load and operating conditions. This thermostat is actually very important in helping control engine emissions as well as overall efficiency. However, when the heating element fails inside this thermostat it will usually triggers a P0128 diagnostic code.
Now the logic is like this.
The wax in ur thermostat WILL melt and open up thermostat at a fixed temperature.
The electric heater is actually to melt the wax even sooner, based on engine load.
If ur Gremlin is software based, it can only open up the thermostat sooner, not later...because the wax melting temperature is already fix and you can't cheat it.
Now, another possibility. Gauge is too slow to respond or not accurate at certain readings, such things happens.
Your gauge reports X temperature from a coolant sensor, your OBD Icarsoft also read from the same sensor The only difference is, your dashboard shows mechanical movement of the gauge and Icarsoft is digital value.
All else being equal, digital value is more accurate and instant because it does not need to deal with mechanical movement issue, if indeed there is such a mechanical issue on the gauge.
You described this : I dug out my icarsoft reader--no codes all systems 100% Using the live data feature on the icarsoft I have done the following”
Start car drive the temperature will sometimes climb to 117 degree engine coolant temperature on the icarsoft (car gauge reads 110+) Turn off dash hvac, the temperature drops quickly to 90 Carsoft and about 93 gauge. Coolant fan runs on high with hvac on--runs low with hvac off. If I run car with hvac on but with the ac off the temperature goes to 117 Icarsoft--gauge 103.
Our fuel gauge and temperature gauge is usually a stabilized one. Its does not produce reading instantly like digital Icarsoft one. Give it 10-15 seconds to read dashboard gauge value vs Icarsoft.
Fuel gauge is heavily stabilized.
Unfortunately, you can't reliably use an infrared heat gun on a metal skin temperature of the thermostat housing if the coolant heat rise is a short time, you need to measure the coolant itself.
Also infra red reading is a unique art in itself and 10C error for a 90C reading can happen easily between reading dark color matte object vs shiny object, it is called emissivity value. https://www.thermoworks.com/emissivity_table
I dont trust infra red gun with laser dot, not only the emissivity issue but the narrow or wide angle of the sensor itself and the accuracy of the laser targeting towards sensor reading area.
I use FLIR type thermal gun and I usually place a dark non reflective sticker first if shooting alumimun kind of shiny surface.
Below is an example of a C-Tek 5 amps charger bottom side reading. https://www.ctek.com/products/vehicle/mxs-5-0
The Sp1 at 64.6C is because that is a shiny sticker with barcode, production sticker. 6.8C "hotter" than Sp2 57.8C at due to simply matte surface vs shiny, while temperature is the same.
Avoid using the term HVAC in this post for highest clarity of information.
HVAC is heating, ventilation and air conditioning. It can be heat or cold or simply fresh air from outside. Some compressor can do reverse cycle ( home ) and make heat.
Described like this : Your so called AC , called it AC COMPRESSOR.
If you turn on the blower fan inside the car, call it blower fan, don't call it HVAC.
If you turn on the heater, call it heater, but this is no use as information..... as it uses car coolant and no extra load whatsoever to your engine.
Case 1 If I run car with hvac on but with the ac off the temperature goes to 117 Icarsoft--gauge 103.
So, you turn ON the blower fan and AC compressor is OFF, gauge read 103C and icarsoft OBD reads 117C ...correct ?
Did you observe for more than 15 seconds this temperature difference ?
Case 2 Turn off dash hvac, the temperature drops quickly to 90 Carsoft and about 93 gauge.
So you turned off everything. Blower fan and also AC compressor...correct ?
Did you observe for more than 15 seconds this temperature difference ?
Case 1 and 2, were you at cruising speed or at a stop already ?
When testing passenger car cooling system try to be stationary, as speed of vehicle aka windspeed is a great deal of variable which may confuse your troubleshooting.
A car at good speed can generate more wind force than its electric fan , for the radiator system or/and the condenser for the AC compressor. See ....why it is important to do a stationary test.
If a car can survive stationary idling test for 30 minutes with AC compressor running and set at lowest temperature and set to outside fresh air, blower fan at maximum and all lights are ON and ambient temperature
outside is say 32C and coolant temperature reading is say 90C... your radiator is probably okey. Engine idling speed is lowest coolant flow from the water pump and stationary is zero wind speed help to the radiator.
Do this stationary test with AC compressor and blower fan OFF and ON and note down the temperature reading and make sure you observe the reading for 30 seconds.
This can tell if your temp gauge is the culprit at certain readings or your radiator itself is loosing its cooling capacity as Arrie described.
Yes, a gauge can have non linear error.
I don't know M276 3.5 liter non-turbo engine. Never seen one.
However, my M276 3.0 Turbo, which is its twin sister, 90C is the standard highest temperature regardless. But this is on the road with 34C ambient temperature and bumper to bumper traffic aka zero speed,
but not pushed on a race track. Turbocharged engine runs very hot if I pushed hard, say on the track or at unlimited speed long highway. Track is worse, acceleration is a heavy work load.
Just to be sure on your dashboard temperature gauge reading interpretation, not intending to offend you in anyway. I just want to be sure. Mine is below and it is always 90C.
Your 2010 E350 would have 3 spaces between 80 to 100C, I got 4 spaces
I think the controlled actively description is overstatement.
Using the thermal element MAP can speed up full opening when it senses sudden big load on the engine, but this is still old-fashioned wax that keeps the engine at certain temperature on long run.
Still with OP hesitating to put his hands on troubleshooting, we can debate forever..
You raised some questions in your last response. Did my best to answer them. Really appreciate your help. Learned a lot Fully agree that infrared dot laser is not the best way to diagnose this problem. If anything the low readings at the hoses, thermostat housing and no hot spot in the radiator would indicate they are functioning. Right?? If I understand you, the electrical controlled thermostat, dash temperature gauge and the Icarsoft reader get their data from the same source? Difference between gauge and icarsoft reading probably timing and my interpretation of digital and analog gauge reading.
Question--for testing coolant temperature purposes, it's better to use icarsoft reading or gauge?? Question--what is the source for the data being sent to the thermostat, dash gauge nad icarsoft. Could that be the source of the spike. Would that failure cause an error code??
You would think that if the dash gauge was reading hot- the thermostat would be wide open. Since the thermostat is electronically controlled could it close causing the gauge to read high. Does the thermostat cause the overheat or does the temperature sensor/gauge apparently cause the thermostat to close?? Question--a failing thermostat would result in a code which means it is taking too long for the engine to reach operating temperature (90Degree)? Could the thermostat be the cause of sudden spikes. The thermostat would have to go from open to close and open while cruising. Could the temperature sensor located on the back block (engine temperature control sensor be the problem? Is that the source of the signal to the thermostat, gauge and ecm?? Have none of the typical symptoms that sensor is failing ie--no black smoke, no starting issues-car performs perfectly. Would a failing temperature sensor throw a code??
You questions:
Case 1
If I run car with hvac on but with the ac off the temperature goes to 117 Icarsoft--gaAUGE
So, you turn ON the blower fan and AC compressor is OFF, gauge read 103C and icarsoft OBD reads 117C ...correct ?
Did you observe for more than 15 seconds this temperature difference ?
POSSIBILITY NO THE LAST TIME IT HAPPENED I DID NOT PANIC AND SHUT ANYTHING OFF. AFTER ABOUT 4-5 MINUTES THE TEMPERATURE GAUGE RETURNED TO NORMAL.
Case 2
Turn off dash hvac, the temperature drops quickly to 90 Carsoft and about 93 gauge.
So you turned off everything. Blower fan and also AC compressor...correct ?
Did you observe for more than 15 seconds this temperature difference ? PROBABLY Case 1 and 2, were you at cruising speed or at a stop
A TEMPERATURE SPIKE OCCURS USUALLY WHILE CRUISING. SEEMS TO HAPPEN WHEN I GET OFF THE HIGHWAY EXIT RAMPS. HIGHWAY SPEED 60+ LOCAL SPEED 30-45MPH ONLY ONCE DURING LOCAL DRIVING 30MPH HAS NEVER HAPPEN AT IDLE. When testing passenger car cooling system try to be stationary, as the speed of vehicle aka wind speed is a great deal of variable which may confuse your troubleshooting.
A car at good speed can generate more wind force than its electric fan for the radiator system or/and the condenser for the AC compressor. See ....why it is important to do a stationary test.
PROBLEM IS THAT SPIKE ONLY OCCURS AT SPEED. CAR CAN IDLE LONG TIME WITH GAUGE READING 90 DEGREES. The spike does not occur every time we drive--days can pass with no spike then it will happen. Tough to troubleshoot a random occurring problem. THE TEMPERATURE IN NEW JERSEY IS TOO COLD TO RUN ANY TESTS WITH THE AIR CONDITIONER ON. (SOME SNOW ON THE GROUND ALREADY)
WOULD THE MERCEDES STAR SYSTEM PICK UP an ERROR CODE THAT MY ICARSOFT DOES NOT?? Without a code they would probably tell me they cannot find a problem sine spike can not be reproduced in their shoP BASED ON MY KNOWLEDGE OF COOLING SYSTEMS THE FOLLOWING COULD CAUSE THE PROBLEM WATER FLOW FROM RADIATOR LACK OF COOLANT
BAD THERMOSTAT
BAD/FAILING WATER PUMP
BAD/FAILING ENGINE TEMPERATURE CONTROL SENSOR
ECM--I HOPE NOT DID I MISS SOMETHING?? TO BE CONTINUED!! THANKS AGAIN FOR YOUR PATIENCE.
You raised some questions in your last response. Did my best to answer them. Really appreciate your help. Learned a lot Fully agree that infrared dot laser is not the best way to diagnose this problem. If anything the low readings at the hoses, thermostat housing and no hot spot in the radiator would indicate they are functioning. Right?? If I understand you, the electrical controlled thermostat, dash temperature gauge and the Icarsoft reader get their data from the same source? Difference between gauge and icarsoft reading probably timing and my interpretation of digital and analog gauge reading.
Question--for testing coolant temperature purposes, it's better to use icarsoft reading or gauge?? Question--what is the source for the data being sent to the thermostat, dash gauge nad icarsoft. Could that be the source of the spike. Would that failure cause an error code??
You would think that if the dash gauge was reading hot- the thermostat would be wide open. Since the thermostat is electronically controlled could it close causing the gauge to read high. Does the thermostat cause the overheat or does the temperature sensor/gauge apparently cause the thermostat to close?? Question--a failing thermostat would result in a code which means it is taking too long for the engine to reach operating temperature (90Degree)? Could the thermostat be the cause of sudden spikes. The thermostat would have to go from open to close and open while cruising. Could the temperature sensor located on the back block (engine temperature control sensor be the problem? Is that the source of the signal to the thermostat, gauge and ecm?? Have none of the typical symptoms that sensor is failing ie--no black smoke, no starting issues-car performs perfectly. Would a failing temperature sensor throw a code??
You questions:
Case 1
If I run car with hvac on but with the ac off the temperature goes to 117 Icarsoft--gaAUGE
So, you turn ON the blower fan and AC compressor is OFF, gauge read 103C and icarsoft OBD reads 117C ...correct ?
Did you observe for more than 15 seconds this temperature difference ?
POSSIBILITY NO THE LAST TIME IT HAPPENED I DID NOT PANIC AND SHUT ANYTHING OFF. AFTER ABOUT 4-5 MINUTES THE TEMPERATURE GAUGE RETURNED TO NORMAL.
Case 2
Turn off dash hvac, the temperature drops quickly to 90 Carsoft and about 93 gauge.
So you turned off everything. Blower fan and also AC compressor...correct ?
Did you observe for more than 15 seconds this temperature difference ? PROBABLY Case 1 and 2, were you at cruising speed or at a stop
A TEMPERATURE SPIKE OCCURS USUALLY WHILE CRUISING. SEEMS TO HAPPEN WHEN I GET OFF THE HIGHWAY EXIT RAMPS. HIGHWAY SPEED 60+ LOCAL SPEED 30-45MPH ONLY ONCE DURING LOCAL DRIVING 30MPH HAS NEVER HAPPEN AT IDLE. When testing passenger car cooling system try to be stationary, as the speed of vehicle aka wind speed is a great deal of variable which may confuse your troubleshooting.
A car at good speed can generate more wind force than its electric fan for the radiator system or/and the condenser for the AC compressor. See ....why it is important to do a stationary test.
PROBLEM IS THAT SPIKE ONLY OCCURS AT SPEED. CAR CAN IDLE LONG TIME WITH GAUGE READING 90 DEGREES. The spike does not occur every time we drive--days can pass with no spike then it will happen. Tough to troubleshoot a random occurring problem. THE TEMPERATURE IN NEW JERSEY IS TOO COLD TO RUN ANY TESTS WITH THE AIR CONDITIONER ON. (SOME SNOW ON THE GROUND ALREADY)
WOULD THE MERCEDES STAR SYSTEM PICK UP an ERROR CODE THAT MY ICARSOFT DOES NOT?? Without a code they would probably tell me they cannot find a problem sine spike can not be reproduced in their shoP BASED ON MY KNOWLEDGE OF COOLING SYSTEMS THE FOLLOWING COULD CAUSE THE PROBLEM WATER FLOW FROM RADIATOR LACK OF COOLANT
BAD THERMOSTAT
BAD/FAILING WATER PUMP
BAD/FAILING ENGINE TEMPERATURE CONTROL SENSOR
ECM--I HOPE NOT DID I MISS SOMETHING?? TO BE CONTINUED!! THANKS AGAIN FOR YOUR PATIENCE.
OP,
Don't get into this vast amount of information that is or is not useful for you. Keep it simple as possible. Check that radiator coolant level first after you have spend that much time and money already.
Your iCarsoft reads an electrical signal for the temperature and I also believe this same signal is displayed in the gauge in dash. if there is a small difference between them I would not worry about it.
If you don't have radiator cap, with cold engine remove the coolant return hose at the top of the radiator. You can then use a bent tube or something to reach in to see if radiator is full. Actually, when you remove the hose you should have coolant come out if the radiator is full. If you don't then it means it is not completely full but how much underfilled you can only find out by filling it up and see how much it takes to make it full.
When you remove the return hose from the radiator the small reservoir should empty itself in the radiator and if the radiator is full then it should leak out from the hose connection you just opened. If the reservoir does not empty in the radiator then the line from reservoir to radiator or a valve in it does not work,
Strong believer in the KIS (keep it simple) approach. The radiator is full and appears to be working properly. The car has no issues most of the time. The car can run for hours with AC on in traffic with no overheat spike. If there was an issue with the radiator and or coolant level the car should overheat --it does not. When I check the hoses (upper and lower) on the radiator both were firm with water.
Since the thermostat is electrical controlled it could it be getting a signal to close from a faulty sensor? It could have a bad thermostat. (would not be the first time I got a defective MB part out of the box. Or it could be a bad sensor sening a fale signal to the gauge and thermostat. Not sure if the gauge and thermostat get the signal from the temperature sensor air vice versa?
Using the infrared gun it would appear that the engine is not really overheating. Next time the problem occurs I will have to confirm that.
It would help if the proble occured more often--very difficult to trouble shht a problem that occurs randomly. I know if I took it to a dealer they would tell me no issssues found.
Strong believer in the KIS (keep it simple) approach. The radiator is full and appears to be working properly. The car has no issues most of the time. The car can run for hours with AC on in traffic with no overheat spike. If there was an issue with the radiator and or coolant level the car should overheat --it does not. When I check the hoses (upper and lower) on the radiator both were firm with water.
Since the thermostat is electrical controlled it could it be getting a signal to close from a faulty sensor? It could have a bad thermostat. (would not be the first time I got a defective MB part out of the box. Or it could be a bad sensor sening a fale signal to the gauge and thermostat. Not sure if the gauge and thermostat get the signal from the temperature sensor air vice versa?
Using the infrared gun it would appear that the engine is not really overheating. Next time the problem occurs I will have to confirm that.
It would help if the proble occured more often--very difficult to trouble shht a problem that occurs randomly. I know if I took it to a dealer they would tell me no issssues found.
Ok, just trying to help here.
A couple comments on your post.
I don't think it is it is possible to feel the coolant well in the upper hose. It will be hot with engine running as any coolant running thru it will make it hot and pressure in the hot system can make it feel full but this does not mean the radiator is full.
Running hours in traffic with A/C on...are you sure the A/C is actually on or is it just the light on the button on? During cool days A/C compressor runs only in cycles and does not work at all times even when the light on the button is on but there is a very simple way to test for this. Change your cabin temperature setting low enough so the compressor will stay continuously running and see if your engine temperature goes up in 10-15 min. This would tell if the problem is with radiator fill.
If if you are 100% sure radiator is full then you have only one possible source for the trouble, the thermostat.
I do not know what kind of a thermostat it really is but based on other posts in this thread I understand it is NOT electronically controlled. It is the good old wax expansion controlled valve with heating element to heat the wax quicker than what engine coolant does during some driving conditions to improve engine cooling. After coolant is hot the heating element does nothing.
It is hard to believe a new thermostat like this goes bad but it is possible. It just is that normally when they fail they stay in failed mode and do not work intermittently.
The latest "spikes" have occured when the temperature was in the 40 degree "F" so I am sure that the air conditioner was offf. The temperature still went up. Based on other posts in this thread it would seem the thermostat is electronically controlled. Based om your profile the 2010 E550 has the same part. How would you check the water level in your E550.?? If the radiator coolant level was the problem, I would think it would happen every time we drive the car. I am famiiar with old school temperature sensitive thermostats where all you needed was coolant, thermostat and water pump to cool the car. The original was replaced due to the slow heat up problem which produced a cel code.
What confuses me is that the temperature spike occurs randomly. Like you said thermostats like water pumps go bad they go bad. Mercedes are great cars that have many sensors. Could a bad sensor be sending a message to the thermostat closing it or be telling the car the coolant is hotter than it should be?? It would hep if I got a CEL message. Kinda working in the dark. Hate to blindly replace prts to solve the problem,
Based on your pictures my normal operating temperature on the gauge is 90-93.3. when spike occurs gauge go to near the 120 line.
Dumb question--do you know what type of warning Mercedes gives when the car is hitting the overheat maximum. Is just the gauge red light the only warning or does a larger message show on the dash iisplay? Does the car shut down or go into limp mode?
You are not reading the replies and links.
The thermostat is still old wax-powered and only small electric "boost" is added.
And yes, for last 25 years on digital cars the computer will kill the engine when you force it to bad overheating.
Obviously not too many owners actually try that, but we do have few reports.
You are tired if throwing parts in the car trying to fix this issue but don’t want to check coolant level in radiator. If I had problems like you that would be the very first thing I would do.
I don't have radiator cap so I would remove the upper return hose and see if coolant comes out and if not I would fill it until some runs out.
Very low coolant level can cause foaming in the system and when this happens the pump loses pumping capability and coolant flow can go down significantly. Foamed up coolant also does not do cooling as well as clear liquid. And this foaming up can be totally random.
11-27-2019, 03:17 PM
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