Temp needle going crazy
06-20-2024, 12:34 PM
#1
Junior Member
Thread Starter
Temp needle going crazy
Hi everyone, i have a problem and i can't find the solution since like a year... mercedes changed some stuff but still got the problem.. i'm explaining...
I have an A207 E250 211CV, When i am driving at a moment the temp needle going crazy and goes from 84° to 120 then 90 then 85 then 100 etc... in half a sec... and if i'm steel driving it goes finally into the redzone but then goin back at normal... i changed the thermostat.. the thermostat sensor.. now they are telling me it's maybe head gasket but i've no symptomes of head gasket..
I got the feelin like the temp needle going crazy when the vent starts to turns : ON (he's running well..) cause when i activate the air cond the needle goin crazy faster...
here is a short video of the problem.. :
thank's in advance...
I have an A207 E250 211CV, When i am driving at a moment the temp needle going crazy and goes from 84° to 120 then 90 then 85 then 100 etc... in half a sec... and if i'm steel driving it goes finally into the redzone but then goin back at normal... i changed the thermostat.. the thermostat sensor.. now they are telling me it's maybe head gasket but i've no symptomes of head gasket..
I got the feelin like the temp needle going crazy when the vent starts to turns : ON (he's running well..) cause when i activate the air cond the needle goin crazy faster...
here is a short video of the problem.. :
thank's in advance...
06-20-2024, 01:34 PM
#2
Senior Member
Join Date: Jan 2018
Location: Atlanta GA
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2012 E350 Cabriolet now SOLD to my son
Make sure to have the coolant system properly filled and then bled
Find and check the coolant sensor. Look for corrosion on the connector or leaks that drip down on to it. Clean and repair any electrical connectors and leaks.
Find and check the coolant sensor. Look for corrosion on the connector or leaks that drip down on to it. Clean and repair any electrical connectors and leaks.
06-20-2024, 01:37 PM
#3
Junior Member
Thread Starter
i have already changed the coolant sensor... everything is ok... and i have nothing on OBD diag... i guess an elec failure would have told me there is a pbm somewhere... or at least mecede's one would have...
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WRC-LVR (06-22-2024)
07-06-2024, 12:38 PM
#5
Junior Member
Thread Starter
I just up there... i checked and i had some bubbles in the coolant system.. tried to bleed it by my own (just blowed over and over from expansion tank to motor output coolant system ..) i added some K-seal... i tried and then it's not going crazy as it could be.. but when i accelerate from 30 Mph to 60 mph kickdown pressed. the needle is doing like 85° going to 90° for 2 seconds and then comeback to 85.. tried from 40 mph to 80 mph .. it did the same.. idk if it's normal or if the needle should stay at 85° constantly ?
should i go to mercedes or buy pump to bleed it correctly ?
should i go to mercedes or buy pump to bleed it correctly ?
07-06-2024, 04:05 PM
#6
Super Member
K-seal? Do you have a leak? If not, I would not use it. It's a last resort thing.
Leaks show up as water in the oil, or steam out the exhaust, and/or exhaust gas in the coolant. You can check the latter by running it with the cap off and smelling the tank. Also watch for air bubbles entering the tank, but the tank must be filled to the top to see it. With a full tank it'll also blow water out the overflow when driving, or you floor it.
So if you aren't using water, and no overflow issues, I'd say odds are good there is no leak.
If it's a small leak from the cyl/gasket to the coolant then it can vent out of a tank and you won't even know. This is one reason to fill the tank all the way, so it'll blow water out as well so you can see it. But you should be able to smell it in the air of the normally half tank as soon as you remove the cap.
My temp increases when floored, but not nearly as quickly as yours.
Normally I don't have problems getting air out because it just comes out on its own. When uncooperative, I park on a steep hill and rev it. I've only had to do this on one vehicle, and only because it had a custom cooling system that trapped air.
My first attempt would be to simply fill the tank all the way with water, then drive it until full warm, and floor it uphill. Then check the tank which should have less water in it now, if that plan worked. Repeat and top off the water as needed until the water level no longer moves. Ideally this should be done with the radiator cap off, but these engines can boil water if you're not careful. Boiling may actually help you get the air out, but if you don't know what you're doing you could get the eng too hot in certain spots. Hard to explain in text, but if you're not comfortable, just leave the cap on.
Side note; if the radiator cap is defective and leaking, you can have the same problem with boiling water. Btw, the eng doesn't need to be boiling hot to get a small hot spot inside that is boiling. Google "engine hot spots" if you're curious.
Optionally, I would park on a steep hill, steepest you can find, front of the car up. Same deal, rev it to get the water moving. I always do this with the radiator cap off, but up to you. Rev it for maybe 10 seconds, turn it off. Check the tank, fill if needed, repeat until it seems good. I'd rev it to at least 3000. Water pumps flow better with more speed, to a point, but 3k should be enough and is a pretty safe #. Me, I'd rev it from 2k to 5k to be sure I hit the max flow, wherever in that rpm it may be.
It's also possible there are air pockets that just don't want to come out like that. I've never had it happen, or seen it, but if so, then I guess you need that vacuum?
I'm not much of a "proper tool" guy, especially if it's expensive, so if I wanted vacuum I'd use engine vacuum from the brake booster line. Or vacuum from another cars engine.
The problem I see is you still need to run the eng to get the air out, but a vacuum will collapse the hoses. Catch 22. Plus, if they collapse, you risk sucking water out of the tank and into the vacuum source. If so, then you have to be careful how you go about it. The only way I could see it working with vacuum is if your hoses are reinforced with an internal spring. Maybe they are, for exactly this reason, but I doubt it.
From memory, dealers use vacuum to suck an empty system down with the eng off, then back fill it with water. This doesn't make sense to me except to get "most" of the water in the engine, which should happen default anyway? Maybe it's gimmick to charge you more, who knows. But you already have most of the water in there so my guess is it won't help.
If you suck it down as-is, with the eng off, you would no doubt move the air pocket. Then running could get some/most to the tank? It depends on the eng design and where the air pocket is, but worth a try if all else fails. I can't imagine needing to go that far, and I'd instead suspect a cyl leak is the cause, replenishing the air pocket minutes after you clear it, which is likely happening all the time as you drive. Again, check that tank for exhaust smell, and/or filling it 100% to see if it bleeds out water. I don't believe that K-seal can fix a leak from the cyl, but who knows, might get lucky. It's generally for water leaks where water is exiting the system, not air getting pumped in. Like that flat sealer goop that can plug a hole in a tire, but if you pumped air into the hole it would just blow off the seal it had made.
Leaks show up as water in the oil, or steam out the exhaust, and/or exhaust gas in the coolant. You can check the latter by running it with the cap off and smelling the tank. Also watch for air bubbles entering the tank, but the tank must be filled to the top to see it. With a full tank it'll also blow water out the overflow when driving, or you floor it.
So if you aren't using water, and no overflow issues, I'd say odds are good there is no leak.
If it's a small leak from the cyl/gasket to the coolant then it can vent out of a tank and you won't even know. This is one reason to fill the tank all the way, so it'll blow water out as well so you can see it. But you should be able to smell it in the air of the normally half tank as soon as you remove the cap.
My temp increases when floored, but not nearly as quickly as yours.
Normally I don't have problems getting air out because it just comes out on its own. When uncooperative, I park on a steep hill and rev it. I've only had to do this on one vehicle, and only because it had a custom cooling system that trapped air.
My first attempt would be to simply fill the tank all the way with water, then drive it until full warm, and floor it uphill. Then check the tank which should have less water in it now, if that plan worked. Repeat and top off the water as needed until the water level no longer moves. Ideally this should be done with the radiator cap off, but these engines can boil water if you're not careful. Boiling may actually help you get the air out, but if you don't know what you're doing you could get the eng too hot in certain spots. Hard to explain in text, but if you're not comfortable, just leave the cap on.
Side note; if the radiator cap is defective and leaking, you can have the same problem with boiling water. Btw, the eng doesn't need to be boiling hot to get a small hot spot inside that is boiling. Google "engine hot spots" if you're curious.
Optionally, I would park on a steep hill, steepest you can find, front of the car up. Same deal, rev it to get the water moving. I always do this with the radiator cap off, but up to you. Rev it for maybe 10 seconds, turn it off. Check the tank, fill if needed, repeat until it seems good. I'd rev it to at least 3000. Water pumps flow better with more speed, to a point, but 3k should be enough and is a pretty safe #. Me, I'd rev it from 2k to 5k to be sure I hit the max flow, wherever in that rpm it may be.
It's also possible there are air pockets that just don't want to come out like that. I've never had it happen, or seen it, but if so, then I guess you need that vacuum?
I'm not much of a "proper tool" guy, especially if it's expensive, so if I wanted vacuum I'd use engine vacuum from the brake booster line. Or vacuum from another cars engine.
The problem I see is you still need to run the eng to get the air out, but a vacuum will collapse the hoses. Catch 22. Plus, if they collapse, you risk sucking water out of the tank and into the vacuum source. If so, then you have to be careful how you go about it. The only way I could see it working with vacuum is if your hoses are reinforced with an internal spring. Maybe they are, for exactly this reason, but I doubt it.
From memory, dealers use vacuum to suck an empty system down with the eng off, then back fill it with water. This doesn't make sense to me except to get "most" of the water in the engine, which should happen default anyway? Maybe it's gimmick to charge you more, who knows. But you already have most of the water in there so my guess is it won't help.
If you suck it down as-is, with the eng off, you would no doubt move the air pocket. Then running could get some/most to the tank? It depends on the eng design and where the air pocket is, but worth a try if all else fails. I can't imagine needing to go that far, and I'd instead suspect a cyl leak is the cause, replenishing the air pocket minutes after you clear it, which is likely happening all the time as you drive. Again, check that tank for exhaust smell, and/or filling it 100% to see if it bleeds out water. I don't believe that K-seal can fix a leak from the cyl, but who knows, might get lucky. It's generally for water leaks where water is exiting the system, not air getting pumped in. Like that flat sealer goop that can plug a hole in a tire, but if you pumped air into the hole it would just blow off the seal it had made.
