RichW

Hey guys,

I'm having an issue with the heat in my car -- 2002 C230 Coupe (which isn't good since it's -20C here right now). The car warms up really slow, and the heat gets warmer gradually (but never really hot), then all of a sudden *poof* the air out of the vents turns cold. Sometimes the heat stays completely cold no matter what, othertimes it only turns cool when I stop at a light, then warmer (but not really hot) as I accelerate.

I checked my coolant fluid which was about a litre low (radiator was replaced recently after an accident so I think they didn't fill it up correctly). I topped it up and the problem still persists.

Looking at my engine temperature on the info display I can see the car takes forever to reach 87C, and once it does it does a nose dive down to around 75C. Then again takes forvever to get to 87C (at which time the heat is not too bad).

Could this be a faulty Thermostat? Air in the coolant lines? System losing coolant pressure? I'm stumped, and I need some help!

Thanks in Advance,

Rich...

splinter

Freezing your vitals off at -20C. Burrr.

Doesn’t get that cold here, but when I venture up to the white stuff in the mountains during winter holiday, the engine’s antifreeze still heats to its normal range (<80C) within a few miles from a cold start. It gets pretty darn cold where the cars were engineered too.

Seems to me like your diagnosis of a defective thermostat is spot-on. The thermostat, # A111 200 17 15, is an integral piece with its housing, so it’s slightly more costly (~$35US excluding VAT) than some. The requisite O-ring is included with the assembly.

There is an auxiliary electric water pump mounted to the front of the antifreeze reservoir that forces fluid toward the heater core during low speed operation. One can confirm its functionality by feeling it vibrate slightly when the HVAC controls are set to heat. Start with the thermostat though, as it’s likely the culprit for your heating woes.

Let us know if you need more info on its R&R…good luck.



************************************************** **************

mleskovar

I remember reading that you can get different thermostats depending on your environment. Your symptoms definitely sound thermostat related. Go to the MB dealer and ask.........

Moviela

Excellent post from Splinter, with part numbers and isometric drawings. Help does not get any better than that.

My own experience with German thermostats started when Porsche went to wasserwerks on their engines. What I quickly discovered was that if you let air get to a used thermostat when the cooling system is open for repairs, it will fail soon after you button it back up, so you might as well change it when you do the water pump, radiator, or hoses.

Rust forms on the internal parts of the thermostat as it dries out, and the pin that moves the plate open and closed gets stuck.

It was 20 degrees C in LA today too. Plus Twenty!

Glyn M Ruck

Wonderful post as usual.

RichW

Thanks for the response! I'm going to order up a new Thermostat from the dealer today. I also suspect the thermostat might have been exposed to the air for many many weeks, as the rad was cracked in the accident and it took over 2 months to fix. So this all makes sense.

Is there an easy way to bleed the coolant after, since I assume I'll have to flush the coolant to change it? (Bleed screws etc) Or should I just use put the car's front end on a ramp, open the coolant reservoir, warm up the engine and wait till all the air bubbles come out?

Oh....and isn't it fire season in California right now? No worries about that here...nothing....and I mean nothing....burns at -20C.

Rich...

mleskovar

Ask about getting one for extreme cold environments.

splinter

When the thermostat housing is removed, some antifreeze will be discharged. There is no need to flush the system unless you’re unsure that the repair shop used the proper HOAT G-05 (# BQ1 03 0002) antifreeze, or its concentration is insufficient.

There is no bleeder valve in the circuit, as the reservoir is ostensibly at the system’s highest point. Upon reassembly, some have found it useful to repeatedly squeeze the upper radiator hose while refilling in order to help evacuate any remaining trapped air. Continue to fill the reservoir with a 50% antifreeze/distilled water mixture until it reaches the specified level, which is to the top of the white portion. A 50% (by volume) concentration will protect against freezing down to -37C, whereas 70% works for the Ice Road Truckers at -45C. Under no circumstances should one exceed that ratio, as frost protection will actually be incrementally compromised. Verify that the reservoir’s antifreeze mixture level is as it should be after several heating and cooling cycles.

Note that the housing bolts’ (#5) torque specification is only 10 Nm/7.4 ft.-lbs. – so go easy.
Warmer motoring beckons as our winter solstice rapidly approaches.

RichW

Ok sounds good. My Thermostat ($53 CAD at the dealer) should arrive next week so I will do the install then and update everyone as to how things went.

I'm not entirely certain the autobody shop used the correct MB coolant fluid, as the fluid is orange and I recall the original being yellow. How critical is this?

Rich...


Rich...

mleskovar

[QUOTE=RichW;3214283]...I'm not entirely certain the autobody shop used the correct MB coolant fluid, as the fluid is orange and I recall the original being yellow. How critical is this?..QUOTE]

Yellow? Haven't heard that color yet. Mine came with blue. Orange is generaly the color of the extended use...5 yr....coolant. It has more chemicals in it for extended use with aluminum blocks/heads/parts and is what they should be using. Did you ask about a thermostat for a colder environment? It's easy to check thermostat opening/closing temperatures by just sticking them in water and bringing it to boil while watching the valve and checking temperature with a digital/meat thermometer.

Glyn M Ruck

[QUOTE=mleskovar;3214496]Coolant MUST be phosphate free

RichW

Hey guys, thought I'd give an update to my issue . Ok, the dealer FINALLY got my thermostat in after a month, so I went ahead and replaced it as per the instructions on this thread.

Replacement was pretty easy (15 minutes) with a little bit of coolant leakage, but nothing rags couldn't mop up. So I fired up the car after and the coolant temperature was definitely not jumping around nearly as much, but still jumped around 80C-87C (nothing like before though where it was 70-90C). So the temperature is more stable but doesn't seem quite right still....I recall it being pretty dead on 85-87C without much movement at all).

That all said....my heat still sucks. At idle I get cold air, at speed it's "warmish". If I'm idling and it's blowing cold, I can actually get it to go hot if I play with the heater controls (cycle it on-off-on, put the heat temperature from hot-cold-hot). Then I drive off and it's fine for a while then starts blowing cold air again... very wierd!

Also, if I put the system to "recycle" the cabin air ("tunnel" mode) the heat is actually quite hot, until of course it turns itself back to normal mode in 5 min.

So does anyone else have any ideas? Is there a sensor someplace that is malfunctioning? I don't think it's a vacuum/coolant leak as it doesn't appear I'm losing any coolant...though I haven't quite ruled that out. Air bubbles in the system? Is the climate control unit fried?

Any ideas or guidance would be appreciated!

Rich...

acr2001

Check the aux coolant pump. It is the small cylindrical pump located next to the coolant reservoir. Turn the key all the way to run, but don't start the engine. Then turn the heat on. You should be able to hear that pump and feel it vibrating if you put your hand around it. If that pump has gone bad, it would explain the cold air at idle.

Beyond that I'm not sure what to tell you, you might have a clogged / kinked line going to the heater core, or maybe your coolant pump is pitting and losing its efficiency.

mleskovar

Try blocking a portion of the radiator with a piece of cardboard. You can change the portion covered until you get the car up to 115 (is that the 230 operating temp?).

Glyn M Ruck

+1 aux coolant pump. Frequent cause of your symptom. Even if it's running it might be ineffective due to old age.

mleskovar

I must be the only one reading this problem as being simply it's too cold for the engine to maintain it's operating temperature? What am I missing?

SickSpeedMonte

The thermostat regulates the engine temperature by allowing coolant to flow between the engine and the radiator when the engine surpasses the correct temperature. Even if it is extreemly cold, the engine will not be dissapating enough heat without the aid of the radiator to maintain a temperature below normal.

Glyn M Ruck

+1 - Even in the coldest weather - zero circulation of coolant through the radiator will lead to overheating. The required flow is controlled by the thermostat. As long as you have the correct thermostat & it's operating correctly for your conditions the engine will warm up relatively quickly & remain at constant controlled temperature. If it does not you have a problematic thermostat. - an ailing water pump - or crud or deposits in the water jacket, or a combination of these. You could also have a faulty temperature sender unit or gauge or excessive scale build up on the sensor. Have correct coolant ratios been maintained in the cooling system?

This is not a Power Paraffin Tractor operating with an adjustable radiator blind.

mleskovar

The OP doesn't have an overheating problem. If anything the cooling system is working too well so wear/scaling/etc is not the problem. If he has cabin heat at a motor temperature that cannot be maintained then wouldn't that be a place to start? I believe the rapid reduction of motor temp is the thermostat closing after opening and letting the cool radiator fluid into the system to drop it down again. Then it builds up to the temperature and goes through the cycle again. Or is this just a brain fart caused by old age? :-)

:-) I had a Volvo passenger car with an adjustable blind!

Glyn M Ruck

Wear & scaling can cause erratic operation of the overall system without an overheating situation but the likely cause is an inappropriate thermostat for minus 20 Celsius or a thermostat that is not linear in it's operation. i.e. bounces from wide open to closed & nothing in between. Many of these cars operate at this sort of temperature in Europe without erratic temperature control and the requirement to blank radiators. Something in this cooling system/heater system is out of spec.

What is still not plain to me is whether the cabin heater performance mirrors the temp gauge behavior although I would hope it does. If it does not then other things are at play & the poster should let us know.

Many would liken old, & admittedly extremely durable, Volvos to tractors. Modern properly designed cooling systems do not require radiator blinds.

If it were a racing two stroke, liquid cooled, motorcycle of a decade or more back one might understand the requirement to blind part of the radiator with duct tape.

All that said I believe that there is someting amiss with the heater circuit - likely the Aux pump or a blockage. If the temp gauge is to be believed at 80 to 87 deg C then coolant temp is more than adequate to achieve stable heater operation - the system integrity is suspect.

mleskovar

"takes forever to reach 87C, and once it does it does a nose dive down to around 75C. Then again takes forvever to get to 87C (at which time the heat is not too bad)". Since the temp readouts seem to be consistent and normal I trust them. Thermostat was changed, trust that too. Don't know if OP requested an extreme cold thermostat or if it even exists. I have seen posts referring to different thermostats for different environments though in other models. Maybe the 'computer modeling' for the C left out extreme cold? :-)


My Volvos never, never let me down. :-) The cost of ownership was perfect for a college student and newly married. 'Properly designed' is the key phrase.

Like a TZ 750? I thought the blind was an easy, economical way of determining whether or not the motor was just not capable of maintaining proper upper operating temperature. All you have to do is watch the temperature readout on the console to see if it's getting out of hand or helping the situation.

The primary thing the heater circuit relies on is motor temperature. Start at the beginning. Why is the temperature fluctuating? That's not normal. Either the system or the environment has changed. "...but still jumped around 80C-87C (nothing like before though where it was 70-90C). So the temperature is more stable but doesn't seem quite right still....I recall it being pretty dead on 85-87C without much movement at all)."

Glyn M Ruck

Yes to all - but I also said! (as did splinter)

Quote" Many of these cars operate at this sort of temperature in Europe without erratic temperature control and the requirement to blank radiators. Something in this cooling system/heater system is out of spec." unquote.

Sooo! I am a little suspicious of this cooling system being a little suspect all round & at the vehicles age if it has not been properly maintained that might be why especially when it comes to the heating circuit. Let's discount scaling of the temp sensor or it's deterioration for any erratic behavior in temp gauge for now. Then the likely suspect becomes a thermostat that does not behave like the one that was previously in the car & this needs investigation.

I certainly concede that partially blinding the radiator will show us an overcooling situation when the thermostat is WO - what I'm saying is we know the answer to that already. Yes we are overcooling slightly at WO.

I still say 80 to 87 deg C is sufficient for good heater operation.

Conclusion:

New thermostat does not behave like old thermostat prior to failure - investigate.

Suspect coolant circulation through heater circuit - investigate - possible Aux pump deterioration. Owners says "If I'm idling (and) it's blowing cold,"

Remember this car was in an accident - who knows what got shook up. It has a new, hopefully correct, radiator installed which should be at max efficiency which could exacerbate things. Check that the new radiator is correct & that a tropical unit has not been installed which could lead to some temperature fluctuation at extremely cold temperature nevermind what the thermostat is trying to do. As our friend mleskovar frequently & correctly counsels. " Don't assume anything". I must say I can't imagine what a tropical radiator would be doing in Winnipeg or whether one is even available for the Coupe. Just check it!

I'm not knocking old Volvos - they were agricultural but tough as nails.

noreaga0221

Your new radiator is clean thus alot more efficient than the old one. The increased cooling area (its not dirty) + -20c makes it hard to keep temperature up. Put a piece of cardboard in front of it to reduce its efficiency.

Glyn M Ruck

Don't ! sort out the cooling system to operate as it always has or the day will come that you overheat the vehicle.

acr2001

There is absolutely NO way this is accurate on any modern car.