coolant issue?

[expo5.0]

having problems with my car-

was running properly- i parked car in garage after a long drive and it promptly dumped approximately half a gallon out of the overflow's "vent" or "release".

i attempted to let it cool- refill coolant and move on etc.

however, now the coolant is building pressure, overfilling the tank, and generally not working plus the car would overheat if i actually ran it for long. I must have air in the coolant etc., but why can't i figure out how to fix it?

what is the process you use?

[strictlyspeakin]

Check the fuses for the aux fans. They should be on top of the relays.

My standard method for purging air in the coolant system is to crack the cap to the first stop, run the car up to normal operating temp with the heat on high.

I'm pretty sure that the mb coolant system is supposed to be pressurized. It's designed that way.

Best guesses, air in the lines or a stuck thermostat.

[OzC36]

Insufficient data to diagnose accurately.

Was the coolant temperature in the normal range or in the red zone immediately before the dumping of the coolant?

The coolant system is pressurised to increase the temperature at which the coolant boils. At one atmosphere (1 bar) pressure, the coolant will boil at just above 100 deg C. At the design coolant system pressure (approx 1.4 bar), the coolant will not boil until above 130+ deg C.

The coolant is either boiling and creating its own source of gas...or a pressurised gas is entering the coolant system (ie, blown head gasket).

Fix the source of the overheating problem or fix the head gasket?

[expo5.0]

it was in normal range prior to dumping of the coolant- in fact, it dumped "cool" coolant (cold to the touch 2 or 3 minutes after the fact)

how would a stuck thermostat result in this problem? (blocks the pump from running the coolant through the radiator, thus forcing the coolant to "back-up" into the reservoir "en masse" and also not getting any cooling?--- how will i tell for sure?

where does the car read the temperature?

how is the system supposed to function when it's pressurized? ie- how full should the reservoir get vs. how empty should it be non-pressurized? Can it "gulp" air down the "return" line if coolant is overfilled?


also, likely of note- at times the temp gauge fluctuates up and down rapidly, to me suggesting air bubbles passing through the area where the temperature is measured?

I def. hope it's not a head gasket-

[OzC36]

This thread will tell you how to bleed the air in the coolant system.

http://www.benzworld.org/forums/w202-c-class/1328831-c280-overheating-2.html

I recommend that you replace the thermostat as it is cheap. Do that before you bleed the system so as not to waste any more coolant. The thermostat cover is held on by three bolts (and hose clamp). Remove old thermostat and seal. Replace with new thermostat and seal. Replace the three bolts and hose clamp. Only costs about $20.

Fill the reservoir (overflow tank) to the top of the white section of the tank when the coolant is cold)

If replacing the thermostat doesn't fix the problem, then hope like hell that you have a bad waterpump! Because that is cheaper to fix than the head gasket.

[xvvvz]

>>4. Open the bleed screw on top of the thermostat housing (or loosen hose clamp on top of thermostat hosing if no bleed screw) until all air bubbles escape and coolant flows out. (Caution; coolant is F... hot, so take precautions!).<<

Can you please be more specific about exactly how you bleed if the thermostat housing does not have a bleed screw? The thermostats from autohausaz.com don't have them. If you pull the hose off while it is running, aren't you going to get coolant shooting everywhere? I am going to swap out my thermostat as a precaution and have worried about how to do this.

Thanks.

[expo5.0]

my understanding is that b oth arguing sides on the head gasket issue are right- it is potential than under high boost a leaking head gasket could cuase these issues etc. (but seems improbable under my 5 psi).

this problem is occuring when the engine is not seeing boost

the upper radiator hose and the entire radiator are cold! and i'm 99% sure the problem is my thermostat. I actually ordered the t stat yesterday prior to even getting a chance to look at the car again (which i did this morning). also used the opportunity to pick up the steering stabilizer.

directions for t stat change somewhere? wish me luck that the t stat fixes the problem- i've got a long trip planned in 10 days.

-drew

[aflicted]

I had the exact same problem in a Volvo LPT (low pressure turbo) motor I had a while back. Out of nowhere it presented the exact same symptoms you describe. I did the Tstat, purged the system etc.. Turns out I had a very tiny crack in the block on the back side I couldn't see until it was on a lift. Your purging of coolant is almost certainly related to a leak somewhere in the system that is preventing it from building the necessary pressure. Hopefully it will be something relatively simple.

[OzC36]

How to bleed the system at the thermostat housing cover:

1. Loosen the hose clamp of the "overflow hose" on the top of the thermostat housing.
2. Bubbles of air should emerge.
3. When the bubbles stop and coolant emerges, tighten the hose clamp.

I am not sure if this new thermostat cover and bleed screw, banjo fitting and 2 seals will fit your C230 (it was perfect for my C36). You can buy thermostat housing and bleed fitting at Autohaus:

http://www.autohausaz.com/search/product.aspx?sid=xpskwo451mc3rx452rs1ciup&makeid=800016@Mercedes&modelid=1195512@C36&year=1996&cid=16@Cooling%20System&gid=2204@Thermostat%20Housing/Water%20Outlet

http://www.autohausaz.com/search/product.aspx?sid=xpskwo451mc3rx452rs1ciup&makeid=800016@Mercedes&modelid=1195512@C36&year=1996&cid=16@Cooling%20System&gid=2065@Coolant%20Bleeder%20Screw

http://www.autohausaz.com/search/product.aspx?sid=xpskwo451mc3rx452rs1ciup&partnumber=007603-008100