Coolant Leak Suggestions - PeachParts Mercedes-Benz Forum

jbhebert · #1 01-16-2005, 04:16 PM

Car is a 1995 E300D with 169,000 miles. I just recently started loosing about a quart of coolant every 5 to 7 days. I cannot find any visual clues to where it might be leaking. I do not get a coolant smell in the cabin or film on the windsheild that would indicate I have a heater core problem. I do not get any fluids under the car when parked. Oddly enough, my low coolant light usually comes on it is after the coolant has warmed up and I've been driving a while. I'd figure it would be more likely to be low when cold and not expanded. Anyways, I'm wondering if perhaps it's time to replace the expansion tank cap. I'd had vehicles where the cap failed and couldn't maintain pressure, and coolant would blow off while driving and the system would be low. It also appears that when the car is cold the coolant system is under vacuum. Is this normal for this car? Anyway, would this be a good first step? Maybe the tstat as well? Anything else to look for?

Thanks in advance.

mbshop · #2 01-16-2005, 11:47 PM

you may have a problem with the cyl head. when cold and also when hot
take the cap off. pinch off the overflow hose. now fill up the tank to the top.
crank the engine. if any coolant comes out then you got problems.

george

jbhebert · #3 01-20-2005, 03:22 PM

Quote:

Originally Posted by tkamiya

No, that's not normal. If your cooling system is developing vacume, it's a pretty sure sign that your pressure cap is not functioning correctly. If you look the underside of the cap closely, there is a black disk at the middle of it. When negative pressure develop in the system, that disk is supposed to pop open and let the pressure equalize.... I'd recommend getting a replacement.

Several unusual places to check on your vehicle....

In the passenger side front fender well, behind the cover, there is a recoverly tank. There is a over-flow tank in there. If that tank overfills, the fluid will come out of a hole that is in the fender, near the tire. I have not confirmed this myself, but once the coolant goes into the overflow tank in the fender well, when the engine cools, the overflow does NOT come back to the tank where the pressure-cap is. So, if your cap is not maintaining pressure, the level will continue to go down....

Are you filling the fluid to where the seam is, on the tank? You are not supposed to fill it like other cars where you fill it to the rim....

If you look at the washer fluid tank, you'll notice, there are two hoses attached to the cap. That hose is part of the cooling system. There is a valve at the other side of the cap. This is made of plastic. Sometimes, this piece breaks and let the coolant go into the washier fluid. Is your washer fluid rising when your car is hot?

In your upper tank (where the cap is), if you look underside of it, there is a connector... and behind it, a level sensor. This sensor can develop a leak. The first symptom is a wet connector. Eventually, the fluid will contaminate the contact and the light will come on dimly. It's pretty easy to check.

I ordered a new cap and will try this first. I'm hoping that's all there is to it. I always fill to the seam. If the cap doesn't do the trick, I think I'll bypass the washer fluid heater. It's hard to tell if the level is rising because I use it so frequently.

Thanks for the suggestions.

jbhebert · #4 02-22-2005, 02:54 PM

Well, I finally got around to adding some UV dye to the coolant. The dye, combined with the increased consumption of coolant, lead me to the leak. Directly below the #6 cylinder exhaust port I have significant leakage from the head gasket. I believe only the coolant passage was affected, since I show no signs of coolant/oil mixing. This is a good thing. The bad thing is that it still needs to be repaired. I just called my indy and he's going to get me a quote. If it's too much $$ I will likely do it myself.

I am going to put up a poll over here to see if any other 606 owners have had this problem. My car has about 175,000 miles on it, but I do not know how long the gasket has been leaking. Thanks for the feedback.