Coolant Leak
 

My 300e has a coolant leak. The dealer can't seem to locate it. The first time I took the car he found an oil leak that he repaired. (I was sceptical that this was the problem, but I gave him the go ahead to put some new gaskets - $200). It did not solve the problem - it WAS a coolant leak, as told the dealer. The second trip in the dealer, he said yes there was coolant on the splash pan. He replaced a small fitting on the top of the radiator and pressure tested the system. He said he could not find a leak, but he doubted that he had the problem fixed. He was correct the problem is not fixed yet!

It seems to be temperature related. It does not leak at the dealer. - even though the first time I took the car it was cold (dropped off in the night before), and the second time the car had been running.

The dealer suspects that it is the plastic expansion tanks on the side of the radiator. I am reluctant to pour money into a new raditor when he can't even see the leak.

Does anybody have any suggestions what to do? Also has anybody had good or bad experiences getting the plastic tanks resealed to the aluminum core (I personally have had bad luck with this on a ford).

Thanks for help.

IF it is temperature related, it will be the radiator or the water pump. I would let them keep it over night..
They should park it on a clean floor with the belly pan off.

Thanks, I'll do that. Have you had any experience with radiator repairs or do generally go with replacements. The car is a 91 with 120,000 miles.

I had water pumps go on two different W126 cars. One of the car's leaks started as a slow drip, which I later found was coming from the drain nipple on the bottom of the water pump. You'd have to use a mirror to look at it, or put your hand under the water pump and feel it. I couldn't figure out where the leak was coming from, until I was driving one day and the water pump just gave out and the coolant gushed out.

I've heard of water pumps going frequently in W124's - its a little involved to replace it. I've done it on a W126 with a friend - it took us about 1-1/2 days but never did it before. The W124 requires the radiator removal from what I understand.

After the dealership has had a chance at it, I would ask how much is actually leaking? Are your engine temps affected at all?

With my 300E, the expansion tank went first ($85 fix at dealer), followed by water pump, then radiator. It took six months for the entire cycle to occur.

Your water pump will "weep" as the seal deteriorates, and then ultimately fail with a telltale sign of substantial amounts of coolant on your garage floor (your belly pan won't hide THAT leak). Because of the water pump location, it is difficult to trace the weep hole leak.

If your radiator is original, expect it to fail eventually, as they crack at the joint where the inlet hose is connected. If ultimately, the water pump has to be replaced, get the radiator done as well.