Where's Antifreeze Going?

I have a 190E 2.3 with 130,000 miles. Within the last 6 months I have replaced the radiator, the water pump, the auxiliary water pump, the tank cap, all the hoses (except the one at the back of the head which goes to the heater core, which I can't figure out how to get at the end nearest the firewall.)

After all this, I am still losing anti-freeze. I cannot see any evidence of leakage, nor am I seeing any evidence of anti-freeze in the oil.

I'm stumped. Where's it going? The engine runs great. Am I looking at a head gasket leak into the combustion chamber? I would have expected evidence of that coming out the tailpipe in the form of continuous white vapor.

Any suggestions? I have not had a pressure check since doing all these replacements, but that is my next course of action.

Tim,

A little more info would be helpful - how fast are you losing it? Has it been constant or is the rate increasing? Why all the component replacements, to fix the consumption problem? Is there a sweet smell or steam on the inside when running the heater? A pressure test is definitely in order! When you do this, make sure the engine compartment is clean and dry. Also make sure it is parked on a clean dry area so you can look for leaks on the ground. You may have a leaking heater core or possibly a head gasket that is slightly blown letting coolant into the combustion chamber or external leak. All head gasket leaks do not necessarily get coolant into the oil, so clean oil does not eliminate this possiblity. When doing the pressure test, visually inspect the head to block seal for any leaks. If it does leak down but you can not find the source, lift up the carpet to see if the heater core is draining into the floorpan. Lastly, if you still have a leak but can not find it, pull out your spark plugs and after letting the pressure sit for a good bit of time, using small mechanical fingers, stick a cotton ball into each cylinder to see if there is any liquid. I have never done this, but in theory, it would work.

I would recommend doing the pressure test with a cold engine initially (for safety and so minor leaks will stay in the fluid state, rather that steam) and repeat with a warm engine if required.

Not knowing you level of experience - be very careful working on hot pressurized coolant systems and dispose of any coolant properly, it is deadly to animals!

I will look for any replies should you need help.

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Deezel
87 300TDT
150,000 miles

[Benzmac]

The heater valve will leak on these while driving. It is under the windsheild under the hood.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Benzmac,

Is the heater valve in the supply line to the heater, or in the return line back from the heater? How do you get at it?

Deezel,

Haven't noticed the obvious signs of leakage inside the passenger compartment.

I was hoping on the tank cap, as I've heard that they have been known to leak. It wasn't.

All the other things were definitely leaking and needed replacement. The radiator and water pump were last summer, the auxiliary water pump last week. I replaced the attendant hoses for cheap insurance.

I took a 200 mile trip Saturday and it lost about a half liter of coolant. Not low enough to alarm, but obviously below normal level. I checked the level prior to leaving on the trip.

Thanks

Deezel, Pull each spark plug. If one is exceptionally clean (i.e., it has been literally steam cleaned by the engine coolant), then that is the location where the head gasket surrounding the water jacket let loose. Unfortunately I learned this lesson the hard way sometime well-back in the past. Hope this is of some help to you.

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Fred Prickett
85 500 SEL, 241,500 mi
90 5.0 Mustang LX conv.

This team work is going to make me cry! The point about looking at the plugs is excellent. I didn't know that, but looking at the condition of the sparks after removal is one of the fundamentals, and I never thought of it! The heater valve sounds like a prime suspect as well.

Happy Hunting!

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Deezel
87 300TDT
150,000 miles

Need a little help with how to gain access to the heater valve!