I smell coolant
 

1985 300 TDT - Well it seems I have a coolant leak - I'm thinking it only started after I changed monovalve element. Passengers side has wetness under padded carpet. Does not seem to be getting too hot on the temp scale yet (85 degrees) coolant reservoir still okay. Will have to keep eye on it. Any ideas where to start looking? Thanks in advance. Steve:(

Smartin,

Usually this type of leak is caused by the heater core or one of the connections going to it leaking. This won't affect the engine temperature until it leaks enough to lower the coolant temperature.

You might try putting a leak stop chemical in the radiator.

Also try running with the pressure cap loose to see if the leak stops.

Removing the heater core is a difficult but not impossible job but is very expensive because of the many hours involved unless you do it yourself.

P E H

Thanks for the reply. When you say run with cap loose, if leak slows or stops, then I've confirmed that it is coolant - (Is that what you mean - or am I missing a step) Reason I ask is it really does smell like coolant, I have cleaned up the areas on the floor, and got a good look and smell, (so to speak). leaks ONLY on passengers side down trans tunnel side. Read a post (this forum) about a heat exchanger in near windshield under wiper arms (area) that could leak - this is a California model - I don't know if there is one - I am guessing this was OPTIONAL? Thanks again. Steve As far as the trans tunnel area - to start looking - should I take a look behind radio and ACC unit first or go behind under dash?

Smartin,

By running with the radiator cap ( yours may be located on the expansion tank) loose, pressure is not developed in the cooling system so the coolant is not forced thru small leaks.

I don't know anything about the heat exchanger near wiper arms but if there is one with engine coolant in it, it could leak.

Do a search on Evans coolant. Evans coolant and a stop leak chemical may be the solution to your problem with out removing the heater core.

I would think you would go under the dash to try to find the leak. The heater core and AC evaporator are in a big plastic box and you can't see either the heater core or evaporator. The box is removed with the heater and AC cores intact. I've done it and its a real PITA.

P E H

PEH - Thanks for the info. I did see a drip right under the dash on the carpet mat - pretty high up in the center (left to right) I does not seem reasonable that the heater core leaks as I thought this was more "central" on transmission tunnel. Is that about where it is?

Smartin,

Yes, the heater core is centered over the transmission but the coolant will drip out from the lowest part of the plastic box that has the heater core in it. If you have coolant leaking out where you say it is, it is definitely from the heater core or one of the connections to it.

If your car is similar to my 300SD, the pipes from the heater core are connected by rubber hoses underneath the air intake grill below where the wiper shafts go thru to the outside. You could have a leak there and that would be easier to fix than removing the heater core.

P E H

PEH - Looked under dash this afternoon, can see streaks (coolant) on floor and up firewall (inside car on grey colored insulation - the silver grey surface under carpet) - definitely coming down wall - hard to tell if coming from core - I assume that core is inside black plastic housing - with blower fan far right near passenger footwell. "Cold" air part in black plastic housing is near blower - I can feel the coldness there - heater is before that closer to center - if I have leak in heater core would'nt coolant be inside plastic housing - even at (condensor) core - my point is - could'nt I move blower on right side and have a look - along that same line of thought - if there is coolant inside housing - would'nt it flow out at drain - that is the 1-1/2 inch diameter foam hose clamped to black housing near firewall at center of trans tunnel. More evidence that it could be a connection rather than core - streaks run down above foam drain (on firewall inside) they originate from outside black plastic housing!? You say there are hoses coming from engine side. I guess I could "trace" from near monovalve vicinity. Are these "hot water feeds" under windshield wiper motor in a cavity. Iwas just in there today doing the only cleaning the car has ever seen in its 18 year life. I guess I should go back in. Thanks again. Is that where your hose connections are?

PEH - As I risk redundancy - what I was trying to say was that the streaks - or stains come down the wall AWAY from the plastic housing - seem to originate higher up than housing. There is perhaps a 1 to 2 inch clearance between housing and wall.

Smartin,

If the coolant leaks do not come from the plastic air box, the leak is not in the heater core. It sounds like you might have a leak in the hoses that connect the heater core to the other plumbing.

Take out the air intake screen (from outside the car) and see if you can get to the hoses that connect heater core and try to find the leak. If you find the leak here, consider yourself lucky. You won't have to remove the heater/AC air box.

You have a different model car than I am familiar with so heater hoses may not be where thay are on my car. Do you have repair manual to look at?

P E H

PEH - Thanks - I have to look on the CD. Could not get at them from outside at air intake. Reached in as far as I could - no pipes - I could see where they go in from engine side - 2 I believe, not accessible there (air intake).

Smartin,

If your car is like mine, you have to remove W/wipers and the air intake grill to get at the connections.

P E H

PEH - Well I went back in through air intake grills and looked around - hoses do NOT goe through this area. Not accessible. I wonder if there is another way in (aside from inside car - even that is not a sure access?) Thanks.