coolant leak near outside firewall

[dc36]

my c36 is leaking coolant at the firewall i cant really tell where its from cause its pretty well in there below where the oil filter is located right above the starter. any suggestions. thanks!

[jnenad16]

the leak is most likely from the hose that comes out of the heater and connects to the back of the head.

nenad

[dc36]

thats wut im thinking but it seems like it coming from below where that hose is. maybe its running down the firewall. i just had the head gasket and water pump done so i'm thinkin the next weakest part is going to fail.

[jnenad16]

if you had the head gasket replaced, it could be leaking from there then, however, if the leak existed in the headgasket, you would probably experience engine performance problems.
take a better look at it and determine where it is coming from exactly.

nenad

[viking]

Hello All,

I have been viewing this board the last few months and this is my first post. I got a 1995 C36 last December. I really have enjoyed the car. However I think I have some bad engine mounts that has caused another problem. Recently under hard acceleration from a stop. The Coolant hose mentioned above that goes into the firewall came off. To make matters worse the plastic attachment for the hose into the firewall has cracked. This could be related to your leak? I have the car in my garage and have new engine mounts to install but I am not sure about how to replace the broken hose piece. It goes through a firewall plate that can be removed? and on the other side of the plate another coolant hose is clamped. I am thinking I'll need to replace this two sided plastic coolant hose coupler ( the engine side of mine is cracked/broken ). Has anyone run into this or can give any advice. Thanks!

[benzaddict]

The plastic junction block at the firewall that has a few hose connections is common to failure. They break under stress and make a hell of a mess. You can get the whole thing at any dealership, the hoses along with precrimped plastic block. Sounds like this may be both your problems.

[viking]

Thanks Benzaddict. This junction block has one hose on the engine side and then on the other side (from what I can see looking behind it from near the brake booster) is another coolant hose. The other side is hard to see because it is covered by the windshield base and wiper. It is also a tight fit from the back of the engine to the firewall metal plate that the junction block goes under ( the plate U's over it ). This plate is about 2 1/2 ft long and 8 inches down and curves around the back of the engine compartment. ( insulation is also covering this plate/panel ) A vacuum line to the brake booster is the only thing going through the plate. And there are 2 8mm screws on each end of the plate. Besides being screwed on, the plate seems to be attached with some adhesive.

Has anyone had to remove this plate/panel? I think I am on the right track in removing it, but would appreciate any feedback. Thanks.

[benzaddict]

I'm trying to picture it in my head, it's been a few years since I've replaced one. Is it possible that the plastic junction can twist in the firewall about 45 degrees and come out. If I remember right it is held in by twist-lock clips, because I don't remember having to remove the metal plate you're talking about.

[dc36]

thanks! i was out in the garage chekin it out again and there is a plastic looking peice comin out the firewall just above the starter. its blocked by the starter from under. the only thing i can think of is removing the stater to see it.

[viking]

dc36, if the hose connection you are looking at is right next to the oil filter, you can see the other side from the top. You might have a plastic cover panel over the brake master cylinder? ( mine didn't but the other corner by the passenger side is covered )

I can see it from the brake booster / master cylinder angle. And it looks like this compartment is sealed off at the bottom so if it is the same junction I don't think you can see it from above the starter. Let me know, we might have a similar problem. Thanks

Benzaddict, I'll try to find out how to post a picture of it. I'll try twisting it. If it does twist loose, I guess you just pull junction with the hose connected on the other side out so the hose connected on the other side comes out enough to be access its hose clamp?

Thanks

[viking]

I found out how to post some pictures. First here is a picture of my 95 C36...

http://i76.photobucket.com/albums/j5/viking351/C36.jpg

Here is the broken coolant hose part...

http://i76.photobucket.com/albums/j5/viking351/problemclose.jpg

Here is the right side of the firewall plate ...

http://i76.photobucket.com/albums/j5/viking351/plateright.jpg

Here is the left side of the firewall plate ...

http://i76.photobucket.com/albums/j5/viking351/plateleft.jpg


As you can see, I have already started to try to remove this. Benzadict, I didn't have much luck trying to twist out the broken piece. I think I am going to get the replacement part from the dealer and then proceed with the repair.

Hope these pictures help show the broken piece and what I am trying to do. Any comments are appreciated. Thanks

[viking]

Just an update. I applied some muscle to break the adhesive on this plate and was able to lift it up and out. With that out I had access to the hose and clamp that was on the other side. I have the broken junction out now to get a replacement.

Another question though, I was going to do an oil change on the car. But the oil filter cap is on really tight. This does come off counter clockwise right? There is a clockwise arrow on the cap with some numbers which I assume is tightening torque #'s?

I have a plastic cap filter removal tool which seems to fit ( it is also the same one pictured in a c280 oil change diy a flotool #7) when I apply some good amount of torque it skips. I am thinking i'll probably need to get a different tool but wanted to confirm the removal direction.

Thanks

[dc36]

that is not where my car is leaking from it is below that fitting on the firewall its hard to see but if you look down on the firewall there is a black plastic piece.

[jnenad16]

Originally posted by viking
Just an update. I applied some muscle to break the adhesive on this plate and was able to lift it up and out. With that out I had access to the hose and clamp that was on the other side. I have the broken junction out now to get a replacement.

Another question though, I was going to do an oil change on the car. But the oil filter cap is on really tight. This does come off counter clockwise right? There is a clockwise arrow on the cap with some numbers which I assume is tightening torque #'s?

I have a plastic cap filter removal tool which seems to fit ( it is also the same one pictured in a c280 oil change diy a flotool #7) when I apply some good amount of torque it skips. I am thinking i'll probably need to get a different tool but wanted to confirm the removal direction.

Thanks
I usually use leather glove to remove the cover. you can also get the tool from the dealer.

nenad

[viking]

Thanks Nenad, I tried with a glove but it is on too tight.
DC36 I looked below the hose and saw a plastic piece that looks like it is some kind of air duct from the grill by the wiper?

Also from the behind the plate I removed to get out my broken junction ,that compartment has a drain hole at the bottom, which looks like it would drain above the starter

Here is a picture of the plate and piece removed. You can see the two coolant hoses hanging unattached and the area below where the leaves are is where the drain hole is. I don't know if this will help you but with mine apart it was easy to take a picture and post.

Also the hose to the right goes about 6 inches and then connects to a aluminum connection that goes through the firewall into the drivers area. Does anyone know if the heater core is on the drivers or passenger side? Thanks


http://i76.photobucket.com/albums/j5/viking351/plateremoved.jpg

[dc36]

i think the drain you are talkin about might be a drain for the heater core box. if anyone can confirm this it would be helpful. i have coolant comin out of there. so i'm thinkin its the heater core.

[OzC36]

Yeah had the same problem on my C36. I suspect that the part suffers mechanical distress when the apprentice grease monkeys replace the Oil Filter during routine service. Also note my car had a full Mercedes Service history when I bought it.

Photo 1 (note proximity of Oil filter unit to leak area):

http://img440.imageshack.us/img440/6073/dsc03086ze3.th.jpg (http://img440.imageshack.us/my.php?image=dsc03086ze3.jpg)

Photo 2 (Damaged part coated with talcum powder to show cracked area. Also note end of tube broken off previously):

http://img227.imageshack.us/img227/6286/dsc03099kd1.th.jpg (http://img227.imageshack.us/my.php?image=dsc03099kd1.jpg)

[DANGGERW202]

i had to replace that part on my 280. went to dealership with one hunderd dollars thinking the part would be expensive. and turned out to be 6.97+ tax. :D

it would leak only on hard acceleration and it was pretty annoying to keep refilling the coolant. it cracked just like one in the last picture

was not to bad to replace. all you need is normal hand tools.

[OzC36]

Also a cheap part in Australia (less than AU$25 from memory). The labour charge would have been a lot more.

Took me about three hours, but I work slowly!

[BALLLR]

I had parked my 96 c36 for three weeks and when I finally drove it, this same piece failed and made a mess of my engine bay. I was on the highway when I noticed my temp gauge rising, then I looked back and saw a KM of white smoke trailing from behind me. Coolant falling onto exhaust. Scared the shit outta me, even drained my oil to see if there was coolant in it (head gasket). worse part is that I had gotten my oil changed a few KMs before all this shit happened. If this does happen, make sure doesnt overheat distructively.