Forrest_H

Hey all,

I'm new to this forum, so before I go on, hi

Onwards, I currently own a 2000 CLK430, and I've had little to no issues with it, the engine is pretty much bullet proof. As of late, I've encountered a very worrisome issue.

I received a coolant warning while driving, so I got out to check on it. I looked under the car to see a small puddle forming, but the engine temperature wasn't raising, it was where it always was. I couldn't get a good look at the underside (too dark), so I poured a bit of distilled water into the reservoir, and went on home.

When I got home, I found some pretty scary things.
One, there were coolant splatters in the engine bay. It wasn't a huge amount, but it was freaky to me.

Two, there was coolant pooled in the center of the engine. That freaked me out.

Three, there was a small nut on the bottom of the engine (I'm sure it's the radiator drain plug) that was slowly dripping coolant.

I checked the oil cap today after the problem still persisted, but I didn't see any foam. I did manage to snag some pictures, though, I hope they help.

I would normally just figure it out with my dad, but at the time, he was... uhhh.... hopped up on apple juice

Any help you guys can give would be immensely appreciated, this was my first car, and I'd love to keep it running.

Thanks everyone!

Forrest_H

Oh, also, here are the pictures.

Edit: Hmm, I guess I can't post more than one picture per post... Or resize them. Sorry for the massive pictures! I'm not able to post the other picture, but here's the link: https://i.imgur.com/Yf3Yxdf.jpg

AutohausAZ-Mike

How many miles on the vehicle?

Forrest_H

137xxx.

It might be the water pump, but I replaced it not too long ago... Might just be the heat, this summer has been a hot one.

Thanks for the reply!

MarcusF

Ordinarily I'd suggest pressure testing the cooling system, but I don't know how that's done on these cars. You could contact Autohaus AZ and ask them if they carry or can get a pressure tester for a W208. Chances are they do or can. Autohaus can get just about anything.

AutohausAZ-Mike

Unfortunately, we don't carry a pressure testing tool. If you have a high mileage car you really want to inspect all the cooling hoses. After 100k its best to do a full cooling system overhaul as a preventative service to avoid major issues and breakdowns down the road.

Forrest_H

Hmm, okay. I'll have to find some funds for that

I looked at the center cavity of the engine with a Boroscope, it looks like it's not coming from the water pump, but it's splashing from the rear of the engine up to the front. Still no foam in the oil cap, but the leak is getting worse. What components are in the rear that could cause this? I'm likely going to get it pressure tested soon, but I'd like to know if there's something back there that's causing this that isn't a line.

Thank you guys so much for your help, it's beyond appreciated

CJackson13

Check the little plastic nipple on the radiator that connects to the top right cooling hose. It tends to get brittle and fail since it is plastic. Also check also the hoses for obvious holes and tears.

jonUF02

I can't tell what the picture is, but there is some kind of bleed off valve on the bottom of the water pump I believe, that will release coolant when the pump fails. If you're getting that much coolant flowing out, then it should be easy to dry it out, start the car, and see where it comes from.

Also, I have come across many of these radiators that have plastic fused to metal, where the plastic separates and starts leaking. It happened on my car, and I just replaced the radiator and hoses. I might suggest replacing the water pump for safety with the mileage you have and if you already have the radiator out it will be pretty easy.

While you're in there, might as well put on a new belt, maybe idler pulley and tensioner too. All of these things have needed replacement on my car that has about the same mileage and has been pampered. It will be some good preventative maintenance for the future of your vehicle and would make sense to do it all at once. The most costly part would be the water pump, the rest are relatively cheap.

CJackson13

+1 for this. I've been in the same exact situation. Replace ALL of the pulleys before they fail. Two years ago I replaced my Idler pulley and belt after it failed and shredded. Six months after that I replaced my radiator and hoses due to that plastic nipple fused on the metal radiator. The nipple is fused and is considered as one with the radiator so I had to replace the entire thing, which was fine. Another six months go by and my Tensioner pulley fails (didnt replace it when I replaced the idler) which shredded the new-ish belt, destroyed the water pump, and ended up puncturing the radiator I replaced 6 months prior. That was such an expensive day only because I didnt replace the pulleys at the same time...

Save yourself the potential headache and replace entire systems at the same time.

Forrest_H

I checked that, no avail. I'm truly convinced it's coming from the rear, but I just don't have any way to dismantle it right now (full time job, work over weekends too).

Oh! Sorry. In the first picture, that's actually the center cavity of the engine. I don't know why I didn't think of cleaning everything off, duh. I'll try that tonight.

Will do with checking the radiator, another duh moment .
Whatever it is that's gone wrong, I'll be preemptively replacing everything coolant wise that I can get my hands on. The belt will definitely be replaced too. I'll also go ahead and replace both the pulley and tensioner.

Ouch, that doesn't sound fun

I'll definitely go ahead and replace the entire system.

Thanks everyone! You've been a huge help

Forrest_H

Does anyone have an engine cross section diagram? I'm now convinced the coolant leak is definitely in the center valley of the engine, and I need to know what runs through there coolant wise.

Thanks!

jonUF02

From my memory of taking the intake manifold off, I don't believe there is anything in the valley that would leak coolant. The manifold spans the valley, and below it was just some built-up dirt that I vacuumed out. The only possibility that I can think of would be a head gasket leaking outward. If you do an image search for Mercedes M113 engine, you will come up with some good pics.

If you really want to get into it without tearing down your engine, then I might suggest going to a "u-pull" type junk yard that has a car with the same engine and tear down one of theirs to feel it out.

jonUF02

I just got lost in this awesome thread, but on page 7 are some good pics of building up a 55 engine.

https://mbworld.org/forums/w211-amg/...project-7.html