MM63

Hey everyone i hope you’re doing great.
So i bought my first ever Mercedes like 3 days ago - 2009 C63 Amg - around 65k miles on it - I was aware of the issues with the m156 and specially the headbolts - On the 2nd day of ownership i got a low coolant message i came home and topped it off and thought it was just low then on the 3rd day i checked my coolant reservoir and saw that it had dropped its level though i did not get the coolant message - There is no visible leak i can see so i figured that something is surely wrong - Frustrated and sad as this literally happend on the 2nd day and i basically the guy i bought it from mislead me and told me the bolts were done but later i found out that they were not - So i’m thinking of getting my headbolts changed without lifting the head - Am i good to go or has the gasket been compromised already? - There is no milky stuff in my oil, my oil level is fine - No rough idle or anything car still runs great and no smoke at all - So i need a suggestion from all you pros as i’m a newbie and this is my first ever MB I’ve owned jdm boosted cars before like Evo, Supra etc. - I dont want to lift the head but i needed advice that should i only do headbolts and will i be good to go? Please kindly help me i’m very worried and sad.

note: In my country we dont have MB official dealerships that can service it, but workshops are present here that have done bolts on a few cars but i’m not sure if they had coolant drop issues or they just got them replaced.
The uplifted bolts are readily available here but to get the gaskets i’ve to order them and then they will be shipped which is a long process.

Xavier Smith II

Bolt by bolt COULD work but unfortunately when you have coolant entering the combustion chamber, it’s probably time for a new gasket, also your headbolts are likely to snap while you try to remove them.

I personally wouldn’t risk or recommend the bolt by bolt method.

MM63

The ‘’could’’ in bolt by bolt still gives me hope, i’m not actually in the favour of removing my head and doing the gasket - The car is not showing any symptoms of a bad HG but still is losing coolant, when the car is hot i think the coolant level is fine but when cold i think it drops a bit - I’ve been super worried as i just bought it man i hope only doing the head bolts fixes my issues otherwise i might need to sell it off.

but as i topped off my coolant the other day i surely know it has come down it isnt on that level when i topped it off.

and like i said, oil level and colour is fine, no smoke from the exhaust, no rough idle, no milky oilcap.

mega_rad

I mean this is literally one of the symptoms of a bad head gasket, its likely just not bad enough yet to go full milkshake mode.

If you want confirmation you can have a shop do a leakdown test, and also pressure test the cooling system.

BLKROKT

If coolant is disappearing, you’re looking at heads off.

The very first thing I’d do is go talk to the previous owner. I’d find a way to convince him to at the very least split the repair cost with you. Because there are no such things as coincidences, plus he straight up lied to you about replacing the headbolts. I’d prefer to find a way to get your money back in full, and I would use violent tactics. I hate liars. In many countries that’s grounds for a lawsuit. Sorry.

Diabolis

^ What @BLKROKT said. If the seller lied to you about the head bolts, I would definitely take the issue up with the seller.

And, just replacing the head bolts - even if you manage to successfully pull them out in one piece - AFTER you already have a leak isn't going to solve anything. The heads need to come off and at the very least you'll need new gaskets.

MM63

Hey guys. So basically i got my cooling system pressure tested and we found the culprit.
The thermostat valve - it was leaking and the coolant was drying up very quick due to the heat of the engine and it wasn’t falling on the ground due to the protective under tray. Thankgod, i can sleep peacefully now.

i need a suggestion too, has anyone used the mishimoto race thermostat? Any reviews?

ChrisHimself

Dont mess around with anything aftermarket. thermostat is MAP controlled, the ECU controls the tempurature via fans and t-stat the temp is exactly what the car wants at all times

GarlicBread

This also went out on my car, went with OEM replacement as well.

Xavier Smith II

I personally wouldn’t sleep easy with the old style headbolts still in my engine, and the mishi stat is fine.

BLKROKT

Best possible outcome here, congrats. I think you still need to have a conversation with the previous owner. With a baseball bat in hand. And you should start thinking about getting rid of those old headbolts while you've been given another chance to.

And the Mishimoto tstat is great. I've been using it for 6 or 7 years without any problem. My coolant temps run very low - I'm convinced that the tstat has something to do with it, but I've also made a lot of other modifications to the system.

Ludedude