George993

Cross-posting in case someone on the W221 forum has had this problem, is so, could you please comment at:

https://mbworld.org/forums/m275-v12-...ck-engine.html


thanks for your help!!!

Nickthegreek

I know the V8 has a coolant temp sensor right on the drivers side at the rear of the cylinder head. Let me see if yours has one also. If so i would suspect the gasket on the coolant temp sensor maybe has gone bad. Ill check out alldata for info or bulletins

George993

thanks! good thought

Nickthegreek

There are some coolant lines that run behind your engine. Check to see if they are leaking

Nickthegreek

They are on the passenger side

Nickthegreek

Also theres coolant feed lines under the head behind the turbos it could also be those

George993

Problem is that I have been staring at it for a long time and can't see anything more apart from what I have written - it's so tight around the V12 engine. Some other major part would need to be removed to gain more visibility.

I guess those may be lines going to the cabin heater, but do they ever leak?

Nickthegreek

Also unfortunately the first step in removal/replacement is to remove the engine so that would best be left to a dealership or a experienced indy. They have to drop the engine from the bottom along with the subframe and all.

Nickthegreek

George993

Thanks, unfortunately I have seen this video earlier - a major job. Also I know of at least one case where the turbo coolant leak was fixed for $800 which I'm guessing did not need engine removal. That's why my questions...

Nickthegreek

Im curious if they approached it from the bottom. Not 100% sure never worked on the V12

ItalianJoe1

I had a heater hose break on my CL, from the rear of the engine into the firewall. The plastic fitting in the firewall also cracks and breaks.

Get in there with a mirror and flashlight, lay across the engine and look down there. I fixed mine but i'm a mechanic, and it still sucked. Had to remove the wiper arms, cowl, upper firewall and some little brackets to get access, then use remote clamp pliers to release the hoses, but it was all done from the top.

George993

Thanks to all. I've disassembled enough of the car to see clearly that the leak is at the turbo. Local independent Mercedes mechanics don't want to take it because they are afraid of engine complexities and have never done it. The dealer wants $6,300 to change the turbo seals. So I'm changing them myself, will report later when done (or when busted and towed to the dealer :-)

Nickthegreek

Lmao. Let us know how it goes.

George993

hi, here is an update. I did change the top turbo seals myself, not very complicated but very time consuming. Requires removal of ignition cassettes and many other parts, project lasted several days. No leaks 4 months later. Considering the coolant direction (from bottom to top) bottom seals will last much longer so I don't feel bad about not changing them. But if you get the same problem and if you find a mechanic who can do the top seals for less than $1000 just save yourself time and let him do it. I could not find one - independent shops just did not want to touch the car or like the dealer wanted to do the complete engine-out job. Passenger (USA) side is much much easier. I changed both sides, it is hard to say which one is leaking - there is enough parts below to spread the leak to appear on both sides even if only one is leaking. In any case it makes sense to change both as they will have similar life span. You will also need to change the seals in turbo oil pipes as they use the same mounting. Use brass equipment (I'm using Parker Seal) to remove/install/clear the coolant seals to avoid scratches and leaks. I also did not drain coolant completely, just disconnected a pipe near radiator top and siphoned coolant out to the turbo level. Plus I siphoned a bit more coolant from the turbos directly - just enough to have a dry surface for seals, but leaving the rest of coolant inside just in case you really need to prime them with coolant before starting. Also I know now where the burnt m275 engines come from - the fuel line (driver side, which you need to disconnect in the process) just slides on without any fasteners and probably slides out by itself sometimes causing fuel spill and fire - I've fastened it properly to avoid future problems.

gsholz

Congrats on getting it done! Any pictures?

KNBS550

I don't have the ***** or patience to do these things myself anymore. Cool that we have capable forum members to share their experience. Thanks also for following up on your earlier post!

Nuru

Yes, congrats on getting it done.

Wonders

Just amazing! thought turbo seals had to be an engine out job.


George993 did you first notice a pool of water under car, were there any other symptoms.

George993

Thanks to all for the kind words. First I noticed "Low coolant" or something like that warning light. Added some distilled water. There was a minor dripping which I initially thought could be from A/C condensation. But the "Low coolant" came back and the leak intensified, so I stopped driving the car looking for the problem.

I think the critical discovery (which I have not seen mentioned in any posts) was that the coolant flows from the bottom to the top, so that the cooler lower seals will last longer (or maybe MUCH longer?) and it makes sense to do only the top, and not to take the engine out for a complete job the dealer (and another mechanic) recommended as the only way to do it properly. Of course the bottom seals cold go bad soon as well, time will tell

George993

Driver side turbo - double bolt is oil, single bolt coolant


Here is a photo just before re-assembly (red o-ring/seal on coolant). Interestingly there is no symmetry, the same turbo on both sides and coolant is OUTER on passenger side and INNER on driver. So pipes need to be bent much more out on the driver side - I tried to install the o-ring with a coolant pipe close to the block but it does not work. Also get a few o-rings as they are only a few dollars and impossible to pull out once they drop in some narrow gap (ask me how I know). Oil hole is plugged with a rubber here - there is quite a bit of scraping involved to clean up the oil connector and you don't want any junk to get inside the turbo. The way it is designed the oil pipe should never leak if installed correctly, but since the gasket (get new obviously) is made of steel, I think it will leak if the mating surfaces are not cleaned to perfection.

George993

The oil gasket is painted with a black paint which comes off and bakes itself into the turbo - that's the scraping part

roseawebs

George993@ Thanks for your update. I was searching this kind useful instructions.

robmcnaught

George993 - thanks for the really clear photo on #21. Looks like I have the same symptoms as you described before doing this repair On the passenger side - I'm in the UK so thats driver side in the US which I guess makes access to the coolant pipe that bit more tricky.
Did you buy a replacement oil seals and o-rings set from the dealership, or did you buy them separately? Either way, do you by chance have part numbers which could help me source these?

George993

I bought both from the dealer, considering the amount of work required and the cost of just a few dollars at the dealer, that's the best option in my opinion. I'll check if I can find the part numbers (I think I posted them in some thread already as well). And buy a couple of extra o-rings - they are small and not magnetic, so once you drop one in some narrow spot you will never get it out.