2004 Mercedes-Benz C270 CDI - Boost leak due to loose clamp or bad O-ring?

[ManLikeEnes]

2004 Mercedes-Benz C270 CDI, 2.7L OM612 engine

Greetings folks,

I've had a loss in power in the last few weeks with my Merc which I found out on the dyno and I've been trying to figure out what it is since; the MAF is fresh and clean, I've had the charge pipe between the EGR and the intercooler replaced, previously mentioned turbo boost solenoid replaced, the crankcase breather/PCV valve replaced and the garage I did the smoke test at didn't seem to spot other notable leaks other than the PCV which I replaced.

Whilst replacing my filters yesterday I thought I'd have a quick inspection upon the hoses and on the turbo side of the vehicle, it looks like the clamp for the boost hose might be loose? Would this be the problem or perhaps an O-ring enough to cause the car to lose considerable power? I have no black smoke at all, no limp mode or engine light, no overheating and she drives fine but just not quite as quick as it should be especially with a downpipe and sports cat.

The area between the air inlet and the turbo is also quite dirty but I've cleaned that area up a little bit since the PCV was leaking although it is a reconditioned turbo that was replaced 5 years ago.

 

[star]

You need to replace the housing as its cracked.

 

[ManLikeEnes]

You need to replace the housing as its cracked.

Thank you very much I appreciate your help, I'm looking to take her to a garage to get that boost pipe replaced as soon as possible. Hopefully shouldn't be too expensive I had the charge pipe replaced in the summer! I also wanted to add in the idle is a little rough when cold starting but otherwise isn't too bad and drives fine, hopefully once I've fixed this problem the car should be fine!

 

[DieselDaddy]

Thank you very much I appreciate your help, I'm looking to take her to a garage to get that boost pipe replaced as soon as possible. Hopefully shouldn't be too expensive I had the charge pipe replaced in the summer! I also wanted to add in the idle is a little rough when cold starting but otherwise isn't too bad and drives fine, hopefully once I've fixed this problem the car should be fine!

The injectors might be soiled, hopefully not, have you replaced the fuel filter?

 

[ManLikeEnes]

The injectors might be soiled, hopefully not, have you replaced the fuel filter?

Good morning DieselDaddy (nice name ), I forgot to come back to this forum; I did a pressure test and all the hoses were fine, unfortunately the turbocharger's compressor wheel turned out to have a lot of play in it. I have replaced the fuel filter and I did have an O-ring injector seal leak at one point but I had that injector cleaned and O-ring fixed very promptly.

 

[DieselDaddy]

Good morning DieselDaddy (nice name ), I forgot to come back to this forum; I did a pressure test and all the hoses were fine, unfortunately the turbocharger's compressor wheel turned out to have a lot of play in it. I have replaced the fuel filter and I did have an O-ring injector seal leak at one point but I had that injector cleaned and O-ring fixed very promptly.

Haha, thanks! Is the idle still rough on cold start?

 

[ManLikeEnes]

Haha, thanks! Is the idle still rough on cold start?

I haven't fixed the turbo yet so she does still vary a bit on idle, particularly cold starts she dips to 500RPM for a second before fluctuating back to a normalish RPM again; I was initially going to do it but I've got a CLK 320 petrol at the moment, mostly because of ULEZ and I have been contemplating for a while now what to do with it really. These last few weeks have been very hard for me haha.

 

[DieselDaddy]

I haven't fixed the turbo yet so she does still vary a bit on idle, particularly cold starts she dips to 500RPM for a second before fluctuating back to a normalish RPM again; I was initially going to do it but I've got a CLK 320 petrol at the moment, mostly because of ULEZ and I have been contemplating for a while now what to do with it really. These last few weeks have been very hard for me haha.

Interesting, my injector ended itself recently, and before it did so, during winter (around -5 to -10 celsius) cold starts the rpm fluctuated, stuttered, etc. till the injectors were warm (around a minute or two idling), aswell as this, right before injectors died I started it and had a very rough low rpm idle till I tapped the gas pedal. I will of course update you when I get to a shop tomorrow, maybe it is not injectors as suspected, but keep an eye on that. ULEZ lifehack - angle grinder and ski mask

 

[ManLikeEnes]

Interesting, my injector ended itself recently, and before it did so, during winter (around -5 to -10 celsius) cold starts the rpm fluctuated, stuttered, etc. till the injectors were warm (around a minute or two idling), aswell as this, right before injectors died I started it and had a very rough low rpm idle till I tapped the gas pedal. I will of course update you when I get to a shop tomorrow, maybe it is not injectors as suspected, but keep an eye on that. ULEZ lifehack - angle grinder and ski mask

Hopefully it wasn't the injectors! Depending on the mileage and age of the turbo I would be suspicious of that since my wheel has gone wobbly; I definitely agree with the ULEZ hack

 

[DieselDaddy]

Hopefully it wasn't the injectors! Depending on the mileage and age of the turbo I would be suspicious of that since my wheel has gone wobbly; I definitely agree with the ULEZ hack

OM646 with euro 4 EGR and regenerative DPF

For anyone interested,
It turned out to be either one thing or a mix of, not sure as I didn’t have a scanner with me, the back most egr valve sticking and the high pressure control valve (back of the fuel rail) starting to go, reman of injectors did not do much… only take a lot of money out of my wallet…

The very complicated and probably very easily avoidable story of how I fixed it.

Car started fine, but died around 3-4 seconds after starting, I thought it to be at first the hp control valve, but in my denial I removed this part (EGR mixing chamber?)

Don’t know the name of it, but know what it does, connects egr cooler to intake and allows the charge pipe to click into it, after removing it saw bunch of smoke come out of egr cooler exhaust pipe when revving it, so blocked egr as it had already been removed through software. (From analysis of multiple sources on this and competing forums EGR removal through software usually leaves EGR valve 80-90% closed at times and fully closed other times thus not fully removing it)

To get to the EGR cooler/cylinder head connection point, to block it off you must remove almost everything on the cold side.

I had to remove

- EGR mixing chamber, quite simple, remove the spring from it and the EGR cooler without losing it, when unscrewing you must be wary of the top left screw as it has a nut instead of it threading into the intake manifold.(I lost mine and had to use a 6mm locking nut)

- Fuel rail and fuel pipes, you can remove the return line from the injectors and remove the high and low pressure fuel lines from their metal elbow that rests in the middle of the manifold, and then just throw the fuel lines somewhere to the side

- Fuel filter and bracket, the bracket for the fuel filter is a bit flexible, and the hex screw can be left in.

- Power steering fluid reservoir, unplugging the fatter tube from the pump and aiming it into a container to lessen the spill, the return line isn’t as bad.

-There is a weirdly shaped bracket that uses the middle top screws of the intake manifold, this boomerang shaped bracket holds together most everything that also bolts into the manifold, remove this carefully.

-Thermostat housing, as well as coolant pipe and the little return/bleed pipe I blocked mine off and let it hang down into the engine bay some coolant will spill from the block, it is inevitable, I also suggest changing the thermostat housing gasket, very cheap but worthwhile (mine probably leaks because I was too stupid to buy)

-At the back of the intake manifold there is a corner type of bracket that holds the EGR coolers coolant pipe into it, remove this but do not lose any screws, it will pop off under load and leak if you do not put it back after everything is reinstalled.

-I also found it helpful to unscrew the coolant hoses at the back of the intake manifold that go into the EGR cooler, as it just frees up some much appreciated space.

-Unscrew the top screw for the manual oil stick tube, I had to bend the little hole to get it through the manifold easier.

After, you’re left with just the intake manifold and cables.
Using a 8mm socket and a small ratchet with extension I removed both top and bottom intake manifold bolts, now I am unsure if these stretch, I reused mine as they all seemed the same length, the thread also being fine.
After removing all 8 bolts you can move the intake manifold, it had a harness going right through the middle of it for me, I cut mine, soldered longer cables, heat shrink and wrapped it as to simplify future attempts, but it can be unplugged if you have smaller hands, it is quite simple to unplug by just following the cables.

After getting rid of the cables then comes the hard part of just prying it out of the engine bay, I had to expose the oil stick tube to some unwanted elastic deformation to get it through the manifold.

My intake manifold was full of carbon residue, I suggest cleaning it out with some plastic safe degreaser and warm water if you have this issue and don’t want to purchase a new one.

New gaskets should also be bought for the intake manifold.


Removal is quite straightforward, but be aware that the e-torx bolts come in varying sizes, so colour coding the holes and bolts with markers will help alot.

The EGR cooler

To remove this, it has three Torx bolts and it borrows one from the intake manifold on the top left if facing the cylinder head, I suggest putting a few rags underneath the EGR cooler or removing the starter located right underneath the EGR cooler/cylinder head connection point as some coolant will leak out of it and can soak into the starter.
EGR cooler should now be free to move around, and it should also have a gasket between it and the head that can be used to trace a blanking plate.





EGR cooler had this gasket, very thin and flimsy.
Bottom (BIG) hole is exhaust and top (small) hole is coolant, block off the exhaust hole, and leave a hole for the coolant to circulate.
You can slot in a diy blanking plate around 0.5mm thick into the clips of the gasket as to not need gasket maker, but depending on the material you use for your blanking plate there is still a chance of leakage, so use a little bit of gasket maker to be safe.

Reinstall everything the opposite way you removed it and pray.

I torqued the EGR cooler and intake manifold to 14Nm (read that it should be 15Nm and went with 14 just to be safe).

My story only ended when I replaced the fuel pressure control valve as car kept stalling above 2k rpm as if it didn’t have enough fuel pressure and CEL was on, but I haven’t had a chance to use an obd scanner to check errors, so I cannot confirm, I can only speculate it cut out from that.

If there is an easier way to physically block the EGR I do not particularly want to know as I will cry, but it would immensely benefit others if anyone shared it.

P.S. I am unsure of what I missed as I am half asleep but it isn’t all that complicated, just tedious to get to the egr cooler.

 

[ManLikeEnes]

OM646 with euro 4 EGR and regenerative DPF

For anyone interested,
It turned out to be either one thing or a mix of, not sure as I didn’t have a scanner with me, the back most egr valve sticking and the high pressure control valve (back of the fuel rail) starting to go, reman of injectors did not do much… only take a lot of money out of my wallet…

The very complicated and probably very easily avoidable story of how I fixed it.

Car started fine, but died around 3-4 seconds after starting, I thought it to be at first the hp control valve, but in my denial I removed this part (EGR mixing chamber?) View attachment 95836

Don’t know the name of it, but know what it does, connects egr cooler to intake and allows the charge pipe to click into it, after removing it saw bunch of smoke come out of egr cooler exhaust pipe when revving it, so blocked egr as it had already been removed through software. (From analysis of multiple sources on this and competing forums EGR removal through software usually leaves EGR valve 80-90% closed at times and fully closed other times thus not fully removing it)

To get to the EGR cooler/cylinder head connection point, to block it off you must remove almost everything on the cold side.

I had to remove

- EGR mixing chamber, quite simple, remove the spring from it and the EGR cooler without losing it, when unscrewing you must be wary of the top left screw as it has a nut instead of it threading into the intake manifold.(I lost mine and had to use a 6mm locking nut)

- Fuel rail and fuel pipes, you can remove the return line from the injectors and remove the high and low pressure fuel lines from their metal elbow that rests in the middle of the manifold, and then just throw the fuel lines somewhere to the side

- Fuel filter and bracket, the bracket for the fuel filter is a bit flexible, and the hex screw can be left in.

- Power steering fluid reservoir, unplugging the fatter tube from the pump and aiming it into a container to lessen the spill, the return line isn’t as bad.

-There is a weirdly shaped bracket that uses the middle top screws of the intake manifold, this boomerang shaped bracket holds together most everything that also bolts into the manifold, remove this carefully.

-Thermostat housing, as well as coolant pipe and the little return/bleed pipe I blocked mine off and let it hang down into the engine bay some coolant will spill from the block, it is inevitable, I also suggest changing the thermostat housing gasket, very cheap but worthwhile (mine probably leaks because I was too stupid to buy)

-At the back of the intake manifold there is a corner type of bracket that holds the EGR coolers coolant pipe into it, remove this but do not lose any screws, it will pop off under load and leak if you do not put it back after everything is reinstalled.

-I also found it helpful to unscrew the coolant hoses at the back of the intake manifold that go into the EGR cooler, as it just frees up some much appreciated space.

-Unscrew the top screw for the manual oil stick tube, I had to bend the little hole to get it through the manifold easier.

After, you’re left with just the intake manifold and cables.
Using a 8mm socket and a small ratchet with extension I removed both top and bottom intake manifold bolts, now I am unsure if these stretch, I reused mine as they all seemed the same length, the thread also being fine.
After removing all 8 bolts you can move the intake manifold, it had a harness going right through the middle of it for me, I cut mine, soldered longer cables, heat shrink and wrapped it as to simplify future attempts, but it can be unplugged if you have smaller hands, it is quite simple to unplug by just following the cables.

After getting rid of the cables then comes the hard part of just prying it out of the engine bay, I had to expose the oil stick tube to some unwanted elastic deformation to get it through the manifold.

My intake manifold was full of carbon residue, I suggest cleaning it out with some plastic safe degreaser and warm water if you have this issue and don’t want to purchase a new one.

New gaskets should also be bought for the intake manifold.


Removal is quite straightforward, but be aware that the e-torx bolts come in varying sizes, so colour coding the holes and bolts with markers will help alot.

The EGR cooler

To remove this, it has three Torx bolts and it borrows one from the intake manifold on the top left if facing the cylinder head, I suggest putting a few rags underneath the EGR cooler or removing the starter located right underneath the EGR cooler/cylinder head connection point as some coolant will leak out of it and can soak into the starter.
EGR cooler should now be free to move around, and it should also have a gasket between it and the head that can be used to trace a blanking plate.





EGR cooler had this gasket, very thin and flimsy. View attachment 95837
Bottom (BIG) hole is exhaust and top (small) hole is coolant, block off the exhaust hole, and leave a hole for the coolant to circulate.
You can slot in a diy blanking plate around 0.5mm thick into the clips of the gasket as to not need gasket maker, but depending on the material you use for your blanking plate there is still a chance of leakage, so use a little bit of gasket maker to be safe.

Reinstall everything the opposite way you removed it and pray.

I torqued the EGR cooler and intake manifold to 14Nm (read that it should be 15Nm and went with 14 just to be safe).

My story only ended when I replaced the fuel pressure control valve as car kept stalling above 2k rpm as if it didn’t have enough fuel pressure and CEL was on, but I haven’t had a chance to use an obd scanner to check errors, so I cannot confirm, I can only speculate it cut out from that.

If there is an easier way to physically block the EGR I do not particularly want to know as I will cry, but it would immensely benefit others if anyone shared it.

P.S. I am unsure of what I missed as I am half asleep but it isn’t all that complicated, just tedious to get to the egr cooler.

Situation update: I finally took the time to look at my C270 CDI since I have now moved and made my decisions.
I inspected the turbo, however I found virtually no play and the bearings seemed fine as well, it span just right so I was a bit surprised since the garage said it was the turbo. The turbo actuator also works so I pretty much ruled it out to be the turbocharger (unless the VNT vanes are sticking badly). I've also ruled it out to be any boost leaks since I did a pressure leak test, I've replaced the PCV valve as well as the boost pressure sensor too last year. I am going to check the EGR right now to see if that is sticking or not and I'll give an update back regarding that.

I also had an injector leak earlier on this year which I caught onto very early and had it fixed promptly, the top of my injectors are clean but I'm not sure if there is a bit of back leak? The high pressure fuel pump is also very rusty, I'm not sure if that is potentially leaking fuel out? I did notice a point which may or may not have looked slightly damp. That or the injectors is my top suspicion if the EGR is not blocked since the swirl flaps were supposedly removed on this vehicle.

 

[ManLikeEnes]

As it turns out the EGR looks to be very dirty, presumably it's blocked up. I'm going to remove it and clean it either way but has anyone got any recommendations? Would brake cleaner suffice or should I get something else like carburetor cleaner? Should I use something else to clean her up? Cheers!

 

[LostKiwi]

Best thing I've found to clean EGRs and sooty inlet tracts is oven cleaner. Get the foaming Mr Muscle kind, give it a good spray, leave 20 minutes and hose off.
Remove any sensors etc beforehand.

 

[ManLikeEnes]

Best thing I've found to clean EGRs and sooty inlet tracts is oven cleaner. Get the foaming Mr Muscle kind, give it a good spray, leave 20 minutes and hose off.
Remove any sensors etc beforehand.

Had an absolute nightmare trying to get the bolts off the EGR, one of them refuses to come off and the other one is in the pits of engine bay hell; I have someone coming over today anyways to diagnose the car and hopefully check the boost pressure as well, hopefully they'll be able to take the EGR off for cleaning too but I'll keep you guys updated on what's going on. If it helps she barely smokes as well, I took her to MSL (which is when I discovered the power loss unfortunately) but they tuned her nicely she used to smoke a lot under hard acceleration!

 

[ManLikeEnes]

UPDATE: Turns out the EGR, which was blanked off with a bolt in the vacuum line, wasn't working very well but the EGR clean with carb cleaner, as well as a brush, also helped because it had sooty deposits (not great! ) It's not perfect but the valve works! She does smoke but there's no more rough idle and the turbo sounds glorious! Although the mechanic mentioned that there was a knocking sound? Likely injector knock? Back leak?

I have potentially considered replacing the turbo oil feed and return lines as well just for the sake of the turbo since it's done about 40,000 miles so far. There's no play in the compressor wheel and it seems to spin just fine. It also seems to boost well (although I will do some test runs and eventually run a diagnostic to see the numbers). At this point though I am largely just thinking of preventative maintenance and the mechanic seems content with me doing earlier oil changes (every 6000-8000 miles instead of every 10,000).

Finally, I will probably leave the EGR alone for the foreseeable future-

 

[ManLikeEnes]

Situation update: It's been a while but I completely forgot about the turbo housing that star pointed out, there's quite a crack which I presume is causing my air leak issues. Since then I have taken the old intercooler off as well as the bumper, I've got a J-Line intercooler from Mishimoto, however I am also trying to get rid of a lot of plastic parts in the motor; the housing is one of them (A6110981807). However I can't seem to find a way to bolt a silicone or some sort of pipe onto the turbo's intercooler exit. Not sure if there's an aluminum option or if I could get one custom made, or just a pipe welded onto the turbo since the mouth isn't perfectly round (there's an awkward V shape).

Whilst at it I have done a lot to the car including: Crash bar sanding down and clean, engine block sand down and clean, intercooler pipe cleaning, intercooler cleaning, bumper cleaned, coolant flush and coolant tank cleaning (still in progress). I'm just taking this opportunity to do as much as possible whilst I'm using my other car and figuring out how to improve the turbo's boost piping. The blue Merc is really good otherwise!

In regards to the EGR, the faulty glow plug which is causing a rough idle from cold seems to be more noticeable when the EGR is blanked off. I was suspecting the fuel system but apart from a very slight injector knock potentially? The fuel delivery seems to be fine, no misfires or stalling that I'm really noticing, my problems seem to be stemming from a lack of air at higher speeds because of that boost pipe leak, I will see if I can just convert it to all aluminum and silicone but I might just get the plastic part for the short-term if all else fails.