Turbo pressure test for ML320

chka

Hi all,

I have an ML320 (06 model) and it suffers for almost 2 years from its turbo. I've spent so much time and money on that turbo that I'm getting tired and I've changed 3 different garages because they're unable to fix it. The whole system has been checked visually, then the experts concluded that the turbo has to be replaced. They removed the old turbo, fixed it (replaced all the internals) but the car still displays P0299 (Turbo boost low). Then, they replaced some sensors but the problem is still there. So I can only assume that some pipes are leaking and I've been told that I may need to perform a pressure test. I'm not a DIY guy so I'm looking for a competent garage anywhere in Dublin that can perform that and fix the problem. Any advice welcome

Thanks,
chka

corglass

Does it pull well when you're above 2.5k rpm?

shietpilot

Sounds like the actuator isn't controlling the variable geometry in the turbo correctly. Have they properly checked the vacuum hoses going to the turbo actuator for any splits? The whole vacuum system should be checked for leaks to ensure that the actuator moves to control the boost.

Is there much smoke out of the exhaust when you put the pedal to the floor? Could be a boost leak due to a slit in one of the pipes coming from the turbo to the inlet manifold.

Have a read through: https://www.obd-codes.com/p0299

dieselbug

I don't know of any in Dublin but I do know one in Enfield that I would recommend. I can PM if you wish.

All of the intake system needs to be tested for leaks preferably using smoke and pressure also the vacuum system.

If there's any restriction in the exhaust system it can also cause underboost.

Also the boost regulation controls.

chka

corglass wrote: »

Does it pull well when you're above 2.5k rpm?

It does work fine as long as I'm bellow 2.5k rpm but if it goes above for more than 10-15 sec, the car goes into a go-slow mode and the engine light comes on

chka

dieselbug wrote: »

I don't know of any in Dublin but I do know one in Enfield that I would recommend. I can PM if you wish.

All of the intake system needs to be tested for leaks preferably using smoke and pressure also the vacuum system.

If there's any restriction in the exhaust system it can also cause underboost.

Also the boost regulation controls.

Sure thing, please PM me... Enfiled is not that far away, if these guys can fix the problem

chka

shietpilot wrote: »

Sounds like the actuator isn't controlling the variable geometry in the turbo correctly. Have they properly checked the vacuum hoses going to the turbo actuator for any splits? The whole vacuum system should be checked for leaks to ensure that the actuator moves to control the boost.

Is there much smoke out of the exhaust when you put the pedal to the floor? Could be a boost leak due to a slit in one of the pipes coming from the turbo to the inlet manifold.

Have a read through: https://www.obd-codes.com/p0299

Theoretically, the actuator must be changed when they reconditioned the turbo. I also suspect boost leak from one of the pipes and that's why I'm looking for someone who can test that

fancy pigeon

shietpilot wrote: »

Sounds like the actuator isn't controlling the variable geometry in the turbo correctly. Have they properly checked the vacuum hoses going to the turbo actuator for any splits? The whole vacuum system should be checked for leaks to ensure that the actuator moves to control the boost.

Is there much smoke out of the exhaust when you put the pedal to the floor? Could be a boost leak due to a slit in one of the pipes coming from the turbo to the inlet manifold.

Have a read through: https://www.obd-codes.com/p0299

OM642 engines have an electronic actuator, not a pressure/vaccum operated wg actuator.

Only solution is to try a known working/new turbo

I would also check the pipework from the inlet pipes to the boost sensor

It could well be the actuator itself.
http://www.turbodevelopments.co.uk/turbo-electronic-actuators.php

Full turbo replacment etc isn't the only option if it is the actuator

shietpilot

Augeo wrote: »

It could well be the actuator itself.
http://www.turbodevelopments.co.uk/turbo-electronic-actuators.php

Full turbo replacment etc isn't the only option if it is the actuator

It can be the cost but OP needs proper diagnosis and not a mechanic who replaces anything and everything until the problem goes away.

fancy pigeon

Can you buy the actuator on it's own and get someone to fit it? Who's to say the turbo isn't damaged by operating at the wrong pressure...?

shietpilot

shietpilot wrote: »

It can be the cost but OP needs proper diagnosis and not a mechanic who replaces anything and everything until the problem goes away.

My post was in response to this...

fancy pigeon wrote: »

OM642 engines have an electronic actuator, not a pressure/vaccum operated wg actuator.

Only solution is to try a known working/new turbo

I would also check the pipework from the inlet pipes to the boost sensor

fancy pigeon

fancy pigeon wrote: »

Can you buy the actuator on it's own...............

OM642 turbo actuator's cannot be bought seperately afaik

fancy pigeon

Augeo wrote: »

My post was in response to this...

Well the correct post could have been quoted to avoid confusion

I stand by what I say

Augeo wrote: »

OM642 turbo actuator's cannot be bought seperately afaik

But! Can it be guaranteed that the turbo is not damaged by just replacing the actuator...?

Just to be clear, is there a possibility the turbo is/has been damaged by operating at the incorrect pressure due to a faulty actuator?

fancy pigeon

fancy pigeon wrote: »

Well the correct post could have been quoted to avoid confusion

.....

I'd say you are the only one confused.

fancy pigeon wrote: »

....But! Can it be guaranteed that the turbo is not damaged by just replacing the actuator.......................

I think you know the answer to that.

In this case the turbo has been replaced and the initial issue is still present.

Are you suggesting replacing the entire turbo just in case it's damaged when an actuator refurb for a few hundred is an option?

fancy pigeon wrote: »

..............

I stand by what I say ................

fancy pigeon wrote: »

...........

Only solution is to try a known working/new turbo..........

fancy pigeon

Augeo wrote: »

I'd say you are the only one confused.

Don't be getting angry, chap...

Augeo wrote: »

I think you know the answer to that.

In this case the turbo has been replaced and the initial issue is still present.

But I asked for an answer... Anyway, I offered one solution, others have been offered. I'll leave it at that

Augeo wrote: »

Are you suggesting replacing the entire turbo just in case it's damaged when an actuator refurb for a few hundred is an option?

That is exactly what I'm saying. Some refurb units I've seen had to be returned under warranty as a faulty unit, whether it was overlooked or let out by the supplier by accident, who knows.

But that is what I am suggesting, like it or not

fancy pigeon

fancy pigeon wrote: »

..................



That is exactly what I'm saying. ..............

Great, OP you need to find a known working turbo and install that in your Merc
I'm sure you glad you started the topic now

BTW, you stated there was only one solution, not quite what you are now claiming.

fancy pigeon wrote: »

....... I offered one solution........

shietpilot

Lads you are arguing over nothing. All OP needs is proper diagnosis. The actuator can be replaced on its own. A cheap turbo from a breakers yard would be a handy way to get one but there's no point doing it if it's not the cause.

shietpilot

shietpilot wrote: »

Lads you are arguing over nothing. All OP needs is proper diagnosis. ...........

Indeed.

Full turbo replacement is ludicrous at this stage (not wanting to further anger the chap).

chka

Thank you for all your advice guys. I checked again the invoice for what was done and the actuator has been replaced as well as the turbo engine has been rebuilt and balanced. After that, all gaskets and washers have been replaced, including a full service which replaced oil and air + oil filters (and probably other things were done, not mentioned). That's why I suspect a leak somewhere in some pipe that doesn't show signs of leak - all pipes have been checked visually and we replaced one that looked suspicious

steveshort

Has the wiring from the ECU to the turbo been checked ?

Judging by what u said the turbo is know to be working correctly, and all pipes seem to be leak free.

Another idea worth considering is maybe the turbo is not the correct turbo for an ML and operates at a different pressure

shietpilot

steveshort wrote: »

Has the wiring from the ECU to the turbo been checked ?

ECU would log codes if the wiring was bad.

steveshort

shietpilot wrote: »

ECU would log codes if the wiring was bad.

There is a code being loged, low boost pressure;

If the ECU sends a command too the actuator to increase boost pressure , but the command is block or lost due to bad connections or damaged wires. The actutor will not increase boost when the ECU expects this will trip a eml and limp mode.

Its only a theory , but may be worth exploring.

Mech1

why hasnt anyone fitted a basic dash boost gauge yet?

shietpilot

steveshort wrote: »

There is a code being loged, low boost pressure;

If the ECU sends a command too the actuator to increase boost pressure , but the command is block or lost due to bad connections or damaged wires. The actutor will not increase boost when the ECU expects this will trip a eml and limp mode.

Its only a theory , but may be worth exploring.

There is a separate code for open circuit codes which relates to bad connections. Low boost pressure is either caused by a bad turbo, bad VNT control, boost leak or a bad MAP sensor.

Wouldn't be a bad idea to do some live logging and do a few hard acceleration runs and see a graph of what the MAP sensor is reading.

traco

The actuator is faulty on my 07, common issue on all these V6 diesels. Its matched to the turbo and while it may be possible to replace there appears to be not massive success with the repair. Full turbo rebuilds seem like a viable option but need to be done by a pro and balanced and set up accordingly and then have the actuator travel matched to the the turbo.

I'm not sure yours is an actuator issue though as I can replicate mine all the the time. It will run from from cold but if let idle or sit in traffic the engine goes into limp mode. Get her good and hot even it in limp mode, stop turn off and restart and its good to go, seems the heat eliminates the sticking (seems to be oil that causes it) and maybe increases the clearances slightly. Once that done it will pull away all day once its not allowed cool down.

New turbo going in next week along with swirl flap motor thing etc as this is under the turbo and makes sense to do when in there. From what I have read you need to be very competent at priming the oil lines after reinstall so I'm going with an indy that has done loads of them. Also using a turbo direct from Garrett rather than MB priced and boxed version of the same.

PM me later next week and I'll let you know how it went and if happy can recommend who I used on the North side of Dublin. This will still be a 2k job I reckon but had the car from new and as its essentially worthless I hope to run it forever so justifying the madness that way.

mullingar

Just to ask the obvious,

Low boost pressure could be caused by a leak, such as a damaged intercooler of cracked pipe, was a full leak check carried out on the turbo->intercooler->intake system?

Edit:

DIY leak check tutorial here (on a 300C, but I believe its the same engine)

http://www.300cforums.com/forums/crd-intake-swirl-turbo/93635-charge-air-turbo-boost-leak-test.html