doniv

Hello,
I am currently experiencing a low boost issue in my car, resulting in slower acceleration compared to its previous performance. Upon inspection, I noticed that the wastegate valve is not engaging after turning the car on, unlike before.

To address this, I removed the vacuum pipe and manually applied vacuum to the turbo wastegate vacuum line, confirming that the wastegate valve is responsive and capable of closing.

Further investigation revealed a lack of vacuum in the solenoid input when the pipe was removed during idle. Upon disconnecting the pipe to check the point (indicated by the red arrow in the picture) from where vacuum should be sourced, I found no vacuum at that location as well.

This leads me to suspect a potential issue with the vacuum system, particularly at the point where vacuum is supposed to be provided from the inlet manifold.

I would appreciate any tips or guidance on troubleshooting this issue and identifying the root cause. What could be the possible reasons behind this problem? (GLK-250 4matic 2014 petrol)

doniv

No body have any answer or suggestions in this group?

andreigbs

Did you check for any diagnostic trouble codes? If you have low boost, you likely have the check engine light on and there should be codes. That will lead you in the right direction.

The GLK250 diesel (not petrol) turbocharger wastegate actuator is not simply vacuum-operated, but more of a electrically controlled component. The ECU monitors the boost levels requested vs actual and continually adjusts the wastegate to operate both low- and high-side parts of the turbo system (basically two turbos). I haven't heard of the wastegate actuator fail though it is possible.

More likely, you have a boost leak and if I had to guess, it's probably the intercooler hose on the driver's side. In order to check it 100%, you have to remove it and carefully inspect it in your hands, turning it and gently squeezing it as you go. You're likely to see hairline tears in it. Mine had 2 separate tears, and a lot of us GLK250 owners have had to replaced these. In my case, even my MB dealer didn't fix it right the first time and they even replaced my wastegate actuator for no reason. At least it was free for me.

So, crawl underneath, remove the front half of plastic floor covers, locate the S-shaped driver's side intercooler boost hose, use a flathead screwdriver to pry the lock tabs open and gently remove the hose. Then inspect it carefully in the light and report back. And see if you can scan for codes first.

doniv

Actually I troubleshooted the issue and what I observed is there is no vaccum coming to the waste gauge input and that is why the turbo waste valve is always open and bypassing the exhaust instead of forcing it via the turbo.
Then I suspected the solenoid valve controlling the vaccum on the waste gauge input and I changed it, later I realised there is no vaccum coming at the input of the solenoid valve as well.
When I give vaccum manually, it is pulling the waste gauge, so issue is with vaccum.

1)What I wanted to know is, from where the vaccum is coming in glk250 4matic petrol varient?
2)Is there any vaccum pump in this model?
3)Or is it depending on the input manifold vaccum for all these ?

In picture where I marked red is the vaccum point from where I am expecting a vaccum which is connected to the solenod valve input. Solenoid valve output is connected to the turbo waste gauge to control the waste gauge electronically by ECU.

So my main issue now is there is no vaccum from the expected vaccum reservoir or the shown red colour marked pipe tip right under the air filter.

Any clue ?

andreigbs

My apologies, I know little to nothing about the petrol versions outside the U.S.

You might want to look at https://nemigaparts.com/cat_spares/e...asis=20404761R for vacuum diagram that may be helpful.

John CC

Yeah, all the GLK250s in the US are OM651 Diesels.