ML270 Turbo Pressure test

[ChrisBrown]

Hi, I wonder if anybody on this great site can help. I have been looking around and so far got some great tips off this site, but I am a little bit at a loss with this one.
I seem to have a slight leak on the turbo input side of the ML. I have read the codes which shows a code of “P1470 16 turbo pressure input low” and when the car is driven it starts going OK, but the turbo seems reduced as it goes up through the gears to almost none in top gear.
I have had a look around the net and seen some home made pressure testers being used (charge the turbo system to @ 10psi then chase down any leaks).
The question is, for the ML where would you ‘charge’ the system, and are there any parts that would need to be blanked off prior to the test?
Any pointers would be appreciated. Cheers

 

[Steve@Avantgarde]

I have the proper MB tool that connects directly onto the turbo or charge intake system. It is a simple coupling that you rig up to an airline and charge it with compressed air.

 

[ChrisBrown]

Didnt know they made a specific tool for this, dont suppose you have a part number for that?
Regards,
Chris.

 

[ChrisBrown]

Can anybody tell me where this kit would connect to the turbo lease? (with pic or detailed description if poss.), if I can find that location I may be able to source a kit (either from MB or via after market parts). I really need this car over christams to visit family with the kids and would appreciate any advice on this i can get. regards, Chris.

 

[oigle]

To be honest, I think you might be better off looking for reasons for lacking turbo boost, rather than worrying about measuring it. Have you looked at split hoses, blocked cat, blocked air cleaner etc? Are you sure the motor hasn't gone into limp mode when the power drops off? Often they will start and run OK and then drop into limp mode after a while. Try stopping the engine and restarting it to see if the effect goes away temporarily. If it does, it could be MAF or EGR related as well.
You can check for boost leaks by having someone in the car with engine running, engage the park brake hard and then select drive and gradually apply throttle carefully. Can't use footbrake as it cuts throttle. If you have your head under the bonnet, you should be able to hear any boost leaks - loud hissing.

 

[ChrisBrown]

Oigle, thanks for that. I have already looked at the reasons for the lack of power and as the car is serviced and the filters have been done in the last couple of months I really want to go down the route of a leak check (its erratic on acceleration and unless I am imagining it there seems to be a bit more exhaust noise than normal from the engine bay as its being driven). Hence why I want to do the check. It could well be an idea to do the brake / accelerated test. I only wonder if I can trust my 11 year old kid to do this whilst its on ramps!

Seriously though, its sounds like it could work if I can get a responsible person to assist, Many Thanks for that (it ties in with the turbo struggling as its under more load so makes a lot of sense). Thank you again

 

[Uncle Benz]

Regarding your exhaust noise comment, I'd suggest checking for a blocked cat too.

 

[Alex Crow]

As above, blocked cats or badly leaking swirl flap linkages are the common ones here, to give these symptoms.
Also, the boost hoses often split, a show of oil (downstream of turbo!) is a clue to tracing a leak on the intake side.

 

[ChrisBrown]

To be honest, I think you might be better off looking for reasons for lacking turbo boost, rather than worrying about measuring it. Have you looked at split hoses, blocked cat, blocked air cleaner etc? Are you sure the motor hasn't gone into limp mode when the power drops off? Often they will start and run OK and then drop into limp mode after a while. Try stopping the engine and restarting it to see if the effect goes away temporarily. If it does, it could be MAF or EGR related as well.
You can check for boost leaks by having someone in the car with engine running, engage the park brake hard and then select drive and gradually apply throttle carefully. Can't use footbrake as it cuts throttle. If you have your head under the bonnet, you should be able to hear any boost leaks - loud hissing.

Also, just to note, as said in my first post I have an error code of P1470 16 turbo pressure input low" hence why I would like to be able to do a 'safe pressure test' which is basicly charging the system with air and listening for leaks (safer than reving in gear with the handbrake on). Can anybody advise where the merc tool connects, or the part number for the tool. I really need to get the car sorted by Chrismas and any and all help would be appreciated.
Thanks Chris

 

[Alex Crow]

A small point to note, usually we see 1470 codes in relation to boost pressure issues.
However, there are 2x definitions of 1470 for low or high resistance at the modulator valve, which would usually point to the valve itself, obviously.

Quite likely P1470-016 refers to the duty cycle of the modulating valve being too high.

What vacuum do you measure at the valve input?

 

[ChrisBrown]

Thanks for the reply Alex, To be honest I have not tested the vacuum on this as I was / am looking to do a pressure test on the system first (should be easier and from what I have seen should be the next logical step), however, if this code could relate to a vacuum fault I guess its worth testing. How would I go about doing this test?

 

[Alex Crow]

Firstly, measure the vacuum at the supply to the modulator (small dia pipe on top).
Then, check the output with engine running and pipe disconnected (large dia pipe on top).

And, err, yes you do need a vacuum gauge!

 

[ChrisBrown]

Alex, thanks for that. What reading should I be looking for on this test?

 

[soup nazi]

ChrisBrown
Did you have any luck solving the issue? If so I would love to know the culprit.

 

[ChrisBrown]

Turbo Fixed!

Hi Thanks for the response. I did fix this one in the end, and as Alex suggested previously, it was the small vacuum pipes at fault (I had disturbed one of them when I replaced the alternator). In the end, as I didn’t get a gauge for this (or know what readings to look for) I just checked all the pipes I could find, and found one that had popped out.
Many thanks to all the people on here that assisted with this one.