2.5tdi v6 avant engine issue (00575)

[dualmono21]

a friend of mine has just bought a one owner 1997 2.5 tdi avant
for the most part it is in very good condition , however after checking it over today ive noticed a couple of minor problems i can hopefully sort out with a little help

im getting the 00575 vcds code come up when i scan the car
firstly for not making enough boost pressure then after clearing and retrying for making too much boost pressure
both of these are linked to the n75 valve
this part has been superceeded a long time ago , what i would like to know is if i can fit a newer n75 off
something like a seat leon cupra
has anyone done anything similar to this ?

the other problem i have noticed is the brake servo master cylinder appears to have been repaired at one time or another
but unfortunatly this too has failed again
is it possible to change just the clear plastic level indicator chamber or do you have to replace the entire unit

many thanks
nath

 

[PAULF]

For the boost problem, you need VCDS to test the N75 valve.
Go to Basic settings, block 11 (IIRC) and with the engine running, it will cycle between actuator full up and full down.
If you do not have VCDS, with the engine off, the turbo actuator arm should be away from the stop. When the engine starts it should pull the actuator to the stop.
Try moving the actuator by hand - if it is sticky or restricted, go to the Mr Muscle Turbo clean thread on here.
Another common fault is the hose to and from the actuator/valve/vacuum pump leaking/perishing.

As for getting a different valve - why would you? It's a modulating valve so it is the control of it (ECU) that makes the difference, not the valve.

Your brake reservoir can be changed on its own. Just pull it off. You do not have to bleed the system after changing it.

When you next have a brake repair, be careful when using a pressure bleeder or you will be dong it again - they are prone to popping it seems, as a few of us on here have found this out the hard way!

 

[dualmono21]

thanks for the reply
ive been lead to believe inside the valve the seal can perish and this can cause running problems
ill have another look at everything tommorow

thanks again
nath

 

[dualmono21]

have got the car on vcds now paul
the measurements are slightly differnat for the n75 valve depending on which you use
at idle the car is showing 90.3 duty cycle and goes down as you rev the car in the measuring block section 11
in the settings section 11 the car cycles between just over 100% and 0% on the n75 valve (the only other thing i notice here is the maf reading goes through the roof )
the duty cycle of the egr is only at 15% when at idle but according to vcds should be 40-75%
maf actual is reading high at 329 mg/str

 

[dualmono21]

the full code im getting from vcds is 00575-11-10 .... control limit not reached intermittant

 

[aragorn]

Check all the vacuum pipes and look for splits or perished bits.

Check the movement of the VNT shaft.

 

[dualmono21]

ive checked the vacuum pipes and they appear to be working o.k as when you remove them you can feel the pipe sucking air

ive sprayed some wd40 on the actuator shaft and it does now appear to move a little more
the car is now not giving me a fault code but is still absoloubtedly flat as a fart , the turbo is definately spinning as its getting hot
but i just cant feel it providing much boost and the engine is reluctant to rev beyond 3000rpm when you put your foot flat to the floor

 

[adamss24]

Change MAF...

 

[dualmono21]

im gonna take the car out tommorow and do some logging off the measuring blocks to see what the car is doing under load

 

[PAULF]

It does sound as if your vanes are sooted.

With the engine off, the actuator should be away from its stop (fully down). When you start the car, the actuator should smoothly go up to the stop.

If it doesn't move up, check to see if it is jammed, if not then look for vacuum leaks.
If no leaks, then suspect the N75 valve.
Once it is moving up ok, move on.


Now go to ENGINE, BASIC SETTINGS on VCDS, and I think it is in block 11 - you'll have to check.
The car will then cycle the N75 fully open and closed every 10 seconds.
The actuator should move up and down smoothly full range.
If not, then Mr Muscle it.
If it does move up and down, try moving it by hand to see if you feel any grittiness/hardness caused by carbon in the vane rollers.
If you suspect this, Mr Muscle it.

Do a logging run to check for overboost.
If you have a look here 2.5TDi Sluggish you might get clues on the logging (at the end).Read my graphs, and if you have a max 'dump' signal combined with an overboost, Mr Muscle it and check again.


Once the actuator is confirmed moving correctly, then think about MAF sensor, rod length or stop screw settings.