New member. Tdi115 boosting problem!

[Matt115]

Evening all, new member on here. Had a mk4 115 for about 12 months now. Thought I'd join this forum for advice. On a few others (mainly ford) for advice etc.

Problem: not boosting. Changed the MAF for a reconditioned Bosch unit. Even tried one off a working tdi115. Had plugged into vagcom, showed nothing. Checked wiring to n75, including earth points, resistance etc. All seemed ok. Evan ran an extra earth just incase. Still no better.

Plugged back into vagcom, showed a n75 error. Changed that. No better. Took the inlet pipe off turbo, not seized, turns freely. Took exhaust side pipe off to check if spindle was snapped, all ok. While had it in bits, decided to take turbo/manifold off.

Heard about vanes clogging up from a mate thatworked at vw, was clean. Stripped turbo down, wastegate 'ring' clean and moves freely with the actuator rod.

Still not boosting!!

Booked car in at a garage of a mate of mine, day before it's due to go in the boost comes back and works!! Took car to garage for MOT. Worked fine! Collected car tonight. Worked ok on way home.

Next journey out and the boost stops working!

Any ideas anyone? Im thinking electrical fault??

Problem has been on going for a few weeks now, getting annoying
, especially on motorway journey to work!

Any help appreciated. Regards, Matt

[scarr89]

Ok, so it showed an N75 error, you then replaced (with a known serviceable part I hope) and still no better? Could it be the something as simple as the vac lines to and from the N75 and turbo or 2 bust N75s??

Perhaps the actuator is kaput?

The 'ring' of the turbo can move as freely as poss but I believe that the actuator 'makes' the 'ring' move. You can test the actuator by sucking on the vac line running to the actuator and seeing if it moves when sucked and then goes back to the normal posistion when the vac is released.

Sorry to be stating the obvious if you have already tried 

[Matt115]

N75 change for a genuine vw part. Will check the actuator rod tomorrow. Also going to replace all the small vacuum pipes to eliminate them.

[Matt115]

Possibly a result today!

After checking the small vacuum pipes for holes and leaks found they were ok. Sucked on the actuator pipe and the rod moved.

Decided to remove the boost sensor out of the top of the intercooler. Gave it a clean with brake cleaner and it's back boosting again. Fingers crossed this cures it.

Something for people to check before spending money if they have a similar problem.

Need to remove the washer bottle first to get to the sensor.