Recon Turbo & Limp mode

[CrispDust]

Mt turbo blew up 3 weeks agao (BKD 2.0 TDI) so I replaced it with a reconditioned unit (new "cartridge" ) supposedly fully balanced.
It all went on Ok with new oil feed pipe, gaskets for oil return and exhaust manifold. Oil feed was checked both before fitting turbo AND after fitting oil return pipe to turbo, but not to engine block. At all flowed very nicely (Old turbo did not fail due to oil feed anyway as it dumped most of sump into the inlet and exhaust)
All of the inlet piping was removed and cleaned with degreaser then steam cleaned, including intercooler.
Car goes ok but following symptoms:
1. After about first 50 miles there was a definite turbo spin related "chattering" that lasted for about 5-10 mins. Not heard it since.
2. Turbo definitely has a delay in "spinning up". There certainly isn't the urgency of power delivery that I had previously.
3. The turbo is quite noisy when it does spin up. My original one always had the owl hoot/police siren sound but made no other sound. The recon has quite a loud sound which I can best describe as like a plastic bag fluttering in a strong wind very noticable at any throttle position other than cruising on level. Any hill and the sound is there or more than gentle acceleration.
4. Just done 2000 mile round trip to France mainly motorway. First day /450 miles no problems but second day and worsening from then on the ecu flips into limp mode after about an hours driving, usually on partial load, at speed, say accelerating to overtake lorry. Repeatedly does it after switch off reset. Doesn't do it on 3/4 to full throttle acceleration and far less so when in Sport mode of DSG.
Have checked several times with VCDS and each time showing Boost regulation error.
Have I got a duff turbo? Thinking either the variable vane setting is wrong or faulty. The actuator rod works, Ive checked it with VCDS and it moves just fine
Fault code: 16683 - Boost Pressure Regulation
P0299 - 000 - Control Range Not Reached - Intermittent
Freeze Frame:
RPM: 2226 /min
Torque: 230.0 Nm
Speed: 109.0 km/h
Load: 0.0 %
Voltage: 13.98 V
Bin. Bits: 01101000
Absolute Pres.: 2070.6 mbar
Absolute Pres.: 1642.2 mbar

 

[towcester vag]

when you say cartridge do you mean just the impellor section?
so if you didnt clean out the veins then this is why you get boost faults

 

[CrispDust]

Sorry not clear. The recon turbo was the whole unit. It looked as though it had been completely stripped, cleaned, repainted some new components on the vane actuator and a new complete inlet/exhaust turbine cartridge. It came with a printout of the shaft balance test printout.

 

[towcester vag]

turbo

ok mate i read it wrong
i know you can get just the cassette part ie the impellors seperately and fit them to your old turbo
i would check the vacuum piping and the egr operation as this can affect turbo operation
also just for piece of mind check the variable vein actuator to see if it moves freely from stop to stop

 

[CrispDust]

I've checked the actuator for variable vanes, it moves ok and it moves when activated via Vagcom, so no leaks. I cleaned the egr (disconnected anyway) and the MFV when inlet piping off. Might check that the egr valve is correctly seated in the inlet body. i guess if there was a leak it might affect it BUT the egr recyles back in at the inlet manifold. Unless its leaking and the exhasut pressure isnt high enough to drive turbo?
What I can't tell from vagcom is if the limp mode is caused by overboost or underboost? Presumably if underboost it wouldn't need to protect engine with limp mode?

 

[CrispDust]

I'm thinking possibly the cat is bunged up with oil making exhaust flow difficult, or maybe the boost pressure sensor in the bottom inlet pipe is duff from oil contamination?

 

[@udi A3]

check vacuum leaks, and operation of n75. also log n75 duty cycle, should be around 70-80%. if its too low there could be a boost leak that noise you describe, or the rod to the actuator is too short on re assembly.

 

[majesty78]

(Old turbo did not fail due to oil feed anyway as it dumped most of sump into the inlet and exhaust)

Did you check crankcase venting system before installing the "new" turbo?

If oil is dumped out of turbo into compressor and turbine side, in 99% of cases the crankcase venting is blocked or crankcase pressure is to high (to much blowby gases)
In this case the oil return flow of turbo is not working correct anymore and the new installed turbo will fail again.

 

[CrispDust]

majesty thanks for your reply. Crankcase ventilation is just the short top hose on top of the cam cover. this was thoroughly cleaned when all the inlet ducting was cleaned. The oil blew into inlet because the turbine shaft completely broke in 2 allowing oil to flow out of the turbine "bearings".
Have done a little experimentation on a 200 mile round trip to Newcastle I have observed the following:
1. The limp mode would engage when doing steady 70mph on any long incline. It didn't do it at any other time.
2. This could be prevented by putting DSG into 5th t bottom of incline, forcing a higher RPM so presumably a higher turbine spin.

My assumptions;
Either
1. a leak as suggested inlet or exhaust side or
2. turbine is "stiff" an not spnning up quickly or fast enough
3. N75 is defective on "new" turbo or some other issue with the VNT system.

Strip down tomorrow.

 

[CrispDust]

Found the problem quite easily - not much detective work involved. I usually keep engine bay clean and spotted new oil deposit/drips on chassis rail and aircon aluminium pipes.
The turbo outlet 90deg elbow rubber pipe had split. i assume that a small shard of inlet impellor blade had imbedded itself in the rubber when it self destructed and with the heat from engine and turbo pressure, it gradually worked through and split.

Temp repair with selfcure silicone and 2 part hose wrap whilst I track down a replacement. Suspect its going to be a rip off price from Seat dealer...