james007d

I recently bought a 2001 1.8t A4 and it's got almost no boost. Maybe 2-3psi at best. I've checked the DV, it's good. I've bypassed the DV solenoid, so it's not that. I've disconnected the wastegate solenoid (both electrically, and the vacuum line going to the wastegate), and there was no change. So now I've just performed a boost leak test with the pvc cap method. First I tried it with the throttle still connected. I couldn't get the pressure past about 7psi, and I could hear no leak. However, when I cut the pump off, I could hear a gentle repeating sound that was like "blurb blurb blurb" while the pressure bled off and I could not isolate the sound. So next I disconnected the throttle tube and plugged it and pressurized again. It went to the same psi and would not go past, and gave me the same noise as before. Next I disconnected the TIP with the DV hose still connected and plugged all the openings and pressurized. It went to 15psi before blowing the pvc cap off, which I suppose was not on tight enough. But it did the job of showing me that the TIP and the DV hose were not to blame.

So as I figure it, I'm left with four possible places my leak could be. The turbo outlet hose, the metal pipe that sits below the radiator, the hose before the intercooler, or the intercooler itself. I gave the hoses some good squeezings while the system was at 7 psi and I heard nothing so i think they're good. And I know there's noise to be heard at 7psi if there's a leak, because I heard air coming out of the TIP at my pvc cap when I didn't have it tight enough. But when everything is tight, I get no typical air escape noise, only 'blurb blurb blurb'.

I need advice and suggestions and input. Please help.

4Driver4

Not sure what you checked, but the diverter valve/bypass valve is a mechanical piece activated by vacuum. There is no solenoid.


I think your waste gate flapper is missing. Unbolt the cat, pull it back and look at the flapper.

james007d

N249 controls vacuum to the DV, does it not? In any case, I bypassed it so the DV is getting manifold pressure.

4Driver4

True enough. Sorry about that.

james007d

I'm still not convinced that there's no leak somewhere between my turbo outlet pipe and the TB, but I may as well check the wastegate flap anyway. Can the cat be unbolted and moved away from the turbo enough to see the wastegate without having to unbolt the cat from the downpipe? I'd rather do this without having to get under the car, and also without having to aim pb blaster at dp/cat nuts from below.

turbo510

I had low boost on our Passat, plus a rattling sound on deceleration that turned out to be the wastegate. The wastegate flapper was OK, but the linkage was loose. I had to take the turbo out to reach the adjusting nuts on the actuator (the oil drain line under the turbo was a little frustrating), but the boost was back and no rattling. I adjusted the flapper preload by guess and so far it works fine.

On the Passat at least, I think that the exhaust system can move back enough to check the wastegate if you first disconnect an exhaust support under the car, just behind the cat.

ECS Tuning-Audi

Along with inspecting the waste gate pull the turbo intake pipe and check to see if you even have a compressor wheel intact.

Also see if it spins. Its not uncommon for the oil supply line to the turbo to get sludged up and starve the turbo of oil causing it to seize up.

Jason

james007d

Found my problem. Or both of them, I should say. It appears that my wastegate actuator diaphragm is leaking like a sieve. Any pressure that I put on it with my mityvac bleeds off immediately. When I attach a small air compressor to the actuator, I can see my wastegate move, but not much. When I cut it off, pressure falls almost immediately to zero.

Also, I unbolted the cat from the turbo to have a look at the wastegate, but it looks like the wastegate isn't seated properly. It is attached to the arm, and it does move when the rod pushes it. I can only look at it with a mirror because of the angle, but it doesn't look right. Has any one else encountered this? I guess I'll have a better view of it when I pull the turbo to replace the actuator.

Does anyone know where I can get a replacement actuator that doesn't cost >$180? I'll look for a used K04 before I spend that much on a K03 part.