Turbo Hissing loud air release

2000 A4 TDI Jetta 1.9L

So I have been dealing with no turbo power for months. I thought it was going into limp as when I hit about 70 going up mountains it would slowly lose power. I started looking at why and my little bit of knowledge got me no where. I checked all vacuum lines they looked good and were connected.

I took it to my mechanic and here is what he found and did. The oil line to the turbo was clogged and the turbo was leaking oil. It also sounded like a mean cat when I started the car. Diag was to replace turbo. So he installed it and cleaned everything associated with the turbo. Gave it back and I thought it was running good. A day later (1st time up the mountain) I was about half way up and I hit about 78 MPH. I was not increasing at all, but was not decreasing. I put it in 4th gear to see if I could get a little boost out of it and I lost all power and dropped to 60MPH until I got to top of mountain. It then seemed to have no turbo again. I could also hear my turbo hissing as soon as it hits 2400 RPM's. If I stick in the clutch and take it to above 2400RPMs it does not make this hissing noise. Only when in gear and moving.

I took it back to the mechanic and he said that he thinks the vacuum line to the wastegate is cracked. So he replaced that. It seem to work for a day and now it is back to hissing at 2400 RPMs. It is coming from the passenger side as when I put down both windows it clearly is coming from the passenger side.

I have no idea what to do, but wanted to ask you fine folks what you would look at next. I was thinking about replacing the wastegate since it is pretty cheap, but before I start getting crazy I thought I would ask you all. Any help would be appreciated.

Cris

When you loose power pull over, shut the car for 5 seconds, start it again and see if you have power again.
If so it could be 'limp mode' (search here for it)
I sprayed soapy water on my boost hoses & connections to find a leak I had.
If you have a scanner, scan the car for codes after it looses power but before you shut the car.

I think you need to find a new mechanic. The car has no wastewagte.

Why not look for s boost hose that is split, cracked, or has a bad seal? Could be that the loud hissing is loss of boost.

What was the replacement turbo?

I could see perhaps not getting the actuator rod adjusted perfectly, resulting in limp mode, but getting hissing (still)? I'm thinking a split boost hose (or a junk turbo).

UhOh said:

What was the replacement turbo?

I could see perhaps not getting the actuator rod adjusted perfectly, resulting in limp mode, but getting hissing (still)? I'm thinking a split boost hose (or a junk turbo).

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.....or a boost hose clamp not installed correctly, or a cracked/leaking intercooler etc.......look for oily grimy areas indicateing a leak.

Find someone experienced and qualified to work on tdi's.....your mechanic isn't.

Boost leak. It's big enough you can hear it. My bet is the connection under the passenger side headlamp. It's really hard to get at IME especially if you don't have the remote spring clamp plier tool thingy.

So I want to get back on and let everyone know the fix was. So as I stated "I" was going to replace the wastegate. My mechanic did point out as well as someone on here my car does not have a wastegate. The mechanic started testing pressure between all points and found that my N75 Turbo Boost Pressure Solenoid failed. He also at the same time replaced all my vacuum lines. He said that there were two troubled areas on the lines. Once these two things were fixed as well as the car is running good again!

Thanks for everyone's help.

Did you get the old turbo? Likely still works.

BobnOH said:

Did you get the old turbo? Likely still works.

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Yes I got it, and when it was replaced there was a huge power difference and that is when the hissing started.

There was no hissing or power before turbo was replaced. I do have it as I wanted to get a rebuild kit and see if I could rebuild it.

Does anyone have any recommendations on a good kit?