Volvo 850 T5 boost issue

dennisye · Post by **dennisye** » 19 Dec 2019, 08:08

Hello guys,

I have a question about my 1994 855 T5. I replaced the TCV because I had almost no boost (the meter only just went into the white). The first couple days everything was amazing, boost went 2/3'rds into the white on the meter, throttle response was alot better and the car became alot faster.

But this week I'm feeling almost no boost, although the meter still shows it's going 2/3'rds into the white.

Things I´ve checked or done:
-Play on turbo shaft
-State of turbo
-Replaced all vacuum lines
-Replaced TCV with new Pierburg one
-Replaced wastegate membrane
-Replaced PCV system

I just find it very strange, the boost gauge in the car reads full boost but the car feels as if it isn't boosting at all (or very little), anyone know what to check next?

Post by **matthew1** » 19 Dec 2019, 08:29

Wow, you've done all the Usual Suspects.

However...

The first couple days everything was amazing, boost went 2/3'rds into the white on the meter, throttle response was alot better and the car became alot faster.

This makes me think you blew something off. A vac line. Did you do your list before or after the first couple days?

Hello from the US, thanks for joining.

Post by **volvolugnut** » 19 Dec 2019, 08:39

The pressurized intake tube from turbo to intake may be loose. The extra boost you enjoyed, may have partly blown off the tube. Just reposition and tighten the clamps.

volvolugnut

dennisye · Post by **dennisye** » 19 Dec 2019, 10:03

matthew1 wrote: 19 Dec 2019, 08:29 Wow, you've done all the Usual Suspects.

However...

The first couple days everything was amazing, boost went 2/3'rds into the white on the meter, throttle response was alot better and the car became alot faster.
This makes me think you blew something off. A vac line. Did you do your list before or after the first couple days?

Hello from the US, thanks for joining.

Thanks for the reply,

Yesterday I replaced all the vacuum lines to the turbo, and that didn't solve the problem unforunately. None of those was loose either. Or could it be a vac line somewhere else. Because it's just not transfering all of it to the turbo.

dennisye · Post by **dennisye** » 19 Dec 2019, 10:07

volvolugnut wrote: 19 Dec 2019, 08:39 The pressurized intake tube from turbo to intake may be loose. The extra boost you enjoyed, may have partly blown off the tube. Just reposition and tighten the clamps.

volvolugnut

Do you mean the one with the MAF sensor on it? I removed and put it back on yesterday to replace the vacuum lines. Didn't change anything unfortunately..

Post by **volvolugnut** » 19 Dec 2019, 10:26

I mean the large, about 2.5 inch (maybe 6 cm) tube from the turbo outlet to the intake manifold/ throttle valve. This tube will have the full turbo boost pressure and if end clamps are not tight enough, they will get loose or blow off completely. Also, check that the tube under the connecting hose has not been crushed and collapsed creating a leak for the boost pressure.
The small vacuum tubes should not get blown off, but may degrade over time.
volvolugnut

Post by **volvolugnut** » 19 Dec 2019, 10:27

Also check that the electrical connector to the TCV has not gotten loose.
volvolugnut

dennisye · Post by **dennisye** » 19 Dec 2019, 10:29

volvolugnut wrote: 19 Dec 2019, 10:26 I mean the large, about 2.5 inch (maybe 6 cm) tube from the turbo outlet to the intake manifold/ throttle valve. This tube will have the full turbo boost pressure and if end clamps are not tight enough, they will get loose or blow off completely. Also, check that the tube under the connecting hose has not been crushed and collapsed creating a leak for the boost pressure.
The small vacuum tubes should not get blown off, but may degrade over time.
volvolugnut

Okay thanks, I will check this first thing in the morning, I"ll let you know what happened.

Post by **erikv11** » 19 Dec 2019, 10:31

He means the intercooler hose path, from the turbo through the intercooler to the throttle.

Edit: redundant now, you've got the answer up there.

Post by **volvolugnut** » 19 Dec 2019, 10:34

Thanks erikv11. That was not very clear on my post.
volvolugnut