Advice please...I`m bleeding boost!

[bob dixon]

Hello everybody,
I`m new to the list, hope you don`t mind me jumping straight in with a technical query. I have a T5R,slightly modded with an uprated ECU and exhaust system. The car has always run superbly but last week developed a strange fault. As the revs approach 3000 it starts to hiss as if its bleeding off boost and at 4000 revs dumps all the pressure and won`t rev beyond that. I assumed that it must be a faulty dump valve but for the life of me can`t locate one under the bonnet! Do T5Rs have a dump valve? If so where is it!
Alternatively, any ideas what the problem might be?
Many thanks, bob

[t5tart]

:welcome:
sounds to me like a faulty bcs
or the recirc valve has popped up and is stuck open a bit

in my limites knowledge

unless you have a mbc

oh and no DV as standard it has a recirc valve which is built into the turbo

[thunderace]

hello bob welcome to the forum.......you will find the answer here. there is a wealth of info available. good luck

[fraz13]

How does the car run apart from the hiss and loss of power at 4k? Does it run rough like it wants to die? It sounds like a massive air leak to me.... First thing to do is go round all your vacuum pipes including intercooler pipes and make sure there all in good condition replacing those that need replacing....

[bob dixon]

Hello again everybody,
The car runs perfectly well, idle is spot on, its just that when it hits 4000 it dies amid a loud hissing noise, by very gently feathering the throttle it is possible [just] to drive through the flat spot and take it up to 5500 rpm.
I think the recirculating valve theory sounds feasible. Does anybody know how accessible this valve is? Is it possible to remove it for cleaning?
Thanks, Bob

[fraz13]

I still say a vac or intercooler pipe as the recirc DV only has 1 way of air escaping and thats through a vac pipe.... but the recirc DV is a bit of a pain but a novice can do it.... Its a case of it has 3 bolts but you cant get to them all from above or below so 1 from above 2 from below.... Its a diaphram DV and its all rubber inside so it work or it dont....

[SaffronC70]

What year is the car ?

I have swapped out a failed recirc valve to cure symptoms you are describing.

Easy job your main problem will be build up of road dirt and oil over the years making it hard to keep the spanner on bolts, lol.

Chris

[bob dixon]

Hi Chris , It`s an 'M' reg T5R, one of the original batch
Bob

[elliot]

The DV is located on the turbo,i very much doubt its that they normally only make a small difference in peformance,and by the sounds of its noticeable!The DV will also cause you to get alot of compressor stall evey time you lift off,it will sound like several chirps in a row like a WRC car.I am going with split boost pipe one of the big dia ones.

[SaffronC70]

Agreed, after reading this again without the manager looking over my shoulder, lol.

Chris

[bob dixon]

Thanks everybody!
I will investigate and report back.......
Bob