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Unusual boost leaks ?
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MartinF
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PostPosted: Tue Oct 17, 2017 7:06 pm    Post subject: Unusual boost leaks ? Reply with quote Reply with quote including images

I'm looking for peoples experiences of unusual boost leaks.

I'm still battling with one on my Rev1 Turbo engine, in that I can drive and boost fine up until 14psi (boost controller set for this) and then all of a sudden there is a quiet pop and boost drops back to around 4psi. I then change gear and boost will still be stuck at around 4psi, but if I stop accelerating and then give it a couple of seconds and accelerate again boost will start to build again OK to 14psi.

I have eliminated most things, intercooler, connectors (replaced with silicone couplers), etc. I have pressurised the intake, and it's not possible to do this at 14psi with the compressors i have access to, and only found a couple of small leaks which i've now fixed.

So what experience do you guys have of any unusual boost leaks ?
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Tsia
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PostPosted: Tue Oct 17, 2017 7:25 pm    Post subject: Reply with quote Reply with quote including images

Sounds like your wastegate might be getting stuck open, perhaps? [Think]
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MartinF
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PostPosted: Tue Oct 17, 2017 10:05 pm    Post subject: Reply with quote Reply with quote including images

Nope, have confirmed that it isn't by using a camera on it.
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shane34




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PostPosted: Wed Oct 18, 2017 6:10 am    Post subject: Reply with quote Reply with quote including images

Boost solenoid issue?
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MartinF
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PostPosted: Wed Oct 18, 2017 7:14 am    Post subject: Reply with quote Reply with quote including images

Nope, I had the same issue before fitting a boost controller, and now afterwards.
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Tsia
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PostPosted: Wed Oct 18, 2017 7:22 am    Post subject: Reply with quote Reply with quote including images

Potentially the wastegate flap fouling on something? Although that'd surprise me if it were a 'new' issue. If my memory serves correctly, it catches on SOME downpipes on a stock turbo. Throwing ideas in the air here [Sad]
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MartinF
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PostPosted: Wed Oct 18, 2017 5:16 pm    Post subject: Reply with quote Reply with quote including images

Confident it's not my wastegate, see my other thread here: http://www.imoc.co.uk/forums/viewtopic.php?t=193076&highlight=

Tsia wrote:
Throwing ideas in the air here [Sad]


I understand, but would really appreciate peoples experiences with strange boost leaks they have come across before, which I may have.
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shane34




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PostPosted: Wed Oct 18, 2017 5:52 pm    Post subject: Reply with quote Reply with quote including images

I had a 75mm throttle body not holding boost, but that could have been as it was 2.1bar!


No return valve failed anywhere?
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pbmr2
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PostPosted: Wed Oct 18, 2017 7:10 pm    Post subject: Reply with quote Reply with quote including images

seen the tvis vsv's fail and boost leak but only seen them leak all the time and not on/off like you describe. it's the diaphragm that splits in them.

could be a similar issue with the actuator.

other vsv's could also fail like this. spose if it was an odd tear then it may act like a flap. that's a long shot though.
The recirc valve is also a vsv as is the carbon canister.. infact that has a non return valve, might be getting stuck open at these pressures? or the NRV for the brakes, seen a couple of them fail.

has to be something that is moving or could move. so other options are the idle valve. maybe that is boost leaking at +14psi?

how is the idle control? does it ever struggle to control the idle level? thinking maybe sticky a little.

seen spark plugs burst out, but they don't go back in on their own and normally there is damage that needs to be fixed first.

was reading the other day about head lift at higher boosts. this causes the boost to go into the coolant and super heat it. maybe this is happening but the boost leaks out and not into the coolant?

these are all just brain farts from years of what I've seen go wrong with them.
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shane34




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PostPosted: Wed Oct 18, 2017 7:49 pm    Post subject: Reply with quote Reply with quote including images

I personally would get a proper compressor test. Remove or block the vent into the rocker cover and the brakes lines.

I've had a Bov leak air after x psi. With testing it To the correct pressure and use soapy water from an old coke bottle. I've Found so many this way
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MartinF
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PostPosted: Wed Oct 18, 2017 11:00 pm    Post subject: Reply with quote Reply with quote including images

Thanks guys, these are all good inputs now and have me thinking.

It's unlikely to be the recirc valve as I've replaced this with a known working one. My idle is good, but now you have me wondering if maybe the idle control valve gasket is leaking as that hasn't been subjected to the soapy water test yet [Laughing]

However to drop from 14psi to around 4psi makes me think it must be something quite large opening up, and then closing again.

My next course of action was going to be to start eliminating various non-essential items by blocking popes to them, like the TVIS.
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shane34




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PostPosted: Thu Oct 19, 2017 6:01 am    Post subject: Reply with quote Reply with quote including images

All I can say is persistence pays off. Bov jammed/cracked open could be another?
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MartinF
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PostPosted: Sun Nov 26, 2017 8:02 pm    Post subject: Reply with quote Reply with quote including images

OK, so I'm still persisting with this, have reverted back to stock boost control, just in case but exactly the same symptoms, accelerate fine boost builds to around 14psi and then there is a small pop sound and boost drops back to around 4psi. It will not build again until I change gear and stop accelerating and then start again.

However today I noticed something curious when pressurising the intake, the cam cover is also pressurising (the vent hose from the throttle body to the cam cover is disconnected). Roughly I have around half the boost pressure building in the cam cover, i.e. if I pressurise the intake to 18psi, i see 9psi in the cam cover. When pressure is removed then the intake pressure decreases first and the cam cover pressure does not decrease until the intake pressure reaches the same level.

This doesn't seem right to me, but wondering if anybody has ever noticed something similar ?
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Gazza_DJ
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PostPosted: Mon Nov 27, 2017 12:05 pm    Post subject: Reply with quote Reply with quote including images

Have you tried running it on actuator pressure only? Have you swapped out the BOV for a known good one?
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MartinF
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PostPosted: Mon Nov 27, 2017 12:14 pm    Post subject: Reply with quote Reply with quote including images

MartinF wrote:


It's unlikely to be the recirc valve as I've replaced this with a known working one. My idle is good, but now you have me wondering if maybe the idle control valve gasket is leaking as that hasn't been subjected to the soapy water test yet [Laughing]



I tried running with the boost controller off, so in effect just actuator pressure and I was seeing around 4 - 6psi. I've now reverted back to stock boost control.
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Gazza_DJ
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PostPosted: Mon Nov 27, 2017 12:18 pm    Post subject: Reply with quote Reply with quote including images

Might be worth just trying it with it completely disconnected, just to rule out anything funky going on with the controller, solenoid, hoses, etc.

I'd be surprised if the IACV could leak with enough volume to make 10+psi of boost disappear... Worth a test though.
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Gazza_DJ
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PostPosted: Mon Nov 27, 2017 12:19 pm    Post subject: Reply with quote Reply with quote including images

Have you tried swapping the actuator out as well?
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markstevieandmads




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PostPosted: Mon Nov 27, 2017 4:00 pm    Post subject: Reply with quote Reply with quote including images

Havent read through everything but are you still running the plastic vtv valve and if so have you checked this for damage?
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MartinF
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PostPosted: Tue Nov 28, 2017 4:43 pm    Post subject: Reply with quote Reply with quote including images

Gazza_DJ wrote:
Have you tried swapping the actuator out as well?


I had the same issue on my original CT26 turbo, which had it's own actuator. So in reality two different actuators have been used.
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MartinF
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PostPosted: Tue Nov 28, 2017 7:23 pm    Post subject: Reply with quote Reply with quote including images

markstevieandmads wrote:
Havent read through everything but are you still running the plastic vtv valve and if so have you checked this for damage?


Yes, it is working fine as per the BGB
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