Testing for a Boost Leak

Gaijin · 7 Dec 2011 at 16:42

Just wondering if anyone has tested and isolated boost leaks before.

I've had a boost leak since I had to remove the top IC and intake pipes whilst I did my clutch.

It currently won't hold more than 0.5bar of boost without leaking. I'm hoping it's not the BOV.

I've tried removing and reseating hoses and tightening the crap out of the fixings but to no joy.

I've read about using a bung with a air valve on the turbo inlet, warming and setting engine to TDC, and compressing the system using a compressor, but I don't have access to a compressor and am wondering if there is any way to do this without one?

Usually I'd just go and buy one but as I'm moving to Ireland in the next few months, I don't want to add to my logistical woes.

I'm gonna give it a proper go again next week but just wondered if anyone had any tips before I have to limp it to the nearest tuner (miles away).

sigma · 7 Dec 2011 at 16:49

If you can find the right type of nipple/attachment, I've heard of people using a bicycle pump with a gauge on it to leak test.

Have you double checked the obvious?

Gaijin · 7 Dec 2011 at 17:42

Apparently it's not practical - plus achieving and maintaining 1.4 Bar of pressure is apparently hard work.

As for your question, depends what you'd consider the obvious!

Concrete · 7 Dec 2011 at 17:58

Could you not fit a snorkel to the intake, fire it up and then completely submerse the car in water and look for air bubbles?

Surely its most likely to be a hose thats developed a split and annoyingly the best thing to do is pull and inspect them one at a time?

MarkLP · 7 Dec 2011 at 18:13

We use a smoke tester at work. Really is very good. Although i'm not sure if its something local garages would have?

Matt82 · 7 Dec 2011 at 18:33

Most garages have a smoke tester. Don't need a specialist

breadturbo · 7 Dec 2011 at 18:47

if you're sure the hoses are on tight, id remove the IC seal the ends and dunk that in water
to see if it's that leaking.

also could remove BOV, make up a quick alloy plate to go in its place and test it then.

Dogbreath · 7 Dec 2011 at 18:50

Gayjin said:
Apparently it's not practical - plus achieving and maintaining 1.4 Bar of pressure is apparently hard work.

As for your question, depends what you'd consider the obvious!

The way you are describing it it would be, since you are effectively performing a leak down test on the engine as well. If you can take the hose off the throttle body and put a bung in that, take the hose of the turbo outlet and make a bung with a schrader fitting you have minimised any parasitic losses through e.g. turbo bearings or cylinders.

However if must be a reasonably large leak to limit you to 0.5bar and it can only be hoses, intercooler or BOV/recirculating valve so close inspection of these parts is the first port of call. Intercooler leaks often give themselves away by oil stains, and close inspection of the inside and outside of the boost hose should show any damage. For some reason (sods law?) they very oftem seem to fail on the bottom side of the hose so you need to remove them. Do you have any way of temporarily bypassing the BOV?

Matt82 · 7 Dec 2011 at 19:31

ps boost leaks normally make themselves easier to spot if they blow out oil mist that it picks up from the breather

ie look for joints which are WET with oil

and im banking on the dump valve

Fuzz · 7 Dec 2011 at 23:09

Are you sure you haven't cocked up the boost control pipework as half a bar boost is most likely actuator pressure. only two pipes to the control solenoid under the battery tray, so 50/50 chance of getting it wrong

That or you've re-fitted the dump valve on backwards.
If you made it to Gibbos RR day, as it's only a small one, I could have a look on the dyno. It's much easier to get it under load and have the ability to nosey under the bonnet at the same time.

Fuzz · 7 Dec 2011 at 23:13

Dogbreath said:
Do you have any way of temporarily bypassing the BOV?

You don't need to "bypass" the BOV, just clamp the hose shut with a pair of long nosed mole grips

Virdi · 9 Dec 2011 at 08:23

I've used a tool like this in the past and it's great!

http://www.seatcupra.net/forums/showthread.php?t=269836

Dogbreath · 9 Dec 2011 at 12:07

Scubascorpion said:
You don't need to "bypass" the BOV, just clamp the hose shut with a pair of long nosed mole grips

Depends on the type of valve and how it's mounted, may not have a hose to clamp in some cases.

dwarf · 9 Dec 2011 at 13:05

This is how I do it:

Fill a spray bottle (the ones that cleaner and stuff like that comes in) with water and some washing up liquid. Spray the solution over all the intake pipes. Rev the engine a bit and look for bubbles being created. That should show you where the boost is leaking from.

Easy

Gaijin · 10 Dec 2011 at 00:20

Thanks for your responses guys. Currently in Ireland visiting the fiancee with only my *generic tablet computer* so replying is pretty tough.

Concrete said:
Surely its most likely to be a hose thats developed a split and annoyingly the best thing to do is pull and inspect them one at a time?

Indeed it is most likely to be, will pull it all apart when I get back and check but thought I'd ask for other things to check in advance.

MarkLP said:
We use a smoke tester at work. Really is very good. Although i'm not sure if its something local garages would have?

Worth a shout although I've heard that smoke isn't suitable for high(er) boost applications, but I can't remember the reason why. I'll take a look again.

breadturbo said:
if you're sure the hoses are on tight, id remove the IC seal the ends and dunk that in water
to see if it's that leaking.

Really don't think it's the IC. Only started happening since I removed the pipework to get the gearbox out, so it's no doubt the retardiness of my reinstall.

Gaijin · 10 Dec 2011 at 00:29

Dogbreath said:
The way you are describing it it would be, since you are effectively performing a leak down test on the engine as well. If you can take the hose off the throttle body and put a bung in that, take the hose of the turbo outlet and make a bung with a schrader fitting you have minimised any parasitic losses through e.g. turbo bearings or cylinders.

However if must be a reasonably large leak to limit you to 0.5bar and it can only be hoses, intercooler or BOV/recirculating valve so close inspection of these parts is the first port of call. Intercooler leaks often give themselves away by oil stains, and close inspection of the inside and outside of the boost hose should show any damage. For some reason (sods law?) they very oftem seem to fail on the bottom side of the hose so you need to remove them. Do you have any way of temporarily bypassing the BOV?

Thanks for the advice, Yeah if it comes to it I'll bung at the TB. People have reported loss at the valves, blow by, and at the TB so it makes sense.

Matt82 said:
ps boost leaks normally make themselves easier to spot if they blow out oil mist that it picks up from the breather

ie look for joints which are WET with oil

and im banking on the dump valve

Thanks for this, will keep an eye out.

Scubascorpion said:
Are you sure you haven't cocked up the boost control pipework as half a bar boost is most likely actuator pressure. only two pipes to the control solenoid under the battery tray, so 50/50 chance of getting it wrong
That or you've re-fitted the dump valve on backwards.
If you made it to Gibbos RR day, as it's only a small one, I could have a look on the dyno. It's much easier to get it under load and have the ability to nosey under the bonnet at the same time.

just the sort of things I'd hope people would mention. Thanks mate, it's perfectly possible as I had to put everything back on quick. However its a long way to go for me with no boost so I'll prob try and sort it here. I'll post a pic of the pipes in any case. Really appreciate the suggestions though