So I rigged up the boost leak tester last night as the idle was horrendous. Unsurprisingly I found some big leaks on a couple of nipples left over from deletes that I hadn't noticed or weren't noted on that famous Vac diagram from Z32 wiki.

 

So the info I've read says to pressurise to 5psi max. I can do this, but how long should I reasonably expect it to stay there, or how long to bleed out? I totally appreciate it's not an airtight system by any means, but I have no idea what I'm looking for or what is acceptable.

After working on mine for a long time to make sure all leaks were gone I managed to get mine to gradually bleed down over about 30 seconds. I'm sure there might be a few very small ones but I was happy enough. To get any more I think I would need a smoke machine

After working on mine for a long time to make sure all leaks were gone I managed to get mine to gradually bleed down over about 30 seconds. I'm sure there might be a few very small ones but I was happy enough. To get any more I think I would need a smoke machine

 

Ah that's great thanks bud, does she run well? Mine took about 90secs to bleed down from 5psi.

 

On a different note, I was looking for answers on http://www.boostpro.net/guidesz32basic.html who made my boost tester. I noticed they recommend 7psi so I tested again at that which exposed a massive leak from a hose clamp that I hadn't done tight enough. It was holding fine at 5psi

You should, should stick to 5 psi. As you say though leaks do appear higher at times which is frustrating. The trouble is if you start putting much more than 5psi though it your going to risk popping oil seals out, apparently the cam seals are a favourite for this. This because the crank case becomes pressurised in the process with the stock PCV system. You might get people tell you you can put loads more through the system and they test it at 15psi, that's fine and they are welcome to carry on, if and when it goes wrong they will stop doing it. The 5psi is recommended by the FSM and its that for a reason.

Yeah I'd heard of people blowing oil seals, that would not be cool! I never noticed the 5psi in the FSM but will stick to that cheers :thumbup:

I'm sure you would get away with it 99/100 or even higher but I wouldn't want to strip the front end off the engine for a cam seal, or removing the gearbox and flywheel blah blah for the crank seal. Not worth the risk imo.

its a constant 5 psi that will find the leaks,no good just squirting a blast of air in as the inside volume will swallow it up plus the leaks your looking for..So an ideal senerio will be a small compresser with the regulator set to 5 psi and leave it connected as your scrabbling around looking and hearing for the leaks:wink:

Just read this with interest as it mirrors a lot of thread of similar content on here of recent times, the boost leak testing you guys are doing and the info you have seen on pressure levels with the recommended 5 to 7 psi as a max.

 

With 15 years of undertaking boost leak testing with a professional compressor and air line I can confirm to of never blowing a seal, never ever in fact. the trouble with testing at low levels is only the obvious leaks from open ends on vacuum lines etc will show out, loose clamps will often hold tight at low levels and require a higher testing pressure to find those, and by their nature will also require a higher volume of air to find them not just higher pressure, this volume is not possible on foot pumps or small compressors designed for inflating tyres, they simply cannot replace the lost air quick enough. This was often evident when we did a boost check on a customers car who had already done a low pressure, low volume test and thought it was all ok until we did our test using the garage compressor and would find problems with turbo cuffs etc.

 

So unless you have the facility to high volume boost checking you will not know for sure if you have high load / boost pressure leaks other than struggling boost, boost noise or especially with boost controllers pulsing boost at wide open throttle. Going back to the 5 to 7 psi boost test level as max...why? when the standard system can be easily run at 15 psi and higher, the pipe work prior to the turbo gets tested also when leak testing and this is more than capable of holding 15 psi as is the cam end seals and rear crank seal. so 5 psi really is not going to cut it, similarly if there is a huge leak like a cuff off at an inter-cooler then it would be impossible to find with foot pump or small compressor, best bet is to get into a garage with a compressor and most important good knowledge of the engine pipework layout as there are common placed where they leak.

(PowerZed)

Edited September 16, 201510 yr by JeffTT

hey Jeff..do you miss it??;)

hey Jeff..do you miss it??;)

 

What do you think ? :sad:

What do you think ? :sad:

 

Hi Jeff , You must be :) at least a little

This might be worth a read mate if you've not done it before;

http://www.thumper300zx.com/z32/boostleaks/boost_leak_guide.htm

 

I appreciate what your saying Jeff and as I said 99/100 it's likely fine. However when the manual says to do it a set way and many of the best minds in the business agree why take the risk? You wouldn't just make up a bolt torque so why make up a test level? I bow to your experience and if you or others feel comfortable doing it that way, that's fine but il keep following the advice laid out by the FSM and several big names in the zed game, certainly I wouldn't recommend to deliberately not follow those intrusions. I'm sure you can understand this.

As times and technology change the smoke tester has become standard now,they are crazy expensive but for those times a huge leak is found they are great,ive used one but currently don't own one but its on my list,the best thing is they are low pressure but ramming air behind the smoke at a higher pressure soon shows where the leak is.As Jeff has said 5 psi is simply not enough for those annoying hard to find leaks as they simply wont show.Many leaks from ill seated hose clips etc need a little more to be found.

Hi Jeff , You must be :) at least a little

 

Mmm.........yes.

There must be some legal route that we can take to have you "imported" back to the UK?:thumbup:

There must be some legal route that we can take to have you "imported" back to the UK?:thumbup:

 

Ho Hum.....

 

Ho Hum.....

 

[ATTACH=CONFIG]90689[/ATTACH]

 

God the memories of them small commando books are coming back!

Thanks for the input Jeff. I have a hefty compressor with regulator at the workshop but I'll have to find something to connect to the airline and then clamp onto the tyre fitting of the MAF blank. At present I'm using a press on tyre inflator.

Get yourself one of these, not expensive..

 

 

I too used more than 5 psi as I don't have pcv's so I wasn't worried

 

I probably have a few more to find but the car ran spot on after I blew an intercooler hose off on my first run ( no hose clamp fitted).

 

Next time I'm back I will probably run it up to 15 psi

 

I used a big compressor to do this.

I too used more than 5 psi as I don't have pcv's so I wasn't worried

 

I probably have a few more to find but the car ran spot on after I blew an intercooler hose off on my first run ( no hose clamp fitted).

 

Next time I'm back I will probably run it up to 15 psi

 

I used a big compressor to do this.

 

Worth remembering a boost leak check does not find issue`s with recirc valves as they can leak back into the system, the upshot of this is no obvious leak but an issue with low and pulsing boost, will find the link to a thread of mine that explains it.

 

Jeff

Here you go recircs explained

 

http://www.300zx.co.uk/forums/showthread.php?127063-Recircs-revealed-Inside-out-feature&highlight=Recirc+valve

Great repost Jeff

 

My old zed suffered from this and you sorted them out :thumbup1: