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Old 06-12-2017, 10:18 AM   #1
whiterabbitrexy
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Default boost leak down test on plenum

hi everyone i em wanting to build and hold pressure inside the intake manifold plenum on a ej20 v4 wrx ...... reason im wanting to hold preussre is becuase i want to find all the vaccuum leaks and see if theres a leak becuase on boost that manifold sees 14 to 16 psi of pressure when im on 1 bar or boost....i know this becuaze i got a boost gauge directly plugd into one of the vaccuum line in the manifold....

when i pressurrize the system (intake manifold plenum) at the Tb i pump in 17 psi and i can only build 7psi of pressure?? LEEAAKKKEe??? even for a quick 10 seconds i pumped in 2 bar of boost from my air compressor into the plenum again and only went to 9 psi .... WHERE the crap is all the air escapping to ?

my question is long but short ........ Can i always buildi and hold pressure in the manifold ? ? if my car was in perfect show room condition ?
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Old 06-12-2017, 02:31 PM   #2
Stags4
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So the main reason you are leaking is actually not necessary a bad thing. You are leaking because the air is 1) getting around the throttle body and 2) some valves may be open and allowing air to go through the engine and actually out the exhaust (or past rings etc etc).

I bet there is a spot on the crank where all valves are closed fully but not 100% sure where that is.

The ghetto way is to take off the boost tube from the throttle body. Seal it up with a nice silicone plunger/cap. Then pressurize the intake manifold with compressed air using a bleeder line. If you can't hold pressure, pull the fuel pump fuse and coils from the spark plugs and blip the starter. Try and hold pressure again. Repeat until you can get a fairly steady pressure (or maybe a slow leak). Then light a cig (or your dumb vape juice *** stick) and go to town on finding leaks.

Someone might have a faster way to find the sweet spot on where all the valves are closed.
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Old 06-13-2017, 07:00 AM   #3
2milehi
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Overlap for the intake/exhaust valves occur at TDC. Rotate the crank to TDC and then rotate 90 more. No cylinders will be in overlap.
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Old 06-15-2017, 10:20 PM   #4
whiterabbitrexy
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Quote:
Originally Posted by Stags4 View Post
So the main reason you are leaking is actually not necessary a bad thing. You are leaking because the air is 1) getting around the throttle body and 2) some valves may be open and allowing air to go through the engine and actually out the exhaust (or past rings etc etc).

I bet there is a spot on the crank where all valves are closed fully but not 100% sure where that is.

The ghetto way is to take off the boost tube from the throttle body. Seal it up with a nice silicone plunger/cap. Then pressurize the intake manifold with compressed air using a bleeder line. If you can't hold pressure, pull the fuel pump fuse and coils from the spark plugs and blip the starter. Try and hold pressure again. Repeat until you can get a fairly steady pressure (or maybe a slow leak). Then light a cig (or your dumb vape juice *** stick) and go to town on finding leaks.

Someone might have a faster way to find the sweet spot on where all the valves are closed.
hmmm ok cool i didnt know there was overlap on such small wrx v4 cams ...... wow thats cool you can pressurize the intake plenum just by puting air in the brake vaccum line..... that is very Pimp ..... can somone else confirm this technic about the brake line ?

2miliehi so what your saying is line up the harmonic balancer to tdc the just ass another 90degree and all valves will be closed ?

thing is i dont think im geting air escaping through the exhaust valves .... becuase i cant hear any noise what so ever at the end of the exhaust if i put my hear in my cannaon....

my oil filler makes a bit of tinny noise..... was thinking air was geting into my pcv .... but i put my hand over the oil filler and i cant build pressure nor will my boost leak pvc coupler change in psi when i blook the oil filer...
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Old 06-19-2017, 09:22 AM   #5
no694terry
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V4 still had the stand alone IACV right? I believe theres a check valve on the turbo models but it could also be leaking out of there back into the intake preturbo.
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Old 06-19-2017, 10:34 PM   #6
2milehi
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Quote:
Originally Posted by whiterabbitrexy View Post
hmmm ok cool i didnt know there was overlap on such small wrx v4 cams ...... wow thats cool you can pressurize the intake plenum just by puting air in the brake vaccum line..... that is very Pimp ..... can somone else confirm this technic about the brake line ?

2miliehi so what your saying is line up the harmonic balancer to tdc the just ass another 90degree and all valves will be closed ?
Just about all engines have overlap. Size doesn't matter.
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Old 06-27-2017, 10:37 AM   #7
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ok so today i did a smoke boost leak test by capping off the silicone turbo intake and removed 2 pcv hoses off the turbo intake and 3rd one was on the plenum manifold all was capped affter ... was then only pushing smoke through the boost control solinoid hose .....everything was plumbed off...

still couldnt build more then 4 or 6 psi on my mamaba teck boost leak pressure regualtor when connected to my front section turbo intake after afm .... i can hear a squeak noise ....cant pin point it ....

my question is how do i find the sweet spot on the crank angle position to clear my self from running into cam overlap ..

also sorry 2nd question im using a party smoke machine to dump THICK white smoke into a industrial watter office galon..... from the lid i have a 2 way port to push air into the Galon and smoke comes out the other port, witch is then connected to my (BCS) hose and pressureising the whole turbo intake system..... Succes i found a leak Rh side underneath plenum manifold....

BUT ..... BUT a very very big freaken but..... i think i might of chocked my motor with water...
..... when i left a fair bit of smoke in the office watter galon ....there was some water left over .? .... this smoke turns into water if left untouched in a confind spot.......

has anyone had any problems with using a smoke machine to perform a smoke leak test ????
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Old 06-27-2017, 11:20 AM   #8
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1st things first. Please fix your spelling and punctuation. Most people here don't really care too much, but the above post is just criminal. You look foolish. Don't be that guy.

100% don't leave standing water in the cylinder for ANY amount of time. Some things in engines do rust (crazy huh?).

I would pull the spark plugs and try to use a shop vac with a long tube and get any standing water out. Once you think you have the majority of it, just put the plugs back in and run it and allow the engine to get up to temp and burn all the condensation off.

Condensation gets in your engine, it's not really that harmful (pending it isn't a crazy amount). In some cases water in the air is "good" for an engine (ex. meth injection). As long as you don't let it sit with it and when you run it you get the engine up to temp your fine. Also do a sanity check on your oil to ensure there isn't a large amount of water in it.
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Old 06-27-2017, 03:48 PM   #9
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In general, when you're boost leak testing, you should cap off all the lines on the turbo inlet (if you hook the boost leak tester up to the inlet just after the MAF) otherwise you will just be pushing air into the PCV, BCS, Evap, or who knows where. Make sure you track all of the lines and make sure they're either capped, plugged, or going to the intake. Otherwise you will never get it to hold pressure.

Once you have done that and you have the intake pressurized, get a spray bottle with soapy water and start spraying around everything intake related, especially at connections. Spray liberally and you will find leaks where the spray bubbles up.

On my car I found significant leaks on the TGVs and the fuel injectors using the above method.
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Old 06-28-2017, 10:55 PM   #10
whiterabbitrexy
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Quote:
Originally Posted by Stags4 View Post
1st things first. Please fix your spelling and punctuation. Most people here don't really care too much, but the above post is just criminal. You look foolish. Don't be that guy.
Hate to brake it to u stags4 .....but i em that type of guy who cant spell nor read and write well .... i have a poor learning skills.... will try my best to fix spelling sorry...
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Old 06-28-2017, 11:03 PM   #11
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ok so last night i did another boost leak test ...... pushing 14psi and can only build 10 psi.....at the start its at 7psi and if held for 10second pressure only builds up to 10 psi.....

did a smoke test found some basic leaks but they arnt making me miss out on 4 psi..... thing is i cant hear it .... its got me lost .... i cant seem to find that sweet spot on the crank to close all valves..... makes me think its impossible to close all valves because if u get one side closed the other side will be open????

also will a lose pcv hose cause a boost/vaccum leak ?
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Old 07-06-2017, 08:19 AM   #12
whiterabbitrexy
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ok so here is an update from last night...... i think i found my boost leak

so i pressurized my system from the turbo intake pipe via air from air compressor....and found a leak at throttle body, bpv hose, ..... i can now build pressure in the system to about 9psi when i pump in 10psi.....

have i found my leak ? im askng if you guys can tell me if it should be 10 psi in the system if u pump in 10 psi ?

also it takes me a good 10seconds to build 9 psi .... is that too long or do i still have a leak ??
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Old 07-06-2017, 09:42 AM   #13
Charlie-III
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Quote:
Originally Posted by whiterabbitrexy View Post
ok so here is an update from last night...... i think i found my boost leak

so i pressurized my system from the turbo intake pipe via air from air compressor....and found a leak at throttle body, bpv hose, ..... i can now build pressure in the system to about 9psi when i pump in 10psi.....

have i found my leak ? im askng if you guys can tell me if it should be 10 psi in the system if u pump in 10 psi ?

also it takes me a good 10seconds to build 9 psi .... is that too long or do i still have a leak ??
A perfect seal in whatever you're testing should show the same pressure as the supply.
Use your ears, lit cigarette, soapy water, etc. to locate any other leaks.

How fast it takes to build test pressure depends on many factors, the size of pump, size and length of hose, fitting size, how big a volume you're filling, etc.
A big pump into a big tank feeding a 3/8" ID short hose will pressurize things faster than a 12VDC tire pump.

Once you build pressure, will it hold or does it leak down?

Last edited by Charlie-III; 07-06-2017 at 09:48 AM.
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Old 07-07-2017, 03:30 AM   #14
whiterabbitrexy
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A perfect seal in whatever you're testing should show the same pressure as the supply.
Use your ears, lit cigarette, soapy water, etc. to locate any other leaks.

How fast it takes to build test pressure depends on many factors, the size of pump, size and length of hose, fitting size, how big a volume you're filling, etc.
A big pump into a big tank feeding a 3/8" ID short hose will pressurize things faster than a 12VDC tire pump.

Once you build pressure, will it hold or does it leak down?
yeah thats what i thought too a perfect seal will hold pressure fast and the amount of air u push thats how much u should have so for 10 psi u pump in u should have 10 psi....

Im on the same page with u charlie about diffrent set ups will take diffrent amount of time to pressurize..... thats why i want to ask how long should it nornally take to pressurize on a stock tmic setup....

it takes about 10 seconds to build 9 psi
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Old 07-09-2017, 09:42 AM   #15
Charlie-III
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Quote:
Originally Posted by whiterabbitrexy View Post
yeah thats what i thought too a perfect seal will hold pressure fast and the amount of air u push thats how much u should have so for 10 psi u pump in u should have 10 psi....

Im on the same page with u charlie about diffrent set ups will take diffrent amount of time to pressurize..... thats why i want to ask how long should it nornally take to pressurize on a stock tmic setup....

it takes about 10 seconds to build 9 psi
Your 10 seconds does not sound bad, again, how big is the tank and what size fittings.
At 10PSI, you're not moving a lot of CFM into a few cubic feet of intake plenum.
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Old 07-10-2017, 07:41 AM   #16
whiterabbitrexy
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Your 10 seconds does not sound bad, again, how big is the tank and what size fittings.
At 10PSI, you're not moving a lot of CFM into a few cubic feet of intake plenum.
i was thinking its stil bad because the valves are half closed..... i have a 30 galon air compressor

still would love to hear from someone who knows 100% he dont have a boost leak and tell me how long it takes him to build 10 psi on a stock tmic setup ....

still think i have a leak
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Old 07-10-2017, 08:04 AM   #17
no694terry
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when i did my leak test, i was pumping the air in at 150psi at the compressor nipple. Capped turbo inlet through ~10ft fmic tubing, fmic, throttle body, plenum and probably some open valves. I could feel air coming from exhaust. I logged it and sorta video taped it. heres links if it helps compare. I found my to only have a very minor leak at the BOV (turbo xs rfl)

datalog mostly just to see the 3 bar map limits for rom setting, but you can see how long it took for pressure to fall off once i let off the air

http://datazap.me/u/terryjr/3-bar-om...data=2-3-5-6-8


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Old 07-10-2017, 06:56 PM   #18
whiterabbitrexy
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Quote:
Originally Posted by no694terry View Post
when i did my leak test, i was pumping the air in at 150psi at the compressor nipple. Capped turbo inlet through ~10ft fmic tubing, fmic, throttle body, plenum and probably some open valves. I could feel air coming from exhaust. I logged it and sorta video taped it. heres links if it helps compare. I found my to only have a very minor leak at the BOV (turbo xs rfl)

datalog mostly just to see the 3 bar map limits for rom setting, but you can see how long it took for pressure to fall off once i let off the air

http://datazap.me/u/terryjr/3-bar-om...data=2-3-5-6-8


Boost leak test - YouTube
wow 150 psi through your fmic setup u pumped in ? sorry to ask but did u have any problems after driving the car ? i would have thought more then 60 psi u would really do some damage on some stuff like even simple little rubber vacum hoses would pop/split

thanks for the video no694terry that helps me understand it takes alot of air to pressurize the system....... 150 psi u pumped in and only 30 psi u got ?? hmmmm must be 2 valves open completely to only get 30 psi...
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Old 07-10-2017, 08:00 PM   #19
no694terry
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Quote:
Originally Posted by whiterabbitrexy View Post
wow 150 psi through your fmic setup u pumped in ? sorry to ask but did u have any problems after driving the car ? i would have thought more then 60 psi u would really do some damage on some stuff like even simple little rubber vacum hoses would pop/split

thanks for the video no694terry that helps me understand it takes alot of air to pressurize the system....... 150 psi u pumped in and only 30 psi u got ?? hmmmm must be 2 valves open completely to only get 30 psi...
Just the air compressor was at 150psi so i could get enough cfm's to pressurize the system to 30-35psi. Air was getting past iacv and out the exhaust so i had to out flow that.
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Old 07-11-2017, 07:42 AM   #20
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Just the air compressor was at 150psi so i could get enough cfm's to pressurize the system to 30-35psi. Air was getting past iacv and out the exhaust so i had to out flow that.
no694terry bro u have a big massive leak man no joke sorry to say....
today i pressureized the intake system again and i turnd the crank pulley to open and close the valve to get that sweet spot where the valves are closed as much as possible....

best i got was i push in 19 psi and i can build pressure 13 psi...... Iam missing/losing 5 psi
even when i got my valves open and air was escaping out from the rear of my cannon exhaust i lost 8 psi ......

so im really really lost and confused how u managed to get pump in 150 psi and only get 30 psi ???? thats like 120 psi missing ?? i hope im wrong no694terry and u dont have a boost leak.....
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Old 07-11-2017, 07:47 AM   #21
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ok so here is a video of me doing a boost leak again..... im slowly getting it better but im still missing 5 psi ?.... is it impossible to get a full perfect seal when doing a boost leak ?



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Old 07-11-2017, 09:08 AM   #22
no694terry
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Never tried to rotate motor. Figured there was no way to shut all the valves without removing timing belt.
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