How do I make / buy / use / troubleshoot a boost leak tester? [merged]

[Turbo Monk3y]

All boost leak tester threads are combined here.

i read somewhere maybe the Vfaq about making or buying a boost leak tester of some sort but never found it.... the reason being my acceleration seems slower than normal and all ive done to my stock car so far is take out the air box put on a K&N filter and cut the dump tube i have my boost guage sitting in a box not hooked up yet. and since those 2 mods it when i go wot on the car i can hear the turbo spool up and it sounds nice but i can also hear a sound as my rpm increases the SHHHHHHHHHHHHHHHHHHHHHH sound does too. the sound comes from the same area as the BOV i think maybe i got a #@%#@%#@%#@% stock bov and it cant handle over 11-13 psi??? Then i shift and it makes the nice BOV sound WHOOOOSHHHH... but my car seems to be a little slower.. any ideas before i go check every tube clamp and tube????

 

[FORMONTOYA]

Injector seals can leak at the base of the injector where it installs into the intake manifold. If one's leaking, replace all 4, plus go ahead and replace the top seals if you need to take it apart. Also, when you're doing the test, rotate the throttle body plate (like you were stepping on the gas) and listen for a pitch change. If you have a pitch change then it's the throttle body seals.

 

[TurboFever]

Injector seals can leak at the base of the injector where it installs into the intake manifold. If one's leaking, replace all 4, plus go ahead and replace the top seals if you need to take it apart. Also, when you're doing the test, rotate the throttle body plate (like you were stepping on the gas) and listen for a pitch change. If you have a pitch change then it's the throttle body seals.

I searched Napa for the parts I need and I found something for the fuel injectors is this what i need ? http://www.napaonline.com/masterpag...er=1580423&Description=Fuel+Injector+Seal+Kit

But I only saw a throttle body gasket, would I have to get the seals from the dealership?

 

[kenamond]

I searched Napa for the parts I need and I found something for the fuel injectors is this what i need ? http://www.napaonline.com/masterpag...er=1580423&Description=Fuel+Injector+Seal+Kit

But I only saw a throttle body gasket, would I have to get the seals from the dealership?

The url picture looks like two insulators and one o-ring. You need 4 injector o-rings (they seal the top of the injector at the fuel rail) and four insulators (they seal the injector to the intake port, and this is where you'll be leaking if you have an injector boost leak). I've been told that you also want to replace the high pressure fuel line o-ring and fuel pressure regulator o-ring when you pull the injectors. You have to disconnect these (after depressurizing the rail) to pull the rail off and get the injectors out.

I got all of the insulators and o-rings for about $35 at my local mitsu dealership, but I'm still not sure if the high pressure fuel line o-ring is the right part (haven't installed these yet - this weekend ).

The throttle body gasket you get from Felpro works for both TB gaskets (one on each side), but it was felt (stock are metal) - yuck, so I just kept the stock ones and used some copper gasket maker which fixed my leak. If you don't have a leak there, you don't have to worry about a TB gasket.

To fix the injector boost leak, you don't have to pull the TB off. However, it looks like you're still guessing about whether the leak is at the injector insulator or not. It might be leaking under the injector from the IM/head gasket. Spray the whole area down with a spray bottle of super-soapy water. You should be able to see the bubbles of the insulator foaming up (you have to stick your head way up under the hood to see, but you can see it - use a flashlight if necessary). Make sure you know where the leak is before you go buying parts and tearing things apart.

Also pull your valve cover breather line off and see if air leaks out from the valve cover during the test. If it does, check your PCV valve (unscrew it from the VC, repeat the test, and see if air is coming through it). If it's leaking, get a new one, but DON'T get one from Autozone, Napa, Carquest, etc. These weren't designed to handle boost pressures. I tried two (Carquest, Autozone), and both leaked badly out of the box. The OEM ones were designed for this application and only cost ~$4 at a mitsu dealership.

If your PCV valve isn't leaking but air is leaking from the VC breather, it could be leaky valve seals or worn rings, and a compression test and possible leakdown test would verify that.

 

[TurboFever]

The url picture looks like two insulators and one o-ring. You need 4 injector o-rings (they seal the top of the injector at the fuel rail) and four insulators (they seal the injector to the intake port, and this is where you'll be leaking if you have an injector boost leak). I've been told that you also want to replace the high pressure fuel line o-ring and fuel pressure regulator o-ring when you pull the injectors. You have to disconnect these (after depressurizing the rail) to pull the rail off and get the injectors out.

I got all of the insulators and o-rings for about $35 at my local mitsu dealership, but I'm still not sure if the high pressure fuel line o-ring is the right part (haven't installed these yet - this weekend ).

The throttle body gasket you get from Felpro works for both TB gaskets (one on each side), but it was felt (stock are metal) - yuck, so I just kept the stock ones and used some copper gasket maker which fixed my leak. If you don't have a leak there, you don't have to worry about a TB gasket.

To fix the injector boost leak, you don't have to pull the TB off. However, it looks like you're still guessing about whether the leak is at the injector insulator or not. It might be leaking under the injector from the IM/head gasket. Spray the whole area down with a spray bottle of super-soapy water. You should be able to see the bubbles of the insulator foaming up (you have to stick your head way up under the hood to see, but you can see it - use a flashlight if necessary). Make sure you know where the leak is before you go buying parts and tearing things apart.

Also pull your valve cover breather line off and see if air leaks out from the valve cover during the test. If it does, check your PCV valve (unscrew it from the VC, repeat the test, and see if air is coming through it). If it's leaking, get a new one, but DON'T get one from Autozone, Napa, Carquest, etc. These weren't designed to handle boost pressures. I tried two (Carquest, Autozone), and both leaked badly out of the box. The OEM ones were designed for this application and only cost ~$4 at a mitsu dealership.

If your PCV valve isn't leaking but air is leaking from the VC breather, it could be leaky valve seals or worn rings, and a compression test and possible leakdown test would verify that.

Thanks so much for the info it helped alot. Well I did another leak and it seems that its the insulators that are leaking. I am going later to pick up the parts from the dealership but the parts guys was confused when I asked if they had a BISS screw o-ring, is there another name for this?

 

[Jake90GSX]

on my compressor I drain all the air out of it then turn it on and watch the compressors pressure gauge, i switch the compressor off at 15 psi, then release that into my tester, also make sure to have the crank in the propper position when you do the test

 

[kenamond]

on my compressor I drain all the air out of it then turn it on and watch the compressors pressure gauge, i switch the compressor off at 15 psi, then release that into my tester, also make sure to have the crank in the propper position when you do the test

I've heard some folks talk about crank position during a boost leak test, but that never made sense to me on a car with stock cams. Could someone enlighten me?

 

[FORMONTOYA]

I've heard some folks talk about crank position during a boost leak test, but that never made sense to me on a car with stock cams. Could someone enlighten me?

The reason for turning the crank to roughly 30 degrees after TDC is to assure that in all 4 cylinders there is a least 1 set of valves closed, either intake or exhaust.

There are a few points on the crank/cam rotation where both the intake and exhaust valves are open at the same time, even with stock cams. If you did a boost leak test in that configuration your boost pressure would flow through the intake track-cylinder-out the exhaust=big leak. If you hear a boost leak coming out of the exhaust that could be the cause and the first thing you should try in order to fix it.

Another possibility for hearing leaks at the exhaust is the EGR valve.

 

[idt512]

ive put together the hardware to perform a boost leak test, however i have a few questions:

do you perform the test with the throttle butterfly open or closed? or does it even matter?

With it closed, then the intake manifold wont be part of the test... but with it open wont the compressed air just escape through the intake and exhaust valves?

 

[zippyshoe]

During a boost leak test, it doesn't matter whether the throttle plate is open or closed - even when its "closed", there is a space between the throttle plate and the throttle body itself that the pressurized air can easily pass through. Therefore, the intake manifold IS included during a boost leak test. The air will not escape through the valves because the intake and exhaust valves for a particular cylinder will not both be open simultaneously. Hope this helps.

 

[kenamond]

Maybe this is an unfounded rumor, but some have said that there is a small bit of valve overlap in the 2g. I've never run into it during a test, but if you get unlucky, you could have one of the four cylinders at this critical crank angle.

Someone who knows the stock cam profiles would be able to confirm this.

Even if this is the case, you just need to turn your motor over a bit and try again.

Trust me, the air will get past the butterfly in the TB during your leak test.

 

[steve]

Maybe this is an unfounded rumor, but some have said that there is a small bit of valve overlap in the 2g. I've never run into it during a test, but if you get unlucky, you could have one of the four cylinders at this critical crank angle.

Someone who knows the stock cam profiles would be able to confirm this.

It's not specific to the 2G. The "proof" was posted years ago in a thread on the cam differences.

http://www.dsmtuners.com/forums/showpost.php?p=181202&postcount=19

I couldn't remember the specifics when I told oldman to turn the crank to 30* before or after TDC to be safe but it looks like 30* BTDC or 15* ATDC works. That way no cylinder has more than one set of valves open.

Steve

 

[kenamond]

It's not specific to the 2G. The "proof" was posted years ago in a thread on the cam differences.

http://www.dsmtuners.com/forums/showpost.php?p=181202&postcount=19

I couldn't remember the specifics when I told oldman to turn the crank to 30* before or after TDC to be safe but it looks like 30* BTDC or 15* ATDC works. That way no cylinder has more than one set of valves open.

Steve

Thanks Steve!

 

[zippyshoe]

It's not specific to the 2G. The "proof" was posted years ago in a thread on the cam differences.

http://www.dsmtuners.com/forums/showpost.php?p=181202&postcount=19

I couldn't remember the specifics when I told oldman to turn the crank to 30* before or after TDC to be safe but it looks like 30* BTDC or 15* ATDC works. That way no cylinder has more than one set of valves open.

Steve

Yeah, thats some good info Steve.

 

[steve]

I should have also pointed out that the engine makages to get air to idle when the throttle is closed so it will pressureize the intake as well. The air goes through the ISC/IAC, the FIAV, and the BISS. Opening the throttle doesn't hurt. Moving the throttle is a good idea so you can see if it leaks in one position and not in another.

Steve

 

[kenamond]

It's not specific to the 2G. The "proof" was posted years ago in a thread on the cam differences.

http://www.dsmtuners.com/forums/showpost.php?p=181202&postcount=19

I couldn't remember the specifics when I told oldman to turn the crank to 30* before or after TDC to be safe but it looks like 30* BTDC or 15* ATDC works. That way no cylinder has more than one set of valves open.

Steve

I'm suprised I never ran into an overlap problem during a boost leak test. You have a 1 in 3 chance of it happening. And I assume this means that the 1g and 2g cams and cam timings are the same.

 

[steve]

You have a 1 in 3 chance of it happening.

Not much of a mathematician are we. Neither am I, but I would think it's more something like (degrees of overlap * cylinders)/720 since it not just one shot per cylinder.

Why it doesn't happen as much as you would expect has to do with the physics. Pushing both sets of valve springs down is work, more work than one set and a lot more than none. So the engine tends to come to rest in other states than in overlap.

Steve

 

[90BLKTALONTSI]

I got a quick question, I recently did a boost leak test and with the throttle closed I had no pressure build up but when I opened the throttle plate I started building pressure. I have bumped the engine over a couple of times to try and ensure that the valves are closed but if air does get past either way, why is it that I was only able to build pressure when I opened the throttle plate? Any feedback would be helpful...

 

[kenamond]

Not much of a mathematician are we. Neither am I, but I would think it's more something like (degrees of overlap * cylinders)/720 since it not just one shot per cylinder.

Why it doesn't happen as much as you would expect has to do with the physics. Pushing both sets of valve springs down is work, more work than one set and a lot more than none. So the engine tends to come to rest in other states than in overlap.

Steve

You don't miss a thing.

So 1 in 6 if you ignore physics and CORRECTLY do the math. I don't think the valve springs are going to have that much of an effect, because of the complete lack of leverage of the rocker/rollers on the cams. I would expect the compression and power strokes to be a much bigger player in the probability of where the motor stops (maybe 90* ATDC where the power and compression strokes are balanced - which would be good for a leak test), but I'm probably wrong AGAIN.

 

[speedy_talon28]

I did a search on this and I took this from 2gGSX: the inlet itself is actually 2 1/8" but the black ring inside the stock pipe makes it 2.25"

 

[S_Ranger]

Like the title says which should I go with? I have an air compressor that plugs into my lighter but I think it's a little loud and I'll miss the hisses. Bike pumps on the other hand, make me worry because I feel like I gotta constantly pump and move around. The tester is being built right now but some feedback can help me out.

 

[Spooling99]

If you can, use the air compressor and have one of you friends watch you boost gauge. When it gets to 20 stop and let the air run out and listen for leaks. http://www.dsmtuners.com/forums/showthread.php?t=169435

 

[JayRolla]

A bike pump will work. have a buddy watch the boost gauge and just pump to 20-30psi whatever you run for your daily boost.

Beat me to it, and yes either bike or compressor pump will work.

 

[S_Ranger]

Ah, I get it! In the beginning I thought you pump air and just move around while still pumping. My boost gauge isn't connected to an a-pillar or nothing and has enough slack to reach the manifold. Which is good because it's within visibility. Thanks for the teach!

 

[wret]

Either may work, unless you have a leak, in which case neither may work. You need something with a good flow rate, which neither of your devices have. If you have any leaks, you won't be able to build any pressure with your mini-compressor and it will be so loud that you won't be able to hear the leaks.

The cheapest solution is an air tank for about 25-30 bucks at harbor freight or Walmart.

 

[SBstar]

Wret beat me too it. But like he said if you have some pretty good leaks then you won't be able to create enough pressure with either the bike pump or the small compressor. If you are lucky enough to have very small leaks, or none at all you may be able to get away with either of your choices. However I do suggest using a real air compressor or Wret's suggestion.