Boost Leak Test Results

NoQuarter

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Nov 24, 2017
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I did a quick look to check for any boost leaks. Mostly just to make sure I had everything right to test properly.

Going into this, I have no reason to think I have a boost leak. Logs look good, no codes, etc.

Below you can see the inlet plugged with 1 1/2" fittings. The front one I used a 1 1/2" to 2" adapter so I could then use a 2" plug that had a flat face on it to mount the tire stem valve. The rear one is 1 1/2" cap - (those come with rounded tops at my Lowes store)
20180808_203513.jpg


I started to add some pressure, determined to keep it below 10psi so as not to pop off the inlets at the turbo housing (inlets are not fitted to hold pressure).

It took me just a couple seconds to find out something was wrong, but the engine was too hot and the time to late to pursue it. I am bit confused. The leak seems massive but the car runs great. This makes me think the rear inlet could be leaking under pressure but it was just a small amount of pressure and a visual inspection of the inlet connection looks solid.

In the video clip, you first hear the air going in THEN the leak, and repeat...

 

NoQuarter

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It may be nothing if it is in fact the rear inlet. I would have to sort that out then try the test again but, as I mentioned, I am skeptical that is it but I am skeptical for any leak this bad.

hang on..... I know what I missed! I didn't plug the PCV port at the rear inlet!
 
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RSL

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Aug 11, 2017
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It may be nothing if it is in fact the rear inlet. I would have to sort that out then try the test again but, as I mentioned, I am skeptical that is it but I am skeptical for any leak this bad.

hang on..... I know what I missed! I didn't plug the PCV port at the rear inlet!
Yep. That thing will smoke out of the exhaust the next time you start it. No air leak at the oil cap like that?
 

GotPwned

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Apr 3, 2018
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When i didnt cap off my rear inlet, it smoked really bad for maybe 10-15 minutes. Scared the hell outta me cause it was enough smoke to cover the street while driving down. Do a couple WOT runs and dont mind the people looking at you driving a BMW that looks like its about to die.
 

doublespaces

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So how are you blocking air from going into the motor, just the throttle body? Seems like that isn't air tight and some valves will be open? I've actually tried doing something similar to this but I must either have bad luck with some valves being open on Intake and exhaust, or I have a huge leak somewhere.
 

NoQuarter

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Don't expect the system to hold pressure for long, It should escape past the throttle body.

The expectation is that it holds some pressure just long enough to check for leaks. After a few moments, expect to have to add more air again and repeat.

Don't think of it like a leak down test. More like blowing air into a tank full of holes and you chase down all the ones you can find.
 

buster84

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For future reference dont forgot to block the PCV port and remove the oil cap. If you leave the oil cap on and you pressurize your crankcase you could blow lots of gaskets and the first to go is usually your valve cover or headgasket.
 

NoQuarter

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For future reference dont forgot to block the PCV port and remove the oil cap. If you leave the oil cap on and you pressurize your crankcase you could blow lots of gaskets and the first to go is usually your valve cover or headgasket.

This is a good tip but I imagine this takes some serious effort to screw it up so bad you blow some gaskets. I can't imagine the turbo inlets staying on long enough to hold that much pressure.
 

buster84

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This is a good tip but I imagine this takes some serious effort to screw it up so bad you blow some gaskets. I can't imagine the turbo inlets staying on long enough to hold that much pressure.

I was able to do a boost least test to 30psi on mine. You just have to make sure you clamp down the plugs really good and i even used inferior worm clamps. At this kind of PSI with worm clamps just make sure your not standing anywhere near the small 1" plugs because if you are and it decides to blow, you could get hurt. When i first started creeping up to 30psi one of mine blew off when my psi climbed to 35 rapidly and it blew off. Thankfully it hit a box behind me and i had no damage to the car or me. After this i decided to add a big zip tie around the plug and the hose to help prevent it from blowing off that seemed to help and it also helped me feel comfortible again doing the test because after that popped it sounded like a gun went off and I really didnt want to stand anywhere near those plugs again after that :tearsofjoy::tearsofjoy:

Just be extra safe when pushing these higher boost leak tests. Only go as high as you plan to go on the turbos. Just dont do as i did and add to much air to fast lol. I learned my lesson from this innocent and now i have two regulators to keep the psi in check, one right after the tank and one at the end of the handle; when it was just the one at the end of the handle thats when the air creeped up to fast to 35psi and popped off.
 
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NoQuarter

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So you had no trouble with the inlets staying attached at the turbo? You have stock inlets or silicone with a clamp?
 

buster84

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So you had no trouble with the inlets staying attached at the turbo? You have stock inlets or silicone with a clamp?

Actually i never had any issues with that, they stayed on just fine. My problem was with the 1" plugs (or maybe it was 3/4" plugs i forget now lol) that i used to plug the inlets bypass valve recirulation ports on both of the inlets. I also had to keep an eye on my pcv plug since i unplugged it from the catch can and it was another location where the little plug could go flying at me. That was the only location where I didnt use a zip tie since i had nothing to tie it to to block it from blowing out. (its hard to describe but on the inlets I put the zip tie over the top of the plug and around the inlets themselves incase the warm clamp failed to help prevent it from becoming a flying projectile)

As for my mods there in my signiture, but if your on your phone you probably cant see lol, but i do have VTT silicone inlets. Id never suggest going higher than 18psi on any stock plastic because you'll just break it.
 
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LessIsMore

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Aug 21, 2017
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inlets (stock or silicon) will be the first thing to leak, but dont think they should blow off the turbo if theyre on tight. Anyone actually had that happen? Its important to do a high pressure test (20-25 psi), some leaks dont show up at 10 psi.
 
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frontside0815

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Nov 9, 2016
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So please tell us when you tested again, no quarter.
I also tried a boost leak test and had exactly the same like you, but: I have no BOV or PCV Connection on my inlets (Relocation Inlets)... I also think the inlet is not 100% leak free, because installing it sucks ass. I will have a look in the next weeks, but would be interesting what was the problem in your case.