[Alpine-F80]

After discovering I most definitely have a boost leak after running some MHD logs, and then re-adjusting the charge pipe coupling where I thought it may be leaking originally and tightening the bungs, re-running logs and STILL having very high WGDC% (80%) for only stage 1, I decided to try and rig a basic boost leak test up to try and pinpoint the exact location(s).

I don't have an actual large compressor though, just a small tire compressor which I know is too weak, but I figured it could potentially help run down the leak as long as everything else is capped off and/or with some soapy water....but I can't get to that point because too much air is escaping from the intake tube which I've tried to cap off 2 different ways, with a 3" rubber cap + clamp around the outside of it, which was definitely a no-go, way too many protrusions from the end of the intake tube to do that, and then this which is a threaded 3" pvc end piece which slides in super tight, but still seams to leak from the edges.

Anyone have experience running a boost leak test on an N55 that could help me with this?

[e46m3to335i]

Originally Posted by Alpine_F30

After discovering I most definitely have a boost leak after running some MHD logs, and then re-adjusting the charge pipe coupling where I thought it may be leaking originally and tightening the bungs, re-running logs and STILL having very high WGDC% (80%) for only stage 1, I decided to try and rig a basic boost leak test up to try and pinpoint the exact location(s).

I don't have an actual large compressor though, just a small tire compressor which I know is too weak, but I figured it could potentially help run down the leak as long as everything else is capped off and/or with some soapy water....but I can't get to that point because too much air is escaping from the intake tube which I've tried to cap off 2 different ways, with a 3" rubber cap + clamp around the outside of it, which was definitely a no-go, way too many protrusions from the end of the intake tube to do that, and then this which is a threaded 3" pvc end piece which slides in super tight, but still seams to leak from the edges.

Anyone have experience running a boost leak test on an N55 that could help me with this?

Interested to know as well.

[XxThe_RemedyXx]

Pull the intake off and cap off the tube with a rubber glove (like a doctors glove). Might sound ghetto, but it works!

[thejeremyman9]

Bumping this thread - did you ever figure out an ideal way to perform the boost leak test?

I plan to make something this weekend to do it. I do have a small air compressor, so i am thinking of making something like you did but with a regular air compressor quick connect, which will connect to the flexible rubber section of the intake tube (I think that is circular?). I would then set the regulator to ~15psi and check for leaks.

The only other thing i have read is that i will need to remove and cap the port for the vacuum line that goes to the 8AT.

I searched through a ton of boost leak threads but most of them were just people posting questions without answers, so i welcome any input if someone has DIY a pressure/boost leak test on a N55 8AT.

[Alpine-F80]

Originally Posted by thejeremyman9

Bumping this thread - did you ever figure out an ideal way to perform the boost leak test?

I plan to make something this weekend to do it. I do have a small air compressor, so i am thinking of making something like you did but with a regular air compressor quick connect, which will connect to the flexible rubber section of the intake tube (I think that is circular?). I would then set the regulator to ~15psi and check for leaks.

The only other thing i have read is that i will need to remove and cap the port for the vacuum line that goes to the 8AT.

I searched through a ton of boost leak threads but most of them were just people posting questions without answers, so i welcome any input if someone has DIY a pressure/boost leak test on a N55 8AT.

I honestly I didn't end up getting a solid boost tester beyond a few psi, but I think once I do I'm going to cap off the intake and then use one of the bungs from the CP for a compression fitting.

[thejeremyman9]

Originally Posted by Alpine_F30

I honestly I didn't end up getting a solid boost tester beyond a few psi, but I think once I do I'm going to cap off the intake and then use one of the bungs from the CP for a compression fitting.

There seems to be two options - pressurize from the CP (bung or 8AT vacuum port) and plug the intake, OR, pressurize from the intake and plug the 8AT vacuum port. In both cases, it looks like you will need to somehow plug (what i think is) the PCV that goes from the valve cover to the turbo inlet. If you did not plug that and/or the 8AT vacuum port, that is probably why you could not get pressure sustained. That, or just leakage past the throttle body (not sure how tight it seals).

I just went out and took a closer look at the car and took some measurements. It looks like I will need to get a 3.5'' PVC "plug" to clamp into the turbo inlet. I will probably put a compressor fitting into that and pressurize from there; that is how i have made pressure testers for other cars in the past. I would then remove the vaccum line from the CP for the 8AT and cap/plug that port before pressurzing the system. I would also need to somehow plug the PCV hose, probably by removing from the valve cover and putting a plug into it.

Does anyone know how to undo that clip? It didnt seem obvious and i didn't want to break it. See images below.

[BowzerF30]

I was just attempting to boost leak test my bmw tonight. I have a pure stage 2 and my car is not hitting full boost. It's supposed to be 22 psi but I'm at 14-16psi at the top of a 4th gear pull, boost is inconsistent and it spikes a bit after I let off.

I removed that pipe by pulling it towards the passenger side while prying the main 3 visible clamps up gently using a pick. Once those 3 were lifted still applying a light pull I pried the bottom clip down and pulled the hose out.

My only issue now is plugging those 2 holes, I tried getting pressure but got leaks past the inlet seal on that valve cover hose.

[T_H_O_M_A_S]

post some logs man , that difference can also be tune related
if your wdgc is 100 percent all the time it could be an indication

[thejeremyman9]

Originally Posted by BowzerF30

I was just attempting to boost leak test my bmw tonight. I have a pure stage 2 and my car is not hitting full boost. It's supposed to be 22 psi but I'm at 14-16psi at the top of a 4th gear pull, boost is inconsistent and it spikes a bit after I let off.

I removed that pipe by pulling it towards the passenger side while prying the main 3 visible clamps up gently using a pick. Once those 3 were lifted still applying a light pull I pried the bottom clip down and pulled the hose out.

My only issue now is plugging those 2 holes, I tried getting pressure but got leaks past the inlet seal on that valve cover hose.

I think to plug those 2 holes, i will stick part of a nitrile glove, ziplock, or something like that over the hole then slide the connector back on - that should form a seal and prevent any air from going down the tube(s).

As mentioned, you should post a log (on another thread probably) to get some more input as to whether it is a boost leak. If you get a boost spike after letting off, you are probably not looking at manifold boost, you are looking at boost before the throttle body.

Originally Posted by T_H_O_M_A_S

post some logs man , that difference can also be tune related
if your wdgc is 100 percent all the time it could be an indication

I posted my logs on the MHD thread. I also emailed MHD and they replied saying i "have a pretty huge boost leak". I am suspect of my O-rings on IC connections as i posted in the Oring thread.

[Alpine-F80]

Originally Posted by thejeremyman9

There seems to be two options - pressurize from the CP (bung or 8AT vacuum port) and plug the intake, OR, pressurize from the intake and plug the 8AT vacuum port. In both cases, it looks like you will need to somehow plug (what i think is) the PCV that goes from the valve cover to the turbo inlet. If you did not plug that and/or the 8AT vacuum port, that is probably why you could not get pressure sustained. That, or just leakage past the throttle body (not sure how tight it seals).

I just went out and took a closer look at the car and took some measurements. It looks like I will need to get a 3.5'' PVC "plug" to clamp into the turbo inlet. I will probably put a compressor fitting into that and pressurize from there; that is how i have made pressure testers for other cars in the past. I would then remove the vaccum line from the CP for the 8AT and cap/plug that port before pressurzing the system. I would also need to somehow plug the PCV hose, probably by removing from the valve cover and putting a plug into it.

This is great, didn't think about the PCV valve, this is why a decent sized compressor is ideal. I was gonna say I recommend capping/covering the intake side and use one of the bungs on the CP, plugging the 8AT outlet.

[thejeremyman9]

Originally Posted by Alpine_F30

This is great, didn't think about the PCV valve, this is why a decent sized compressor is ideal. I was gonna say I recommend capping/covering the intake side and use one of the bungs on the CP, plugging the 8AT outlet.

My meth bungs on the CP are buried down low, and i am pretty confident they are sealed since i teflon taped them and put the plugs in tight. I will probably just leave those in place and pressurize from the turbo inlet.

Hoping to do that this weekend and will report back.

[JaredG_F30]

Are you just pressurizing or smoke testing as well?

[thejeremyman9]

Originally Posted by JaredG_F30

Are you just pressurizing or smoke testing as well?

I am just going to pressurize. I dont have a smoke machine, and while i considered buying a fog machine for a DIY smoke machine, I think i am going to hold off on that.

I already ordered O-ring as described here: https://f30.bimmerpost.com/forums/sh...2#post25335022

If i can at least confirm i have a boost leak with a pressure test, I should be able to isolate where it is from and will just replace Orings as necessary. Thankfully, there arent too many connection points on this car (unlike my 3000gt which has about 15 couplers and 20 vacuum lines).

[thejeremyman9]

Following up - my attempts were uncessful. I got the 3'' PVC fitting to try and go into the turbo inlet, but that alone was a nightmare. The turbo inlet, while flexible, is a hard material and is actually slightly smaller than 3 inches. After a LOT of messing around i finally got the fitting in there (with a air compressor connect tapped in) so i could at least attempt to pressurize the system.

I also removed the PCV hose to the valve cover and plugged that. Removed the 8AT vaccuum line from the charge pipe and plugged that hole. I thought that was everything... However when i tried to pressurize, i still got air coming out of the other side of the 8AT vaccum line that would normally go to the intake... which led to to believe air was getting past the throttle body and letting air into that hose from wherever the other connection point is? Not sure honestly. But in addition to that "leak", air was indeed seeping back passed where i was pressurizing from the inlet. You would have to fab something custom up that is slightly less than 3'' and ideally made from rubber or silicon to get it to seal in that location under pressure. Even then, i think air is going to leak passed the throttle body, so you would somehow have to block air from going from the top of the CP to the TB.

So, after about 2 hours of messing around, i eventually gave up on being able to pressure test and proceeded to completely remove the IC+CP i installed last weekend, to install larger Orings and double check everything as i describe here: https://f30.bimmerpost.com/forums/sh...2#post25335022

[thejeremyman9]

Update: I was able to successfully create a pressure tester after some trial and error. Details and photos below.

What you will need:

1. 3’’ threaded PVC/ABS cap
2. Air compressor and male quick connect fitting and a pressure regulator
3. Duct tape / electrical tape / Teflon tape
4. Various size rubber plugs – I could not find these in store so I ordered these: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

You will need to remove the intake as you will be pressurizing from the accordion part of the turbo inlet. Note, the 3’’ cap will not fit/seal properly without modification. While you can force it into the intake tube and try to clamp it down, air will leak past the threads and it will pop out once you build pressure.

Start by drilling a hole in the center of the cap for the quick connect fitting and then just thread it in (I did not even tap the hole – I just drilled it out smaller than the thread size and forced the threads in; it didn’t leak). Then, you will need to sand down the outer diameter from the 3’’ cap, ideally with a taper so that you can easily slide it into the intake, as shown in the pictures below. The easiest way to achieve this is to connect a drill to the quick connect fitting. You really don’t want to try and manually sand this down because (1) it will take forever, and (2) you risk creating low/high spots. You need to reduce the OD perfectly around the circumference or it will not seal. Once you get it connected to the drill, just hold sand paper around it while you spin with the drill. Once you have reduce the OD a bit (test by sliding it into the intake), you will need to add some sort of rubberized tape around the circumference so that it will seal once clamped into the intake tube. Teflon tape worked well for me, but it kindof made a mess (shredded) when I pulled the cap out. Electrical tape was OK, gorilla tape was the best.

Depending on how much you sanded down, wrap the tape around the circumference a few times until the cap is difficult but not impossible to get into the intake. Make sure that you installed it PAST the first lip or it will definitely pop out once you start building pressure (had this happen several times at first). It need to be even with or slightly in further than the hose clamp area. Once it is secured you need to move on to plugging various points along the intake system that could leak/bleed air.

First, remove the PCV hose (from the valve cover, not from the intake) and cap with the appropriate size rubber plug. Surprisingly I didn’t need to secure this beyond just pushing the plug in tight; it held ~15psi. See picture below. Next, remove the 8AT vaccum line from the charpe pipe (if you have it). Again, use the correct size rubber plug to plug that hole, or a vacuum cap if you have it (I didn’t get one with my CP). For this plug, I put a zip tie around the CP to hold the plug in place because the fit was not as tight. See picture.

Finally, which may not be absolutely necessary, use a small plug to cap the other end of the 8AT vacuum line there it would go back into the intake. What I observed is that air seemed to come out of that hose even with the side that goes to the CP disconnected, at least for a few seconds. There seems to be some sort of valve that takes a second or two to switch closed – when you first start pressurizing the system, air comes out, but you can hear an audible change in sound and the air stop flowing after a few seconds. I assume this is how you don’t have a permanent boost leak through the CP-8AT connection.

After you have all the plugs in and everything connected, start slowly increasing pressure with your regulator. Remember it will take a few second to fill everything with air so don’t go quickly or you could overshoot target PSI. Once you start building pressure in the system the gauge on the regulated size of your compressor will reflect that. I would start at only about 5psi and you will see if there are any obvious leaks. Increase to 15-20 psi (no reason go to over that if you are on stock turbo) and check for any smaller leaks. I used the soapy water in a spray bottle method but it wasn’t even really necessary. There are only a few connection points and it is very obvious if one of them is leaking once you pressurize.

I wrote about my horrible experience with a boost leak at VRSF IC-CP connection and what I had to go through to get that to seal over on this thread: https://f30.bimmerpost.com/forums/sh...6#post25393576

Pictures below

[DeeM55]

Originally Posted by thejeremyman9

Update: I was able to successfully create a pressure tester after some trial and error. Details and photos below.

What you will need:

1. 3'' threaded PVC/ABS cap
2. Air compressor and male quick connect fitting and a pressure regulator
3. Duct tape / electrical tape / Teflon tape
4. Various size rubber plugs – I could not find these in store so I ordered these: https://www.amazon.com/gp/product/B0...UTF8&psc=1

You will need to remove the intake as you will be pressurizing from the accordion part of the turbo inlet. Note, the 3'' cap will not fit/seal properly without modification. While you can force it into the intake tube and try to clamp it down, air will leak past the threads and it will pop out once you build pressure.

Start by drilling a hole in the center of the cap for the quick connect fitting and then just thread it in (I did not even tap the hole – I just drilled it out smaller than the thread size and forced the threads in; it didn't leak). Then, you will need to sand down the outer diameter from the 3'' cap, ideally with a taper so that you can easily slide it into the intake, as shown in the pictures below. The easiest way to achieve this is to connect a drill to the quick connect fitting. You really don't want to try and manually sand this down because (1) it will take forever, and (2) you risk creating low/high spots. You need to reduce the OD perfectly around the circumference or it will not seal. Once you get it connected to the drill, just hold sand paper around it while you spin with the drill. Once you have reduce the OD a bit (test by sliding it into the intake), you will need to add some sort of rubberized tape around the circumference so that it will seal once clamped into the intake tube. Teflon tape worked well for me, but it kindof made a mess (shredded) when I pulled the cap out. Electrical tape was OK, gorilla tape was the best.

Depending on how much you sanded down, wrap the tape around the circumference a few times until the cap is difficult but not impossible to get into the intake. Make sure that you installed it PAST the first lip or it will definitely pop out once you start building pressure (had this happen several times at first). It need to be even with or slightly in further than the hose clamp area. Once it is secured you need to move on to plugging various points along the intake system that could leak/bleed air.

First, remove the PCV hose (from the valve cover, not from the intake) and cap with the appropriate size rubber plug. Surprisingly I didn't need to secure this beyond just pushing the plug in tight; it held ~15psi. See picture below. Next, remove the 8AT vaccum line from the charpe pipe (if you have it). Again, use the correct size rubber plug to plug that hole, or a vacuum cap if you have it (I didn't get one with my CP). For this plug, I put a zip tie around the CP to hold the plug in place because the fit was not as tight. See picture.

Finally, which may not be absolutely necessary, use a small plug to cap the other end of the 8AT vacuum line there it would go back into the intake. What I observed is that air seemed to come out of that hose even with the side that goes to the CP disconnected, at least for a few seconds. There seems to be some sort of valve that takes a second or two to switch closed – when you first start pressurizing the system, air comes out, but you can hear an audible change in sound and the air stop flowing after a few seconds. I assume this is how you don't have a permanent boost leak through the CP-8AT connection.

After you have all the plugs in and everything connected, start slowly increasing pressure with your regulator. Remember it will take a few second to fill everything with air so don't go quickly or you could overshoot target PSI. Once you start building pressure in the system the gauge on the regulated size of your compressor will reflect that. I would start at only about 5psi and you will see if there are any obvious leaks. Increase to 15-20 psi (no reason go to over that if you are on stock turbo) and check for any smaller leaks. I used the soapy water in a spray bottle method but it wasn't even really necessary. There are only a few connection points and it is very obvious if one of them is leaking once you pressurize.

I wrote about my horrible experience with a boost leak at VRSF IC-CP connection and what I had to go through to get that to seal over on this thread: https://f30.bimmerpost.com/forums/sh...6#post25393576

Pictures below

Thank you for your efforts and write-up. Just to confirm, was your leak coming from the vacuum hose connections to the intake?

[thejeremyman9]

Originally Posted by DeeM55

Thank you for your efforts and write-up. Just to confirm, was your leak was coming from the vacuum hose connections to the intake?

No, my leak was from my VRSF IC to VRSF CP connection. Everything else was fine. I wrote about it in detail here, including how i solved it:

https://f30.bimmerpost.com/forums/sh...5&postcount=23

I also heard some air on the turbo side of the engine once pressure was built up for 10+ seconds, but i thought that might be the DV? I have a video that i will try and upload when i get time, but i wasnt as concerned about that because i never touched anything on that side. It was right up by the turbo where i couldnt reach or see - everything from the TIC-IC connection onward was leak free. I also thought it could be the inlet where it connects to the turbo since it is not made to hold boost, but not 100% sure.

[DeeM55]

Ahhh gotcha. Ok. I fear that I have the same issue. I'm only 1 to 1.5 psi from target just like you. I've reinstalled the CP twice myself and had a shop do it a third time.

I ordered the 4mm o-ring but haven't gotten around to install it. Looks like I'll have to order the 4.5mm o-ring and use your method to seal that leak. Thanks again! I'm hoping that this works because this leak is becoming a huge PITA.

Forgot to mention. I have the G-Plus IC to VRSF CP.

[thejeremyman9]

Originally Posted by DeeM55

Ahhh gotcha. Ok. I fear that I have the same issue. I'm only 1 to 1.5 psi from target just like you. I've reinstalled the CP twice myself and had a shop do it a third time.

I ordered the 4mm o-ring but haven't gotten around to install it. Looks like I'll have to order the 4.5mm o-ring and use your method to seal that leak. Thanks again! I'm hoping that this works because this leak is becoming a huge PITA.

Forgot to mention. I have the G-Plus IC to VRSF CP.

Yeah, i dont think the issue is with incorrect installation. Its simply the connection between the parts that can cause the leak if their sizes are out of spec. I think the only way you could incorrectly install the CP to the IC is if you forget the Oring or let it get twisted, which in my experience if very difficult to do (and pretty much impossible with the aftermarket ones i think).

I would perform a boost leak check and confirm the location of any leak(s) before going through the hassle of reinstalling things, but it definitely wont hurt to have those Orings on hand. If you are going to be ordering from the Oring store, i would probably order the larger one for the CP-TB connection as well. I didnt do my boost leak check until after I installed that one, so i can't confirm if it would have leaked with stock Oring, but the connection was definitely better with the 4mm x 81mm Oring for VRSF CP-throttle body connection. Since the Orings are so cheap and the main cost is shipping, i would just order any ones you think you might need... start with the largest CS size and go down until one fits.

[Bmwdoubles_]

This is great I just posted looking for this. Should've used search lol

The link to the rubber stoppers is huge thank you.

[dalderks]

Originally Posted by thejeremyman9

If the connection was loose when you were test fitting it, you most likely have a leak. Trust me, i know from experience... See these two threads here and have a read:

https://f30.bimmerpost.com/forums/sh...als+for+charge

https://f30.bimmerpost.com/forums/sh...oost+leak+test

There needs to be some resistance when you install the CP onto the IC. If it just "falls" on and you can rattle/wiggle it back and forth easily even once it is all the way on and clipped, its probably not going to be air tight.

I'm jumping from the BM3 v7.0 thread to here after confirming I have a boost leak. Thanks again for the inputs thejeremyman9. I created the boost leak tester you described in this thread and found a leak at the top of the coupler immediately. I tightened it down, tested to ~10 PSI (got nervous going higher), and ran another log. Unfortunately, the log was still junk (still on same gas) (https://www.bootmod3.net/log?id=5e8b...729b14ca1ecde9).

Did you have any problems pressurizing the whole system through the turbo inlet pipe to 15 PSI with this setup? I'm thinking about adding a pressure gauge in line with the cap because I'm not sure how accurate the regulator on my compressor is.

[thejeremyman9]

Originally Posted by dalderks

I'm jumping from the BM3 v7.0 thread to here after confirming I have a boost leak. Thanks again for the inputs thejeremyman9. I created the boost leak tester you described in this thread and found a leak at the top of the coupler immediately. I tightened it down, tested to ~10 PSI (got nervous going higher), and ran another log. Unfortunately, the log was still junk (still on same gas) (https://www.bootmod3.net/log?id=5e8b...729b14ca1ecde9).

Did you have any problems pressurizing the whole system through the turbo inlet pipe to 15 PSI with this setup? I'm thinking about adding a pressure gauge in line with the cap because I'm not sure how accurate the regulator on my compressor is.

Are you a EWG? Also, it would help if you go further in your log so we can see boost up top (say, 6500). Your are off by only 1 psi, which isnt horrible, but the "wavy" nature of the boost control is strange.

In terms of pressurizing, the main thing is that air is going to go past the TB no matter what. So, you cant really pressurize and "hold" that pressure without a constantly supply of air. Assuming you capped off the PCV and the bungs/vaccuum source on the chargepipe, you should be able to set your compressor regulator to the desired pressure and let it continuously flow air to maintain that. You will hear some air going past the TB, etc, but a air leak into the ambient air sounds distinctly different (as you probably heard with the leak you found). I used a cheap harbor freight 3 gallon compressor and its built-in regulator so whatever you have is probably fine. The smaller the compressor the less time you have to find your leak because it has to be off to hear things and the pressure does down pretty quickly. You can also add a gauge inline if desired (or a regulator with built-in gauge, they sell those too).

When i tried to go to like 20psi or higher i did have issues with the tester popping out of the intake. My leak was obvious at 15psi so i didnt really feel the need to go any higher for a sustained period of time.