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Best Book leak check method

753 Views 12 Replies 3 Participants Last post by  BPUed
Okay I am almost convinced i have a bad boost leak somewhere!
Wha'ts the best method of checking it? I tried spraying down all the tubes seeking for bubbles. Yes the water had a tad bit of soap, maybe not enough. But I didn't see any bubbles rise. What's the main troublespot for boost leaks?!

1994 57k miles, downpipe, & manual boost controller greedy set for full boost. I only hit 1.0 Bar.... maybe 1.1 bar for a sec or two going 70+ in 3rd gear. the boost doesn't drop anymore since I baught a downpipe. I haven't touched the BCC (if it has one).
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When you pour the soapy water on the hoses, did you just let it sit while the car idles or did you pull on the throttle cable a couple of times? If you are using the soap water test, you have to rev the engine to see the leaks.

Also, make sure your car has a BCC and that it is tuned properly (check for info on how to tune to correct voltage). Without a BCC, your car will hit fuel cut at 1 BAR.

I was experiencing boost leaks and just replaced all the vacuum hoses with silicone ones from Hose Techniques. You wouldn't believe how bad some of those rubber hoses look with 50k miles on them. ~$150 for the kit and I recovered 2 psi of boost

Yeah i let it sit for a sec or two. one person had the spray bottle while one person revved the car. However I didn't pull on any tubes while doing it.
The hoses are void of air, hence the word VACUUM. If one were to be "leaking", it would be drawing air into it -- thus bubbles would not form atop the hose. Probably not a good idea to draw fluid into them, either.
true......... so i guess just replace them all? Surely there is a easier fix or technique.
oh good lord.....

before you attempt any of the suggestions listed above, recreate the same conditions, gets some pvc and step it up from the size of an air compressors air nozzle to the size of the turbo inlet hose. also incorporate a ball valve in their, so you can take pressure off of the air nozzle, set it down, and with the valve closed still holding most of the pressure in, you can look around the car and feel for leaks.
if it doesn't work the first time, repeat the process until you find the leak, i have found numerous leaks with this process, it works great, as long as you have access to an air compressor, it might take a bit more creativity to use some type of household air pump for car tires or something.
lmk how it works.
I tried the method that turbosupra recommended, and my air compressor was only strong enough to create 9psi of pressure in the system. I was able to find one small leak, but the leak that I am look for still, will not show it's ugly face until the system hits 18-20 psi. so I can't find the other leak that is killing me. I should buy new hoses and give up on it. I have a 6 gallon compressor that max's out as 125 psi. So if you want to pressurize the supra's system to 18-20 psi your gonna need a huge compressor
Have you checked your BOV yet? I pressurized my system and found no leaks but I could only boost to 15 psi. I pulled my bov off and found that I could easily blow air through it off of the car. I replaced the valve with another factory bov, which I couldn't blow any air through. Now I can run as much boost as I want.
How did you properly test the bov?

BTW, Where you at in Omaha, I'm in Lincoln.
Did you say properly? I don't have my shop manuals with me. The way I checked the bov was simply trying to blow air through it with my mouth on the large inlet side of the bov with the valve completely out of the car. Don't worry, I used mouthwash first. I was able to breathe easily through the bov on the bad bov. I could hardly blow any air at all through the good bov, the bov was almost completely sealed.
I'll try that and see. I think there might be a more acurate way to check for leaks but I'll try your way a see. Did you come down to Lincoln a few weeks back and race me! Black 93 Auto with HKS Ti
I live in the Millard area. I haven't been to Lincoln in a few months. My car is a 93 black wingless with a Greddy SP exhaust. I've only seen about 5 supras in the area, it's good to see a local on the forums.
We come up to omaha a lot for the street races on Sat. night. We might make it up there this weekend. Kind of depends if we finish this motor swap on sat. Otherwise we'll probably stay here so we can finish it. If you want to email privately, I would love to meet up with you and hang.

If your interested:
[email protected]
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