View Full Version : Boost Leaks

Super XR7
09-10-2006, 03:07 PM
Has anyone tried to find boost leaks with the method listed under FAQ Forum? Basically pressurizing the system to 20 psi and searching for escaping air? Wondering how well it works.


09-10-2006, 05:28 PM
Has anyone tried to find boost leaks with the method listed under FAQ Forum? Basically pressurizing the system to 20 psi and searching for escaping air? Wondering how well it works.


I tried the recommended method of propane during idle around all the fittings. It just doesnt work very well. I made a pressure tester with a pressure regulator to pressure up the entire intake system and it will find leaks you probably didnt think you have. Sometimes a leak around a hose clamp might not show untill you have 10 or 15 lbs of pressure


09-10-2006, 06:38 PM
I've read the post from Vernon about boost leaks. Well I set my regulator to 20 lbs and pressurized the system. I had my wife in the car watching the boost gauge and it barely moved 1 pound. (mine gauge when the car is off is at about -2 and it never got to zero) Plus the only leaking I could find was at my connection where I hooked into the system.

So my first question is this. Did I connect into the right place? I have attached a photo of where I thought I should connect into the system.

09-10-2006, 08:16 PM
Mike are you suspecting leaks or just trying to be proactive?

I just added a 5% JS pulley and got tons of low end torque but I'm only seeing about 13 lbs of boost at 5K. I suspect I have a leak but don't know where to start. Then I saw your post, thought this might be the solution, and then asked you if I could add to your thread.

Well the first thing I found is that I needed to plug the hose that connects to the bottom of the air intake. I also had to cut off part of the hose that has the hose clamp on it, it was leaking around the clamp. Now I am getting about 2 pounds on the gauge.

I can hear what I think is a leak under the bypass valve, but I cant find it.

Suggestions anyone?

Super XR7
09-10-2006, 08:23 PM
Proactive at this point as I did have a vacuum leak for a long time which I could not find but last week I found it. My supercharger top was leaking where it mates to the supercharger. I hope this is the only leak but with the shoot out coming I want to have a way to check for others. I have replaced all vacuum lines and zip tied all the ends but that is not absolute. Once I get done with the differential I will try to pressure test the intake system and go from there.


09-13-2006, 07:25 PM
Can anyone tell me should I be able to see the boost gauge higher than 5 with the regulator set at 20?

Someone has to have done this and have some insight. Please chime in.

09-13-2006, 07:59 PM
i actually just did this last week, you need to hook up to the point that the boost gauge is hooked to (of course your boost gauge won't read anything being as it's unplugged) it's located just a little further towards the driver side from where your picture shows, you will need a 3/8" hose i believe is what i bought to plug in. the process worked great for me, blower top was really bad, the big nut was leaking a little and theres a vacuum tree right behind where the boost gauge hooks too, it's up under the cowl, will be hard to see, but soak it with the soapy water, that was the other really bad point in mine, and it's hidden rather well. if that is leaking it is rather easy to get to to fix it by removing the driver side cowl panel. hope this makes some sense to you :)

09-13-2006, 08:20 PM
All that checked out fine. I believe it is coming from somewhere near the base of the supercharger on the back side. But I can't see back there to find it.

09-13-2006, 09:38 PM
First off, by way of the FAQ, you are not going to maintain that pressure. The TB and IAC are "capping" the system which they will NOT due...especially the higher psi you go. So your boost reading only 5 is probably accurate.

The Kenewagner does it (I do it the same way) is to cap off your PCV valve and your crossover breather (intake tube to driver's valve cover). This way, you don't end up pressurizing your crank case. You don't want to do that because it will artifically show you that you have a leak.

Then you want to pressurize the system from the intake tube where the MAF would attach to. By doing this, you WILL pressurize the entire system...(air gets right by the TB through this, but you could turn the key on to open the IAC as well) Then I do it every 5 lbs...spray each joint with soapy water. This will blow bubbles if there's a leak...very easy to see.

Make any adjustments as you go...work everyplace (to include vacuum lines) to ensure that there are no leaks. Then when you're done, go up another 5 lbs and check again. Repeating this process will eliminate any leaks that you never knew that you had. Some vacuum lines are under boost when the car is, so it is also good to check them. And it works great to find any other leaks that may be occuring along any of the other vacuum lines as well.

It'd help to have Ken's nice little tester. If you like, you can check with him to find out how to get one if you'd like.

09-14-2006, 07:33 AM
Thanks for your input. I was pressurizing the crankcase and blocking off the crossover breather.

I'll have to block them off and try again and see what happens.

Just from what I have found so far, I've gained about a pound of top end boost, so this is definately a good thing to check.

09-14-2006, 09:31 AM
For 4 years I had experienced a noticeable drop in my mid-throttle performance. I always suspected a vacuum leak, but could never locate it. I recently pulled the blower off to replace my injectors and install a 70mm TB. This task included replacing the stock plenum with ported one. Here is where two discoveries were made.

1. The hard line for the PCV valve, coming out of the backside of the plenum, practically fell off upon removal of the plenum. I'm sure that this was leaking! I placed JB Weld around the hard line of my ported plenum to keep this from happening again.

2. I noticed a stain on the top of the intake that appeared to be motor oil. When I flipped the blower over, there was oil all over the bottom side towards the back where the plenum bolts on. When I took the plenum off I found a gasket that looked to be made of cellophane. The top part of the gasket was fine, but the bottom was discolored and missing big chunks!! Eureka....I had just found the elusive leak!! It looked like the motor oil in the intake system had deteriorated the gasket over the years.

After I resolved the above mentioned problems I put everything back together using the stock TB. (The used 70mm needed work.) The "Love Affair" is now back on with my Bird. Mid-Range Torque Restored!!!! I went driving all around that night looking for cars to pass on two lane roads!! So, you might want to check these areas.