Boost Leak Tester ?'s

[Fubar231]

Im going to be doing a boost leak test on my car soon using the air compressor style DIY ones... What should i block off etc when i do this? Take off the accordian hose, stick the boost leak tester on the turbo inlet, run 14-15psi (what i run daily) and go from there. Just asking though, are there any hoses i have to block off?

Thanks

 

[gaboonviper85]

Cap off the pcv port on the throttle and that's it...if you run 15 pounds of boost then leak test at 25 pounds.

 

[Fubar231]

I always heard do the leak test with what psi you run... Anyone else confirm this? And cap the PCV port between the TB and the 2 lines going into the valve cover, so i don't pressure the head?

 

[gaboonviper85]

Yes you need to cap the throttle port as you'll pressurize the whole engine and risk blowing your main seals....

Nothing wrong with adding a few more pounds as what if there is a weak spot that 15 pounds doesn't effect but may come loose while Rollin down the highway...

Make sure your engine is at operation temps as your throttle itself can actually be a boost leak while cold.

Other than that leave all vac lines attached as they need to hold boost also.

 

[Fubar231]

Wait, if i don't plug it off at the end of my IC piping (Before the TB) then wont the air just run straight out the car due to cams overlaping @ certain times? Theres no time when all valves are closed so.

 

[suprajztwenty]

sorry for the newbness...when pressurizing the manifold, you dont get any leaks/whistles from a cyl on valve overlap?

when we pressure test intake systems on the semi's at work we have a plug on one end and we only pressurize the intercooler and hoses.

just assumed the process would be the same...i mean if the intake had any "boost" leaks itll have a vacuum leak too.

as for pressurizing the system 5psi more than normal boost is a good rule of thumb. if youre running 10+ on stock ic piping and hoses i wouldnt do more than 12, you might split a hose if you charge it with 20

 

[gaboonviper85]

Wait, if i don't plug it off at the end of my IC piping (Before the TB) then wont the air just run straight out the car due to cams overlaping @ certain times? Theres no time when all valves are closed so.

Valve overlap is more of a na cam timing...not really so much on turbo as air is forced in instead of drawn in....you need to pressureize the whole intake all the way to the head as even injector O-rings can cause a boost leak.

 

[suprajztwenty]

cool, less parts to buy too! thanks for clearing that up

 

[max-89supra(t)]

on semis they block off the pipes cuz past them there is pretty much nothing to leak besides the intake manifold gasket- and if that is leaking you could see oil leaks where boost is escaping. on a semi if there is a boost leak its the intercooler 95% of the time or one of the two big intake hoses 5% of the time

 

[suprajztwenty]

youre forgetting about egr systems...sometimes the egr valves dont close 100% and you get that whistle through the whole intake...well depending on the truck, but you get the point

for me i get about 75% loose clamps, 15% cac (intercooler/charge air cooler) and 10% are the boots/o-rings

 

[max-89supra(t)]

ya lol i was thinking about that right after i posted lol your right, i hate isx egr systems, working on them anyway:nono:

 

[roadboy]

hmm.. i jst tried this...blocked off the pcv off on the throttle body, used a kinda loud compressor and it showed psi around...1 to 5 thats what it looked like. cant even hear any leaking...what kind of air compressor do you guys use?

 

[ogre]

If you cant hear leaks put soap and water in a squirt bottle and squirt all couplers and anything you think could leak...

 

[Flateric]

Wait a second unless I totally miss my understanding here there is no point at which the engine will have all the valves sealed up and allow the intake mani to be pressurized. And a valve leak isn't the same as a boost leak either I don't think. I don't think you can boost leak test your intake mani in the test while it is still bolted to the head. It's not possible I don't think.

Would the motor even run if there was a point at which the valves were all sealed completely? And if so then we would be turning the motor to ?? degrees to or from TDC to place the valves here for the boost leak test. Wouldn't this also cause possible valvestem seal issues too?

I may be wrong but this is my understanding of a boost leak test.

isolate the entire IC system from the turbo outlet to the TB and see if pressure is held. check for leaks, correct any, test again.

Intake mani can be tested off engine if all runners are plugged and pcv valve port is sealed up too.

Right?

---------- Post added at 01:09 AM ---------- Previous post was at 01:07 AM ----------

Oh, and I run the test at a little above the peak boost the system will ever see to be sure it will hold the lower PSI without issues. And ya, I use the spray bottle with soapy water to look for smaller leaks shown by bubble generation.