View Full Version : boost leak symptoms?

12-12-2004, 06:50 AM
hi guys, i'm having a series of little problems with my swap atm.i thinking it might be a boost leak but i'm not sure.i'm just woundering if all the symptoms sound as though they are related to one another..

The symptoms: running about 1-2psi less boost, car is backfiring/popping between gear changes after WOT and after coasting.After driving it hard and i put my clutch in quickly as i come to a stop at a turn or traffic lights the idle drops REALLY low for one second(400rpm like its about to stall)then it jumps back up to the normal 800-900rpm

my boost guage seems normal. its reading at 19-20in"mg vaccumm at normal op temp.it seems to take longer to get to that reading thou..

After recently changing to a new (smaller more powerful cca)battery i noticed that the old battery had been rubbing on one of my silicon piping for my IC. it has a small cutmark in it (dont know if it goes all the way though...)

thanks in advance guys! Celicatech is sweet :)

12-12-2004, 07:03 AM
I honestly know nothing, but do you have a BOV venting to atomsphere?

12-12-2004, 07:22 AM
car has no type of bov fitted.

ideas?? :wiggle:

12-12-2004, 05:33 PM
sounds like boost leak to me!

anyone here have luck building a proper boost leak tester? i tried to make one, but my local hardware store donst seem to carry any 2.75in piping.

12-13-2004, 07:05 AM
thanks for your help lagos :D So your pretty sure it sounds like a boost leak huh? well today i was driving home with both my windows down and listening carefully to the sound of the engine. it does sound as if it's "hissing" a bit under boost.i'm also going to check the my piping from the AFM to the turbo closely and see if one of the clamps are loose.

Any other opinion please?! thanks guys :)

12-13-2004, 11:46 AM
All of your symptoms definitaly sound like a boost leak to me.

Things to do, tighten all of the clamps before and after the turbo. Look around for visible leaks, as well as listening for audio cues (hissing, abnormal noises) that could tip off a potential leaking point. Another tactic is to spray some carb cleaner around suspected areas, if the leak is where you sprayed it, you will notice your car to stumble, and it will change tone for a second as it burns the carb cleaner.

Another thing you can do is build a leak tester. Just head off to Home Depot, hit up the plumbing section, and you will find all that you need. You will also need a schneider valve (i think thats how its spelled) from a bike tire or equivalant. Just take a PVC endcap, drill a hole in it for the valve, and seal it up with some glue. Source an air compressor, turn the pressure down to around 20-30 psi, and slowly let air into the sytem. You will know pretty quickly where your leaks are.

Your vacuum readings are somewhat abnormal for a boost leak, but that can easily be explained by the engine shifting during actual driving situations. At idle, perhaps the leak seals, as soon as you get some movement, the leak opens up, very possible, and most likely your issue.

Another thing that comes to mind is your Air Flow Meter, you havent messed with it at all have you?


12-13-2004, 05:35 PM
This is going to sound kind of nasty, and mean, but I know to test a boost leak, if you dump some oil into the turbo and then boost it, there will be oil all over where the leak is.

Ive used that to find a leak in my MR2.

12-14-2004, 07:10 AM
thanks for your help guy :D i will be looking for a boost leak. as for the AFM i have played around with it abit. i swapped it over with my spare, and then back again. i also sprayed some contact cleaner on the plug and terminals. i really, rreally hope its not that!!
hopefully its just a boost leak.