Toyota MR2 Message Board - View Single Post - 3S-GTE USDM Turbo Engine Find Intake Leaks!!

jholder · 07-05-2009, 04:32 PM

wierdness. So I bought vacuum gauge the other day to see what exactly my vacuum was like when it was stalling. Just to be easy, I tried to T into the line that runs from the throttle body to valve cover. I thought I had screwed things up because I was showing 0 vacuum (with the car running of course). none at all. After i unhooked it and tried the mouth test, and then reconnected it and tried pinching off the lower piece of the tubing, I realized that even though the TB was sucking air, i couldnt make a vacuum while allowing it to pull air in from beyond the valve cover's hose. I could pinch off the line going to the valve cover, and I would see it shoot up. (Though only still to 13 in hg, unless it was revved up.)

I recently replaced the valve cover gaskets (then I pulled the VC again for powdercoat) so I've had it on and off a few times (though I've had this problem long before i changed anything).

I also tried blocking off the PCV hose while i had the gauge hooked up. That didn't seem to make any difference though. (i.e. block the pcv hose, left the tb->vc hose unclamped, and saw no increase in vacuum.

*sigh*

Is the valvecover _supposed_ to have, or be able to make a vaccum? I have a feeling it's not

Anyway, I moved the T over to the line running to the stock boost gauge. I couldn't get an even reading no matter how hard I tried. At first it seemed ok as I rev'ed the engine, but as I let it sit there at 1000rpm, it just kept dropping and bouncing between 10-13 in hg. If I let go of the throttle, it would immediately dip to ~500 rpm and around 6ish in hg. before stalling out.

I'm serioously thinking the worlds biggest vacuum leak, but I'm just not finding it. Would a leak in teh pre-turbo intake track cause something like this?

On a side note: Someone smarter than me can probably figure this out. There must be some way of isolating the leaking area. For instance, if you had two clamps, you could plug hose X1 and C2, and find out if part Z was leaking. (basically, there must be an order of plugging hoses that would help you locate the source of a leak.

I love wikipedia. Let me answer my own question. the pcv system basically pulls fresh air from the pre-turbo intake tract, and pulls it into he throttle body to be recombusted. IT would make perfect since that this would never present a "real" vacuum. Well damn. The leak is somewhere else.

07-05-2009, 04:32 PM	#37 (permalink)
jholder I put the ho in 'hosale Join Date: Nov 2007 Location: Huntsville, AL Posts: 468 Thanks: 8 Thanked 16 Times in 12 Posts iTrader Rating: (4/100% )	wierdness. So I bought vacuum gauge the other day to see what exactly my vacuum was like when it was stalling. Just to be easy, I tried to T into the line that runs from the throttle body to valve cover. I thought I had screwed things up because I was showing 0 vacuum (with the car running of course). none at all. After i unhooked it and tried the mouth test, and then reconnected it and tried pinching off the lower piece of the tubing, I realized that even though the TB was sucking air, i couldnt make a vacuum while allowing it to pull air in from beyond the valve cover's hose. I could pinch off the line going to the valve cover, and I would see it shoot up. (Though only still to 13 in hg, unless it was revved up.) I recently replaced the valve cover gaskets (then I pulled the VC again for powdercoat) so I've had it on and off a few times (though I've had this problem long before i changed anything). I also tried blocking off the PCV hose while i had the gauge hooked up. That didn't seem to make any difference though. (i.e. block the pcv hose, left the tb->vc hose unclamped, and saw no increase in vacuum. sigh Is the valvecover _supposed_ to have, or be able to make a vaccum? I have a feeling it's not Anyway, I moved the T over to the line running to the stock boost gauge. I couldn't get an even reading no matter how hard I tried. At first it seemed ok as I rev'ed the engine, but as I let it sit there at 1000rpm, it just kept dropping and bouncing between 10-13 in hg. If I let go of the throttle, it would immediately dip to ~500 rpm and around 6ish in hg. before stalling out. I'm serioously thinking the worlds biggest vacuum leak, but I'm just not finding it. Would a leak in teh pre-turbo intake track cause something like this? On a side note: Someone smarter than me can probably figure this out. There must be some way of isolating the leaking area. For instance, if you had two clamps, you could plug hose X1 and C2, and find out if part Z was leaking. (basically, there must be an order of plugging hoses that would help you locate the source of a leak. I love wikipedia. Let me answer my own question. the pcv system basically pulls fresh air from the pre-turbo intake tract, and pulls it into he throttle body to be recombusted. IT would make perfect since that this would never present a "real" vacuum. Well damn. The leak is somewhere else. Last edited by jholder; 07-05-2009 at 05:04 PM..