Boost leak test results

[GSLENK]

Are there any spots that "should" be leaking? I can bring the intake track after the turbo inlet to about 20psi, which pretty much maxes out my air compressor flow (tire inflator attachment). I hear one leak around just above 20 psi comming from the intake tube (all factory here) i guess that is the BOV letting air recirc? then i hear a little leak near the throttle body. Its not the vaccuum hoses on top, i sprayed them with soap water. doesnt seem to be the gasket either.

My understanding was.... that some air will leak past:
-the throttle butterfly plate
-valves depending on crak position
-BOV (at around 22psi)

All other connections seem to be airtight.
there is some rubber dryrot, but no leaks on the turbo->smic->intake "rubber tubing"

can anyone confirm what are acceptabel leaks? while i get a hose and listen closely...

thanks

So to confirm everything: (using soapwater/stethescope)
Bov leaks past ~21 psi
crankcase leaks out of the breather line (when i plug the breather nipple, it builds pressure till i let go.

I think the throttle body is leaking, the source seems to be the spring (winding metal spring) that rotates when the throttle is opened/closed.

any fixes? or is that normal?

I have reason to believe most these noises are normal and i dont have a real boost leak. the whole system leaksdown in about 45 seconds completely. pressure is lost pretty uniformly until the last few psi which slowly bleeds off.

 

[99gst_racer]

I think the throttle body is leaking, the source seems to be the spring (winding metal spring) that rotates when the throttle is opened/closed.

any fixes? or is that normal?

That's leaky shaft seals. Time for a throttle body rebuild.

 

[g4ebguy90]

+1 on the throttle body rebuild. Mine did the same thing, but I didn't notice till after my turbo failed, probaly from working so hard to make boost...

 

[GSLENK]

yeah i did some more searching after the no response... probably didnt need to ask this question...

Ill see if thats the end of my boost leaks.

But to clarify, it is ok for the pressure to leak down through the engine and out the exhaust and valve cover nipps (nipples )?

 

[Calan]

But to clarify, it is ok for the pressure to leak down through the engine and out the exhaust and valve cover nipps (nipples )?

It's normal to get some leakage past the valves and rings on an old stock motor, and even on a tight new one depending on the cams and overlap. It should get better with the motor warm.

If you want some peace of mind, do a leak-down test on it to check for any leakage in the valves, rings, and head gasket.

 

[Boostinsideways]

Yeah air leaking from around the TPS, or Throttle Return Springs is an indicator of worn shaft seals.

I have a hellllllllllllllllllooooooffffaaaa leak around my tps. I am suprized I was seaing any boost to the manifold with a leak so big. Shaft seals should be here tomorrow Can't wait.

 

[sugarfree]

easiest way for me to tell when i blt'd mine was turning the throttle plate while pressured up, you will actually hear the leak get worse/stop the idle screw o ring is a common culprit as well but the easiest imo because you can just fill the hole with soapy water and watch the bubbles foam!

 

[XiKeiyaZI]

From my personal experience, with valves, not all of the valves will fully seat/seal at the same time as.. some may not know, all cylinders do not fire at the same time. If you remove a head and turn the cams, you will see, normally, 1 cylinder completely seal, and the rest either just partially open/close but not sealed, or wide open.

Verified on 4 heads so far - all 4 couldn't be bad, could they? (crickets)

 

[GSLENK]

I did rotate the throttle and the noise changed so i know for sure its at least seals. I never looked for the BISS, What are the odds that that is leaking too? is that an easier fix or am i gonna have to scour the internets to find it?

 

[Archer Fabrications]

good information, i think its time for me to rebuild my TB also.. damn that spring

 

[GSLENK]

the spring itself shouldnt be too bad. use chalk/sharpie/whiteout to get a line across it while it is installed. that way you know you are back to where you started for sure when you install it and all the marks line back up. no guessing.