Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum - View Single Post - Boost Leak Test Question

Traininvain · 05-13-2018, 07:56 AM

At my wits end here trying to get my car to run right, hoping Zilvia can help me rule out one possible issue anyway.

- When boost leak testing, when I hook my tester up to the intake of the turbo, I get a steady stream of air coming out of the head/crankcase (ultimately it comes out the T fitting on the valve cover as that connection that goes back to pre-turbo/post-MAF on the intake track is off). Enough air such that it would blow a paper towel away or something, I don't have a way to measure it.

At first I thought this was simply air leaking past the rings into the crank case, but this is a fresh built motor. It has literally 1-1.5% leakdown and compression reads 180-182 on all 4. So then I tried moving my test point -

- If I instead hook my tester up to the hot side piping where it would exit the turbo outlet, the whole system holds air up to 25 psi like theres no tomorrow. Sure it will eventually lose pressure but its super super slow.

So I took the turbo off, put it on the bench, and capped off the outlet. When pressurizing in the inlet . . . that same steady stream of air comes out the oil fittings.

Is this normal? Should it leak any air at all? It sort of seems to me that it shouldn't leak any at all, as this would disrupt oil flow through the turbo? It's a 2871R.

05-13-2018, 07:56 AM	#1
Traininvain Join Date: Oct 2012 Location: MA Posts: 32 Trader Rating: (2)	Boost Leak Test Question - ? At my wits end here trying to get my car to run right, hoping Zilvia can help me rule out one possible issue anyway. - When boost leak testing, when I hook my tester up to the intake of the turbo, I get a steady stream of air coming out of the head/crankcase (ultimately it comes out the T fitting on the valve cover as that connection that goes back to pre-turbo/post-MAF on the intake track is off). Enough air such that it would blow a paper towel away or something, I don't have a way to measure it. At first I thought this was simply air leaking past the rings into the crank case, but this is a fresh built motor. It has literally 1-1.5% leakdown and compression reads 180-182 on all 4. So then I tried moving my test point - - If I instead hook my tester up to the hot side piping where it would exit the turbo outlet, the whole system holds air up to 25 psi like theres no tomorrow. Sure it will eventually lose pressure but its super super slow. So I took the turbo off, put it on the bench, and capped off the outlet. When pressurizing in the inlet . . . that same steady stream of air comes out the oil fittings. Is this normal? Should it leak any air at all? It sort of seems to me that it shouldn't leak any at all, as this would disrupt oil flow through the turbo? It's a 2871R.