WTF? Do I have engine trouble? Really? Please set me straight.

[mtocrs1]

Fixing an exhaust leak so i presurized the down pipe with 10psi shop air to find the leak. Got that fixed but now it appears as if I am losing the shop air through the exhaust valves? What am I missing? I have the rocker arms removed and the shop air sounds like it is leaking into the crankcase. I know the valves are not really designed to seal on the backside but 10psi?
Is the next step a leakdown test?

 

[GNVYUS 1]

Before you go pulling the engine

1) Is the TB blade completely shut closed - NO, if it were you're IAC sensor reading would be super high. So air is getting by the TB blade.

2) Are all 12 valves 100% closed = No, if so you'd have bigger problems.

 

[ericttype]

dont forget about vacuum lines pcv will put pressure in crankcase, the throttle plate will still let air by

 

[mikestertwo]

Probably going past the PCV valve.

 

[mtocrs1]

Guys, Sorry I meant to say pressurized the downpipe! My mistake. I will edit the original post. Please re-read it. Might make more sense now. I am pressurizing the exhaust to find an exhaust leak. The shop air on the exhaust side is somehow making its way into the crankcase.

 

[mtocrs1]

Any Ideas?

 

[chevellejoe]

I would check to see if its coming through the valve guides, which is normal to have some air escape. If that’s not the issue and its going into the cylinders, then I would take the plugs out and find out which cylinder it is. At least that would give you a better idea what valve is leaking by.

 

[mtocrs1]

I would check to see if its coming through the valve guides, which is normal to have some air escape. If that’s not the issue and its going into the cylinders, then I would take the plugs out and find out which cylinder it is. At least that would give you a better idea what valve is leaking by.

Good call. I never thought of it leaking past the valve guides. I will check it out. Thanks.

 

[turbofabricator]

A leaking EGR valve is possible, too. Before you get too excited, take a mallet and give all the valve stems a good whack a few times to help unseat any carbon between the valves and seats. If there is alot of miles on the engine, the exhaust valves WILL leak measurably. Do a leak-down test, too.
Pressurize each cylinder to verify which one is leaking.

 

[protracracing]

You could be leaking past the valve itself to.Do a leakdown test on the engine.


Dennis

 

[mtocrs1]

Did you unbolt the rocker shafts?If not I am sure one or two exhaust valves are open.
Your presure could be going past the rings going into crank case.


Dennis

Yes the rocker shafts are removed so, the shop air should not be able to get into the cylinders to leak past the rings. Hopfully I can spend some time investigating further this weekend.

 

[pdzz]

I may be wrong, but, if you're pressurizing the exhaust side, even with the valves closed, it could be going thru the EGR ports in the heads themselves. Might be nothing. Leak down individual cylinders, that'll tell you. Hope this helps. Phil.

 

[mtocrs1]

I may be wrong, but, if you're pressurizing the exhaust side, even with the valves closed, it could be going thru the EGR ports in the heads themselves. Might be nothing. Leak down individual cylinders, that'll tell you. Hope this helps. Phil.

Thanks for the reply. So the EGR gets pulled through the exhaust ports in the heads? All the EGR systems I am familiar with pull from a fitting on the exhaust manifold. My EGR is dissabled in the TT chip. If this is what is happening shouldnt the EGR valve be stopping the flow?

 

[pdzz]

You can leave it, or buy a block off plate. Either way. Phil.

 

[GNVYUS 1]

Not fair, part of my answer now doesn't make sense. :redface:

No worries mate, now just get it all sealed up and run 30psi the other direction.

 

[mtocrs1]

EGR Questions

Finally had time to make it back to the garage today. So I removed the EGR valve. Next I plugged the hole in the intake that the egr valve is sopposed to seal. No pressure should be getting to crankcase right? Wrong, with the egr hole plugged the shop air is still getting into crankcase. My best guess is that the intake manifold gasket is leaking around the EGR port hole (where intake meets head)? Is this really a problem? Should I tear it down further or forget about it?

 

["Reaper"]

I would think that its fine. 10lbs of air is still alot on pressurized system.You are putting air on the back side of the valve so may just be leaking there and filling up all the cylinders with 10lb of air was well.Think of what just 10lb of boost does to your car.Best thing is to check each cylinder separately.

Shaun

 

[bison]

Have you verified it's not leaking past the ex valves? Regardless I've seen engines with bent valves still not lose noticeable power even though leakdown sucked. If it runs ok and you don't plan on a teardow anytime soon I'd leave it alone

 

[TurboBuRick]

The air would have to get past the closed valve before it can enter the egr port.

Like already mentioned, a leak down test would be the way to find out whats going on.

 

[mtocrs1]

Have you verified it's not leaking past the ex valves? Regardless I've seen engines with bent valves still not lose noticeable power even though leakdown sucked. If it runs ok and you don't plan on a teardow anytime soon I'd leave it alone

No I have not done a leakdown yet. I will start by pulling the plugs with the shop air hooked up. Then I will make a trip to harbour freight and buy a cheepie leakdown tester. It runs good but it does seem to have a slight miss cruising real light throttle with converter locked. Could be unrelated.

The air would have to get past the closed valve before it can enter the egr port.

Like already mentioned, a leak down test would be the way to find out whats going on.

Where exactly are the EGR ports on these things? If its before the exhaust valve wouldnt that be in the cumbustion chamber?
Does anyone have a pic of an old head lying around they could snap a pic of to show the EGR ports? I just cant seem to get it straight in my head.