Vacuum leaks with smoke tester - EGR problem

[kas_lar]

Hi everyone,

Sadly, my 1995 5.0 didn’t accept a ported GT40 intake very well. The mechanic who did the work is pretty good, but we never managed to get the engine running right.

The stock intake is now back on the car, and I’m trying to diagnose the problems one step at a time.
So I decided to start with a smoke test.


1. EGR valve
The first and biggest leak I found is the EGR valve. Smoke is coming out around the diaphragm/vent holes.
Video:

Dropbox

www.dropbox.com

Is this a definite sign that the EGR diaphragm has failed?
Would you simply replace the EGR valve, or is there something else I should check first?


2. Vacuum T-fitting behind the intake
The second leak was from the vacuum T-fitting at the back of the intake.
Video from before the fix:

Dropbox

www.dropbox.com

This one seems to have been simple. I pushed the hose firmly back onto the fitting and the leak stopped.
I can replace the hose if needed.


3. Small leak underneath the intake
I can also see a small amount of smoke coming from somewhere underneath the intake.

Dropbox

www.dropbox.com

It’s not a big leak, but obviously smoke shouldn’t be coming from there. I’m thinking the next step is to remove the upper intake and find exactly where it’s escaping.


4. IAC valve
Finally, there is a very small amount of smoke around the IAC valve.

Dropbox

www.dropbox.com

Again, it’s not much, but I’m wondering whether this is normal during a smoke test or if I should replace the IAC gasket.


So at the moment my plan is:

• Replace the leaking EGR valve if the diaphragm is bad
• Replace/check the vacuum hose at the rear T-fitting
• Remove the upper intake and find the leak underneath it
• Check the IAC and gasket

Does that sound like the right approach?
And most importantly: would you consider the amount of smoke coming from the EGR a significant vacuum leak that could affect how the engine runs?


Thanks!

 

[Wmac]

1) A small amount of leakage is normal. A vacuum pump (mityvac) can be used to test the EGR valve. Goggle the procedure.

2) That's excessive. Repair/replace.

3) Find and repair.

4) Try a new gasket.


Curious what the issues were with the Explorer intake. Maybe update that thread?

 

[96blak54]

The manifold gaskets to the head can be a pain. Sometimes you gotta reset the manifold with new gaskets to get it right.

 

[kas_lar]

Thanks guys. A small update after doing some more testing and replacing a few things.


1. EGR
Following Wmac’s suggestion, I did a basic diaphragm test by applying vacuum directly to the EGR vacuum port by mouth.
The diaphragm holds vacuum, the valve visibly moves/opens when vacuum is applied, and it returns when the vacuum is released.
So unless I’m missing something, the diaphragm at least seems to be functioning. I haven’t tested it with a Mityvac yet.
I’ve also replaced both small vacuum hoses related to the EGR.

The EGR will presumably still show some smoke from the diaphragm/vent area when I repeat the smoke test, since I haven’t replaced the valve itself. If the amount of smoke shown in my original video is considered normal and the diaphragm holds vacuum, am I correct in assuming I should just leave the EGR valve alone?


2. Rear vacuum T-fitting
I’ve replaced the vacuum hose at the rear T-fitting as well, rather than just pushing the old hose back on.


3. Leak underneath the intake
I haven’t taken the intake apart yet. I’m going to do another smoke test first now that the obvious hose leaks have been repaired. Hopefully that will make it easier to pinpoint exactly where the remaining smoke is coming from.

I’ll definitely keep the lower intake-to-head gaskets in mind if the smoke still appears to be coming from that area.


4. IAC
I also did an IAC RPM drop test.
With the IAC connected, idle is around 900 RPM. If I disconnect the IAC while the engine is running, it stalls immediately.

I haven’t replaced the IAC gasket yet, so I’ll check it again during the next smoke test.

I also tested the TPS while I was at it:

• Closed throttle: 0.94 V
• WOT: 4.63 V
• Smooth voltage increase throughout the throttle movement with no dead spots

So the TPS seems OK.

I’ve also updated my old GT40/Explorer intake thread with what happened after the intake was installed.

For now I think my next step is another smoke test with the new vacuum hoses installed, before I start taking the intake apart again.