Egr solenoid motor hissing at shutoff

[87xjmike]

So my 93 hisses and has a leaky sounding egr solenoid motor (located at driver side intake manifold). I took the solenoid off and cleaned it out with carb cleaner, but the hissing persist for about 8 seconds only right at engine shutoff. Runs great otherwise. Sounds and feels like it's coming from the cap of the unit. Should I swap it out? Anything else that would cause this?
I also sprayed out my charcoal canister with some carb cleaner, and replaced my egr valve.

 

[Wolfie_85]

I would replace it if you're positive it's not some other vacuum related issue. All those vacuum lines are right around that area. So before you replace it, examine the vacuum lines carefully. Not saying you're wrong, just saying don't spend until you know what to spend on.

 

[MrShorty]

Are you sure this is a sign of a fault? I ask because I recall this same issue on my BII. Researched the issue and discovered that the EGR solenoid was designed to have a small vacuum leak through it -- the vacuum leak was an integral part of its normal operation. If the later 4.0 EGR solenoid is of similar design to my earlier 2.9 EGR solenoid, this vacuum leak may be normal.

Can anyone with a better knowledge of the newer EGR systems verify this?

 

[malohnes]

If it's original, that'd be a sign to replace, but in and of itself perhaps not. Verify other sources of vacuum leaks first.

I have understood you don't ever do anything to vapor canister, contrary to popular belief. Replace it routinely and be done.

 

[87xjmike]

Did a new egr solenoid motor and the damn leaky hiss persist. I can not figure out where this is coming from. I think I have to try replacing the canister box next. Or do a smoke test.

 

[natenkiki2004]

The only place to hold vacuum after the engine is shut off is the brake booster. Very simple to test, when you hear the hissing, pump the brake pedal. If the hissing goes away quicker then your booster is leaking. You can also test once the hissing stops, the pedal should get a lot firmer after 3 or so pumps. If it's firm on the first pump then your booster has lost all vacuum in the hiss.

Mine leaked but it was due to the grommet at the one-way valve, it was cracked:
https://dl.dropboxusercontent.com/u/464376/vehicles/1991 Explorer/Pictures/IMG_20131114_125741.jpg

New grommet and valve are cheap, NAPA part UP 89000.


*EDIT*
I take that back, there is another place that holds vacuum, the reservoir on top of the blower box. But that's on the other side of the engine, probably not your problem.

My point was, the intake manifold doesn't hold vacuum if the engine isn't running. Thus, none of the vacuum lines will either, unless they have a one-way valve. Thus, your hissing should only come from the brake booster or vacuum reservoir.