First off, long time listener, first time caller:

1998 Cherokee Classic 4.0L 4x4 bone stock 141k

I have this tapping that is behind the dash on the passenger side that has been driving me nuts. It is only audible when the engine is started and idling and is much harder to hear when the HVAC fan is blowing. What I have not had is any spare time to even look into what it might be. Today at lunch, I was able to steal a few minutes and go out and mess with it a little to see if I could figure out what it might be. During all of this time, I have gone through all of the doomsday scenarios and thought about all of the awful things that it might be and today found what I think is causing the noise. What I don't know, is exactly what it is.

I have attached a picture of the part. There is a rubber mount that I suspect is to insulate the part from the firewall. When I remove the part from that mount and just hold it, a co-worker says that he is no longer able to hear the noise inside the cabin with the doors closed. As soon as I reconnect it, he can hear it again. I can feel a clicking or tapping inside the device that matches the noise that I heard. It was dumb luck that I put my hand on this thing to look past it and chack something else, or I would have never felt the clicking in it.



At any rate, I would appreciate any input or experiences that any of you may have had with this part.

Thanks

 

 

That's not a heater control valve, thats part of the evaporative emissions system, its a purge valve I believe. Remove it and have fun staring at a constant CEL!

 

Edited. Don't mind me

 

vapor canister purge valve appears to be the winner

I see that the part is $25-29 at rockauto.com. What I don't know is whether this part tends to tap/click by design and that noise is just something I should get used to or if it is a sign that it is about to die. I don't want to throw new parts at it if it is behaving as it should.

 

I would say that it isn't normal. Mine definitely does not do that. I would try replacing it and see if a difference is made

 

My 99 does that too, been meaning to take a pic and post it up...thanks, subscribed!

I don't notice it from incab, but i can clearly hear it with the hood open. Unplug the connector, idle remains the same, clicking goes away, no CEL (disconnected for only a few seconds...but thats enough to trip CEL with coolant temp swityhc on tstat hsg).

At least I know what the part is now.

 

It IS normal for it to tick. Means it's working and doing its job.
If it's not normal then all 6 XJs I've had have the same broken part but ran forever lol.
Leave it alone.
Spen your money on a new air filter or plugs.

In fact, go out to ANY pre 01 (probably later models too, but never had one) Jeep TJ LJ YJ XJ MJ and when they're running hold a finger on that part. You'll feel it ticking at idle on all of them. Some are just noisier than others. I'd be more concerned if it didn't tick anymore lol.

Ironically , many new Jeepers have misinterpreted that tick for a lifter at start up only to be pleasantly surprised when they, like me, found the evap purge solenoid to just be doing its job.

 

Amen to that ... I definitely was thinking that I had some larger underlying issue, but feel some relief that this was the noise. Well, at least THAT noise. I can cross that one off the list ... now, on to the other 15 noises that it makes.

 

Dayum! U only have 15 noises to go.....what did u do with the other 25 or 30? LOL

 

Some don't tick loud enough to actually hear them from inside the cabin. I have a 98, and my purge valve isn't audible.

If I recall, it's mounted into a rubber bushing type thing. I think mine is square in shape. It could just be this part needs to be replaced. It may be vibrating too violently, and that's what your might be hearing more so than the actual ticking noise.

 

Those were my thoughts. Thank you for formulating them into words

 

No problem.

I only recently became familiar with these purge valves due to a evap leak. It wasn't my purge valve... Though I poked around it well enough to know.

 

Just a little contact can "radio" the noise to the cab. noise. If the pad, mount is bad. Kind of neat when somebody showed me if you touch the base of a tuning fork on your tooth you can hear it just fine. (Handy if the band is loud).