kpatz

Back in April I got a CEL with a code P0456 - EVAP system small leak detected (see link for original thread). Back then I replaced the N80 purge valve and the problem went away for a few months. Now it's back.

Here's what I've tried so far:

1. Tightened hose clamps in area of purge valve
2. Retightened gas cap (this made problem go away but then it would come back), so I bought a new gas cap.
3. Replaced Y hose to right of purge valve (had to make one out of vac lines and a tee), as one end was starting to fall apart.

None of these have helped. Could my purge valve have gone bad again? Last time I was messing with it I plugged the line on the passenger side of the purge valve and the leak test passed. But it would also pass after reseating the gas cap.

I haven't had a chance to mess with it yet today (CEL went on this morning), but I'm just wondering if these valves have a high failure rate, or if I should be looking elsewhere...

Thanks...<ul><li><a href="https://forums.audiworld.com/a4gen2/msgs/1038932.phtml">Old EVAP Leak Thread</a></li></ul>

x1rider

maybe a problem with the evap canister. I had a CEL a few years ago that was evap related (before I had a Vag-Com, the work was done at the dealership) and it turned out to be a problem with the evap canister and leak detection pump. Might be worth checking out.

JBSMOOTH

Check you lines and your gas cap... I would say if you have an original gas cap, replacing it may be a cheap way to start troubleshooting.

1heartaudiworld

If any black stuff comes out you have a bad charcol canister and it may have clogged up your new valve.

kpatz

I pulled the purge valve and blew through it while cycling it in output tests, and it is working fine.

I then hooked everything back up, ran leak test, failed. I then pulled the hose on the canister side of the valve, plugged, tested, failed. Pulled the hose on the other side of the valve, checked the check valve, plugged, tested, failed. Pulled the vacuum line, plugged, tested, passed! Reattached vacuum line, tested, passed. Cleared codes (to get rid of pesky CEL), tested again, still passed. Maybe that vacuum line needed to be reseated. Time will tell if it comes back again.

kpatz

I've quintuple-checked everything in the area of the purge valve now. Guess I should dig into the rear end of the car next.

Any tips for tracking down these pesky leaks?

1heartaudiworld

was the pump changed.. possible it got pinched..

kpatz

Update - CEL came on again today, so I did some digging in the rear end of the car this time. Checked the charcoal canister and leak detection pump and hose connections. About the only thing I noticed is the way the hoses connect on the bottom of the canister, they aren't very tight leak-proof type fittings. I ran some leak tests and they failed, until I pulled the small hose off the canister and plugged it as well as the hole in the canister, and then the leak test passed. So I put it back on and then put a bunch of silicone sealant on it.

Time will tell if that fixes it or not, as the problem is intermittent. I can go several days without so much as a code thrown, then 2 days later, CEL comes on.

JBSMOOTH

Did you change your gas cap?

kpatz

Yes, a few weeks ago.