compression issue

Jay_Lude · Post by **Jay_Lude** » Thu Jul 10, 2014 11:21 am

Not sure what to think of this problem or even if it's a compression problem, but when I start the engine it runs perfectly fine

Yet as soon as I switch it off, it makes a hissing noise for about 3 seconds like it's letting pressure out somewhere

Anybody got any ideas?

Post by **Vtecmec** » Thu Jul 10, 2014 12:13 pm

Could be the EVAP cannister or anything similar really, try to pinpoint the source of the sound with your head under the bonnet. Also check for snakes.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Thu Jul 10, 2014 12:15 pm

All of my 4th gens do that. I had no idea what it was but hadn't bothered investigating - charcoal canister is a great suggestion Mec!

Jay_Lude · Post by **Jay_Lude** » Thu Jul 10, 2014 12:26 pm

It's seems to be coming from around the air con valve area, and I know it's dangerous to have an air con fluid leak

Post by **Merlin** » Thu Jul 10, 2014 12:50 pm

It is the EVAP system. My 4th did this but after I ripped out the EVAP system it no longer makes that noise.

Post by **Thebusofwoe** » Thu Jul 10, 2014 1:12 pm

Yea, both my 4th gen and my Aerodeck do that. Its normal

Jay_Lude · Post by **Jay_Lude** » Thu Jul 10, 2014 2:32 pm

I never really noticed it Till the other day haha, no worries then if it's supposed to make that noise

Post by **Vtecmec** » Thu Jul 10, 2014 3:36 pm

I don't think it's supposed to, mine does not anyway.

mercutio · Post by **mercutio** » Sun Jul 13, 2014 9:52 pm

it isn't supposed to do it but many do its possibly a leak from your intake

Post by **Thebusofwoe** » Sun Jul 13, 2014 10:43 pm

I think its a mix of the evap system, and the vac tank for the iab's letting off the vac. Its even louder when you have a open filter. Also vac from the motor idling will be releasing at the same time.