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Hissing cylinder!

Carlosfandang0

Carlosfandang0

Autocross Newbie
Hi, What would cause a hissing noise (think small nail in tyre) in cylinder #4 only? It can be heard with the plug removed but also a little with the plug still in place, my guess is crank pressure entering past the piston rings/oil ring, I have had a bit of oil fouling on the plug in this cylinder which was the reason I had a new head fitted but it’s back again (the noise is new though), it makes the noise for about 5-10 minutes after switching off the engine, any thoughts?? Thanks.


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M

Mk6 Steve

Ready to race!
Auxiliary coolant pump??
 
Carlosfandang0

Carlosfandang0

Autocross Newbie
Mk6 Steve said:
Auxiliary coolant pump??
Click to expand...



Don’t think it would be that as the sound is (I’m 99% sure) emanating from the spark plug hole! It’s a Sort of Psst Pssst Psssssss Pssst Psss Psssss Psssst noise if that’s at all understandable? With other longer hissing in between.


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jettaglis

jettaglis

Go Kart Champion
Carlosfandango said:
Don’t think it would be that as the sound is (I’m 99% sure) emanating from the spark plug hole! It’s a Sort of Psst Pssst Psssssss Pssst Psss Psssss Psssst noise if that’s at all understandable? With other longer hissing in between.


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Click to expand...

Pcv valve- the little hole on the right side when looking at it. Try placing your finger over the little hole to see if any change. If so, just replace the pcv.
 
B

BudgetPhoenix

Autocross Champion
jettaglis said:
Pcv valve- the little hole on the right side when looking at it. Try placing your finger over the little hole to see if any change. If so, just replace the pcv.
Click to expand...

It's a noise he can hear coming out of the cylinder with the engine off and the spark plug removed
 
jettaglis

jettaglis

Go Kart Champion
BudgetPhoenix said:
It's a noise he can hear coming out of the cylinder with the engine off and the spark plug removed
Click to expand...

Yea, that's exactly what I'm talking about too. The crank case pressure will
still try to escape, possibly past the rings out the top (spark plug hole) or through the pcv valve (if stuck).
 
B

BudgetPhoenix

Autocross Champion
jettaglis said:
Yea, that's exactly what I'm talking about too. The crank case pressure will
still try to escape, possibly past the rings out the top (spark plug hole) or through the pcv valve (if stuck).
Click to expand...

Good point thanks for the info makes sense. I just remembered diagnosing bad PCV on my car when it was running and I could feel it sucking a ton of air through the pin hole to the right of the diaphragm cap.
 
Carlosfandang0

Carlosfandang0

Autocross Newbie
I checked the PCV myself recently and all seems good, I had an oil change today and they also checked the PCV and said it’s good, the noise I’m hearing is only coming from cylinder #4, the other three don’t do it, using google I can’t find any info on an issue like this! Presumably it’s crank pressure passing the rings? But as stated by one of you guys earlier the PCV should control the pressure, could it be the injector maybe??? Removing the oil filler or coolant cap doesn’t alter or stop the noise either?????


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