Head Gasket Possibly??

[Sparky1]

I purchased a Husqvarna 2548 garden tractor approximately 18 years ago (got 230 hours on it already)! LOL. The tractor is equipped with a Kohler CV730S motor. In the past few days I have noticed a hissing sound when shutting it down. Happens most times but not all the time. The noise is almost exactly like an unloader on an air compressor; just much shorter in duration.

I do not have a leak down tester but did do a compression test this morning. Both cylinders read exactly 115 PSI. That confuses me cause I assumed the motor one bad head gasket.

I's sure this occurrence has been discussed to no end but would appreciate any current views.

 

[Bertrrr]

Never heard of a Head gasket leak sounding like a hiss, if it's leaking you will get a blowby from the combustion chamber and your machine will not run good or even at all. Can't imagine what is hissing

 

[Rivets]

I would definitely be looking for a bad head gasket. See this many times in the past.

 

[Scrubcadet10]

seen quite a few head gaskets try to make you think there is a snake around! lol, hisss hiss.
Start the mower and get it up to operating temp. shut it down, remove the dipstick, and check any amount of smoke coming from the dipstick tube. that can also be another head gasket symptom.
you may also want to check compression on both cylinders when hot and see if there is a difference between the 2.