Hissing from Oil Dipstick

[MOPARJ]

I have heard some hissing upon shutdown on my 2000 mile 318 with stock internals and a
Comp XE268 cam and lifters. I have cast pistons, moly rings. It runs great, but have heard a two or three second long hiss coming from the dipstick. I opened the hood today, shut the motor down and quickly pulled the stick. Released pressure and the hissing stoped.

Does this sound like a restrictive ventilation system? The pcv is not too old, but I put a different closed tyoe breather on it that I had a hard time blowing air through. Could this be the culprit? i cannot figure out what else it would be.

It does not smoke at all and runs awesome. I have a K&N (very unrestricted) breather that i can use instead if needed.

 

[340mopar]

Is it pressure or a vacuum hiss? I thinking it is a vacuum hiss. Usually pressure pushes the dipstick out, had it happen before.


Chuck

 

[MOPARJ]

Is it pressure or a vacuum hiss? I thinking it is a vacuum hiss. Usually pressure pushes the dipstick out, had it happen before.


Chuck

Its defiantely coming from the dipstick, as I heard it from there upon shutdown and when I pulled the stick out, it released pressure and it stopped hissing. The dipstick is not being pushed out.

You mean vaccuum from a leaky hose? I dont think so, as it runs fine and the hissing stops when pulling the stick.

 

[340mopar]

No, I mean you have vacuum in the crankcase and not pressure. When you pull the dipstick you relieve the vacuum. The crankcase can have vacuum if the pcv is working and the breather on the opposite valve cover is plugged.


Chuck

 

[MOPARJ]

No, I mean you have vacuum in the crankcase and not pressure. When you pull the dipstick you relieve the vacuum. The crankcase can have vacuum if the pcv is working and the breather on the opposite valve cover is plugged.


Chuck

Got it...it has to be one of the two. I will check them out and see. Nothing major I am sure. Runs too damn good.

 

[340mopar]

Vacuum in the crankcase can actually be good. In the racing community we try to put a vacuum in our crankcase on purpose. I have a pan-evac system on my drag car that works off of the headers to "pull" a vacuum in the crankcase. The best systems are belt driven vacuum pumps for this purpose. Rings seal better when there is a vacuum present in the crankcase.

The negative to having a vacuum in the crankcase is it will try to pull dirt and moisture in if the motor is not sealed well or if the vacuum overcomes seals or gaskets.

Chuck

 

[Aquick408]

That is not exactly a bad problem to have. It really just means that your engine is sealed very well. Check your breather and PCV valve, but like stated it is just crankcase vacuum.