Is it normal to hear a hiss while turning the engine during a valve adjustment?

[Noel]

I just completed my first DIY valve adjustment this weekend and was curious about something. I noted a faint hissing sound when I rotated the engine by hand. Is this normal? Do I have air leaking past valves or rings? Should I get a leak down test done? Am I panicking?

BTW, I left the plugs in while adjusting.

Thanks

[cowtown]

It is normal if you do not remove the plugs - and IMO you should leave the plugs in to avoid carbon falling in the valve gaps when adjusting.

[ken_xman]

Sounds like you need a full rebuild and should sell you car as "parts car".
I will pay you $50 and cart your worries away.

......... it should be fine.

[john70t]

It a good panic though. A loud hiss is a sign of good/normal cylinder sealing-so tight the trapped air is under pressure to escape.
There are three sets of rings and all normally have gaps when they are cold. The rings expand so the ends touch when hot, also the piston expands so it fills the cylinder.

It's probably easier, but not necessary, to remove the plugs while turning the crank.

What's important is the crank's at the right location and the gap is correct. Measure twice, cut once. A wire feeler gage is better than a blade because it's not affected by being at an angle, but the job is a back-breaker so I've heard. Get good kneeling/leaning cusion and take your time.

[Tim Polzin]

Originally posted by john70t
A wire feeler gage is better than a blade because it's not affected by being at an angle

John, I've never seen one of these at .004" before. Can you elaborate?

Tim

[Noel]

Thanks guys, I definately feel better.

[ken_xman]

Might be a snake living in the radiator. You should check tonight.

[john70t]

quote: "John, I've never seen one of these at .004" before. Can you elaborate?"
I was speaking hypothetically/ and don't think these are made for the difficult to reach boxer(or any) valve adjustments because they would bend/break too easily.
At least in spark plugs the flat blade can commonly throw off an otherwise perfect drag/feel if it's at an angle, but a round gauge should not.
I've never done a valve adjustment on a Pcar but it seems like an expensive mistake if the adjusting nut is torqued wrong or the vave is too tight(especially).

One trick was after everything was set: try and slip a feeler gauge several thousands over in. It shouldn't go.

[ckissick]

A wire instead of a blade could be more of a problem, since the foot of the thingy attached to the rocker arm swivels. The foot won't be straight, leading to a false reading. Maybe that's why the only alternative is the dial gauge method and not a wire.

Charlie
Montara, CA
1970 911E
1950 VW

[vash]

Originally posted by ken_xman
Might be a snake living in the radiator. You should check tonight.

now you are being plain silly ken! everyone KNOWS snakes dont really hiss. it is just a hollywood trick to emphasize snake phobia. snakes dont have vocal cords! it must be some type of hissing gecko living in the radiator! get your facts straight.

[Noel]

Might be a snake living in the radiator. You should check tonight.

Fortunately, I just changed the coolant and had the radiator flushed, so I KNOW that is not the problem.

[ckissick]

You know, I provide valuable insight into feeler gauges and you guys talk about snakes.

Charlie

[no substitute]

I suspect the car is commenting on your valve adjusting technique.