98 GS whistles

My 98 GS (130K miles) is whistling loudly from under the hood. I removed the belts and started the engine, and the whistle remains. I then removed the oil fill cap and the whistle stopped. With the oil fill cap off, I put my hand over the fill hole and it is drawing a vacuum.

My daughters fiance said that sounds like a head gasket.

What do you think?

Thanks, Dave

I've heard of similar problems including feeling vacuum pushing out the oil filler cap. Do you have any driveability problems, overheating, misfires, SES light, oil in coolant, coolant in engine oil?

Also, when was the last time the PCV valve was changed?

I have none of those problems. I "tuned it up" last August including the PCV valve. It only started whistling a few weeks ago.

I have none of those problems. I "tuned it up" last August including the PCV valve. It only started whistling a few weeks ago.

Without any symptoms of a blown head gasket or supercharger/lower intake manifold gaskets/seals it is hard to say. Sounds like it would be related to crankcase ventilation. Have you tried running a vacuum test with an automotive vaccum gauge ( 0 - 30hg)? Engine vacuum should be nothing less than 15 inches but normally much higher around 20 inches hg.

I've seen those aftermarket breathers with filters that you install in place of the oil filler which may or may not help. How about the o-ring seals on the filler neck and the oil cap.