Intake problem?

98 K1500 with 350 and I have a loud "chirping" noise which at first I thought was a bad pulley or belt. Checked them and all are good. While running I pulled the dipstick and the noise went away. Put it back in and noise comes back.

I took the oil fill tube cap off and am getting a strong vacuum there. I can only figure that I have a bad intake gasket allowing vacuum into the valve covers.

Anyone have an idea ?

Thanks

Or you have a bad PCV valve.

98 K1500 with 350 and I have a loud "chirping" noise which at first I thought was a bad pulley or belt. Checked them and all are good. While running I pulled the dipstick and the noise went away. Put it back in and noise comes back.

I took the oil fill tube cap off and am getting a strong vacuum there. I can only figure that I have a bad intake gasket allowing vacuum into the valve covers.

Anyone have an idea ?

Thanks

crankcase vent system does create a slight vacuum at idle. this may mean the PCV / crankcase system has a defect. PCV , hoses on pcv/crankcase vent collapsed /plugged etc...

with this PCV GM recommends replacement every 12,ooomiles. no one does that interval ..I replace at around 40,ooomiles. these valves[pcv] wear out ...then they suck too much..or if the engine is not properly maintained fouled with sludge..this then plugs them ...

I would say it is the vent. opening the cap and giving it a supply of incoming air making the valve quiet says so. I would check the vent for a blockage.

Checked the PCV and it was good, had vacuum at the grommet in the valve cover. Decided to pull the intake and found that the intake gasket had slipped allowing the vacuum to pull through the oil return ports into the valve covers. The new Felpro gaskets are bonded to a metal strip which will prevent the gasket from slipping.

Checked the PCV and it was good, had vacuum at the grommet in the valve cover. Decided to pull the intake and found that the intake gasket had slipped allowing the vacuum to pull through the oil return ports into the valve covers. The new Felpro gaskets are bonded to a metal strip which will prevent the gasket from slipping.

did the intake hardware loosen up causing the gasket to move out ?

The bolts were still tight. It looks like the design of the gasket allowed it to "bow" between the front and back bolts. The new gasket has the metal strip which should prevent that bowing effect from happening again. I was surprised when I seen the gasket bowed like that, I would not have thought it could move. I changed the gaskets well over 3 years ago so I don't think they shifted whey reassembling otherwise I would have seen problems sooner than this.
I understand that the V6 Ford engines have a similar problem with the intake gaskets doing the same thing.
Live and learn I guess

The bolts were still tight. It looks like the design of the gasket allowed it to "bow" between the front and back bolts. The new gasket has the metal strip which should prevent that bowing effect from happening again. I was surprised when I seen the gasket bowed like that, I would not have thought it could move. I changed the gaskets well over 3 years ago so I don't think they shifted whey reassembling otherwise I would have seen problems sooner than this.
I understand that the V6 Ford engines have a similar problem with the intake gaskets doing the same thing.
Live and learn I guess

thanks for that info. 3years and it failed again not good. possible the intake is distorted....