strange noise

[da_raabi]

Oil pressure could be a failing sender? Do you have EGR or anything like that? Is the air pump still hooked up to the exhaust manifolds? The old air pipes could be leaking down around the manifolds maybe?

 

[MrMarty51]

Use a propane torch, one of the torches that a propane bottle screws onto.
If the nozzle on the end of the torch will unscrew off, then unscrew that nozzle.
Pull the egr valve and adapt some hoses from the dipstick tube to the propane torch, with the torch hooked to the dipstick tube, turn the torch on.
See if the idle changes, if the idle changes, You Mine friend, has a intake manifold gasket that is leaking on the inside of the enjun That could be causing the squeal noise.

 

[MrMarty51]

Get a mechanical oil pressure gauge hooked to the engine so You will know that it is or is not the gauge in the dash causing the oil pressure drop or if it actually the oil pump going bad, which could also make a squealing noise.
My 93 GMC, 350 V8, dropped about 15 PSI on the dash gauge, I dropped the pan, replaced the oil pump and now the oil pressure is back where it used to be, about 50 PSI cold and about 40 hot.
I think I should drop the pan and install a set of .001 under size bearings though as I think the bearings is getting quite worn too, with 251,000 miles in the engine and have not had a head off yet.
I did have to replace the leaking intake manifold gasket once though, it too was making a very slight squeal and was also leaking prestone on the front corners of the intake gaskets.

 

[87sierra]

I plan on buy a oil pressure gauge and testing it that way also the truck has 144k how hard is it to drop the oil pan in a 2wd truck