Engine Chirp / Squeak When Hot...no One Can Figure Out

swhsah · April 5, 2009

I have a 2002 chevy silverado 2500hd with a 6.0L engine and 220k miles. When the engine is cold at start up All is OK. When the engine reaches operating temperatures I get a engine chirp. The chirp increases in frequency with engine rpm and is no longer audible above 1800 rpm.

I removed the front a/c belt and the main serpentine belt to eliminate them as a source. I then unbolted the torque convertor in addition to isolate the area of the noise. The noise is definately in the engine. To me the noise seems to be coming from the center of the oil pan as is louder when listening from under the truck than from the top of the engine.

I thought of a bad rod bearing but the noise is a definate chirp and not a knock. I then decided to pull the oil pan and inspect the rod bearings anyway. All looked OK, so I installed a new set of rod bearings .001 undersize due to the mileage of the truck. I then filled the crankcase with straight 30W oil and test ran. I had no change and the squeak comes back when hot.

I then had a tech look at it and he was convinced noise was in the valve train with the pushrods being worn into the rocker arms. I installed a new set of rocker arms and pushrods. Again no change. the squeak still comes back when hot.

I am starting to think the cam may have spun a bearing causing the squeak / chirp. I am a Caterillar certified technician and not being able to find this is driving me nuts. Any help would be greatly appriciated.

Thanks

Scott

Alljackedup408 · April 5, 2009

I have a 2002 chevy silverado 2500hd with a 6.0L engine and 220k miles. When the engine is cold at start up All is OK. When the engine reaches operating temperatures I get a engine chirp. The chirp increases in frequency with engine rpm and is no longer audible above 1800 rpm.

I removed the front a/c belt and the main serpentine belt to eliminate them as a source. I then unbolted the torque convertor in addition to isolate the area of the noise. The noise is definately in the engine. To me the noise seems to be coming from the center of the oil pan as is louder when listening from under the truck than from the top of the engine.

I thought of a bad rod bearing but the noise is a definate chirp and not a knock. I then decided to pull the oil pan and inspect the rod bearings anyway. All looked OK, so I installed a new set of rod bearings .001 undersize due to the mileage of the truck. I then filled the crankcase with straight 30W oil and test ran. I had no change and the squeak comes back when hot.

I then had a tech look at it and he was convinced noise was in the valve train with the pushrods being worn into the rocker arms. I installed a new set of rocker arms and pushrods. Again no change. the squeak still comes back when hot.

I am starting to think the cam may have spun a bearing causing the squeak / chirp. I am a Caterillar certified technician and not being able to find this is driving me nuts. Any help would be greatly appriciated.

Thanks

Scott

weird.... piston sleeve damage? not much else is moving.. pistons, rings, camshaft, lifters,... did you check them? basically all thats left lol

L29er · April 5, 2009

i`ve seen a few cracked flywheels sound pretty nasty.... easy to inspect and varify.

swhsah · April 6, 2009

I have not torn the engine down to far to find out as I need the truck to get back an forth to work. The chirp is rpm dependent and has a metalic sheet metal sort of sound. I did check the flywheel when I had the torque converter disconnected. From underneath the truck it sounds like it is toward the center of the oil pad as it is louder when listened to from under the truck. You can see about 70% of the cam with the pan down but to be honest I did not look very hard to see if a cam bearing had walked out. I may just be reserved to drive it untill it quits and buy a bone yard replacement engine as I see them for around $1300 and up. Then I could tear it down and find the source.

Thanks

Scott