Noise from engine 1997 Tahoe 5.7

[BobG999999]

I'm very afraid of what this sound is ...

Is there a way to attach a sound file?

It started out as a "random" noise, sort of a clunk, and then it was only on slowing down after revving. Within 15 minutes, it became an all the time noise. Seems loudest at the right rear of the engine, but you can also hear it very clearly in the left front wheel well. Varies with RPM, and doesn't appear to be the fan. Just changed oil about 2 weeks ago, and oil level is good.

Not sure what else to say. I'll try to zip the sound file and see if that can attach.

Thanks in advance.

 

[bsamole]

I know you said it doesn't appear to be the fan. To me it sounds like the fan blade is hitting something since it varies with rpm and it has a hollow reverberating sound not a hard knock.

 

[BobG999999]

That's what my brother thought as well. A little too "clangy". I'll go double check and see. The fan appears to be spinning freely, and I don't see anything. It also appears to be louder towards the rear of the engine, though that can obviously be deceiving in the engine bay.

 

[OR VietVet]

I have not heard it but the description could mean a starter drive tapping the flexplate teeth. Or, cracked flex plate. Or, exhaust shield.

Cannot open the noise file.

Finally opened the noise file: Still sounds like coming from the rear flex plate area. Not the starter drive teeth.

 

[BobG999999]

I have not heard it but the description could mean a starter drive tapping the flexplate teeth. Or, cracked flex plate. Or, exhaust shield.

Cannot open the noise file.

Finally opened the noise file: Still sounds like coming from the rear flex plate area. Not the starter drive teeth.

That's also what my brother thought. Any quick way to detemine that?

 

[OR VietVet]

That's also what my brother thought. Any quick way to detemine that?

It always helps to FIRST, have a Mechanic's Stethoscope and then remove the inspection cover at bottom front of the transmission and get a flashlight and watch in there with the engine at idle. Before removing the cover, get some time with the stethoscope and listen all over the engine for the source area. Noise can travel. But, it sure sounds like something in the flex plate area.

in a pinch, you can use a long screwdriver and put the point at the supposed noise source area and put an ear against the handle end and that can help pinpoint noises but the stethoscope really pins it down.

 

[BobG999999]

It always helps to FIRST, have a Mechanic's Stethoscope and then remove the inspection cover at bottom front of the transmission and get a flashlight and watch in there with the engine at idle. Before removing the cover, get some time with the stethoscope and listen all over the engine for the source area. Noise can travel. But, it sure sounds like something in the flex plate area.

in a pinch, you can use a long screwdriver and put the point at the supposed noise source area and put an ear against the handle end and that can help pinpoint noises but the stethoscope really pins it down.

Thanks for the additional info. I have QuickJacks, so that will make it easier to check things out.

 

[OR VietVet]

At 71 years old, I don't have an efffin' clue what QuickJacks is, but whatever works. Don't forget the flashlight to sight check with. Surprised you right. Thought I was gonna say start a fire for light, huh.

 

[West 1]

I had a flex plate crack, had the odd noise at the rear of the engine. Tranny has to be slid back to change it, nothing fun about that job if that is it.

 

[OR VietVet]

I had a flex plate crack, had the odd noise at the rear of the engine. Tranny has to be slid back to change it, nothing fun about that job if that is it.

You can change it without moving transmission. It's tight but can be done. Check some videos. The torque converter has to be unbolted from flex plate and pushed back into transmission bell housing while turning clockwise. Then reach in and unbolt flex plate from crank.

 

[BobG999999]

At 71 years old, I don't have an efffin' clue what QuickJacks is, but whatever works. Don't forget the flashlight to sight check with. Surprised you right. Thought I was gonna say start a fire for light, huh.

I was wondering how to get the fire light in that tight space ... . QuickJacks are a pair of hydraulic lifts that are movable and give about 27" of lift. Little cheaper than a two post lift and take up less room.

 

[OR VietVet]

I was wondering how to get the fire light in that tight space ... . QuickJacks are a pair of hydraulic lifts that are movable and give about 27" of lift. Little cheaper than a two post lift and take up less room.

I thought you were going to say that the "Jacks" part was something like "ear jacks" or ear buds and works thru the cell phone. Hell, I am 6'4" tall and weigh 285 and I can crawl under and listen with a stethoscope, without lifting.

 

[West 1]

You can change it without moving transmission. It's tight but can be done. Check some videos. The torque converter has to be unbolted from flex plate and pushed back into transmission bell housing while turning clockwise. Then reach in and unbolt flex plate from crank.

That would save a ton of work.

 

[BobG999999]

Well, it turned out to be loose bolts. Finally got the inspection port off, turned the engine and found one bolt was finger tight and another (out of three) was out about 1/4 inch. Removed them one at a time and replaced with some loctite.

Of course, to get it down, we had to drop the exhaust, which required disconnecting at the flange just before the muffler. Of course, the three studs were rusted and all three broke. Now I have to figure out how to get that back together. Why couldn't the geniuses at GM have routed that exhaust 3 inches to the rear?

Any thoughts?

 

[OR VietVet]

If they broke on the manifold side, correct? Either replace a manifold or drill through and use through bolts, washers and nuts.