Metalic Screeching Sound When Engine Running

[EdmundasD]

Hello folks!

Did some research but was unable to find any forum post/video that resembles the issue I'm having, thus posting this for some guidance but also record keeping.

Vehicle: 2009 M35x w/ 5AT

Issue: So the engine of the vehicle was removed for some non-invasive maintenance work and then put back in. Currently, when the car runs, it is making a horrible metalic screeching sound.

Notes:

• The sound appears to be coming from under the car, in the torque converter area.

• Both front CV axles and the drive shaft are disconnected, as well as the accessories belt removed, and the issue persists whether in Park, Neutral, or Reverse.

• Mating the engine block with the transmission was effortless without the need to force the bolts to mate the two together. Also, the torque converter bolted up to the flex plate just fine.

• The torque converter (TC) was removed at one point. I noticed the gear inside of it had a little bit of play. Not sure if that is expected or not. When the TC was installed, I ensured it was seated all the way in the back and spun freely.

• When turning the engine by hand, there are no sounds of any scraping at all.

• The last time I tried running the engine, I ran it a little bit longer than usual (I'd say about about 30 seconds) and I noticed the RPMs dropping, as if the car was going to die. Turned it off then. It kinda hurts letting it run like this without knowing where the issue is coming from.

Video: Here is the link to the video. It's uploaded to Dropbox: https://www.dropbox.com/scl/fi/9zrihjps ... 4&e=1&dl=0
FYI, the smoke is coming from a hole in the catalytic converter.

Thoughts: So I recently purchased the car so it didn't run before the engine was pulled, thus I am not certain as to whether the transmission is in good shape. However, to me it sounds like the torque converter is rubbing against the housing. Maybe that gear play is not supposed to be there? Also, I did not check the shaft coming from the transmission...maybe it's bent or broken?

Appreciate any and all thoughts and guidance. Will likely pull the engine again, bit will be in a few weeks (from today).

[VStar650CL]

The computer I'm on right now won't run the vid, I'll look at it later. However, the TC is bolted to the flexplate and can't possibly go anywhere or rub on anything if the flexplate is intact. The stator, sprag clutch, and turbine are splined and the former float when the TC is disconnected from the trans, so what seems like "slop" in those is normal. So your noise could be the result of a cracked flexplate or something broken inside the TC, but probably not from anything loose. Get a mechanic's stethoscope for $8 and at least you can narrow down exactly where the screech is coming from.
https://www.harborfreight.com/mechanics ... 63691.html

[VStar650CL]

After listening to the vid, that definitely sounds like metal on metal. On VQ's there's supposed to be a pilot bushing for the TC in the end of the crankshaft, is it there? If not, the TC may be bolted up off-center.

[EdmundasD]

Thanks for your response. Since the engine is in the car, I can only be almost certain that the pilot bushing is in there. I distinctly remember seeing it when trying to line everything up. I agree, it would be odd for the TC to be off center if all of the torque converter bolts threaded in as expected. Maybe the flex plate is slightly bent? The clearances there are very tiny, though looking through the torque converter bolt access hole, I do not see any wear on the flex plate or metal sprinkles.

I began taking things apart again but unfortunately won't get to separating the engine from the transmission for a few weeks. But as soon as I do, will report back with observations/findings/pictures.

[EdmundasD]

Was finally able to continue the investigation and happy to report that the issue appears to be resolved.

Culprit: Flex plate.

Investigation: First, I looked at the starter. Noticed the end of the gear was a bit worn but didn't seem damaged. Assumed it was normal wear and tear. Next, I took off the flex plate. I had another one from the same engine and put one on top of the other. I tried to line up the teeth of the gears perfectly and noticed tiny play when pushing the top flex plate at various angles (hope my description paints a clear picture in your head ). So I used the other flex plate, put the engine back in the car, and it runs fine now.

Bizarre issue but not at all surprising given how tiny some of the clearances are when stuff is put together. Thanks for you suggestions VStar650CL.

[VStar650CL]

Glad to help. Happy motoring!

[Datniqqamycole]

Hope it's okay to keep running off this post. I swear I was having the same issues. When my car was even just idling I had a nasty sounding grinding noise or something as to yours. So I had no choice to use the car the other week for work. With my foot all the way down it was only going 25-30mph. I barely made it up a hill. At lunch break as I was driving I was going Neautral to Drive.. N to D. N to D. I pulled up to get my food and sort of heard a clunk.. now it's driving good. I can't believe it. It's back from the dead and I'm in love all over again. Do you think it is the same issue? This is the 2nd trans I put in. The last one and this one did come dismantle yard though. I'm willing to dump all my checks little at a time into this M45. I'm trying to upgrade it. Someone posted on a thread i posted awhile ago but don't know exactly how to go about or to what shops to go to.