I've been having some trouble with my 5.3L LM7 lately. I removed it from a 2000 Silverado last year, mated it to a T-56, and swapped it into my RX-7. Everything ran fine last year and I put about 30 miles on the car before storing it for the winter. I started it up this year and have been getting an incredibly loud squealing sound once the car warms up. Here's a video of what I'm experiencing:




Here's what I know:

• The sound is only heard when the engine is hot. It begins after the thermostat opens, but before the rad fan kicks in.
• It seems to be coming from the back of the engine bay where the transmission bellhousing meets up with the engine block. I've also noticed a slow oil leak from this same location.
• It goes away temporarily if I blip the throttle and quickly returns as the engine settles down to idle again. It also goes away at very low RPM.

Has anyone heard something like this before? Exhaust? Engine seal? Help!

 

Exhaust leak maybe?

 

big vacuum leak

 

You think an exhaust leak could be that loud and that pitch?

Coming from where though? I've double and triple checked the MAP behind the intake. I've even disconnected it and plugged it with my finger and plugged it back in...same effect.

 

I don't think it's a vacuum leak. Vacuum leaks would be present at idle but should go away under acceleration. It sounds more metallic to me.

Is this something new or has it been present since installation? Were there changes/mods made prior to this noise?

I would guess that something is expanding or warping when it gets hot. This could reduce the clearance.

Good luck.

Because the noise is more toward the rear of the engine I would check the flexplate/flywheel bolts.

 

It's difficult to troubleshoot any specific problem in this case because everything was made custom for fitment into my RX-7 chassis (exhaust, mounts, hoses, etc.) The car never made this noise last year when it was first built, but it's occurring now after a combined total of maybe 30 miles of driving.

I'm going to be taking off the exhaust today to re-do the right-hand header. While I'm in the area, I'll take a look around down near the starter and such. If anyone has any other opinions or ideas of things for me to look at, please don't hesitate to let me know while the car is up in the air.

 

check the starter too, just to be safe, make sure it's disengaging after starting.

I found this video that sounds a bit like your issue but doesn't seem to follow your progression but it's worth checking.

 

I'm currently checking the starter for clearance to the header, but I can see for sure that the spindle is retracting properly. Thanks for the idea though!

 

*Bump*

I'm almost done re-building the header now. I also noticed a very slow oil leak coming from the back of the engine right where the tranny bellhousing meets up with the block. Thoughts?

 

The header is now complete and has lots of clearance to everything - noise still persists.

It's beginning to sound to me like metal-on-metal interference. I'm running out of ideas here guys, please forward this on to anyone who might be able to help me out. Any help would be greatly appreciated!

 

Change oil, try a heavier oil and see if that fixes the squeal. If you are running 5-30 go to 10-40. What is your oil pressure?

Does it go away when the cooling fans come on?

BTW, badass RX7! I'd love to see that thing run!

 

Thanks for the kind words haha

I'm running 10W30 synthetic. I didn't check the oil pressure exactly, but it looked right on the gauge. I suppose I could use my scanner and see what the sensor is reading exactly... What do you suspect?

No, the sound doesn't go away when the fans come on, it gets louder the hotter the engine is.

 

Oil issue. The hotter it gets the thinner it gets. The worse the squeal gets. That's the thought I have on it. Maybe a thicker oil will help. But that should be plenty thick.

Does this happen while driving in gear?

 

I rebuilt the top end (lifters, trays, rockers, cam, heads, intake, etc.) but I didn't touch the bottom end other than swapping oil pans.

I understand what you're saying about switching to a heavier oil, but my question still remains...WHAT is physically making that noise that wouldn't be an issue with a thicker oil?

 

Yup, squeal is present both in and out of gear, in neutral and under load.

 

Not sure, but I'm thinking possibly a main bearing.

I asked about the gear thing because it could've been the pilot bearing or something related to the transmission input/clutch assembly to engine. But it happens in gear (which would make the clutch, pilot bearing, input shaft, etc all spin 1:1 with the engine and eliminate the squeal), so it's likely not related to that.

It doesn't sound like an exhaust leak to me, but I can't hear it in person (camera's pick up and play back ambient noises our brains filter out) so I can be wrong.

I'm interested to see what the fix is. Hopefully I'm very wrong about the bearing thing.

 

Does it get worse w/ revs? I too like stated above would look at the mains.

 

Yes, I thought that it was the slave cylinder or the throw out bearing at first as well, but depressing the clutch doesn't effect the noise at all and neither did being in gear, so there goes that theory...



I rebuilt the whole right side header to make sure, I'm fairly certain it's safe to say that it's not an exhaust leak.



You and me both, brother!


It seems to be somehow related to revs, but not directly. It doesn't get any better or worse at different RPMs, it's just silent below a certain threshold (around ~600 I'd say) and audible anywhere above that.


Thanks for the help guys, I feel like we're getting close!! Keep the ideas coming in!!

 

Hmmm, I discovered something new...what do you think?




Now I'm thinking that it has something to do with crankcase pressure, PCV, or some vacuum lines somewhere. Maybe I capped off something I shouldn't have?

 

Turns out the rear PCV valve was capped off and now that I have it routed to the intake manifold, the squeal is still present. I'll be searching for PCV valve part numbers tomorrow so I can order a new one.