Rotary Madman

I just finished rebuilding my engine, I started it up and it ran fine for about 8 minutes then this noise started and does not stop. Car is pretty much stock, only DP and Cat-back installed.

It makes this whining, squealing constant pitch, constant volume sound at all rpm's. well... idle to 3500 RPM. I'm still breaking in the motor so I haven't gone higher.

Found this video on youtube. This is the exact same noise and I bet the same problem. See link below


I found if I pull the booster line off or crack open the secondaries with my finger for a second it goes away momentarily.

The idle is rough, jumps between 1000 and 1500rpm and it jumps pretty high when I turn the headlights about 3000rpm, which could be a separate issue. Right now I want the noise to stop. It is loud and annoying.

It is not the throwout bearing, or belts, or Smog pump. ruled those out. thinking it is a vacuum leak but I cant find it. Don't want to spray carb cleaner just yet because I just freshly painted the entire motor and it will ruin the spray paint.

Also toying with the idea that it is the transmission input shaft bearing but this seems it would change pitch with RPM. I will try tomorrow and see if it is only when the engine is warm or not. Today was the first start on my new motor. It may not be there when the motor is cold. I will update.

Been playing with RX7's for years and years. This is a hard one. I Will post the solution for the rest of you when I figure it out or someone on here figures it out for me

PLEASE HELP. I AM GOING NUTS TRYING TO LOCATE THIS! I bet there are more of you guys who have run into this mysterious occurrence?

Dvst8

iTrader: (6)

Sounds like a tiny leak seeping through causing that sound. I had a similar sound from the 1" tubing to the stock BOV. I replaced it and the sound was gone. I'd start push/pull some hoses.

XLR8

iTrader: (52)

^ Good advice.

Also, if it is a bearing such as the pilot bearing, try using an automotive stethoscope to pinpoint it. They work pretty well.

In the video, the noise disappears when it's rev'd, and reappears when the engine starts pulling vacuum again. Does yours do this?

Rotary Madman

I actually have a doctor's stethoscope that I rigged with a coffee straw that I have been using for years. So far no luck. It gets quiet and loud all over the place. I did stick it in the bell housing and it seems louder but that could just be the air-movement inside that I am hearing from the spinning parts.

My noise does not dissapear when reved. The primary doesn't effect the sound but if I open the secondarys with my finger or enduce a vaccuum leak in the secondary tunnels it goes away for a second until it re-gains vacuum. not 100% but I'm pretty sure it is vacuum. BUT WHERE THE HELL IS IT? Gonna tear the whole motor apart trying to find it.

I will play with the BOV and tubing tonight. and run some more tests to see if I can get closer to the root. Gotta work late though so I will have to do it in the dark tonight

Thanks for your assistance! Love this sight!

Rotary Madman

Thanks for the suggestion. I will do this too tonight and report tomorrow.

Thanks!
keith

RENESISFD

iTrader: (13)

My guess it the LIM to block manifold gasket, or the UIM to LIM gasket. Do you have the xcessive LIM?


Do you have the metal or paper LIM gasket?

korea_senpai

iTrader: (25)

That's my video, lol. It was the gasket between the UIM and LIM. There was a grounding wire or something that I erroneously placed between the two manifolds, that was leaving just enough space for air to escape causing the gasket in between the UIM and LIM to whistle/squeal. When it starts making the noise, feel around where the UIM and LIM meet and you may find your problem.

Rotary Madman

Oh.. cool.. sorry I had to plagiarize it... where do I send the check? haha... Your problem is identical to mine.

Thanks for the answer. Yeah I read through your posting dated back to 2011 and didn't see a firm conclusion.

Last night, I added RTV to both metal gaskts on the UIM. NO STATUS CHANGE.

I'm still unsure of the root but I am starting to go after the LIM. Pretty pissed about it too. I just got the whole car together. now I gotta rip half the motor apart again. Wish it was a N/A motor. gotta rip the turbo's off and everything. If changing the LIM gasket doesn't fix it I'm gonna light a bomb and walk away.

On a good note, besides the idle problem my new motor is working like it should.

Rotary Madman

I used an old (used) metal gasket w/ RTV. I have a new paper gasket on my workbench but decided not to use it because the metal one looked good and I figured the RTV would pick up the loose ends. Could have been a bad call....

My LIM is a stock USDM manifold.

Thanks,
Keith

Rotary Madman

Alright everyone reading this. Here is the final verdict.

I replaced the LIM gasket to the engine and all the problems are gone! no more noise or idle issues.

Thanks to everyone for their support

It was a vacuum leak. I assume it was between the layers of metal in the gasket because I used silicone on the outsides. I also assume the leak was around the backside of the gasket that faces the opening in the bell housing which is why I was getting louder sounds with my stethoscope in the bell housing. lastly the hole was big enough to allow considerable air because the idle was jumpy between 1500 and 1000rpm and now it is smooth as glass!

WORD TO THE WISE! DO NOT.... use a used metal LIM gasket. It's not worth the headache for 35 bucks. Its a lot of disassemble on a stock motor to replace this gasket. I knew better too.... I even had one available during assembly and opted not to use it?

LIVE AND LEARN.

Thanks RX7 CLUB! Hope this helps some poor fool down the road!