355 Engine compartment noise

I have a noise that sounds like it's coming from front of the engine, sounds like a bearing going bad. It only happens at idle around 1000 RPM, and disappears about immediately when I rev it slightly, but comes right back when it drops to 1000. Any ideas? Is it serious?

 

Yes it is serious. you need to isolate the noiise and see what bearing is causing it. The bearings in the front of the engine are all pretty serious ones, and they almost always require an engine drop to get to.

Are you handy?

 

Don't panic, it may be an alternator or it may be the air con. Best thing to do is take to mechanic put up on hoist and determine where to noise is coming from asap

 

Jeff, another possibility since your noise occurs in a very narrow rev range is the power steering pump bracket rubbing on the hose crimp collar. I was chasing a similar noise months back and the shop that handled the major told me that it was likely the crimp collar on the hose making light contact on the bracket. I was convinced it was an alternator tensioner bearing instead, but they were right.

 

It wouldn't hurt to still check the tensioner bearing for the alternator.

 

I chased a noise around with similar rev-range symptoms. Was less prevalent when the engine was hot. Turned out to be the left hand cam belt tensioner. I dropped the engine and changed tensioners and bearings.

To isolate The sound I used a home made stethoscope (don't laugh now) which was a length of hose with a funnel at the ear end. You place the narrow hose near each suspect item and you can selectively listen to each item. It's surprisingly effective. You need to be a bit careful at the front of the 355 engine when it's running as it's quite tight to the firewall.

 

I would check the ac tension and the alternater belt tension & bearing.
With a little effort you can remove either belt/ start the car and see if you have identified the noise in question......before you go through dropping the motor.

 

My alternator tensioner bearing went. It was a simple repair.

I may or may not have had this noise you describe at start up. My bearing "went" during some spirited acceleration. Made a terrible noise. When we got the car up on a lift, you could see that the bearing was fried.

I just wished I replaced the bearing with a Hill engineering one. But I was so relieved that the bad noise was not a really expensive repair, I forgot to think about using a Hill replacement.

 

Yep, excellent advice and that is what I would do.

Drop one belt off at a time and see if the noise goes away. Do that and report back to us.

 

Well, I was all set to take to a pro today but it stopped making the noise last night. I took it out this morning, nothing. My neighbor who's a mechanic heard it last week and thought it was not a bearing but something like a heat shield, metallic rattle like (coming from front of engine). Maybe it has loosened enough now that it doesn't vibrate. I've got the home-made hose stethoscope ready if it comes back, I'll keep you posted. Thanks as usual for the excellent advice.

 

Aye, probably even harder to find the cause of that noise now it has gone away.

Rattles are a pain, hopefully the noise doesnt come back.

 

Don't want to scare you, but you have described the exact replica of my symptoms which turned out to be timing belt tensioner. You should try to check the belt tension somehow, maybe by squeezing a small camera or something down there. Once I dropped the engine on mine you could see the staining on the tensioner where the damping oil had come out.

Take a look here:

http://www.ferrarichat.com/forum/showthread.php?t=127651&highlight=355+tensioner+rattle

 

Mystery solved! The noise came back so I just jacked it up, removed the under panel, started it up and crawled under it with my homemade stethoscope (thanks spagetti). After sticking my ear on it I was pretty sure it was coming from the alternator tension pully but the stethoscope (flexible plastic tubing) really made it obvious - plus I could see it shaking and it wiggled by hand. So I ordered a new one, shipping and all was 47 bucks and it arrived the next day (wow!). I researched how to change it and looked at it myself and was pretty unsure how to get to the top nut and then how to remove the studs that hold the pulley bracket in place. So, my mechanic neighbor who's out of a job at the moment said he'd do it for 50 bucks so I said have at it and I'd watch and help. He was able to get to the top nut by just going over the pully with a slim wratchet, and he had stud removers too and made quick work of the whole thing. She's quiet as a church mouse now, thanks for all the advice.

Jeff

 

Sweet, Jeff! Again, Occum's Razor. Sometimes a complicated explanation is warranted, but mostly, it is the simplest explanation that satisfies.

 

Wow Jeff, you need to start pimping out your neighbor for other people's repairs! $50 in labor to replace a pulley was a great deal.

 

Good to hear! Cheers for the update.