Rattling noise

Now that the cooler days are coming around here in the south I'm getting some of the old winter maladies and some new ones. For the first time I heard what sounded like rocks in a bearing rattling noise when I fired the car up after it had sat for a couple weeks. The noise became less frequent and stopped after about 20 to 30 seconds. It occured just a small amount the next day on startup. If I had to guess the location based upon listening from above and below I'd say it was the alternator. Does anyone have any experience with such a noise and is it common for the alternator to go in this manner. I have no charging issues.

I've heard the belt cracking type sound and it isn't that.

 

Try isolating the sound------------------- the bearing noise in mine was on the AC clutch. lost
If you don't have a scope use a piece of tubing or large screwdriver.

 

see if the noise goes away with the clutch pushed in. the drop gears can make noise like what you described. make sure its not low on gear oil.

 

PV Dirk...ever figure out what that rattle is? I have same on an 87 mondial as well.

 

I have not. I'm home 8 days per month and went to a car show instead of tearing it apart.

 

An easy way to isolate the noise and get a better idea of exactly where it is coming from -- take a piece of garden hose (if you don't have an old hose to cut up, you can buy some 3/4" to 1" plastic tubing at the hardware store) about 3' long, and while the engine is running, carefully probe around with one end of the hose, while holding the other to your ear. I know it sounds rudamentary, but I learned that trick 40+ years ago and still use it.

Sounds are very hard to judge from a distance. But the hose will help you pin-point where it is coming from. On that side, it could be the alternator. It could be the AC. Or it could be one of the bearings for your timing belt, either the idler or the lower drive. Obviously, the least problematic and easiest to fix is the alternator. But if you put the car up in the air, remove the wheel well and listen carefully with the hose, you'll identify it pretty accurately.

Let us know what you turn up. By the way, sounds to me like its either your alternator or water pump bearing that's going. But you really, really want to be sure it's not the timing belt tensioner bearing.

 

sounds really bad, like rocks in the engine after startup. happens sometimes, not often. goes away fast when i drive off. i think it only happens when it idles, or i do no hear it while driving? i just got used to some strange noises with older cars as long as they do not persist. its not driven much. sometimes it sits for 6 months in heated garage. still would like to know what it is. if you just bought a 308 and then you hear that you probably think you just destroyed the engine! by the way: where is the starter? can i change it myself without disassembling a lot? thanks a lot, martins
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From my experience its the ACC belts. Try some belt dressing. Older belts take a set and when you fire it up they clatter untill they become warm again. the dressing helps keep them stiky and pliable. Dont use WD40 as some on here say....

normally that is what I have found on my old 308... not a big issue. most likely will go away when you put new belts on. if it was a bearing it would stay all the time, and or get noiser as speed increases.

Again its the ACC belts - NOT TIMING BELTS

 

Martins, nice cars!! Love it.

BTW, one other possibility to look for -- loose baffles in the muffler or catalytic converters. I had that problem on my first F-car, a 1984 Mondial QV, drove me crazy. Rattled and buzzed when started, then went away once the car warmed up or drove faster. Only really heard it at idle. Finally figured out where it was coming from, changed the muffler and no more noise.

 

In my experience, dry accessory belts squeak, not rattle.

My vote is, a bad bearing somewhere...

Greg

77 GTB

 

I had this problem with the water pump belt before my service and used the belt dressing and it went away immediately, and only when cold. That was the most joyous fix to my Ferrari ever. Sadly that isn't it this time. I'll be home in two weeks and if it isn't raining I'll dig into it. I'll do exactly what is mentioned above, jack it up, partial disassemble and fire it up. I'd also thought of alternately loosening the accessory belts one at a time to be absolutely certain, but I expect the hose will pinpoint the issue. My vote right now is alternator, but can't run the risk of it being something more critical. Thanks for the input y'all.

 

Welcome Martins,

The starter is one the front firewall side of the motor, you can barely reach it on top of the front header.....

 

thanks, i will jack it up and see what i can do, would like to change it myself.
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You are a very lucky man. My wife would never let me put my car in the living room. Or maby I just need a better garage.

 

I had a similar noise 2 years ago........ It was the timing belt tensioners.

Bob.

 

I suspect my rattle is a baffle, but I was worried about something like the timing belt tensioners. Both are possible sources apparently... Time to check those tensioners and belts!

 

Or at least the problem has been found. It was the A/C pump. I have a Sanden unit. When I purchased the vehicle the pump was in a box, it has just been rebuilt and the prior owner never installed it. (he remove it because it was making a rattling sound) When I did the service in March I installed it with the belt but didn't hook up the lines and never presurized the system, just in place for when I wanted to. I put the car in the air and pulled off the fender well and dust cover to see the three belts. I tried to start it up and use a tube to isolate the rattle but I didn't have any luck and only had 30 seconds to a minute before the rattle went away. I removed the water pump and alternator belts and fired it up again, rattle still there. I started loosening the a/c pump but realized the pump has to come out in my case to remove the belt and I had no short term plans to do anything with the a/c so I just cut the belt. Viola! No more noise. I put it back together, took it out for a few miles and it sounded and felt great. Now I'm enjoying a beer. I'll be certain to drive it tomorrow and Sunday. I might wash it and do some touch up on the nose too.