Author Topic: Exhaust box vibration (Read 6459 times)

DavieH · « **on:** July 22, 2005, 06:05:16 PM »

I've had my BIS for about a month now, and its running really well. Had an oil leak initially from the oil pressure sensor, but that was only a fiver to replace. However, I have an intermittant vibration from the exhaust backbox.

It is due to resonance as it only kicks in at a particular engine rpm. Unfortunately this coincides with the rpm that is reached on start up with the choke on about 75% It also appears on overrun in 2nd gear coming up to roundabouts on occasion.

It sounds like the exhaust is knocking off the engine block somewhere. The noise is definitely due to the backbox ringing and its very loud.

I've tried to see where it is contacting to no avail and have tightened up the mounting fixings. But it creeps back in occasionally still.

Has anyone experienced this before? Any ideas?

ChrisRLewis · « **Reply #1 on:** July 22, 2005, 06:22:33 PM »

Possibly a loose baffle in the silencer?

126dave · « **Reply #2 on:** July 24, 2005, 09:10:01 AM »

good one cars,we have three operational bis (bi?) here,all of them have destroyed the baffles inside the box,with the resultant rattles and knocks that come with that,you can usually spot little cracks around the spot welds that hold the baffles in place.
shame there was never a sports exhaust for them.

ChrisRLewis · « **Reply #3 on:** July 24, 2005, 10:26:41 AM »

A loose baffle is very hard to locate!
It may be an idea to take the exhaust off, easy job on the bis, and give it a good shake..you may be able to hear it rattling.
It always pays to get a genuine manufactures exhaust if possible they are manfactured much better than the pattern ones!
C

DavieH · « **Reply #4 on:** July 26, 2005, 09:44:44 PM »

Well I'm baffled!!

It could well be the baffle, but it sounds more like a ringing noise, than the kind of baffle thudding that I've heard before on other cars.

Still, I'll try and pop it off and give it a good shake. I'd be a bit miffed if it was a baffle as it was replaced not too long ago apparently

Thanks for the replies

Chris Lakin · « **Reply #5 on:** July 26, 2005, 11:01:24 PM »

i think new exhausts for Bis's are ?60 a company up north still produces them for that. Otherwise ricambio. Thats if you need a new one, i do!!

regards

Chris

maxlee · « **Reply #6 on:** July 26, 2005, 11:28:52 PM »

if the exhaust has been replaced dose it still have 2 washers on the nuts/bolts that hold it on? there should be a washer and a locking washer.

the fiat 126 dosen't have a exhaust ring just to gasgits from the head
if there is nothing in the back box try putting a thin strip of rubber between the exhaust mounts and the exhaust

Milky · « **Reply #7 on:** August 05, 2005, 09:41:58 PM »

I had the same noises before taking the exhaust off the clean it of oil leaking from somewhere.

When I put it back on, all was well and quiet.

I had to take it off again to fix another leak, and it rattles like a bugger now.

I will do the same checks, and try and get hold of some rubber

I assume the do it yourself gasket sheet I made the rocker cover gasket out of would be no good??

Chris Lakin · « **Reply #8 on:** August 05, 2005, 11:09:44 PM »

i dont know, might be, but it has to with stand high tempretures!

give ricambio a ring www.ricambio.co.uk make sure you state your a 126 club member and get you 10% discount,s ay your membership is in the post, any probs i can sort you out with a membership number, if they require one, before your package arives.

Chris

maxlee · « **Reply #9 on:** August 06, 2005, 02:18:16 PM »

rocker cover gaskit is ment to be rubber i think

if there is a fiat dealer near you pop in as a hole engine gasket set is around ?30 so a rocker cover one should be cheap

Chris Lakin · « **Reply #10 on:** August 06, 2005, 05:26:04 PM »

Cork or rubber.

Maxlee, i was looking at your engine pics again, you engine looks very clean? in those pics had you already cleaned it up?

Chris

Chris Lakin · « **Reply #11 on:** August 06, 2005, 05:26:25 PM »

Cork or rubber.

Maxlee, i was looking at your engine pics again, you engine looks very clean? in those pics had you already cleaned it up?

Chris

maxlee · « **Reply #12 on:** August 07, 2005, 02:23:53 AM »

no not yet

only cleaned the oil filter and striped it down to find were the nocking was coming from

want any more pics of the engine/parts, let me no as i have nicked my m8s p,c so its easyer now as my old p.c runs on steam..