exaust blowing

Chat about your MKIII (86C) inc GT/G40 Polo
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DanW
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exaust blowing

Post by DanW »

or at least when the engine's cold it sounds a lot deeper. Do you think this is anything to worry about?
:roll:
Tahrey1043
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Post by Tahrey1043 »

Give it a good look over..... last year mine started sounding a little rorty, didnt think too much of it, then I went over a pothole in the middle of backwater anglesey nowhere and it turned into a 70s dodge v8. The weld where the middle pipe goes into the backbox had rusted and fatigued straight through - the rortiness (which I quite enjoyed, though knew it was a prob) was from the small and rather uniquely shaped/placed hole which it started as. Altered a little with bumps, and got slowly worse, as every time the exhaust swayed on it's mounts it made it a bit larger.

Give your pipework a good inspection :)

At least that one left the car mostly drivable - i've had other dodgy exhaust problems that left it hanging on the ground. This way, there's still enough of the pipe going into the silencer to hold the whole lot together. Just makes an enormous noise.
Why did I leave it? Well apart from being a poor student, I thought it was the return of another problem I'd had, which took months to manifest, the two parts of the underchassis pipe (like, where the part connected to the cat joins onto the part connected to the silencer) broke free of the mounting (didn't notice) and stressed the join where they're jubilee clipped together. Eventually it completely went and one was simply sitting inside the other unsecured and very loose. Was a bit noisy, but nothing terrible - until, roughly every other trip til I got it sorted, a bump or a sharp takeoff would jolt the one out of the other. Then it would run unsilenced, and the front of the backbox pipe would be dragging loudly on the ground too - tilting forwards no less, so its a miracle it never caught a pothole and sheared completely off the rubber mounts holding the box up.

Got that fixed first of all at a place in Bangor for a fiver, took the bloke all of four minutes including getting the car up on the jack, looking, finding the part in the office and fitting. Bargain, and didn't give me any trouble until the box went. Then that was fixed for rather more money (fifty quid?) in Birmingham. The guys didn't use enough of whatever strange sealing stuff they used on the middle joint (or didn't tighten the clip enough) and it started blowing the very next day, but in the end it was sorted.

The middle support was never replaced, but regardless after that, I had no more trouble with the middle section...

On a sidetrack, non-noisy/non-blowy - Something different occured recently when the rubber mounts themselves just perished after about a decade of abuse, and the backbox itself dropped because of this. Didn't hit the ground but ended up about an inch from the road on a very weak, springy support (ie all the pipework from the manifold and catalyser down!). Was on the way to work at the time and freaked when it came free at 60mph and made a thud and clangy noises. After figuring out the prob, limped in 10 mins late at 20mph. Luckily the boss had some wire ties in his Jeep (for just the same problem!) to keep it off the floor temporarily, and next day, two fresh mounts from halfords were about £1.70 each.
Think that escapade may have damaged the manifold though, which is why my (exhaust) gasket has developed another leak. Sounds like a beetle driving sewing machine operator farting through a box of scissors when I floor it :D



Enough info for ya? Basically look over it and try to judge the nature of the problem. Most of it wont be too tricky or expensive to fix - the supports and join were mere minutes and a fiver or so each. The back box, fifty quid and a half day. Fixing the manifold, thats about twenty pounds and a couple of hours tops (because at that price the labour cant be much!)


Oh yeah. And stay away from the temporary fixing things you might see in the petrol station or halfords. Gun gum, metal wraps, the silver heatproof tape, all that sh**e. I spent at least twenty quid and far too much time and effort wriggled under my car applying that stuff, only to have it fail me 10 miles down the road, and the mechanic repairing it for the same price (and less hassle) later on to look at it sadly, shaking his head and whispering "you muppet...". :D
DanW
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Post by DanW »

Tahrey1043 wrote:Sounds like a beetle driving sewing machine operator farting through a box of scissors when I floor it
hahahahaha...


Uh hum, cheers m8, so the rading over the bumps in the road may have at last taken it's toll :roll: . The middle section or some part at least of the exhaust pipe has been replaced by the last owner, so maybe the garage didn't put enough of that sealant on it or something... Well I'll soon see what happens with my car 2moro.



Cheers Dan
hardhitter
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Post by hardhitter »

Get underneath it and you should see where its blowing. If it's from the join it might need re-sealing providing it's not rotten away.
DanW
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Post by DanW »

the thing is, it only does it when it's cold so it's probably a very small crack if it's there. :cry: :roll: . Even stops after the first blip...
Tahrey1043
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Post by Tahrey1043 »

you need to do the old bicycle tyre test

submerge part of the exhaust system in a bowl of cold water and keep rotating along to the next bit til you see bubbles :D

or if you're brave, see if you can 'feel' where it is, move around undemeath to where its loudest etc


if its only doing it in the first few seconds after starting though.... i dunno. it might well be the engine just aging a little more. mine generally sounds like a tractor for the first few secs running after being stood a day or two!
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