exhaust blowing

Get a lump of rag in your hand and put it over the end of the pipe with the engine running. What happens? If it's blowing the blow will become more pronounced.

Steve

Yes. However, gum gum or whatever it is called these days never worked for me.

Really? Most exhaust fitters use exhaust paste.

Chris

It was a long time ago when I last tried to repair a hole in an exhaust.

The actual silencer part can become less efficient with age.

Hi,

I reversed onto a pair of car ramps and had a look underneath. I don't know the technical terms but there is a "metal strap" holding up the back box and this is all rusted. Is this because the strap and exhaust are two different metals in contact or am I making that up? It looks as though it has rusted through.

I tried the rag up the exhaust but it didn't seem to do anything.

There is a straight section of exhaust from the engine and then near the back it bends through a right angle. I think this is to divert past the fuel tank. On the bend the top of the exhaust is quite rusted. At what point does this become a concern?

It is the original exhaust. I am sure the back box needs changing now but I'm wondering whether the middle section will need changing because of the rusty bend or whether than could last several more months.

Thanks.

I don't know this car or exhaust.

Generally nowdays the exhausts are made from martensitic stainless steel this contains iron this will attribute to the pipes having rusting appearance. The brackets are made from mild steel which will rust far more.

So the appearance of surface rust may not indicate the pipe has to be replaced.

The rag should have chocked the car, and if it didn't, will allow the exhaust gas to escape, from the leaking hole or crack ( does on a petrol car.)

Exhausts rust out or wear thin on the inside more so at the rear of the car where there is not so much heat to dry them out. (petrol)

Not sure what happens to a diesel maybe they don't burn dry heat??. if anyone is familiar like to know.

Diesels, old ones at least, tend to suffer less from internal exhaust corrosion than a petrol as the emissions seem less acidic, but rather more from bracket failure due to vibration.

If I was looking at changing a car in the next few months, I wouldn't consider replacing an exhaust unless it failed completely.

Chris

FWIW: An exhaust fitter told menever to do this - after I'd told him I had. Reason - it will make any very minor leak much more pronounced, and replacement almost certainly required.

Also on petrol cars, minor exhaust leaks can lead to high lamba (too much oxygen in exhaust) in MOT emission test = fail.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember James saying something like:

If the pipe's in such a bad state that bits blow off it, it's due for replacement anyway. If the pipe's in a decent condition, temporarily blocking the exit highlights the leaky joints, which can be sorted.