Technical Exhaust

[Night35]

My exhaust was blowing- sorted few months back. Now when I open the car door with engine run and genty press the accelerator I can hear a slight noise. Sounds like the blowing is back!!

Safe to assume the garage has mucked up when they replaced the part?

 

[dac69er]

Probably just stuck a load of exhaust paste around it as per most garages.
It either needs fixing properly or the exhaust itself is knackered and needs replacing.

 

[varesecrazy]

My exhaust was blowing- sorted few months back. Now when I open the car door with engine run and genty press the accelerator I can hear a slight noise. Sounds like the blowing is back!!

Safe to assume the garage has mucked up when they replaced the part?

Hi

If its a 1.1 or 1.2.. its probably the back.box

If you park with the back left wheel up on the kerb.. you can see around it quite well

 

[DaveMcT]

You can get a cheap system for the 1.2 for under £80. It's easy to fit and lasts about 3 years. You can spend double and have a system that's rusty in 4 years.

I usually run them for a few weeks then paint some copper grease around the welds - they always rust first and that slows it down a bit.

 

[09 johno]

cold weather, metal shrinks and breaks the seal, remove exhaust clamps, pack with exhaust paste or gum gum tighten clamps back on.
I had to do this this morning on my Goldwing's stainless exhaust as it was -3 degC and the joint had opened up, normally I would wait until it was warmer, but the MOT was at 0900! (which it passed )

 

[jrkitching]

paint some copper grease around the welds

From experience, this works.

Even better, do it when the exhaust is new, and do the whole thing.

Just be aware it will smoke quite a bit when it first warms up, and there is a slight fire risk, so do the first run up outside, well clear of any buildings, and consider having a fire extinguisher handy.

If you want to see a good example of smoke on first start after a corrosion inhibitor has been used, watch this video - not a fire extinguisher in sight!

Once the volatile components have been vaporised, it's then completely safe, though it might smell a bit for a few days.

I've had an original factory fit mild steel exhaust last at least ten years after doing this; more than once.

 

[koalar]

From experience, this works.

Even better, do it when the exhaust is new, and do the whole thing.

Just be aware it will smoke quite a bit when it first warms up, and there is a slight fire risk, so do the first run up outside, well clear of any buildings, and consider having a fire extinguisher handy.

If you want to see a good example of smoke on first start after a corrosion inhibitor has been used, watch this video - not a fire extinguisher in sight!

Once the volatile components have been vaporised, it's then completely safe, though it might smell a bit for a few days.

I've had an original factory fit mild steel exhaust last at least ten years after doing this; more than once.

OEM always last. Especially when used for long journeys and even more so if its a diesel.


they rot from the inside mainly so short journeys leave pools of water inside


no amount of copper grease will help here


when I was doing 35 miles each way in a Ford diesel the exhaust lasted nearly 200,000 miles. When it did fail it didn't blow it snapped in the middle.



Some pattern parts only last a couple of years is used for short journeys

 

[koalar]

cold weather, metal shrinks and breaks the seal, remove exhaust clamps, pack with exhaust paste or gum gum tighten clamps back on.
I had to do this this morning on my Goldwing's stainless exhaust as it was -3 degC and the joint had opened up, normally I would wait until it was warmer, but the MOT was at 0900! (which it passed )

I agree that something flexible is more reliable than paste

I use High temp silicone sealant from the pound shop

but can't be used upstream of the O2 sensor

Never had one fail .......... Yet

 

[koalar]

My exhaust was blowing- sorted few months back. Now when I open the car door with engine run and genty press the accelerator I can hear a slight noise. Sounds like the blowing is back!!

Safe to assume the garage has mucked up when they replaced the part?

you need to look at it


if you say just had the back box replaced the garage may charge for the front regardless of whether or not its needed


put you hand over end of the exhaust. any blowing will be obvious

 

[jrkitching]

they rot from the inside mainly so short journeys leave pools of water inside

They rot from both sides. You're right in saying that treating the outside won't do anything to stop internal corrosion.

short journeys leave pools of water inside

This is a real problem on cars mainly used for short journeys. It's worst with backboxes (often the first part to fail), since they're the last part of the system to warm up. Most modern silencers have drain holes to alleviate the problem; some folks have been known to mistake these for leaks.

Corrosion is often localised to a seam; they can rust and split catastrophically whilst the rest of the system can look almost pristine, so anything which helps protect the seam must surely help.

Copperease isn't going to give complete protection and any mild steel exhaust will still ultimately fail, but it will definitely postpone the day when the inevitable happens. Given the low cost in both effort and materials, it's worth doing.

I once worked for a company that manufactured exhausts for both OEM and aftermarket use; we had seperate factories for this. The design criteria for OEM exhausts is that they had to be sufficiently durable to enable the car to pass its first MOT after 3 years; exhausts for the aftermarket were engineered to just meet the minimum MOT standards when new, and rarely lasted anything like as long; sometimes failing after as little as 18 months.

Quality has improved a little since then (most aftermarket exhausts have a two year guarantee now), but the difference still remains.

If you think you're likely to keep a car for longer than the life of an aftermarket mild steel replacement, it's worth considering going stainless, particularly on a car only used infrequently or for short journeys, when the internal corrosion risk is greatest. An aftermarket stainless exhaust might not be any more expensive than an OEM mild steel one.

Most stainless exhausts will be guaranteed against corrosion for life, but the bigger risk is that they are more brittle, and prone to fracture on any welded seams or connections.

Another often overlooked life limited component is the humble exhaust hanger; commonly a synthetic rubber material, these need to be checked at least annually, and replaced before they break. No matter how durable or well protected your exhaust may be, it isn't going to survive long if the hangers break loose. And if you do use copperease, keep it off any rubberised components!

 

[koalar]

You can get a cheap system for the 1.2 for under £80. It's easy to fit and lasts about 3 years. You can spend double and have a system that's rusty in 4 years.

I usually run them for a few weeks then paint some copper grease around the welds - they always rust first and that slows it down a bit.

you have to look at my old posts from memory

£20-£25. per section

 

[DaveMcT]

From experience, this works.

Even better, do it when the exhaust is new, and do the whole thing.

Just be aware it will smoke quite a bit when it first warms up, and there is a slight fire risk, so do the first run up outside, well clear of any buildings, and consider having a fire extinguisher handy.

If you want to see a good example of smoke on first start after a corrosion inhibitor has been used, watch this video - not a fire extinguisher in sight!

Once the volatile components have been vaporised, it's then completely safe, though it might smell a bit for a few days.

I've had an original factory fit mild steel exhaust last at least ten years after doing this; more than once.

The pipes are built from aluminised metal which is welded and sprayed over but mill scale on the welds quickly flakes off taking the aluminium with it. I leave them a week or two for the welds to flash rust. The copper paste sticks and stays put with a top up wipe over once a year keeping it good.

The cheap runny stuff is best. The more expensive "high temperature" anti seize has to be wiped on with a finger. That's messy and there's always the risk of finding a spiky bit of MIG welding wire.