How Necessary Is The Flexi Pipe?

[Skezza]

Tried writing this three times so I'll keep it brief.

Missus has a luxury ka. Back box hangers broke the other day while she was driving. Back box fell and the mid pipe twisted. She didn't stop and ended up tearing her flex pipe off at the manifold end.

She needs it for work so I did a quick bodge to get her by. Got underneath, replaced the hangers with brand new ones so it sits right, glued the flex pipe using putty and wrapped it at the broken end with two bean cans. It's quieter but still roars a bit when accelerating.

While under, I had a look at how the pipe is replaced. There are two markers to be angle grinded and then you either weld or clamp the new one in. A cheap aftermarket replacement is £27. All sounds a bit of a ball ache.

So, my question:

How necessary is the flexi pipe? I've installed performance exhausts on transverse FWD cars before and none I can think of came with a flexi pipe. Could I install a piece of generic exhaust extension pipe and clamp it using some universal clamps? I could rip the rest of the flexi pipe off using some vice grips, there's enough space to fit a universal clamp before the buffer for the flexi?

Has anyone done this? Is it likely to damage the manifold through vibrations etc?

Thoughts?

Thank you

[Skezza]

OK, an update:

I've been told that the flexi joint is still required with a KA because there isn't enough movement in the hangers to withstand the engine rocking. That's fine, no problem replacing it.

Do you reckon a 42mm at both end would work? I know it would at the inlet end but apparently the outlet diameter is 39mm.

Can you crush an exhaust pipe by 3mm? :D

I'm guessing not lol. Thoughts?

[Skezza]

So an update on this:

Replaced the flex pipe on Saturday with an aftermarket OEM'ish replacement (as in the ends were the OEM diameters). Wasn't quite as straightforward as I'd hoped but job done in the end, no welding and the car sounds nice and quiet again and has rediscovered a bit of it's bottom end. All done on stands too, so while it was a bit uncomfortable I'd still recommend it over taking it a garage :P

My GF's KA is a 2003, so has this exhaust layout:

Decided to go for this:

http://www.ebay.co.uk/itm/161721862276?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Now I know what you're thinking and you can get an OEM style replacement flex pipe with the matching gasket (about £50-£60). http://www.bestpartstore.co.uk/1339087 and http://www.amazon.co.uk/Bosal-717-877-Exhaust-Pipe/dp/B00CEFFMOS

However, you'll still need to cut through the inlet manifold downpipe so there's no benefit from that regard and the gasket was totally seized up. It really was. I think I'd have ended up making the job a lot harder going down this route. There was no way that gasket was coming apart without a fight. The nearest bolt was solid as a rock. After all, the car is over 10 years old. I know some people swear by sticking with OEM, however it's got 103k miles on, it's old, it's geting a bit tatty and it's just a work grinder, so I feel no real shame doing it with an aftermarket part that gets rid of that gasket at the end of the day. I know people have mixed feelings over universal exhaust clamps, but ultimately, Ford OEM recommend one at the downpipe end, so meh, who cares? ;)

Got the car up drivers side and dropped it on a stand (you really don't need both wheels in the air). So the first problem I faced, because she'd ripped the entire flex pipe off at the IM end, there was no rigidity to the rear pipe whatsoever. So when I tried to use my chain exhaust cutting tool, it was just flapping about. It was a bit like spreading butter one handed. So, when all else fails, grab the angle grinder eh? I held the pipe while my gf's old man went through the pipe. Wasn't the easiest job because the gasket was knocking the main body of the angle grinder, but we eventually got through it, not the cleanest cut ever but meh, was good enough.

Then the rain started. Ha. Of course. It waited until we'd made the car completely immobile before starting (my temporary fix was still just about working after all, that was until we got out the angle grinder lol).

Next, I moved onto the manifold downpipe. Nice and rigid, so worked great with my ratchet chain cutter. I'd say it took about 10-15 minutes with the cutting tool, although it would have been quicker if I hadn't undone the ratchet. Got a cleaner cut, although not the cleanest. I made the cut right next to the flex pipe so I knew we wouldn't be short of pipe going into the flex joint.

By this point, it was proper hammering it down so not ideal, but we figured we may as well just crack on and not give up.

On a dry run fitting the replacement flexi, it would go on the rear pipe, but for some reason, there was a slight deform in the manifold downpipe (only a tiny one). Perhaps I had overdone it slightly with my pipe cutting tool? Either way, it meant that while the new flexi would go over the rear end, it was too tight going over the manifold side.

Cracked out the angle grinder again and shaved a mm maybe off the deformed side of the pipe. Just enough to take the kink out of the pipe. The flexi pipe now went on, although it was still pretty tight. So I took it off again and filled both ends of the flexi pipe with generous amounts of silicone quick gasket and slide it over both ends, doing a bit of twisting to ensure the silicone was nicely spread. We tightened up the universal clamps nice and tight (have to be careful though, they can sheer off).

Finally, we put a nice generous bead of silicone quick gasket over the both ends of the flexi pipe to ensure nothing was getting in. The rain was pretty mental by this point, and there were thunderstorms!! My trousers were completely drenched. I'm pretty sure the cough I have right now is partly due to it!

Left the car for 18 hours, before starting it up. Moment of truth. Started, nice and quiet. Left it to idle for about 5 minutes before taking it for a trip. Get any moisture out. Dead quiet now.

Your local garage will charge about £80-£120 for this job (what we were quoted anyway). This cost £20 for the flexi pipe and £2.50 for the silicone quick gasket (of which I still have plenty left).

Bargain.

[Skezza]

[stef123]

I read this the other night and got side tracked so I forgot to reply lol.

Only thing I would have done is turn the clamps round. At least your exhaust system allows you to for a clamp on flexi, most don't which means welding one in.

[Skezza]

I read this the other night and got side tracked so I forgot to reply lol.

Only thing I would have done is turn the clamps round. At least your exhaust system allows you to for a clamp on flexi, most don't which means welding one in.

I did think about trying to get the clamps upside down (just for neatness), but the rain was coming down hard and I was rapidly losing interest :P

Why can't you clamp a flexi on? So long as the flexi is under the car it should be possible right? I know some cars have the flexi up at the back of the block, which would make it a tricky job.

I could have replaced the manifold + downpipe which would have come with a new flexi pipe, but for me, this way was easier, cheaper and in my opinion a bit more modular. I like modular exhaust components. This is another part, where if it fails in a few years (or before the car dies) again, I can easily replace it with not much effort.

[stef123]

I did think about trying to get the clamps upside down (just for neatness), but the rain was coming down hard and I was rapidly losing interest :P

Why can't you clamp a flexi on? So long as the flexi is under the car it should be possible right? I know some cars have the flexi up at the back of the block, which would make it a tricky job.

I could have replaced the manifold + downpipe which would have come with a new flexi pipe, but for me, this way was easier, cheaper and in my opinion a bit more modular. I like modular exhaust components. This is another part, where if it fails in a few years (or before the car dies) again, I can easily replace it with not much effort.

Haha yes the good old rain does tend to do that

In most cases the bends are too close to the flexi meaning there is no room for the long sections where the clamps fit, where as on a weld on flexi they are very short.

[Skezza]

Haha yes the good old rain does tend to do that

In most cases the bends are too close to the flexi meaning there is no room for the long sections where the clamps fit, where as on a weld on flexi they are very short.

Oh I see, yeah that does make sense.

I hate the thought of welding under a car though, especially if it was on !Removed! axle stands!!! Plus, it's not always that easy to get a perfect bead around the pipe.

I wonder if anyone has tried using something like chemical metal or JB weld, then using a small band clamp to ensure it doesn't move? The only issue I see with that is the limited length of metal coming off those weldable flex's.

She's a very lucky girl. I say that £80 to £120 to replace was what we were quoted, not including VAT, however some garages are charging up to £200 for this job.

Yep, it took a few hours, and I've covered in cuts, but it's worth it :D