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Author Topic: Changing backbox on estate  (Read 445 times)

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terry paget

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Changing backbox on estate
« on: 12 April 2019, 19:12:45 »

V828 2.5 petrol manual estate
This car has got noisier in the last week (it passed MOT 2 weeks ago) and now I see why.

I have this stainless steel silencer, retrieved from my dead estate. I imagine it should fit.

It does not look quite the same. Please advise how I should go about fitting it. My idea is to remove the cat section back from the car complete, then place the LONGLIFE  beside it and decide where to cut off the existing pipes; then replace the central exhaust, pop on the backbox, clamp the pipes and hang the backbox on the car.

Sounds like heavy work. Please advise.
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dave the builder

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Re: Changing backbox on estate
« Reply #1 on: 12 April 2019, 19:24:10 »

just cut the old box off at the clamps where it failed,angle grinder (PPE  :y)
offer the new box up ,on hangers, mark where new pipe meets up ,cut remainder of mid sections off,leaving enough to slide inside the SS pipes and be clamped

no point in disturbing anything else  :-\
unless i'm missing something
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Doctor Gollum

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Re: Changing backbox on estate
« Reply #2 on: 12 April 2019, 19:58:20 »

It's on the bench upside down. Remove old, refit 'new' and do something more important  :y

Might be prudent to drop the heat shield above the silencer and deal with what you find above it :y
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terry paget

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Re: Changing backbox on estate
« Reply #3 on: 12 April 2019, 22:18:17 »

just cut the old box off at the clamps where it failed,angle grinder (PPE  :y)
offer the new box up ,on hangers, mark where new pipe meets up ,cut remainder of mid sections off,leaving enough to slide inside the SS pipes and be clamped

no point in disturbing anything else  :-\
unless i'm missing something
Good thinking, Dave. That sounds like a better approach.
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Nick W

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Re: Changing backbox on estate
« Reply #4 on: 13 April 2019, 00:04:02 »

Always fit non-standard stuff on the car.


Considering how cheap a complete system is, you would be better off buying an appropriate standard backbox and moving the stainless one on to some other mug. Sucker. Person.


Used exhausts are not worth the effort no matter how cheap they seem
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terry paget

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Re: Changing backbox on estate
« Reply #5 on: 13 April 2019, 09:42:33 »

Always fit non-standard stuff on the car.


Considering how cheap a complete system is, you would be better off buying an appropriate standard backbox and moving the stainless one on to some other mug. Sucker. Person.


Used exhausts are not worth the effort no matter how cheap they seem
Thanks Nick. That is my back up plan, to buy the complete system we found recently at 94 and pop it on. But I should have to await delivery, probably not before Easter now, so it seems worth attempting to use the old box, especially as I have got it off the other car now. 
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Enceladus

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Re: Changing backbox on estate
« Reply #6 on: 13 April 2019, 16:51:00 »

I suggest not cutting too close to the clamp. Cut between the pipe sockets and the silencer so that you preserve as much of the middle section pipes as possible. You'll then have to remove the remains of the sockets and the clamps from the middle section pipes.

Looking at your photo the Bristol Longlife box is smaller than an Omega original. The Bristol stainless box has had the tubes extended to make it fit an Omega. So there may not be much, if any, excess on the centre tubes left to cut back.

That said it looks like at least one of the centre pipes is rusted through within it's socket. You might find nothing left to join into the Bristol box. Or you might not get a gas tight seal. It might be easier to ditch the centre pipes and replace with new.

Also is that a big crack in the nearside rear brake backplate?
« Last Edit: 13 April 2019, 16:53:25 by Enceladus »
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Doctor Gollum

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Re: Changing backbox on estate
« Reply #7 on: 13 April 2019, 17:01:03 »

Stupid boy Pike ;D

The back plate has a segment notched out of it for the caliper ::)
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Enceladus

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Re: Changing backbox on estate
« Reply #8 on: 13 April 2019, 17:48:47 »

Yep, of course it's the caliper cut-out.

Anyway my guess is that the Bristol Longlife is made to fit to unmodified centre pipes. And I suspect that the downstream ends of the centre pipes on this Omega are rusted through and there may not be enough sound tube left to connect. 
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johnnydog

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Re: Changing backbox on estate
« Reply #9 on: 13 April 2019, 22:59:11 »

I would not try to mate up a stainless and a mild steel with male/female sliding joints due to the different expansion rates of the different metals, which will be likely to result in it blowing eventually on the joint.
Either all mild steel or all stainless - not a combination.
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Enceladus

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Re: Changing backbox on estate
« Reply #10 on: 14 April 2019, 16:38:07 »

I would not try to mate up a stainless and a mild steel with male/female sliding joints due to the different expansion rates of the different metals, which will be likely to result in it blowing eventually on the joint.
Either all mild steel or all stainless - not a combination.
It appears the stainless silencer appears to have been on the donor estate for at least six years. If the downstream ends of the centre sections on this estate are rotten as per usual then it's probably best to replace them rather than attempt a patch. A complete, cats downstream, exhaust sytem is not much more than the pair of centre sections. That would give you new a mild steel rear silencer.
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terry paget

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Re: Changing backbox on estate
« Reply #11 on: 15 April 2019, 20:14:57 »


Job done.
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dave the builder

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Re: Changing backbox on estate
« Reply #12 on: 15 April 2019, 20:19:21 »

well done  :y
is it blowing ,looks like it needs a smear of cement on the joint  :-\
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terry paget

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Re: Changing backbox on estate
« Reply #13 on: 15 April 2019, 21:40:48 »

well done  :y
is it blowing ,looks like it needs a smear of cement on the joint  :-\
I don't think it's blowing, though I do see a possible gap It's much quieter than before. If I do detect a blow I will reseal it with some cement. I had to grease it to get it to assemble. Car has already passed MOT, and next April seems a long way away.
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johnnydog

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Re: Changing backbox on estate
« Reply #14 on: 15 April 2019, 23:04:12 »

Why not use a high temp silicone RTV sealant instead of greasing the joint for an easier assembly of a tight joint?. It allows the joints to slide together easily on assembly, provides a permanent gas tight seal, and seals any minor gaps like those on the last photo. If you need to seperate the joint at a later date, it can be done easily, whereas exhaust paste sets like concrete and is hard to separate any joints.
I use the red HT RTV on my all cars including classic cars, and if is far superior to exhaust paste in my opinion - simply for ease of use and it does the job perfectly.
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