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Hi All

1999 Morgan 4/4 1.8 Ford Zetec engine

The following might be of some help to others

Earlier this month whilst driving along, the exhaust suddenly started to blow. This turned out to be a failed ball joint clamp knuckle adapter that is welded to the Catalytic converter output pipe. The pipe itself looks to be in good condition.

Sourced a new cat converter made by BM catalysts part number BM91634 from this place https://www.ebay.co.uk/itm/143524186403 It cost around £290 but I have since found other ebay companies that sell it cheaper.

The cat converter has a clamp around its canister that has two M6 bolts countersunk within it, to which is attached a heat shield. The clamp was badly corroded so decided to replace it with a large Mikalor supra W2 heavy duty stainless steel hose clamp and a aluminium spacer made from a 3mm x 25mm strip cut from a piece of 3mm sheet aluminium. I managed to form this strip into a “C” shape around a 4 inch sewer pipe straight coupler. I sourced the clip from this place
https://www.bearingboys.co.uk/Mikal...r-Super-W1-Heavy-Duty-Hose-Clamp-86215-p

The original cat converter is about 130mm in diameter across the canister, the replacement is smaller at 100mm diameter. I turned out a couple of stainless steel spacers to fit over the M6 bolts so that I could use the original mounting holes in the heat shield see second picture.

Out of curiosity I spoke to Andy at BHM and enquired about the cost of a MMC replacement cat converter. That was in the order of £1000. Andy said they fit the BM ones and they are o.k. as long as you get them nice and hot for the MOT.

Also interestingly the one listed on Melvin Rutter's site is £1075 plus pp and the listing states they are slightly smaller in diameter than the original. I can't help wonder if this is a BM one. If so someone is adding an eye watering mark up!!

I think the original cat converter is salvageable as it looks to be in reasonably sound condition. The question is, is it possible to grind off the remains of the adapter and its weld and weld on a new one without damaging whatever is inside the cat converter we will see.

Regards Tony

Tony, looking at the old cat I'd call it dead!. Think you've gone in the right direction and to be honest I think the Morgan option is only just good enough hot anyway. I have a spare new Morgan option for when the time comes for may current one to slink out the door. When I acquired my spare dealers were quoting £1300 for it so guess what.... looks like classic spares are coming down. Anyway I didn't pay that, just £300 so couldn't refuse it and you are so right, the general mark up for nothing remarkable is truly atrocious!

I had a Plus8 and the cats (4) had clamps at either end. The entry/exit pipes had formed ends ( think of brake lines forming) and the clamps had gaskets to seal the joint. These were corroding, no leaks, but at some point would fail/leak. I started looking for options for when I would sort it. The clamp half towards the cat would need cutting off as the formed end prevented just sliding it off.
1. V-clamps to hold the cat to exhaust pipe together.
2. Cut the shaped ends off and use straight pipes connectors with Mikalors to seal the overlapped joint.
Exhaust paste used for both.
This was on a list of future proofing the car to keep it. I changed to a Plus Four so didn't go to the above options.
The cats were assumed original as no signs on sevice history of changes. The heat shields were failing so I made new with aluminium sheet and stainless cable ties. I did have an O2 sensor failure due to it's built in heater failing and a fault code triggering the MIL. My OBD identified which sensor ( downstream so not critical verses upstream). Got a replacement from Rimmers. I got my local MOT garage to remove the old one as it was seized solid, Oxy torch needed! They fitted my new sensor. MOT was well away but they did a quick once-over and nothing found. Emissions test with the new sensor was ok.

Sewen sospan

Thanks both for your replies. Stainless steel cable ties are a new one on me thanks for the tip they look very useful.

Sewen its not just because I am a tightwad (which I am) but the old cat looks a lot worse in the picture than it really is, the corrosion is just surface rust and its only done around 30K miles. The failed ball joint adapter is mild steel unlike the cat itself it sticks to a magnet. I can get a new stainless adaptor for about £25. The thinking is the old cat has got the car through the MOT every time without fail, the new one is an unknown quantity. As it happens I get on extremely well with my local MOT man Stewart. Unfortunately he recently had to undergo spine surgary but is expected to make a full recovery, however, for the moment is off work. My plan is to wait until he is back and then get him to run the car through an emissions test and see how the new cat performs. There should be plenty of time to do this since the MOT is not due until November. If all is well then I will probably ditch the old cat. If not then have a go at getting the old cat repaired. The only question is would it be possible to grind off what's left of the old adapter weld and weld on a new one without damaging the cat's contents.

Any thoughts or comments as always welcome.

Regards
Tony

Zack, yes in my opinion the weld wouldn't cause any heat damage at that distance and after all it is an item designed to get blooooody hot! you could replace the coupling with a stainless version as well. It seems most of the cats are in the 200 class. Check Dave Wellings out , he had a new cat fabricated in the 300 range as he always from new has had difficulty getting under the emissions threshold .

Bit of a typo there? Think standard CATs are 400 cell. The higher the cell count, the greater surface area and hence less emissions
Incidentally, I once had a leaky weld on my CAT, on the smaller end of the conical reduction leading to the incoming exhaust pipe. Had it welded up and it has passed 2 MOT s since.

Ditto. Welding is fine.

Sewin Doug RichardV6

Thank you all for your words of encouragement. I checked at our local garage today and Stuart the MOT man will be off for about 8 weeks. The owner/boss said that they have fitted BM cats before and they are o.k. They are pushed for time right now with one man off so I will keep out of their way for now. I will let you all know how things go.

Regards Tony

Apologies John should have said JohnV6 not RichardV6
Regards Tony

Hi All
Just an update. I took the car to my local MOT man today. The MOT is not due but I wanted to check whether the new CAT works OK and that the car's emissions are within limits. Happy to say that BM CAT works fine, however, I have a slight exhaust leak at the joint between the outlet of the CAT and the exhaust pipe this upsets the lambda reading. I believe the joint is referred to as a 'ball joint'. The CAT has an adaptor welded to its output pipe which has a ring around its perimeter. The ring fits into a bell shape on the end of the exhaust pipe and this joint is held in place with a triangular shaped thick steel plate either side of the joint ( see right hand side of my first photo and left hand side of the fourth photo ). The plates are pulled together with three nuts and bolts, one at each corner of the triangle. Does anyone know if there should be some kind of 'sealing ring' fitted between the two faces of this joint, or is there any compound that will not affect the CAT converter that could be used to help seal the joint.

Regards

Tony

For belmouth joints you just smear a light coating of exhaust seal (liquid gasket) it's often like a white paste onto each surface and bolt up the flanges evenly, it cures on heat

Some fitters call it Firegum

Hi Jon

Thanks for that, just a bit concerned about damaging the cat with sealant fumes if applied to cat joints. Must admit I have yet to try tightening the three bolts a little first. They may not be tight enough as I am always a bit bothered about over tightening things.

Regards Tony

Put a BM Cat in my old 96 +4 with no problems, do the BM cats also fit the later cars such as 2007 +4?