M44 Catalytic Converter

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Robert T
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Joined: Mon 12 Jun, 2006 11:35
Posts: 10025

  Z3 roadster 1.9
Location: Cheshire

M44 Catalytic Converter

Post by Robert T » Thu 11 Aug, 2016 07:39

My zed had a bit of a poorly do coming back from the Lakes last week. When I started it up, I noticed a rattling noise, which I initially thought might have been the viscous coupling on the fan, but which turned out to be from under the car and it got worse when blipping the throttle. I needed to get home, figuring that even if it was the cat, it would last a few weeks like this. Wrong! It started to feel like it was struggling for power when pulling out to overtake. Coming over Thelwall, it struggled to maintain 70. Coming off the motorway it could hardly make 50 and the revs were dropping when idling, meaning I had to apply throttle to avoid stalling. Wouldn't rev over about 2500 rpm and exhaust noise sounded sick. Limped it home gently and put it to bed. Next morning drove it down my local BMW specialist, struggling to even achieve 30. Left it with him, but as I walked away I noticed the left rear looked a bit soft.

Got a phone call the next day confirming that it was the cat. Choice between remanufactured OEM and aftermarket. Having heard a few things about aftermarket cats not lasting more than 3 or 4 years and struggling to make MOTs, I decided on a BMW one, mainly because the old one gave 17 years good service, even if it was 3 times the price. I also like the sound of the original exhaust system. Annoyingly the tyre had gone completely flat, and as it had done 25k, I asked for 2 new tyres to be fitted.

Picked the car up yesterday and it sounds and feels infinitely better. In fact after driving it, it feels much more free revving and the exhaust note is much sweeter, making me thing that the cat had been getting slowly blocked up for some time.

A few things to note about the M44 cat section. Firstly it is stainless steel, and mine looked in very good condition externally. Secondly there is a large vibration damper attached to it which had a very rusty clamp. I remember someone finding one of these on their driveway and asking what it was. On my car, I now know this was the source of a slight knocking sound when going over the speedbumps leaving home in a morning. Funnily enough I hadn't put 2 and 2 together to realise it only did it when the exhaust was cold. When hot I assume it must expand and not move as much. I had been silently praying that it wasn't the boot floor!

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So all fixed, but a very large hole in my wallet. Labour was minimal on this and it was not a job I could have done without a ramp.

Cheers R.

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Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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peter2b
Joined: Sat 01 Nov, 2014 18:47
Posts: 963

  Z3 roadster 2.2i
Location: cheshire

Re: M44 Catalytic Converter

Post by peter2b » Thu 11 Aug, 2016 15:35

if you had the time you could have used my car lift
peter2b

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2126

  Z3 roadster 1.9

Re: M44 Catalytic Converter

Post by Del » Thu 11 Aug, 2016 15:52

Thanks for sharing Robert. I didn't have that vibration damper on my M44 (build date 5/1998). It may have been fitted to later models. However, I have had to replace the lower part of the metal shackle (bracket) at the gearbox as the lower section had typically rusted away.

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Robert T
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Joined: Mon 12 Jun, 2006 11:35
Posts: 10025

  Z3 roadster 1.9
Location: Cheshire

Re: M44 Catalytic Converter

Post by Robert T » Thu 11 Aug, 2016 17:58

Thanks for the offer, Peter, but it barely made it half a mile down the road! They had to push it in and out of the workshop. If I have some less urgent underside jobs, I may take you up on the offer.

Thanks R.

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Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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lightning
Joined: Tue 27 Nov, 2007 08:15
Posts: 815

  Z3 roadster 3.0i
Location: Stockport

Re: M44 Catalytic Converter

Post by lightning » Fri 12 Aug, 2016 07:57

I always use OEM parts where possible. But l just had to replace the CAT on my Defender and the price from Land Rover was £750!
So an aftermarket part went on, as you say a third the price of the OEM.

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