V6 exhaust explained please - Page 2

edwardmk · 9th May 2022, 11:15

Quote:

Originally Posted by dave lincs

Why do they say it has failed? Has it failed the MOT on its emissions as V6 cat failure is very rare and if they are fitting an aftermarket part then it will most likely only last for a year and due to them not being very good you will possibly end up with the engine light on and code p0420 due to catalyst performance

if you do have a new one fitted make sure you get the old one back

Dave

Not an MOT fail. Just a sudden very loud noise from the front and sounding like a tractor. I'll definitely ask for everything they take off to be retained for me and report back.

dave lincs · 9th May 2022, 11:29

Quote:

Originally Posted by edwardmk

Not an MOT fail. Just a sudden very loud noise from the front and sounding like a tractor. I'll definitely ask for everything they take off to be retained for me and report back.

If the front pipe has broken/corroded get it removed and welded up rather than get an aftermarket one fitted as i can assure you the replacement will not be anywhere near as good as the original

Dave

rab60bit · 9th May 2022, 15:42

Quote:

Originally Posted by xsport

there are two cats on it. i replaced mine years ago for an aftermarket , when i did the LPG conversion. i kept the old one in the shed. they are stainless and stamped with their manufacture checked serial number on each cat, and are logged. about 12 mths ago i decided to have a clearout in the shed and put it on ebay. i asked £175 for it . and should have asked a lot more. as soon as posted before my kettle had boiled , it was sold . !!! this was downpipes and two cats only. they are indeed worth a fortune now. so if i were you i would tell the garage you want the cats back. people online will come out to collect it for free and buy them these days from you. the precious metals content in them are becoming rarer and rarer. some people get the price of a new exhaust out of it. ...

Right, I stand corrected (but I was partially right that the O2 sensors are on the second cat.). So the first cat is the smaller wire mesh (SS?) covered 'bulge' just aft of the two-into-one junction and the second is the larger 'torpedo shaped' tube a little further aft which has the pre and post O2 sensor fittings. Our MGR OEM design seems to be unique having two in-line cats in the system, any idea why?

trikey · 9th May 2022, 16:35

Win win for the garage, they charge you for a replacement then weigh in the old cats, make sure you get the cats back if you do replace them.

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Tenesmus · 9th May 2022, 22:31

I'd go somewhere else for a second opinion.

edwardmk · 28th May 2022, 21:50

Quote:

Originally Posted by Tenesmus

I'd go somewhere else for a second opinion.

I probably should have done that, but too late now. I got the job done at last but was a bit of a palaver. I have a rubbish cold so will post pics later of the old cat which I managed to retain in the end along with the fuller story.

Dorchester2 · 29th May 2022, 09:42

A few years ago I went for swapping the whole lot and fitting a full SS derestricted exhaust line from MIJ Exhaust for a very sensible sum (don't recall exactly but less than £500 for the lot).
I'm delighted since. Not at all noisy (hard to tell the difference with the old genuine one) and very efficient and I hope & guess long-lasting.
A very bliss!

edwardmk · 30th May 2022, 20:07

Pictures of the catalytic convertor removed from MY05 ZTT.

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SD1too · 31st May 2022, 08:47

Quote:

Originally Posted by edwardmk

The garage was adamant the catalytic convertor had 'blown'.

Quote:

Originally Posted by edwardmk

Just a sudden very loud noise from the front and sounding like a tractor.

Quote:

Originally Posted by edwardmk

Thanks for the pictures Martin.

From your description it looks as though the pipe downstream of the catalytic converter sheared in service. It also appears that the pipe was inserted into the next section?

Simon

edwardmk · 2nd June 2022, 20:31

I think you're right Simon. I don't know what the correct fixing is since I've always left this work to various local garages. The original newish s/s catback exhaust was just too loud for us ( Sorry Rick ). Therefore our first mod was to take off the the two s/s pipes downstream from the catalytic convertor (which being in good nick I've just stored ). The new exhaust supplied was supposedly stock but although much quieter, it has a resonance at 2k revs which I find somewhat irritating.( I think the ZTT rear design may contribute to and amplify the resonance. If the rear is filled with stuff, it's definitely quieter!)
I bought a new backbox from DMGRS intended to be an experiment, to try and reduce resonance, but this turned out to be for the saloon (my mistake). It needs tail pipe extensions or a straight swap for a proper tourer back box, so that also resides in the 'might need one day' parts bin.
Now I have a spare catalytic convertor which might possibly be fettled by someone handy with a welder, but that's not me yet for sure lol! It seems to have three holes for sensors so I guess two of them are O2 sensors (one for each bank on the downpipes ) but I have no idea what the third one was for?

It has a flexible "concertina" connector which I've never seen on an exhaust before but still seems sound.

9th May 2022, 16:35	#14
trikey Premium Trader Rover 75 Join Date: Nov 2010 Location: Devon Posts: 33,764 Thanks: 8,837 Thanked 14,831 Times in 8,030 Posts	Win win for the garage, they charge you for a replacement then weigh in the old cats, make sure you get the cats back if you do replace them. Sent from my SM-G780G using Tapatalk __________________ Lest we forget..

9th May 2022, 22:31	#15
Tenesmus Loves to post Rover 75 Tourer Join Date: Nov 2014 Location: Penzance Posts: 481 Thanks: 17 Thanked 69 Times in 52 Posts	I'd go somewhere else for a second opinion. __________________ 2005 Connoisseur 2.5 auto SE Tourer in BRG with Sandstone Beige and Black piping interior (the 2nd of only 7 Rover 75s produced 5th November 2004, and it’s the 244th of 303 facelift British Racing Green 75 tourers built worldwide). All I've done is add Rover walnut gear knob and handbrake... 2016 Vauxhall Viva SL (Father Jack) "assisted manual" (auto) in purple. Going rusty underneath already...

29th May 2022, 09:42	#17
Dorchester2 incurable Rover addict Rover 75 Saloon V6 2.5 1999 - Rover 25 1.4 2002 - Rover 214i cab 1994 - Rover P5b coupe 1968 Join Date: Sep 2017 Location: Bioule. South West of France. Posts: 1,643 Thanks: 612 Thanked 385 Times in 223 Posts	A few years ago I went for swapping the whole lot and fitting a full SS derestricted exhaust line from MIJ Exhaust for a very sensible sum (don't recall exactly but less than £500 for the lot). I'm delighted since. Not at all noisy (hard to tell the difference with the old genuine one) and very efficient and I hope & guess long-lasting. A very bliss! __________________ Rover 75 V6 2.5 Auto Connie born 1 July 1999, 24 kOhms resistor, 10 kOhms manual starter, full E85, modified airbox, full derestricted SS exhaust line, power & torque remap -> 202 bhp This vehicle was the 7,517th 75 to run off the production line, out of 112,381 This vehicle was the 1,190th 75 2.5 V6 Contemporary to be made out of 8,214 This vehicle was the 2,032nd 75 in Atlantic Blue Pearlescent (code: JEY) to be made out of 2,572 Atlantic Blue Pearlescent 75s

30th May 2022, 20:07	#18
edwardmk Gets stuck in MG ZT 260, Rover 75 Connie SE auto Join Date: Feb 2013 Location: Redruth Posts: 984 Thanks: 1,324 Thanked 399 Times in 271 Posts	Pictures of the catalytic convertor removed from MY05 ZTT. Sent from my iPhone using Tapatalk Pro

2nd June 2022, 20:31	#20
edwardmk Gets stuck in MG ZT 260, Rover 75 Connie SE auto Join Date: Feb 2013 Location: Redruth Posts: 984 Thanks: 1,324 Thanked 399 Times in 271 Posts	I think you're right Simon. I don't know what the correct fixing is since I've always left this work to various local garages. The original newish s/s catback exhaust was just too loud for us ( Sorry Rick ). Therefore our first mod was to take off the the two s/s pipes downstream from the catalytic convertor (which being in good nick I've just stored ). The new exhaust supplied was supposedly stock but although much quieter, it has a resonance at 2k revs which I find somewhat irritating.( I think the ZTT rear design may contribute to and amplify the resonance. If the rear is filled with stuff, it's definitely quieter!) I bought a new backbox from DMGRS intended to be an experiment, to try and reduce resonance, but this turned out to be for the saloon (my mistake). It needs tail pipe extensions or a straight swap for a proper tourer back box, so that also resides in the 'might need one day' parts bin. Now I have a spare catalytic convertor which might possibly be fettled by someone handy with a welder, but that's not me yet for sure lol! It seems to have three holes for sensors so I guess two of them are O2 sensors (one for each bank on the downpipes ) but I have no idea what the third one was for? It has a flexible "concertina" connector which I've never seen on an exhaust before but still seems sound.