Exhaust Noise

webteb · 6th August 2007, 09:34

Hi all.
My 75 (2.5 V6) has the dreaded rattle/buzz/resonance coming from the front area of the exhaust. It only happens through a short span of low revs and is more pronounced as the engine warms up. I don't think it's fatal but it spoils the sound of the car. I have read about Cat failures and front down pipe problems and wonder if anyone has any more specific info. I saw Lates once referred to a service bulletin on drilling a hole in the down pipe and filling it with weld but has anyone any specific info on where the hole is the hole is actually drilled? I have also seen references to using a self tapper in the Cat but has anyone actually done it? I ask these questions as getting a replacement Cat here in NZ will most likely require a second mortgage. I spoke with a couple of exhaust repair shops and they just normally remove broken Cats as emissions are not currently included in the warrant of fitness (MOT) checks here. I am hesitant in trying this as I’m not sure of how the O2 sensors will react and what impact it will have on the ECU. Any help will be greatly appreciated

john adam · 6th August 2007, 09:59

As a relatively new 75 owner, I was somewhat concerned with the clatter type noises coming from the driver's side of the engine bay during warmup. From your post it would appear that it is quite normal.

T-Cut · 6th August 2007, 10:12

Yep, I've got it too.

TC

Dave Goody · 6th August 2007, 10:49

Quote:

Originally Posted by webteb

Hi all.
My 75 (2.5 V6) has the dreaded rattle/buzz/resonance coming from the front area of the exhaust. It only happens through a short span of low revs and is more pronounced as the engine warms up. I don't think it's fatal but it spoils the sound of the car. I have read about Cat failures and front down pipe problems and wonder if anyone has any more specific info. I saw Lates once referred to a service bulletin on drilling a hole in the down pipe and filling it with weld but has anyone any specific info on where the hole is the hole is actually drilled? I have also seen references to using a self tapper in the Cat but has anyone actually done it? I ask these questions as getting a replacement Cat here in NZ will most likely require a second mortgage. I spoke with a couple of exhaust repair shops and they just normally remove broken Cats as emissions are not currently included in the warrant of fitness (MOT) checks here. I am hesitant in trying this as I’m not sure of how the O2 sensors will react and what impact it will have on the ECU. Any help will be greatly appreciated

I recently posted on something similiar on a new cat but get the resonance only, a wahh as I hit 2,200 rpm then nothing until I return to 2,200 1st new cat did it and replaced cat same? I admit they were cheapies [unipart] I dont get a rattle, but did with the original knackered one. I am planning to fit 2 large jubilee type clips around the cat to see if this stiffens things up to remove resonance Dave

Cuda-uk · 6th August 2007, 11:48

Quote:

Originally Posted by webteb

I spoke with a couple of exhaust repair shops and they just normally remove broken Cats as emissions are not currently included in the warrant of fitness (MOT) checks here. I am hesitant in trying this as I’m not sure of how the O2 sensors will react and what impact it will have on the ECU. Any help will be greatly appreciated

As the O2 sensors are fitted before the cat it would make no difference to them if the cat was there or not. The only thing you will notice is a gain in power and torque and maybe a slightly louder exhaust note.. Cats are very restrictive.. HTH

RLeon · 6th August 2007, 11:59

As for the noise and welding:

Our R75 friends from Germany

, www.r75.info , have some info on this. According to them this rattle is most noticable after start with a cold engine. The modification would be to drill a small hole, 8 mm and weld the outer tube to the inner. They have a drawing where to drill and weld, http://www.r75.info/modules.php?name...06371162069363 . To access you have to become a member

.

RLeon

T-Cut · 7th August 2007, 22:27

Has anyone considered compressing the outer case slightly so it tightens on whatever's loose inside. I note Dave's idea of Jubilee clips, but I doubt if they'll compress the steel pipe much. I was wondering whether a judicious belt with a club hammer using a suitable drift might work. Anybody got a thought on this?

TC

crofts · 7th August 2007, 23:19

Think belting it with a hammer may do more harm than good as seem to recall there are ceramic 'goodies' inside.
Could be wrong though but............. it could be an expensive mistake.

webteb · 8th August 2007, 09:09

Thanks guys for the respsonces. It appears this noise symptom is fairly common. Have registered on the German site (thanks RLeon) but the link keeps telling me the module is not active. I'll keep trying. As for what I thought were O2 sensors,(thanks Cuda-UK) what is the one just down stream of the cat. Is it just a heat sensor and will removing the cat altogether have a bad impact. I'll try and pin point the source with a stethascope and get back if I have some success.

Keith · 8th August 2007, 11:02

It is perhaps not the Cat it may be the intermediate box behind the cat the baffles spot welds break free and when the exhaust is cold and rattle in a most unpleasant way.

The drill a few holes and fit some self tappers method works perfectly ok (not sure if it would pass an Mot though)

The rattle is very obvious if you get under the car and listen, four self tappers two either side should do it or at least will prove if that is where the problem is obviously listen to the rattle and try and put them where the noise is coming from

I would not personally recommend doing the same with the Cat as I thought these were a ceramic type structure so surely it would shatter?

6th August 2007, 09:34	#1
webteb Newbie Rover 75 saloon Join Date: Nov 2006 Location: New Zealand Posts: 18 Thanks: 0 Thanked 0 Times in 0 Posts	Exhaust Noise Hi all. My 75 (2.5 V6) has the dreaded rattle/buzz/resonance coming from the front area of the exhaust. It only happens through a short span of low revs and is more pronounced as the engine warms up. I don't think it's fatal but it spoils the sound of the car. I have read about Cat failures and front down pipe problems and wonder if anyone has any more specific info. I saw Lates once referred to a service bulletin on drilling a hole in the down pipe and filling it with weld but has anyone any specific info on where the hole is the hole is actually drilled? I have also seen references to using a self tapper in the Cat but has anyone actually done it? I ask these questions as getting a replacement Cat here in NZ will most likely require a second mortgage. I spoke with a couple of exhaust repair shops and they just normally remove broken Cats as emissions are not currently included in the warrant of fitness (MOT) checks here. I am hesitant in trying this as I’m not sure of how the O2 sensors will react and what impact it will have on the ECU. Any help will be greatly appreciated

6th August 2007, 11:59	#6
RLeon Avid contributor Audi A3 E-tron/Triumph Stag/MG7 (1:18) Join Date: Jul 2007 Location: Limburg Posts: 121 Thanks: 1 Thanked 11 Times in 7 Posts	Exhaust noise As for the noise and welding: Our R75 friends from Germany , www.r75.info , have some info on this. According to them this rattle is most noticable after start with a cold engine. The modification would be to drill a small hole, 8 mm and weld the outer tube to the inner. They have a drawing where to drill and weld, http://www.r75.info/modules.php?name...06371162069363 . To access you have to become a member . RLeon

7th August 2007, 23:19	#8
crofts I really should get out more....... 2003 Rover 75 Conn. SE Auto Tourer 131 ps CDTi Join Date: Nov 2006 Location: Bristol Posts: 2,512 Thanks: 38 Thanked 67 Times in 55 Posts	Cat Think belting it with a hammer may do more harm than good as seem to recall there are ceramic 'goodies' inside. Could be wrong though but............. it could be an expensive mistake. __________________ Rover 75 CDTi SE Connoisseur Tourer (2003) In desirable STARLIGHT SILVER (now restored to it's former glory with all the chrome !)

6th August 2007, 09:59	#2
john adam Avid contributor 1999 Rover 75 2.5 Connoisseur saloon Join Date: May 2007 Location: Carterton, NZ Posts: 106 Thanks: 18 Thanked 3 Times in 3 Posts	As a relatively new 75 owner, I was somewhat concerned with the clatter type noises coming from the driver's side of the engine bay during warmup. From your post it would appear that it is quite normal.

6th August 2007, 10:12	#3
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Yep, I've got it too. TC

7th August 2007, 22:27	#7
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Has anyone considered compressing the outer case slightly so it tightens on whatever's loose inside. I note Dave's idea of Jubilee clips, but I doubt if they'll compress the steel pipe much. I was wondering whether a judicious belt with a club hammer using a suitable drift might work. Anybody got a thought on this? TC

8th August 2007, 09:09	#9
webteb Newbie Rover 75 saloon Join Date: Nov 2006 Location: New Zealand Posts: 18 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks guys for the respsonces. It appears this noise symptom is fairly common. Have registered on the German site (thanks RLeon) but the link keeps telling me the module is not active. I'll keep trying. As for what I thought were O2 sensors,(thanks Cuda-UK) what is the one just down stream of the cat. Is it just a heat sensor and will removing the cat altogether have a bad impact. I'll try and pin point the source with a stethascope and get back if I have some success.

8th August 2007, 11:02	#10
Keith This is my second home ZT400 Join Date: Oct 2006 Location: Ellesmere Posts: 5,948 Thanks: 0 Thanked 43 Times in 29 Posts	It is perhaps not the Cat it may be the intermediate box behind the cat the baffles spot welds break free and when the exhaust is cold and rattle in a most unpleasant way. The drill a few holes and fit some self tappers method works perfectly ok (not sure if it would pass an Mot though) The rattle is very obvious if you get under the car and listen, four self tappers two either side should do it or at least will prove if that is where the problem is obviously listen to the rattle and try and put them where the noise is coming from I would not personally recommend doing the same with the Cat as I thought these were a ceramic type structure so surely it would shatter?