Knock when pulling away (CDTi)

Toby Waters · 5th August 2009, 12:28

Hi there,

My car has suffered with a knocking sound when pulling off in 1st since I purchased it (with 100,000 miles on the clock, has now done 116,000). I thought that the noise was due to engine movement causing the exhaust to hit the cross bracing under the car (knocking appears to be in that area) and suspected the lower rear engine mount (after much reading on the forum).

The knock has got more frequent since I've owned the car. It started off as an occasional isolated knock when pulling away and now can knock and resonate for a few seconds depending on rpm. It now also knocks when going over bumps but only when power is applied (ie. clutch engaged with throttle).

The other day, I got round to changing the engine mount which hasn't fixed the problem. The mount fitted to the car looked fine and I have now swapped them back.

Any ideas? Could it be the DMF on the way out?

Many Thanks.

Toby Waters · 6th August 2009, 12:38

Forgot to mention - All exhaust hangers present and in appear to be in good condition. Heat shield doesn't seam to be causing the noise - is clear of the exhaust and the knock sounds too substantial (would expect the sound to be more of a rattle).

Thanks

Greeners · 7th August 2009, 11:56

welcome along....Can I assume you fitted a second hand lower mount ?

If so, then fit a new one, as they get a lot of punishment and it's not always possible to see if they're worn or not.

Never heard of any of the other engine mounts failing, other common noise comes from the front strut top mounts

Toby Waters · 7th August 2009, 12:25

Thanks for your reply.

The mount was brand new and unfortunately made no difference.

I don't think it is a top strut mount (although mine does knock slightly when parking). The top strut knock is much quieter and sounds like it is coming from the front of the car. This knock however is definately coming from underneath the cabin (although I know it is difficult to pinpoint these things).

I would expect that if it were excessive engine movement, causing the exhaust to hit something underneath, it would be due to the lower rear engine mount. Is this the only mount that prevents movement in that axis?

chris75 · 8th August 2009, 18:40

Have you looked at the front suspension lower arm rear bushes ? THese are located beneath your feet , more or less , and can produce similar symptoms . Usually if they are gone you can physically roll the wheel back and forward with your hands .

chrissyboy · 8th August 2009, 23:15

what about the wish bone bushes or cv joint?,does it clonk if you pull away slow .if it does rock your engine ,if it easy to move backwards and forwards it is a top mounting .on my old car it turned out to be the top mount.rubber was perished

Toby Waters · 10th August 2009, 12:11

Thanks for all the suggestions.

It is possible to pull away gently without a knock. I also noticed yesterday that it knocked a single time when I started the engine.

I've had a look at the front suspension lower arm rear bushes and they appear ok. Will try jacking the car up and rocking the wheel. Will also have a look at the top mounts.

Cheers

Reebmit · 10th August 2009, 13:03

Quote:

Originally Posted by Toby Waters

I also noticed yesterday that it knocked a single time when I started the engine.

Cheers

Mine gives a knock when I start it and stop it, I am still searching........I think it maybe inside the exhaust, maybe baffles. I'll continue my search at the weekend. I have also replaced the lower mount but no change. Mine does not knock when driving, pulling away etc......

Toby Waters · 12th August 2009, 12:19

Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below:

Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below:

This silenced the knock, so the problem is definately the exhaust fouling the crossbrace. Either the engine is moving too much or the exhaust is hanging too low. The exhaust appears to have a join halfway down and I cannot see any MGR markings on the backbox. It does sit very close to this cross brace (approx 5mm).

Reebmit · 12th August 2009, 13:51

Glad you found your problem, still searching mine, I checked that bracket and mine is okay, also checked the crank pulley and that is fine. I can't see any pipes fouling etc so may have to enlist the services of the other half to start and stop the engine while I look around, Oh she will enjoy that!!

5th August 2009, 12:28	#1
Toby Waters Avid contributor Rover 75 Saloon (CDTi) Join Date: Nov 2008 Location: Bromley Posts: 110 Thanks: 3 Thanked 3 Times in 3 Posts	Knock when pulling away (CDTi) Hi there, My car has suffered with a knocking sound when pulling off in 1st since I purchased it (with 100,000 miles on the clock, has now done 116,000). I thought that the noise was due to engine movement causing the exhaust to hit the cross bracing under the car (knocking appears to be in that area) and suspected the lower rear engine mount (after much reading on the forum). The knock has got more frequent since I've owned the car. It started off as an occasional isolated knock when pulling away and now can knock and resonate for a few seconds depending on rpm. It now also knocks when going over bumps but only when power is applied (ie. clutch engaged with throttle). The other day, I got round to changing the engine mount which hasn't fixed the problem. The mount fitted to the car looked fine and I have now swapped them back. Any ideas? Could it be the DMF on the way out? Many Thanks.

7th August 2009, 11:56	#3
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	welcome along....Can I assume you fitted a second hand lower mount ? If so, then fit a new one, as they get a lot of punishment and it's not always possible to see if they're worn or not. Never heard of any of the other engine mounts failing, other common noise comes from the front strut top mounts __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

8th August 2009, 18:40	#5
chris75 same car since 2005 2001 Rover 75 2.0 v6 Connoisseur Saloon Join Date: Nov 2006 Location: Ellesmere Port , Cheshire Posts: 3,818 Thanks: 379 Thanked 549 Times in 466 Posts	Have you looked at the front suspension lower arm rear bushes ? THese are located beneath your feet , more or less , and can produce similar symptoms . Usually if they are gone you can physically roll the wheel back and forward with your hands . __________________ Who said it was simples ?

8th August 2009, 23:15	#6
chrissyboy This is my second home lovely little ford focus. Join Date: Jul 2009 Location: East Dulwich Posts: 7,877 Thanks: 2 Thanked 82 Times in 68 Posts	hi i had the same trouble with a bluebird and these was the 3 poss`s what about the wish bone bushes or cv joint?,does it clonk if you pull away slow .if it does rock your engine ,if it easy to move backwards and forwards it is a top mounting .on my old car it turned out to be the top mount.rubber was perished

12th August 2009, 13:51	#10
Reebmit Gets stuck in Rover 75 Con SE CDTi, 205 GTi 1.9 (x 2), 205 CTi 1.9, 205 GTi Mi16, Ford C-Max 2.0 TDCi Ghia, MR2 GT Join Date: Nov 2008 Location: Alderholt, Nr Fordingbridge Posts: 935 Thanks: 11 Thanked 15 Times in 9 Posts	Glad you found your problem, still searching mine, I checked that bracket and mine is okay, also checked the crank pulley and that is fine. I can't see any pipes fouling etc so may have to enlist the services of the other half to start and stop the engine while I look around, Oh she will enjoy that!! __________________

6th August 2009, 12:38	#2
Toby Waters Avid contributor Rover 75 Saloon (CDTi) Join Date: Nov 2008 Location: Bromley Posts: 110 Thanks: 3 Thanked 3 Times in 3 Posts	Forgot to mention - All exhaust hangers present and in appear to be in good condition. Heat shield doesn't seam to be causing the noise - is clear of the exhaust and the knock sounds too substantial (would expect the sound to be more of a rattle). Thanks

7th August 2009, 12:25	#4
Toby Waters Avid contributor Rover 75 Saloon (CDTi) Join Date: Nov 2008 Location: Bromley Posts: 110 Thanks: 3 Thanked 3 Times in 3 Posts	Thanks for your reply. The mount was brand new and unfortunately made no difference. I don't think it is a top strut mount (although mine does knock slightly when parking). The top strut knock is much quieter and sounds like it is coming from the front of the car. This knock however is definately coming from underneath the cabin (although I know it is difficult to pinpoint these things). I would expect that if it were excessive engine movement, causing the exhaust to hit something underneath, it would be due to the lower rear engine mount. Is this the only mount that prevents movement in that axis?

10th August 2009, 12:11	#7
Toby Waters Avid contributor Rover 75 Saloon (CDTi) Join Date: Nov 2008 Location: Bromley Posts: 110 Thanks: 3 Thanked 3 Times in 3 Posts	Thanks for all the suggestions. It is possible to pull away gently without a knock. I also noticed yesterday that it knocked a single time when I started the engine. I've had a look at the front suspension lower arm rear bushes and they appear ok. Will try jacking the car up and rocking the wheel. Will also have a look at the top mounts. Cheers

12th August 2009, 12:19	#9
Toby Waters Avid contributor Rover 75 Saloon (CDTi) Join Date: Nov 2008 Location: Bromley Posts: 110 Thanks: 3 Thanked 3 Times in 3 Posts	Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below: Checked the front suspension lower arm rear bushes yesterday and there is no excessive play. I placed a rag between the exhaust and the crossbrace, see below: This silenced the knock, so the problem is definately the exhaust fouling the crossbrace. Either the engine is moving too much or the exhaust is hanging too low. The exhaust appears to have a join halfway down and I cannot see any MGR markings on the backbox. It does sit very close to this cross brace (approx 5mm).