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the_lincs_landies

Member Since: 29 May 2023
Location: Boston, Lincs
Posts: 230

Exhaust Knocking on Chassis?

Hi All
When I am driving along I get a metallic knocking noise when going over bumps - almost like something metallic is bouncing and then making contact with something else. I say bouncing as it seems to be a few knocks with lower severity each time. (I’ll try and record at some point)

Whilst investigating i for under the car and noticed there is enough play in the rear exhaust hanger for the silence for make contact with the chassis. Could this be the cause of my knocking, and is that normal to have that much movement? The hangers don’t seem particularly worn, but I genuinely can’t dine anything else that could be making this knocking noise…

29th Aug 2023 9:12pm

MarkBrown

Member Since: 03 Oct 2022
Location: Mid Wales
Posts: 462

1983 Defender 110 Other HT Auto Keswick Green

It could be. I had a similar problem recently, the exhaust was catching the gearbox cross member. It turned out to be the gearbox mounting had sagged and partly broken, this then broke the exhaust rubber and caused a knock from the exhaust over bumps and a vibration when accelerating. If one of the rubbers has gone you should be able to see some marking on the chassis or axle where it's catching and also make a similar noise by wobbling the exhaust.

29th Aug 2023 9:33pm

HardCharger

Member Since: 03 Mar 2013
Location: Manila
Posts: 737

2011 Defender 110 Puma 2.4 SW Stornoway Grey

Check your suspension and shock bushings. Don't forget the the A-Arm ball joint while you're at it.

30th Aug 2023 3:18am

Daysleepers

Member Since: 15 Dec 2022
Location: Suffolk
Posts: 111

2007 Defender 110 Puma 2.4 DCPU Keswick Green

I haven’t had this with a defender but have seen similar things when engine mounts have gone. Often the RMM.

30th Aug 2023 8:54am

devnull

Member Since: 29 Mar 2010
Location: Poland
Posts: 18

Mid exhaust hanger collides with the rear propshaft on the bumps.

30th Aug 2023 10:42am

the_lincs_landies

Member Since: 29 May 2023
Location: Boston, Lincs
Posts: 230

Thanks all, these give me some things to check over at the weekend.

I am hoping it is what devnull has suggested, and I am hoping that I van fix it with a new rubber hanger.

I fear, though, that it could be what HardCharger has suggested, as the advisories from the last MOT do state the rear shocks have "slightly worn" bushes.

It quite a hard knock mind you, its like a loud metallic clank followed by a series of "fading" glangs (assuming whilst the unintended motion slows to a stop)

30th Aug 2023 11:42am

NickMc

Member Since: 01 Oct 2014
Location: Norn Iron
Posts: 1624

Check the hanger mount on the crossmember isn’t on back to front.

30th Aug 2023 4:02pm

the_lincs_landies

Member Since: 29 May 2023
Location: Boston, Lincs
Posts: 230

Thanks NickMc, I’ll add that to the list. Is there a man easy way to tell which way around it should go?

30th Aug 2023 9:09pm

the_lincs_landies

Member Since: 29 May 2023
Location: Boston, Lincs
Posts: 230

So, it turns out I may have fixed this without knowing what it was whilst the car was sat on the drive fora substantial period of time.

The drop plate of this little blighter, being secured by heavy duty bars and split pins, had an amount of play in it when secured. Enough to make it jump about and knock when going over bumps etc. and then the lesser bangs being the subsequent motion where it settled back down to where it rests.

Oh well, that's a knock off of the list, even if most of the stuff suggested does need attention at some point...

5th Sep 2023 3:24pm

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