P38A Strange metallic noise underneath

P38_OTMS · Jun 21, 2018

Hi all,

I have a strange noise coming from under the car. Sounds a bit like metal on metal like a worn brake pad but it’s coming from under the car but only when moving.

I have had an issue with the low range Ecu failing which, whilst I organise a replacement, is unplugged but I’m not convinced they are related.

Any ideas?

P38_OTMS · Jun 21, 2018

Just been and made a quick video, you can really hear it when slowing down.

I did think it might be a wheel bearing but it’s only done 1000 miles since the MOT and sounds like it’s coming from the driveline

jamesmartin · Jun 21, 2018

i cant hear the vid but prop ujs should be checked

P38_OTMS · Jun 21, 2018

I’ll have a look tomorrow but I’ve had UJ’s go before on other cars and there’s always been a pronounced clunk. No clunking noises here. It’s very much a whirring noise, speed related rather than rev related too.

The video doesn’t do it justice. It really sounds like metal on metal on brakes but they are all fine. And it sounds like it’s coming from under the car.

ukadamwest · Jun 21, 2018

P38_OTMS said:
I’ll have a look tomorrow but I’ve had UJ’s go before on other cars and there’s always been a pronounced clunk. No clunking noises here. It’s very much a whirring noise, speed related rather than rev related too.

The video doesn’t do it justice. It really sounds like metal on metal on brakes but they are all fine. And it sounds like it’s coming from under the car.

not heard the vid busy have you ruled out a binding caliper ?

Datatek · Jun 22, 2018

It's a bit off the mark, but my car had a strange metallic tinging noise from under the car, It was one of the underbody heat shields, the retainers had rusted away and one end was resting on the exhaust.

P38_OTMS · Jun 22, 2018

Datatek said:
It's a bit off the mark, but my car had a strange metallic tinging noise from under the car, It was one of the underbody heat shields, the retainers had rusted away and one end was resting on the exhaust.

You know what you might be onto something there... It sounds like a rotational metal on metal sound. I wonder if I've got a dropped heatsheild on the prop or something... I'll have a look later and see what I can find.

Also going to look into a binding caliper. Visual inspection the pads are fine but I can't see the rear pads so am wondering whether the rear pad is stuck somewhere. Again will investigate later...

flat · Jun 22, 2018

What about a stone between the disc shield and disc?
I had similar on my fender - I binned the shields and problem solved

dubbleRR · Jun 22, 2018

Might be something came loose in handbrake drum after mot test spring ,shoe ect,,,,

Bix · Jun 22, 2018

The noise that sounds like something unwinding when you're off throttle? If so I can't help you with the cure, but I have a similar noise on mine that I am investigating, but I am leaning towards the Tbox.
Hope you find a cure.

ukadamwest · Jun 22, 2018

Datatek said:
It's a bit off the mark, but my car had a strange metallic tinging noise from under the car, It was one of the underbody heat shields, the retainers had rusted away and one end was resting on the exhaust.

oh I had similar. the centerbox has heat shield welded onto it, one of the spot welds wasn't welded properly and pinged off. the box had only been on a few weeks. makes a bloody annoying noise. mig welded it back

ukadamwest · Jun 22, 2018

P38_OTMS said:
You know what you might be onto something there... It sounds like a rotational metal on metal sound. I wonder if I've got a dropped heatsheild on the prop or something... I'll have a look later and see what I can find.

Also going to look into a binding caliper. Visual inspection the pads are fine but I can't see the rear pads so am wondering whether the rear pad is stuck somewhere. Again will investigate later...

if the caliper is binding then you get excessive heat buld up on the brake disk and youll start to see blueing. the calipers on the P38 sit in a pin slider with a rubber conecertina to seal. if that rubber is perished or damaged the pin rusts into the slider and either the caliper will move and not slide out on pressure release or will jam tight at which point the semi worn pad will start to rattle about.

best to check for binding calipers as the excessive heat build up cooks the grease in the wheel bearings dry and you end up with a shot wheel bearing

P38_OTMS · Oct 31, 2018

Bit of a thread revival but thought you lot may have wanted to see what the cause of this was. Only just got around to sorting it out... let’s just say I’ve done less damage to rear differentials on drift cars...

Once again thanks to my local P38 whisperer @brianp38dse, we’re back on the road, ahead of a 1200 mile road trip at the end of the month!

brianp38dse · Oct 31, 2018

The diff was shall we say well and truly shot, no pinion bearing left, the rollers were at the bottom of the diff pan but all sorted now.
made a change to work on a car on a 2 poster rather than laying on the floor

jamesmartin · Oct 31, 2018

brianp38dse said:
The diff was shall we say well and truly shot, no pinion bearing left, the rollers were at the bottom of the diff pan but all sorted now.
made a change to work on a car on a 2 poster rather than laying on the floor

was the vc seized

brianp38dse · Oct 31, 2018

We didn't check that, I did think about it but the car was on the lift by then and had no time left when it was all back together,
I thought the VC only popped the front diff but could be wrong and stand to be corrected.

P38_OTMS · Oct 31, 2018

jamesmartin · Oct 31, 2018

brianp38dse said:
We didn't check that, I did think about it but the car was on the lift by then and had no time left when it was all back together,
I thought the VC only popped the front diff but could be wrong and stand to be corrected.

front is the usual but its not the only diff thats put under strain thats all of the drive train,and diffs can fail for a few reasons but its worth checking

jamesmartin · Oct 31, 2018

P38_OTMS said:
VC?

viscous coupling

P38_OTMS · Oct 31, 2018

Ah yea of course. Hopefully is Ok. Gonna wave some spanner’s at it again on Saturday to check over a few bits anyway so will check it out. Everything seemed ok at the transferbox end

P38A Strange metallic noise underneath

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