noise from rear of vehicle

S

Smelf36

Member
 Hastings
So I have noticed on a couple of occasions, a strange metallic sort of 'hissing/scraping' noise coming from the rear of the car.
it is very intermittent, for example I heard it today for the first time in about a week! seems to be from the back nearside and if you dip the clutch and blip the throttle it goes away until you take your foot back off the throttle (clutch engagement does not alter the noise). there are no drive/fueling issues that I can detect, no clutch slip, its not brake squeal and they work fine, in fact the car drives perfectly. No warning lights. Could it be some sort of valve in the exhaust?? just the increased revs made me wonder.
 
mcbutler said:
you may have a small piece of gravel stuck between the disc and the backplate!
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I’m pretty sure it’s not brake related, mainly as it goes away when the Revs are increased?
 
The problem with a lot of cars is sometimes a noise sounds like it is coming from the rear when it is actually the front.
Do you hear this noise with the roof up, down or both?
We had a slight noise that was like a whirring/hissing that could be heard with the roof down and I also thought it was from the rear.
The only thing I could find was the coolant was low and I put the noise down to it being the water pump that I could hear.
I havnt heard it again since.
 
Smelf36 said:
mcbutler said:
you may have a small piece of gravel stuck between the disc and the backplate!
Click to expand...
I’m pretty sure it’s not brake related, mainly as it goes away when the Revs are increased?
Click to expand...
Sorry, just re reading your post. If its related to engine revs and no difference with clutch engaged/disengaged then its your engine.
Does it do it when the vehicle is parked or only when moving?
 
mcbutler said:
Smelf36 said:
mcbutler said:
you may have a small piece of gravel stuck between the disc and the backplate!
Click to expand...
I’m pretty sure it’s not brake related, mainly as it goes away when the Revs are increased?
Click to expand...
Sorry, just re reading your post. If its related to engine revs and no difference with clutch engaged/disengaged then its your engine.only when moving so far, never had a car with a turbo before, something to do with that ??
Does it do it when the vehicle is parked or only when moving?
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only when moving so far, never had a petrol engine with a turbo before, could it be this?
 
My thought is wastegate rattle, but you saying it sounds like it’s coming from the N/S rear is a bit baffling, but as Nictirx said sound can carry in strange ways in cars. Flip the bonnet, from the front listen to the left side of the engine.
 
Waste gate valve? I know nothing about turbo’s, is this a big problem? I noticed today that the valve in the right hand tail pipe is open on tick-over, I thought this only opened above 4000 revs to give more noise? Is this right, could this have anything to do with it???
Oh and the dogs in the wife’s boot, he wouldn’t lay down long enough to shut the lid in the Zed😜
 
Mr roadster said:
Hi smelf36 sorry about joke hope you solve the issue.*
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No need for apologies😉 be good to fix it, although it’s doesn’t seem to be a major issue, car runs and stops fine, just a bit irritating at times 👍🏻
 
Smelf36 said:
john-e89 said:
Or a loose exhaust silencer baffle on the N/S pipe.
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Not really a baffle kinda rattle, had that before, more of a hissing sort of noise, really hard to describe?
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Blowing exhaust perhaps..? Not very likely as it’s a stainless system but worth a shot. Let it idle and put a hand over each tailpipe, you’ll hear it blowing as well as there won’t be much back pressure on your hand.

Wastegate rattle could be the rod linkage has worn causing the rattle, or maybe the wastegate is leaking but you’ll hear this from inside the engine bay. Did you lift the bonnet and have a listen yet? Get someone to hold the revs at increments of 1k up to around 3-4K and listen for a hiss.
 
Zed Baron said:
Can you record the sound?
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Would be tricky, as it’s intermittent and only seems to happen when moving, so would have to have someone in the car at the time, which is unlikely. Had a listen to the engine bay and nothing untoward noted, but it was just idling🤷‍♂️
 
Smelf36 said:
Zed Baron said:
Can you record the sound?
Click to expand...
Would be tricky, as it’s intermittent and only seems to happen when moving, so would have to have someone in the car at the time, which is unlikely. Had a listen to the engine bay and nothing untoward noted, but it was just idling🤷‍♂️
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Idling is no use Smelf it’s not making boost at idle.
 
john-e89 said:
Smelf36 said:
Zed Baron said:
Can you record the sound?
Click to expand...
Would be tricky, as it’s intermittent and only seems to happen when moving, so would have to have someone in the car at the time, which is unlikely. Had a listen to the engine bay and nothing untoward noted, but it was just idling🤷‍♂️
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Idling is no use Smelf it’s not making boost at idle.
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right oh, My son doesn’t need much of an excuse to sit in it and rev it, I’ll have another listen tomorrow, so progressively raise the the revs to about 4000 and listen out fro the noise yes?
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Smelf36 said:
john-e89 said:
Smelf36 said:
Would be tricky, as it’s intermittent and only seems to happen when moving, so would have to have someone in the car at the time, which is unlikely. Had a listen to the engine bay and nothing untoward noted, but it was just idling🤷‍♂️
[/quote

Idling is no use Smelf it’s not making boost at idle.
Click to expand...
right oh, My son doesn’t need much of an excuse to sit in it and rev it, I’ll have another listen tomorrow, so progressively raise the the revs to about 4000 and listen out fro the noise yes?
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Yes it’s worth a shot, also boost pipe failure could be the cause too.
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So the exhaust valve in the tail pipe, seems to be permanently open, could the noise be from the vacuum system used to activate the valve?
 
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