Diagnosis of car/cabin vibrating? Stops when clutch dipped

[visor_down]

Know there are a lot of knowledgeable people on here so thought I would ask if anyone has any pointers on the below.

Car I have bought suffers from a deep bassy vibration that resonates through out the cabin when going over uneven roads.
You can feel it but it is not more noticeable through pedals or steering wheel, it is the whole cabin. It seems to originate from N/S/F however given its low frequency it is difficult to tell.

It happens as the car goes over undulations in the road, not the like of potholes etc, but dips that make the whole car oscillate, it is at its worst as the car reaches the bottom of the suspension travel (for example as you come down the other side of a hump back bridge, however does it on the slightest uneven road). It seems to happen at all speeds above around 20mph, however if it is a flat road and the suspension is not loading/unloading it doesn't do it.

If you dip the clutch it doesn't do it at all, even over undulations

Any ideas on this one?

Cheers

 

[the snooper]

change of mind after reading full post, engine mount / driveshaft

 

[zardoz]

C/V joint, (if the car has them) or more likely, engine mounts/bushes ?

 

[octo0072000]

could be dual mass flywheel, c/v joints, weak shock absorbers,engine gearbox mountings, exhaust catching under body just a few for starters for you
type of car would help

 

[the snooper]

could be dual mass flywheel

I originally wrote DMF but changed my mind when I read it was brought on by road conditions

a ford focus by any chance ?

 

[octo0072000]

I originally wrote DMF but changed my mind when I read it was brought on by road conditions

a ford focus by any chance ?

his older posts say focus st but could be another car now
post also says goes away when clutch dipped still could be DMF
sons done one on a jag that was causing a booming noise at certain speeds i hate DMFs

 

[dan.taylor.1]

If it goes when he clutch is dipped it is driveline related, could be cv joint (usually have grease everywhereas the boot will be split, not so easy to spot if it's an inner one) could be gearbox related (low oil, noisy bearing on diff assuming it's fwd) clutch release bearing, low box oil level.

Knowing the car would help.

Dan

 

[the snooper]

yeah DMF terrible

I did a focus that started to vibrate above 40mph a new driveshaft on drivers side cured it even though I couldn't find anything wrong with the original, I looked on web after that and there are plenty of people with the same problem

 

[visor_down]

Sorry its just a run around Ford Fiesta 1.8TD (DI engine, 2000 model yr), manual 5 spd.
No obvious CV joint leaks.

It definately needs new lower arms, as they are knocking but not sure that this relates

Thanks for replies so far will look into suggestions

 

[the snooper]

It definately needs new lower arms, as they are knocking but not sure that this relates

don't wait until the ball joint pops out lol then you will have some repairs

 

[visor_down]

don't wait until the ball joint pops out lol then you will have some repairs

yes that would increase the parts bill a fair bit! Want to find out what the vibration is first, if it is anything too expensive it won't viable given other issues with the car, would a CV joint / driveshaft issue only manifest itself with the clutch engaged even though they are still spinning with it dipped?

 

[the snooper]

they are not under load when clutch is dipped

 

[AndyStobbs]

What's it like on the over run?

 

[Sean]

It definately needs new lower arms, as they are knocking but not sure that this relates

could do as metal to metal contact will transmit road noise to the chassis ( car cabin) especially after going over humps or bridges when the suspension is compressed

dipping the clutch will un load the suspension and so the noise will go

 

[visor_down]

What's it like on the over run?

Same does it on and off the throttle

 

[octo0072000]

could be the diff bearings is the speedo working ok or is it a bit jumpy as this is a sign of the diff bearings going

 

[visor_down]

could be the diff bearings is the speedo working ok or is it a bit jumpy as this is a sign of the diff bearings going

Speedo is fine, smooth and no signs of any wobble

 

[visor_down]

**FIXED***
Just an update in case anyone ever comes across this on search, solution was as many suggested ..... An engine mount.
The OSF mount was knackered and actually metal on metal as per the attached pic, no wonder it was vibrating!

 

[AndyStobbs]

Good to see you didn't suffer the issue for more than two years.

 

[visor_down]

Good to see you didn't suffer the issue for more than two years.

Fair to say its been a drawn out diagnosis, had some spare time before Christmas so eventually got round to it!​