SimonP1976

Hi (again!)

Car 1.25 Zetec 2001 Fiesta, Petrol, Manual - all at standard, no mods.

Recently had a thread on here concerning a knocking noise that was happening 'occasionally' under the car when turning right - not every time, but especially in one or two specific local places. Only turning right, never left, and felt like something was 'loose' and moving independently of the rest of the car (knock/rattle)

Car was booked in to local, trustworthy, mechanic, as it was due for a service anyway. He had the car for a number of days, determined to find the root cause of the issue. It was also due for an annual service, so everything was going to get sorted in one go.

After a short while mechanic said he thought he'd found source of knocking - steering rack - as a small knocking could be heard from it when turning wheel on full lock to the right.

One reconditioned steering rack later, he then fully checked under the car for all suspension elements, inc. Drop links, CV joints, springs, arms bearing etc, and couldn't find anything wrong with any of them, had to replace one track rod end.

Had the car back about a week now, and when driving over the 'specific areas' (as above) when turning right, the knocking noise is still there, it's VERY frustrating as I cant get it to happen all the time in all places, and it is quite loud inside the car when it happens.

A few months ago, I had issues with exhaust, and result was that car needed new Catalytic converter and O2 sensor, which it got. The knocking noise under the car has only occurred (as far as I am aware) since the new Cat was fitted, but Mechanic can't find anything underneath relating to that which may be causing the knocking.

So, summary.

Car producing a knocking noise, seemingly under centre of car, nearer the front, when occasionally turning right. (Never left/straight etc.)

Suspension all appears ok. (inc. cv joints)

Noise is a 'knocking/rattle' sound in a central location and I can feel it a little bit through footwell when it happens.

Steering is ok (especially since new steering rack)

doesn't happen all the time, just in one or two specific places and only when turning right.

was wondering about possible sub-frame issues, or maybe something linked to cat/exhaust since cat was replaced? really struggling to get this sorted, and as the car has been a little bit of a money trap in last few months, keen to find out what it is to hopefully keep it a relatively inexpensive and small issue, not leading to a larger, more costly, issue.

any help/thoughts gratefully received!

Many thanks for reading.

chris cdti

The drivers side driveshaft gets removed when fitting a new cat onto a 1250 fiesta and maybe the rear engine mount. I would be looking at the related parts to make sure it's all tight and fitted correctly.

FiestaSTurbo

I had a similar problem with the knocking when only turning one way and it turned out to be my drive shaft.