Fiesta Rear imbalance

jimmyw

An 03 fiesta just failed the NCT with the rear drums with an imbalance of 56%.The front discs were 17%, the limit for both back and front is 30% so hence the fail on the rear.The guy says the nearside one is causing the imbalance.At first I was thinking that it must be "grabbing" the drum too quick, but thinking again, that couldn't be the case so it probably means that its not "grabbing" enough I assume.

I've just had a quick look and typical, the drum is held on by the hub nut, but I don't have the correct size socket for it, incidentally the nut looks a bit different to the regular one.Is there a reason for it?.The wheel/drum is spinning freely with the handbrake off.The handbrake passed the NCT with an imbalance of 14% I think.

Is there any precautions to know before I try to take off the drum?

CJhaughey

Just be aware the proportioning valves on them can give some grief, they are nearly best to buy new.

jimmyw

CJhaughey wrote: »

Just be aware the proportioning valves on them can give some grief, they are nearly best to buy new.

Actually, now you mention it, he also said there is a common valve problem with them fiestas, so a possibility.But I will have to check under the drum first though.

dooroy

If the handbrake was 14% imbalance then the problem must be with the hydraulics - maybe a sticking wheel cylinder for example .
The proportioning valve could also be faulty but I thought this valve controls pressure to the rear wheels - don't know about it causing an imbalance between the rear wheels

CJhaughey

dooroy wrote: »

If the handbrake was 14% imbalance then the problem must be with the hydraulics - maybe a sticking wheel cylinder for example .
The proportioning valve could also be faulty but I thought this valve controls pressure to the rear wheels - don't know about it causing an imbalance between the rear wheels

There are separate valve units in these, if one is faulty it can cause an imbalance on the same axle.

dooroy

Thanks for that - learn something new every day:)

jimmyw

Slight update, we pulled off the hub with a little help from a puller to reveal all is dry.Cleaned up the drum which was not to bad.One of he shoes were a little worn as you would expect, near the top,close to the where it sits into the cylinder but otherwise just ok.

Removed the bearings just out of interest with one falling to pieces :rolleyes:.Odd bearings to me because they have a plastic holder holding the rollers ..Got them back in and no play from them before we took them off or after...phew!.Slight discrepancy on the handbrake but acceptable.



Looking to be the pressure valve possibly, but I am afraid that if this is not the fault, then they will be waste.


More odd components fell of the back of the backplate, don't know what these are for? (lower pic below).

cletus

If it turns out not to be the valves, the self adjusters for the handbrakes on the previous model of the fiesta tended to not work particularly well, needing periodical manual adjustment. Not sure if its the same on the mk5

CJhaughey

Any chance you could borrow one from a known good car?
Mark it and see if it makes a difference.
Might save you the price of a new valve?

jimmyw

I know you all could not sleep waiting to see what happened...:D.Well a whole load of grief endured since the last time.Installed the valve, fiddly as hell:mad:.Tried to bleed the rear offside brake circuit and of course when tried to open the rear brake nipple.......yeah you've guessed it, sheared off.

B***X says I, so off to get a loan of another car to search around for a new cylinder and finally got one at a reasonable price at an auto factors even though there was no leaks from the old one.Also had to get a new "Hub nut" (if you can call it that) because I damaged it trying to extract the drum.

Eventually got it in, drum nut on, drum on, bleed and a small wee amount of air came out.Checked pedal, still spongy.Off with the opposite brake (front nearside) no seizure on this one thank F**K and alot more came out as expected.Now pedal is much better.Great I thought but then the father had the car on Sunday and the flippin clutch went kaput :mad::mad::mad:.

Trouble was that a retest is booked for tomorrow I was afraid that it would not be done in time and an extra charge would apply.Luckily its done now so hopefully she will pass on the second attempt.I will let ye know tomorrow.

jimmyw

PASSED!! with 18% imbalance as opposed to 56%, but probably would help if the shoes were changed, but they are not bad enough to change them.

Most other people in the centre were in for retests too I'd say as they had the fail sheets from last time.Nice little earner for the NCT!


Yeah,yeah far more safe cars on the road,bla bla bla:P.