Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Broomies Mate]

My Omega (99, 3.0 Elite in Gay Champagne Colour) has an odd braking problem.

It pulls drastically to the right on heavy braking.

So, It needed new pads, so changed them today, along with the known good calipers from my breaker.  Everything came off and went together beautifully.  A complete brake fluid change, and all ready to go.

Test drive, and the problem still remained.  Got the brakes nice and hot, then squirted them briefly with the hose to see if one brake was getting hotter than the other.  Drivers Front and Passenger Rear are getting VERY hot (normally hot).  Passenger front and Drivers Rear are not.  They are hot, just not as they should be.

I replaced the Master Cylinder with the known good one from my breaker, and the problem still remains.

Can someone confirm my fears that the problem is most likely the ABS unit?  I'm thinking the seals have rotten.

Are there any other possible causes.

Re-Cap;

New Pads
Discs are fine
New Calipers
New Master Cylinder
Fresh Fluid.

How much of a ball-ache is it to replace the ABS module?  I have another on the donor car, and I can re-use the 'good' ABS ECU from my Gay Coloured one.   

[Psychoca]

Sounds like a blockage in one of the lines (I think I am right in thinking that there are dual lines one to passenger front and drivers rear and the other to the other brakes)...

[Broomies Mate]

Sounds like a blockage in one of the lines (I think I am right in thinking that there are dual lines one to passenger front and drivers rear and the other to the other brakes)...

Yeah, from the Master Cylinder to the ABS Module, there are the two lines (as you say, work opposite side left/right and opposite front/back).  From the ABS module, there is one line per wheel.

If there was a blockage, I'd more than likely notice on flushing the system I guess?  All four brakes bled/flushed as expected.

[markspark]

putting cold water on red hot brake discs can warp them then you will need new discs again

Could you not take the car to MOT station and ask them to put it on brake test for you don't think they would charge much for that at least then you would know what each wheel is doing without causing further problems

just another thought what condition are your wishbones in they could cause a pull to one side aswell

[tunnie]

i'd go with the above, check for play in wishbone busehes, get a large crowbar / screw driver in at the side and push the bush out, see how much movement there is 

[Broomies Mate]

putting cold water on red hot brake discs can warp them then you will need new discs again

Could you not take the car to MOT station and ask them to put it on brake test for you don't think they would charge much for that at least then you would know what each wheel is doing without causing further problems

just another thought what condition are your wishbones in they could cause a pull to one side aswell

Yeah, I know it's not the 'proper' way of testing, but it's all I had at the time.  A dash of water on the caliper wont do any significant harm 

Wishbones seem to be fine.  No adverse movement.  I'll take the car to ProTyre for a 4wheel alignment next weekend, see if they pick anything up with the suspension components.  I'll be heading to WIM in a few weeks when I get everything sorted.  Dont want to make the long trip when I KNOW something is wrong.

[Broomies Mate]

i'd go with the above, check for play in wishbone busehes, get a large crowbar / screw driver in at the side and push the bush out, see how much movement there is 

Sounds plausible, but could it be coincidence that the opposite rear brake is working less efficiently too?

I guess I'm trying to figure out whats wrong without actually doing anything 

I'll get the alignment done next week, and go from there.

[tunnie]

i'd go with the above, check for play in wishbone busehes, get a large crowbar / screw driver in at the side and push the bush out, see how much movement there is 

Sounds plausible, but could it be coincidence that the opposite rear brake is working less efficiently too?

I guess I'm trying to figure out whats wrong without actually doing anything 

I'll get the alignment done next week, and go from there.

I've no idea if my rear brakes work, doubt it actually  - How can you tell the rears are not working right?

Did you get the fluid out of the calipers? clamp the cable that runs to the brakes, then push in the caliper? Thats were the really nasty fluid is.

[Broomies Mate]

i'd go with the above, check for play in wishbone busehes, get a large crowbar / screw driver in at the side and push the bush out, see how much movement there is 

Sounds plausible, but could it be coincidence that the opposite rear brake is working less efficiently too?

I guess I'm trying to figure out whats wrong without actually doing anything 

I'll get the alignment done next week, and go from there.

I've no idea if my rear brakes work, doubt it actually  - How can you tell the rears are not working right?

Did you get the fluid out of the calipers? clamp the cable that runs to the brakes, then push in the caliper? Thats were the really nasty fluid is.

I replaced all four calipers.  Yes, all nasty crap was removed.

I know it's an Elite, so handles like the QE2 anyway, but generally speaking, when you push the stop pedal, and the rear wheels leave the ground, you can be sure the rear brakes aren't functioning correctly. 

[Marks DTM Calib]

Check that your getting fluid through both of the feed lines from te master cylinder to the ABS unit

[2woody]

there are dual lines, but they are "front-rear", not diagonal split.

for proof - most cars have 25mm primary master cylinder bore and 20mm secondary, which by it's nature must be front-rear split.

probably not ABS unit IMO.

are you sure the car's plumbed up right ?

what year and model is it ?

[Broomies Mate]

there are dual lines, but they are "front-rear", not diagonal split.

for proof - most cars have 25mm primary master cylinder bore and 20mm secondary, which by it's nature must be front-rear split.

probably not ABS unit IMO.

are you sure the car's plumbed up right ?

what year and model is it ?

It's a 99 (T) Elite, 3.0 V6 Saloon.

I'm not questioning your knowledge, but I was under the impression that all cars had diagonal split braking systems from about 1970 onwards?   :-/

[Brikhead]

there are dual lines, but they are "front-rear", not diagonal split.

So if you had a fault on the 'front' circuit then the rear wheels would be expected to do all the braking? I'll bet that causes the a.b.s. to work overtime, sounds fun!

...are you sure the car's plumbed up right ?

[Broomies Mate]

there are dual lines, but they are "front-rear", not diagonal split.

So if you had a fault on the 'front' circuit then the rear wheels would be expected to do all the braking? I'll bet that causes the a.b.s. to work overtime, sounds fun!

...are you sure the car's plumbed up right ?

Glad I'm not the only one who thinks woody is possibly wrong.  Everything I have worked on (modern-ish) has had diagonal split for obvious reasons. 

[2woody]

you're actually partially right - most English cars in the seventies were diagonally split - and you can still do it that way, but it's almost impossible on a car designed for ABS.

there is a legal requirement ( C&U Reg 15 & 16 ) for the system to be split, but a manufacturer can really only meet the requirements of the braking Directive if the vehicle has a front-rear split. ABS systems are generally designed for front-rear split, too.

the main reason for this is to get the correct adhesion mix for the front and rear axle, where the braking system has to counteract the natural tendancy for the weight to shift forwards under braking.

looking at the Omega, most cars have a master cylinder with two different bore sizes, 25 and 20mm. The 25mm part feeds both front wheels, whilst the 20mm part feeds both rear wheels.

just to go back to a diagonal split, it is possible to make it work to current braking performance requirements, but you need either twin rear wheel adjustment devices ( a pressure reduction valve connected to the suspension ) or for in-line pressure relief valves, but these can't be made to work with ABS.

p.s. I do this sort of stuff for a living