Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: Broomies Mate on 31 July 2010, 14:31:01
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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. :y :y
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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)...
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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.
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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
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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 :y
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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 ;D
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.
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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 :y
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 ;D ;D ;D
I'll get the alignment done next week, and go from there.
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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 :y
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 ;D ;D ;D
I'll get the alignment done next week, and go from there.
I've no idea if my rear brakes work, doubt it actually ;D - 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.
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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 :y
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 ;D ;D ;D
I'll get the alignment done next week, and go from there.
I've no idea if my rear brakes work, doubt it actually ;D - 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. ;)
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Check that your getting fluid through both of the feed lines from te master cylinder to the ABS unit
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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 ?
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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? :-/
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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 ?
;D
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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 ?
;D
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.
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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 ;)
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p.s. I do this sort of stuff for a living ;)
I'll bow to your superior knowledge then, to be honest I've probably picked up my information from either the Haynes book of lies, or possibly, the instructions that come with the 'Eazi-Bleed' pressure bleeding systems... :D ;D
I have always bled brakes starting with the calliper furthest from the master cylinder (usually passenger rear) and then doing the opposite side on the front...
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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.
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Hmm. I'd never realised the two circuits had different master cylinder bore diameters. You learn something every day. :y
Kevin
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I'll hold my hands up and thank Woody for teaching me something which, I guess, we should all have basic knowledge of.
As mentioned earlier, I too bleed brakes 'furthest' then the opposite, etc etc. I've been doing it wrong ;D
Oh well, you live and learn!
So, back to my problem...... I'll get the alignment checked, and see what goes!
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As mentioned earlier, I too bleed brakes 'furthest' then the opposite, etc etc. I've been doing it wrong ;D ......
Mr Haynes gives two different techniques depending on the age of the car
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I'll hold my hands up and thank Woody for teaching me something which, I guess, we should all have basic knowledge of.
As mentioned earlier, I too bleed brakes 'furthest' then the opposite, etc etc. I've been doing it wrong ;D
Oh well, you live and learn!
So, back to my problem...... I'll get the alignment checked, and see what goes!
Why spend money on the alighnment
You need need to sort your brakes out 1st. Fluid may pass though all the pipes when bleeding, but you dont bleed brakes at the operatinh pressure when running. You said a load of crap came out of the pipes.
Check for damaged/corroded pipes, look for crushed pipes where you can.
Rebleed the system.
Take it to an MOT station and ask them yo check it on the rollers, you could simply be losing all your power in an ecpanding flexi pipr to the wheels under hard braking.
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actually, the best way to bleed is to do the lowest circuit first. Not easy, as it involves examining the car and working out which are the highest brake lines.
reason being - if there's any residual air in the system, it'll rise to the highest part, allowing you do bleed that last of all.
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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.
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Hmm. I'd never realised the two circuits had different master cylinder bore diameters. You learn something every day. :y
Kevin
I think yours will have equal 25mm brake master cylinder. As far as I can tell, they changed sometime after facelift, but before 2.6/3.2.
the size is cast into the body of the master cylinder on the top, below the reservoir.
there's also names on the BAS block for the circuits, but they're in German. HR, for example is Hinten (rear) rechts (right).
just looked it up from Bosch - HR = hinten rechts (rear right), HL = hinten links (rear left), VR = vier rechts (front right) and VL = vier links (front left)
mind you, if there's any German speakers on here, I'll be embarrased, 'cos the German above is a complete guess.
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Sounds about right. Vor = before, Vorderseite = front
Hinter = behind. :y
I wonder if they changed when the vented rear disks came in? Just a thought. Rear caliper might have changed piston diameter then.
Worth bearing in mind that the MCs are not interchangeable without affecting the brake balance.
Kevin
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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.
...
Hmm. I'd never realised the two circuits had different master cylinder bore diameters. You learn something every day. :y
Kevin
I think yours will have equal 25mm brake master cylinder. As far as I can tell, they changed sometime after facelift, but before 2.6/3.2.
the size is cast into the body of the master cylinder on the top, below the reservoir.
there's also names on the BAS block for the circuits, but they're in German. HR, for example is Hinten (rear) rechts (right).
just looked it up from Bosch - HR = hinten rechts (rear right), HL = hinten links (rear left), VR = vier rechts (front right) and VL = vier links (front left)
mind you, if there's any German speakers on here, I'll be embarrased, 'cos the German above is a complete guess.
Sehr gut, mein herr!!
if that was a guess, it was a good one.
Du ist nicht ein dummkopf!!
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Yes, the rear piston size changed when vented was introduced.
My "best guess" would be that the 25-25 master cylinder was introduced at the same time as EBD ( electronic brake force distribution )
maybe a rough survey required.