Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: Ady on 25 June 2014, 08:01:24
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Whilst doing 20 mph tried to stop the peddle sunk to the floor, second pump returned to normal and I stopped just in time. Since done about 5 miles (nervously) home and brakes performed fine.
On Monday I replaced rear discs, pads and hand brake shoes, cleaned up very rust calipers.
I know that this was all done correct as have done many before, I followed omf maintence guide and my dad who is a mech supervised. I have done 20 miles since changing and before incident.
My brake fluid is a little high and I suspect that could be the problem do will take done out in a bit,
Does anyone have any other theory's
Thanks
Ady
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Did you disconnect the pipes and not bleed them properly? could you have possibly flipped the master cylinder seals when pushing the pistons back in, often heard of it but took it as an urban myth as i've never come across it actually happening :-\
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Hi omega baron
I didn't disconnect the brake pipes, I cleaned calipers on the car. I did apply brakes without the pads in to check pistons were moving ok and then pushed them back into place.
Never heard of flipping cylinder, is there an easy fix to that?
My calipers where very rusty and the inside pads were rusted in place so rear bakes have scarely never worked properly since I've owned the car.
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Was it to the floor? Fully to the floor, with no braking response at all, or just a lack of servo assistance that felt like no brakes?
Did the car stall or drop revs at all?
Was this first touch of the pedal after a lay up?
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It was fully to the floor pumped it once and it went straight back to normal.
I fitted brakes Monday night, drive home 5 miles then work in the morning another 5 miles then got almost home this happened. Since done another 5 miles with no problem.
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No stalling or rev loss that I noticed but I was paying more attention to the bumper of the car in front lol
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Sounds to me as though a piece of dirt got stuck temporarlly under a valve or a seal and that the second pump of the pedal shifted it. In which case it may never happen again or it may happen the next time you use the brakes. It would be worth doing a very comprehensive flush of the brake system, push at least 1 litre of brake fluid through it, and preferably refurbish the master cylinder first, or fit a new one.
Alan
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Thanks for the advice everyone.
Where can I get a new master cylinder from? Tried euro car parts and GFS but neither stock it on there web sites.
Also is it a job I should get booked in a garage to do or can I do it on the drive? Can do most stuff but never attempted a cylinder.
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Two nuts and a few pipe unions... iirc. Messy but perfectly feasible :y
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Not too bad to change master cylinder.
I presume an autopsy will follow? I'd want to know I'd found the fault personally.
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I have seen a new master cylinder on ebay this morning
Keith B
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Check your brake pads is my advice. I only say this as when I bought the wife's car, the guy I bought it from had not long changed the front pads. We had it a week when the same thing happened. I was driving and when I pressed the brake nothing happened, pedal straight to the floor. Second, panicked, press had them working fine. I got home and went to find the cause only to find one of the front pads had gone. Pad material had separated and vacated the car.
Many little things can be ignored on a car if it is an occasional fault, but not with brakes. Personally I would find the fault if possible rather than just guess and change bits.
At very least give a good check of the whole brake system, just because it was the rears you were just working on doesn't mean the problem won't be somewhere else.
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On my last omega i was going to have all 4 flexy hoses changed as front needed doing so thought while he was at it he may as well do the rears,,,however he advised me that because the master cyl would have of the same age that by changing all four at once and brake fluid that the extra pressure in the master cyl could just turn the seals over as he had this happen before to him ????? so just done the two and all was ok.......I have heard it said that it can happen but i believe it was on the vectra.... :y
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What turns the seals over is pushing the caliper pistons back without opening the bleed valve first. Changing the hoses will have no effect whatsoever on pressure in the master cyl!!!!!!
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. I was driving and when I pressed the brake nothing happened, pedal straight to the floor. Second, panicked, press had them working fine. I got home and went to find the cause only to find one of the front pads had gone. Pad material had separated and vacated the car.
I had the very same thing happen on the wife's Golf, luckily it was me driving and I was going slow....foot to the floor and lights flashing on the dash, I grabbed the handbrake and pumped the pedal and suddenly all was normal. Drove a bit further (as I was on dual carriageway) and on next application heard the sound of metal on metal. Drove home cautiously and when I looked at the pad ALL the friction material had gone from one side.
Looking on the internet it seems it is not that uncommon an occurrence nowadays!!
Nice!!! :-\
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. I was driving and when I pressed the brake nothing happened, pedal straight to the floor. Second, panicked, press had them working fine. I got home and went to find the cause only to find one of the front pads had gone. Pad material had separated and vacated the car.
I had the very same thing happen on the wife's Golf, luckily it was me driving and I was going slow....foot to the floor and lights flashing on the dash, I grabbed the handbrake and pumped the pedal and suddenly all was normal. Drove a bit further (as I was on dual carriageway) and on next application heard the sound of metal on metal. Drove home cautiously and when I looked at the pad ALL the friction material had gone from one side.
Looking on the internet it seems it is not that uncommon an occurrence nowadays!!
Nice!!! :-\
Hmmm. That would seem to add up. Bit like the first press of the pedal after they've been worked on, after a pad change or whatever, as the pistons are pushed back to get the pads out and new ones in. First thing you do on an auto is press the brake pedal to turn the key and engage gear etc. So your guaranteed to do the safety check of pressing the brakes after a brake service etc.
Not the case on a manual as the first thing you habitually do is press the clutch, most likely.
On bikes there's a couple of instances that spring to mind from this. One is a tank slapper. Usually on track, if the rider slides the rear and has a moment, as the rear snaps back into line its said it can shake the handle bars so violently the forks can flex or twist in a torsion motion. That puts pressure on the brake pads as discs move off centre in the caliper, which pushes the pads back in the caliper.
If the rider stays on, he then arrives at the next corner and runs on, because theres no brakes. He pumps the lever and gets brakes on the second press., as the pistons are pushed out to the disc again. But too late to make the corner.
The other instance is a recall on the Yamaha R1. First model. Due to an issue with the pad material not binding correctly to the metal backing.
So for the op, check your pads. Although surely there would be an audible grinding of pad metal on disc?
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What turns the seals over is pushing the caliper pistons back without opening the bleed valve first.....
Hi Alan.
Can you explain where these seals are and how they get turned over? I can't think where that could happen in the master cylinder?
I appreciate its better to push the old fluid through by releasing the bleed nipple, when pushing the pads back, but by nature, a brake system has to allow its hydraulics to move both ways at some point.
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. I was driving and when I pressed the brake nothing happened, pedal straight to the floor. Second, panicked, press had them working fine. I got home and went to find the cause only to find one of the front pads had gone. Pad material had separated and vacated the car.
I had the very same thing happen on the wife's Golf, luckily it was me driving and I was going slow....foot to the floor and lights flashing on the dash, I grabbed the handbrake and pumped the pedal and suddenly all was normal. Drove a bit further (as I was on dual carriageway) and on next application heard the sound of metal on metal. Drove home cautiously and when I looked at the pad ALL the friction material had gone from one side.
Looking on the internet it seems it is not that uncommon an occurrence nowadays!!
Nice!!! :-\
Hmmm. That would seem to add up. Bit like the first press of the pedal after they've been worked on, after a pad change or whatever, as the pistons are pushed back to get the pads out and new ones in. First thing you do on an auto is press the brake pedal to turn the key and engage gear etc. So your guaranteed to do the safety check of pressing the brakes after a brake service etc.
Not the case on a manual as the first thing you habitually do is press the clutch, most likely.
On bikes there's a couple of instances that spring to mind from this. One is a tank slapper. Usually on track, if the rider slides the rear and has a moment, as the rear snaps back into line its said it can shake the handle bars so violently the forks can flex or twist in a torsion motion. That puts pressure on the brake pads as discs move off centre in the caliper, which pushes the pads back in the caliper.
If the rider stays on, he then arrives at the next corner and runs on, because theres no brakes. He pumps the lever and gets brakes on the second press., as the pistons are pushed out to the disc again. But too late to make the corner.
The other instance is a recall on the Yamaha R1. First model. Due to an issue with the pad material not binding correctly to the metal backing.
Although surely there would be an audible grinding of pad metal on disc?
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Didn't on mine, there was some material left on the back plate, not much, but enough to stop metal on metal contact. As it was only one pad I couldn't say I really noticed much difference in breaking, although I did drive it gently home after that and didn't really use the brakes until I found our what had happened. The pedal going straight to the floor at 60mph had me not trusting them much.
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You have missed the point of my comment which was the falsehood that changing the rear brake hoses at the same time as the fronts would somehow be detrimental to the master cylinder. Absolute tosh.
I agree that pushing fluid back through the master cyl is highly unlikely to flip the seals, but it is very slightly more plausible than changing brake hoses causing it.
The main reason for not pushing fluid back through the system is to reduce the possibliity of contaminated fluid being intoduced to the ABS block, but I'm sure you knew that.
What turns the seals over is pushing the caliper pistons back without opening the bleed valve first.....
Hi Alan.
Can you explain where these seals are and how they get turned over? I can't think where that could happen in the master cylinder?
I appreciate its better to push the old fluid through by releasing the bleed nipple, when pushing the pads back, but by nature, a brake system has to allow its hydraulics to move both ways at some point.
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Did you disconnect the pipes and not bleed them properly? could you have possibly flipped the master cylinder seals when pushing the pistons back in, often heard of it but took it as an urban myth as i've never come across it actually happening :-\
Not urban myth but only delco master cylinders usually only on early mk3 Astra's.
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You have missed the point of my comment which was the falsehood that changing the rear brake hoses at the same time as the fronts would somehow be detrimental to the master cylinder. Absolute tosh.
I agree that pushing fluid back through the master cyl is highly unlikely to flip the seals, but it is very slightly more plausible than changing brake hoses causing it.
The main reason for not pushing fluid back through the system is to reduce the possibliity of contaminated fluid being intoduced to the ABS block, but I'm sure you knew that.
What turns the seals over is pushing the caliper pistons back without opening the bleed valve first.....
Hi Alan.
Can you explain where these seals are and how they get turned over? I can't think where that could happen in the master cylinder?
I appreciate its better to push the old fluid through by releasing the bleed nipple, when pushing the pads back, but by nature, a brake system has to allow its hydraulics to move both ways at some point.
Fully understood. But, seeing as other members have now come up with a viable reason for the fault, I'd like to go slightly off topic and persue what I personally believe to be another oof myth re flipping seals. It might be applicable to other models, I wouldn't know. But has anyone seen a shred of evidence the flipping seals applies to the omega?
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I have seen the seals flip on pretty much all types of master cylinder.
If you look at the seal shape and consider the fluid being forced the wrong way, then you can understand how it can happen.
The old mallet job can fix this in most cases.