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[terry paget]

2.6 petrol manual saloon
I noticed while road testing daughter's 2.6 following misfire repair that it needs more pedal pressure to stop than the other 5 Omegas. It has just passed MOT, I could bring in the ABS on a dry road with a good heave, but it requires more force than it should. Vacuum line looks OK. What might cause this?

[sjc]

Brake pad material can have a big effect on the pedal pressure needed.

I've always found aftermarket (even GM aftermarket - i.e. not GM original equipment) pads give much less 'bite'.  The factory fitment pads are about £100 but the GM aftermarket ones are about £40.

Easiest way to test the servo is to pump the pedal a few times with the engine off (to exhaust any stored vacuum) then keep pressure on the pedal while you start the engine and you should feel the pedal sink when the servo assist kicks in.

[terry paget]

Brake pad material can have a big effect on the pedal pressure needed.

I've always found aftermarket (even GM aftermarket - i.e. not GM original equipment) pads give much less 'bite'.  The factory fitment pads are about £100 but the GM aftermarket ones are about £40.

Easiest way to test the servo is to pump the pedal a few times with the engine off (to exhaust any stored vacuum) then keep pressure on the pedal while you start the engine and you should feel the pedal sink when the servo assist kicks in.

Thanks for servo check, I did just that, and the pedal indeed sank towards the floor on engine start.
It's not pad material, that was my first thought. I changed the front pads for Vx Trade Club standard aftermarket, aa fitted to all my Omegas, and nothing changed. Incidentally, I thought mine cost £15, not £40.
I have changed the fluid, so it's not air in the system. I am perplexed.

[sjc]

Personally I've always found the trade club pads to have very little 'bite' compared to the factory pads. Don't know if they use different manufacturers through time too, would imagine they do. TRW pads usually seem ok.

[Nick W]

2.6 petrol manual saloon
I noticed while road testing daughter's 2.6 following misfire repair that it needs more pedal pressure to stop than the other 5 Omegas. It has just passed MOT, I could bring in the ABS on a dry road with a good heave, but it requires more force than it should. Vacuum line looks OK. What might cause this?

The only way it could be a friction problem is if you tried new brake pads to fix the misfire. I doubt that is the case

You've moved/dislodged/damaged a vacuum pipe or fitting as part of fixing the misfire, and the servo isn't as effective as it is designed to be. That does require a pretty bad leak, but is the first, second and third place to check. If you don't find it that way, have a decent lunch and go over the same stuff again.


This is rule one for diagnosing a new fault after fixing a previous one: go over(or better yet, get someone else to go over) everything that you might have been near as part of the job.

[terry paget]

2.6 petrol manual saloon
I noticed while road testing daughter's 2.6 following misfire repair that it needs more pedal pressure to stop than the other 5 Omegas. It has just passed MOT, I could bring in the ABS on a dry road with a good heave, but it requires more force than it should. Vacuum line looks OK. What might cause this?

The only way it could be a friction problem is if you tried new brake pads to fix the misfire. I doubt that is the case

You've moved/dislodged/damaged a vacuum pipe or fitting as part of fixing the misfire, and the servo isn't as effective as it is designed to be. That does require a pretty bad leak, but is the first, second and third place to check. If you don't find it that way, have a decent lunch and go over the same stuff again.


This is rule one for diagnosing a new fault after fixing a previous one: go over(or better yet, get someone else to go over) everything that you might have been near as part of the job.

I take your point, Nick. This is not a new fault, I changed the pads in August 2015 in an effort to cure it, but 'tis true it did seem worse this morning, and as you observe I removed the main vacuum line and its adapter to change the 2-4-6 plugs, so may have stumbled across something. Will investigate further, thanks for the observation.

[terry paget]

Checked car early this morning. Removed vavuum line from coupler, amd coupler from plenum, looked and felt OK. The vacuum hose is short, with a union near servo end feeding vauum to all other vacuum devices - dual rams, etc, which all work.
Took car for test drive, pedal is firm, pedal travel is short. Now it seems more like 'cold pad' syndrome. I have changed front pads. Now I wonder if trouble is in the rear pads. Is it worth changing the rear pads?

[Bigron]

Probably not, Terry, as most of the braking is on the front because of the weight transfer when braking and the rears are mainly for stability.

Ron.

[Nick W]

The next thing I would check is that the calipers slide freely, and that the pistons move.

[terry paget]

Probably not, Terry, as most of the braking is on the front because of the weight transfer when braking and the rears are mainly for stability.

Ron.

Agreed, Bigron. I have never changed the rear pads so I don/t know what they are, but they look all right and are wearing evenly so no seized pistons. I have known seized pistons in the past on Omegas, but it did not affect braking noticeably.

[terry paget]

The next thing I would check is that the calipers slide freely, and that the pistons move.

I suppose that's all that's left, and yet it seems unlikely that both sides would fail similarly, and if one side was sticky the brakes would pull to the other. Also, when I changed the pads last year I did look for these things.

On my X reg estate pedal travel is noticeably longer than on my similar mileage V reg estate. I put this down to master cylinder wear, but soon readjust to it.

I find Omega brakes in general very good. I have known far worse. In particular, a 1978 VW Passat, last car I bought new, had awful brakes, poor when cold and useless when hot.

This car is strikingly similar to a Morris 1100 I used to rally, to which I had fitted a servo and special 'hard' pads, excellent when hot but poor when cold.

[TheBoy]

TC pads, if unused for a few days, need some use to be able to lose that dead feeling.  Though in my experience, a few hundred yards is enough.  OE pads do not have this issue, but cost £80 as opposed to TC £15....

[Nick W]

The next thing I would check is that the calipers slide freely, and that the pistons move.

I suppose that's all that's left, and yet it seems unlikely that both sides would fail similarly, and if one side was sticky the brakes would pull to the other. Also, when I changed the pads last year I did look for these things.

There's plenty of other things it could be, but they're all much harder to examine or prove faulty so you work up to them in a methodical way.

[biggriffin]

i'm with nick on this, you get a misfire, go for a drive,and the brakes seem funny? well they were fine till you removed the coil pack?
check the servo pipes, ALL of them, might even cure the misfire. 

[iansoutham]

The next thing I would check is that the calipers slide freely, and that the pistons move.

On my X reg estate pedal travel is noticeably longer than on my similar mileage V reg estate. I put this down to master cylinder wear, but soon readjust to it.

I know this is going off on a slight tangent, but I had the same with my Omega, with the brake pedal having a long travel but still working. Weirdly, after changing the abs block, the pedal is firmer and still as sharp, if not sharper than before.