Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: doz on 15 December 2012, 11:06:26
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I hate the peddle feel in the Omega. I've replaced the fluid and I know all the air is out but it's always felt soft. Pumping it doesn't make it go hard and the servo seems to being the job. However yesterday I was out and I approached a set of traffic lights. So I knocked the car in to neutral while I waited and as I did the brake peddle sank under my foot. Not by much but enough I felt it. At first I thought it was down to the revs raising. However I couldn't replicate it by blipping the throttle at a stand still. So anyway I continued on my way. Next set of lights knocked it in to neutral same thing happened. Anybody got ideas? Is something just about to break on the brakes? Can you get rid of the crap soft peddle?
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I found a similar thing when I changed my front pads and then pumped the pedal to expand the pistons I was worried at first but was told this is normal and everything has been ok since but I know what you mean about the feel. Not much help but I think that we use a car without thought and then when we do something different we notice something that has always been there.
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I would try a complete fluid change
Make sure this includes all the fluid in the calipers/pstons as per the guide :y
I think this forms part of the service schedule although somewhat extended
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Done that.
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Will the brake pedal go solid with the engine off? Pump the pedal a few times with everything off and it should go rock hard. Add a little pressure to the pedal and start the engine. The pedal should sink a little. Does it do this?
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Will the brake pedal go solid with the engine off? Pump the pedal a few times with everything off and it should go rock hard. Add a little pressure to the pedal and start the engine. The pedal should sink a little. Does it do this?
Just about to type the exact same thing ::)
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Yep. Servo seems to be working fine
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Does the car idle/run ok? Perished connection on one of the vacuum lines perhaps :-\
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Yep. Servo seems to be working fine
I assume you are not losing any fluid, else you would have mentioned it.
Is the Servo vac pipe in good nick? No splits or cracks?
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Engine is very sweet. Haven't checked for any air leaks but with the aircon off gives a rock solid 600 rpm idle. No holding back, whistles etc. I'm starting to think maybe master cylinder.
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Engine is very sweet. Haven't checked for any air leaks but with the aircon off gives a rock solid 600 rpm idle. No holding back, whistles etc. I'm starting to think maybe master cylinder.
That's the next logical step. Fortunately, they are one of the easiest things to change!
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When you changed the pads last did you push the cylinder back in with the bleed nipple closed? If so you may have caused the seal in the MC to flip over reducing it's effectiveness. If this is the case you can try and sort it out with an assistant to pump the pedal while you lightly tap the MC on the sides with a small hammer all around. It doesn't work all the time.
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I would suggest the following......
check CAREFULLY the brake servo vacuum pipe.
Bleed everything again - aim to get at least five litres of fluid through
adjust the brake pedal "off" position. Use the two adjustments that you have, that's the length of the brake servo pushrod ( simple screw adjustment ) and the brake lamp switch position. You want the pedal rod long enough so that the lamps come on and the brakes start working with the pedal moved 5mm or less.
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Hmm wondering if it could be pad "knockback"?always gives a soft pedal
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I'm by no means cirtain, but I think this is normal. :-\
Is it to do with engine load? If knocked into neutral, there's less load, so less tick over throttle is needed to keep the same revs. Therefor less vacume in the plenum and vac pipe to servo, so less servo assistance. Or at least there's an effect on servo assistance, , my simple brain can't work out which way it would affect it ATM, as i'm knackered, but I often wondered what caused the pedal feel to change.
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I'd prefer a more aggressive servo anyway, if anyone has a sensible suggestion.
I realise this is not everyone's taste, but mondo levels of servo assistance suite me fine.
(ie, loads). :)
(sits back and waits for Markdtm's response :-X ;). )
Relevance to the op might mean fixing his problem, if I understand things correctly. :)
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I'm by no means cirtain, but I think this is normal. :-\
Is it to do with engine load? If knocked into neutral, there's less load, so less tick over throttle is needed to keep the same revs. Therefor less vacume in the plenum and vac pipe to servo, so less servo assistance. Or at least there's an effect on servo assistance, , my simple brain can't work out which way it would affect it ATM, as i'm knackered, but I often wondered what caused the pedal feel to change.
Normally less load means throttles closed therefore more vacuum in the intake plenum. If engine is being used for 'engine braking' then you get maximum vacuum. Knock it into neutral & the engine has to open the throttles a little to maintain idle so the vacuum will be less.
The servo should store enough vacuum for 3 or 4 brake applications (if the non-return valve is working).
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I'd prefer a more aggressive servo anyway, if anyone has a sensible suggestion.
I realise this is not everyone's taste, but mondo levels of servo assistance suite me fine.
(ie, loads). :)
(sits back and waits for Markdtm's response :-X ;). )
Relevance to the op might mean fixing his problem, if I understand things correctly. :)
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I'm by no means cirtain, but I think this is normal. :-\
Is it to do with engine load? If knocked into neutral, there's less load, so less tick over throttle is needed to keep the same revs. Therefor less vacume in the plenum and vac pipe to servo, so less servo assistance. Or at least there's an effect on servo assistance, , my simple brain can't work out which way it would affect it ATM, as i'm knackered, but I often wondered what caused the pedal feel to change.
That is interesting to me Chris. You have confirmed what I thought was happening to mine during the problems I had recently with a missing "top hot" 'O' ring on my plenum, along with mis-firing. I had a very noticeable drop in braking power, with the pedal needing to be depressed a long way down before the brakes bit.
I didn't know for sure if the leak in the plenum/drop in engine power would have that effect, but now I do. Thanks Chris :y :y
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Normally if coasting in gear the engine is developing no power (overrun) so throttles closed and maximum vacuum. Suddenly put it in Neutral and the ICV will open to stop the revs falling, so it's plausible that you'd get a little less vacuum in this instance. Moreso if there's a defect causing a misfire or intake air leak.