Brakes issue (lack of)
Discussion
Having in intermittant braking issue on my Griff today. Driving along normally and every so often when I brake, the pedal creeps a bit before any retardation applies, then its normal in feeling the next time. Also I seem to be losing servo assistance, as at least once when braking, the pedal felt hard and hardly stopping the car, but next time its working as normal.
Stop car and turn off engine, pump pedal a couple of times and hold it, start engine and it drops with servo assistance, so servo is working, possible vacuum valve faulty?
Stop car and turn off engine, pump pedal a couple of times and hold it, start engine and it drops with servo assistance, so servo is working, possible vacuum valve faulty?
Have you lost fluid with no apparent leak?
We have seen this more than once where both the servo and the master cylinder have leaks with the result that the fluid is sucked into the servo. On each occasion the fluid has been right up to the vacuum port.
Remove the fitting where the vacuum connects into the servo. A squirt of release oil no the rubber grommet makes it easier to remove the plastic pipe fitting. Once removed you can use a cable tie as a dipstick down into the servo.
I hope that is not the problem as changing the servo and master cylinder is not a fun job (made worse by being 16 stone and 71 YO).
Steve
We have seen this more than once where both the servo and the master cylinder have leaks with the result that the fluid is sucked into the servo. On each occasion the fluid has been right up to the vacuum port.
Remove the fitting where the vacuum connects into the servo. A squirt of release oil no the rubber grommet makes it easier to remove the plastic pipe fitting. Once removed you can use a cable tie as a dipstick down into the servo.
I hope that is not the problem as changing the servo and master cylinder is not a fun job (made worse by being 16 stone and 71 YO).
Steve
With the engine running, press the brake pedal and keep pressing it hard. Does it stay solid or does it creep down? If it creeps down and no loss of brake fluid then suspect the brake master cylinder allowing brake fluid to get past the seals. If it stays solid then a servo fault probably. Check for corrosion at the bottom where moisture collects. If you suspect the non return valve on the manifold, disconnect the pipe at the servo as Steve has said by pulling it out then try blowing and sucking it to check.
Sounds very like you have a small vacuum leak .. the pedal moving down will be that the initial lack of vacuum makes the pedal feel firm and at the very top of its travel, but after a few seconds of overrun the vacuum builds in the servo and the pedal sinks slightly and full braking power is restored.
My Focus had the exact same issue.
My Focus had the exact same issue.
spitfire4v8 said:
Sounds very like you have a small vacuum leak .. the pedal moving down will be that the initial lack of vacuum makes the pedal feel firm and at the very top of its travel, but after a few seconds of overrun the vacuum builds in the servo and the pedal sinks slightly and full braking power is restored.
My Focus had the exact same issue.
Interesting, I'm unfortunately working all weekend, then on nights from Tuesday, so limited time wise to have a real look at it, the intermittent nature of the fault has me considering all possibly options, thanks for the suggestion.My Focus had the exact same issue.
Right back from holiday, and changed the brake fluid, tried the car and the issue is not as bad as it was, pedal is more predictable in action, and no real issue as before ...... until I was slowing down, no throttle, low speed so low revs, and gentle braking, then I felt the pedal harden again, and it felt like no servo assistance, was brief, and I was thinking did I imagine it, but I tried to replicate the situation, and it did it once more, again its 95% better than it was before, and up to that point I had full confidence the issue had been fixed .
So changing the fluid has greatly improved the situation, but there is still a small issue.
So changing the fluid has greatly improved the situation, but there is still a small issue.
Hi, When you replaced/bled the system did you bleed the point on the top of the master cylinder as well as the calipers? I had an issue where I had trapped air at this point and no matter how much I bled through at the calipers it wouldnt shift it.
It is bit of a horror to get at through the clutch reservoir cover, I managed to get a small 3/8 drive socket and wobble joints to reach it, and then stuffed loads of rag underneath to catch the fluid.
It is bit of a horror to get at through the clutch reservoir cover, I managed to get a small 3/8 drive socket and wobble joints to reach it, and then stuffed loads of rag underneath to catch the fluid.
kevd said:
Hi, When you replaced/bled the system did you bleed the point on the top of the master cylinder as well as the calipers? I had an issue where I had trapped air at this point and no matter how much I bled through at the calipers it wouldnt shift it.
It is bit of a horror to get at through the clutch reservoir cover, I managed to get a small 3/8 drive socket and wobble joints to reach it, and then stuffed loads of rag underneath to catch the fluid.
You can get a spanner on it through the grommet for the vacuum pipe.It is bit of a horror to get at through the clutch reservoir cover, I managed to get a small 3/8 drive socket and wobble joints to reach it, and then stuffed loads of rag underneath to catch the fluid.
Steve
Penelope Stopit said:
Surely air in the system won't give a hard pedal, a vacuum leak will
This.Do this test ..
drive along on tickover on a quiet road and press the brake pedal, is there a rock solid pedal right at the top and little in the way of servo assist?
drive down a quiet hill .. don't use the brakes until you have travelled several seconds down hill at highish revs. Does the pedal now travel further than it did in test 1? is the pedal slightly less rock solid, and is the servo assistance immediately obviously working?
If yes to those tests, you have a vacuum leak. No need to bleed brakes or anything - simple test to carry out with no tools.
spitfire4v8 said:
Penelope Stopit said:
Surely air in the system won't give a hard pedal, a vacuum leak will
This.Do this test ..
drive along on tickover on a quiet road and press the brake pedal, is there a rock solid pedal right at the top and little in the way of servo assist?
drive down a quiet hill .. don't use the brakes until you have travelled several seconds down hill at highish revs. Does the pedal now travel further than it did in test 1? is the pedal slightly less rock solid, and is the servo assistance immediately obviously working?
If yes to those tests, you have a vacuum leak. No need to bleed brakes or anything - simple test to carry out with no tools.
Its the random very intermittant issue that's the problem, split hose or servo, problem would be very obvious, as I posted, it was so random I began to question if it really happened the other day, and I had to try very hard to get it to do it again.
Jools, I will try the tests again the next time I take it out, but can say that in both scenarios mentioned, 95% of the time there was no issue, it is that random.
Ok, an update, and hopefully finally resolved.
Its been very random in occurrence, last year I had the one way valve and hose replaced, car seemed perfect since, until a month or so ago, and whilst coasting down towards an island, the pedal felt solid on first light application, and seemed little in the way of retardation, I released the pedal and applied it again, and brakes were normal, random again.
Car has been in for service these last couple of days, and I mention again to the guy about my issues, and he had an idea.
When he replaced the servo one way valve and hose last year, he blew air down the pipe to the engine, all clear, now he racalls there's another valve in the pipe work, at the Plenum take off, its a ball bearing in effect, inside the fitting, he removed the fitting and shook it, but could hear no movement of the ball, sprayed brake fluid in and a load of gunk came out, and now the ball rattles, he thinks that this was the cause of my intermittent braking issue, so now hopefully all sorted, and just a heads up in case anyone else has a similar problem.
Check your balls!! .
Its been very random in occurrence, last year I had the one way valve and hose replaced, car seemed perfect since, until a month or so ago, and whilst coasting down towards an island, the pedal felt solid on first light application, and seemed little in the way of retardation, I released the pedal and applied it again, and brakes were normal, random again.
Car has been in for service these last couple of days, and I mention again to the guy about my issues, and he had an idea.
When he replaced the servo one way valve and hose last year, he blew air down the pipe to the engine, all clear, now he racalls there's another valve in the pipe work, at the Plenum take off, its a ball bearing in effect, inside the fitting, he removed the fitting and shook it, but could hear no movement of the ball, sprayed brake fluid in and a load of gunk came out, and now the ball rattles, he thinks that this was the cause of my intermittent braking issue, so now hopefully all sorted, and just a heads up in case anyone else has a similar problem.
Check your balls!! .
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