Brake woe's.....any hints or tips please

[V70 Graham]

I seem to be getting a spongy brake pedal at the moment, this first happened after TRAX last Sept and I thought it could be because I boiled the brake fluid (don't laugh, I was going well fast lol) anyway had a local guy bleed the brakes using the gravity method ie opening all the nipples and letting the fluid drain through, not sure this is the best way to bleed them though.
Since yesterday the problem has returned, first press of the pedal and it seems to go down more than normal, though press it again quickly and it firms up.....if this makes sense.
Disks and pads all good, replaced last summer by M-R-P and no loss of fluid, gonna try another bleed from my trusted indie Monday week, anything else I should/could get them to look at/for ?
Thanks in advance.

[stribo]

Definitely sounds like they need bleeding.

[merc85]

any loss of fluid graham?

[V70 Graham]

No Gav, none at all.

[oblark]

My brakes are the same but I've got racing pads, the brakes get better when they warm up.

[V70 Graham]

My brakes are the same but I've got racing pads, the brakes get better when they warm up.

Mine are not like it all the time, just started happening for the second time yesterday, pads in my car are normal road ones.

[Volvostorm]

Have a look, or even better change your flexi's, they could be balloning, perfect reason to upgrade to braided hoses

[stribo]

Is it happening when you've been driving for quite a while without using the brakes? If so it could just be the pads rattling away from the discs whilst driving, so the first time you press the pedal the pads have further to travel before they come in contact with the discs, the second time, they're already up against the disc.

[JamesT5]

It could be the master cylinder seals are perished which will result in a drop in brake pressure.

[V70 Graham]

It could be the master cylinder seals are perished which will result in a drop in brake pressure.

Even with no loss of fluid ?
Seems to happen when driving normally, not just after a spell with no braking.

[M-R-P]

I'm liking Paul's idea, it'll be worth a look.

I've been avoiding mentioning the master cylinder, hoping its something simpler.

Give it a bleed mate and check the hoses at the same time. Go from there.

[stribo]

Get them bled and go from there then. I'm sure the system has to be pressurized when they're bled, because of the ABS pump, so gravity bleeding them may not have worked. Or I could be talking out of my §§§§.

[merc85]

Are the caliper slider's greased up well, All this crap weather may be causing them to stick

[JamesT5]

Even with no loss of fluid ?
Seems to happen when driving normally, not just after a spell with no braking.

The system may contain fluid but the innter pistons are worn, hence no loss of fluid.

[M-R-P]

Get them bled and go from there then. I'm sure the system has to be pressurized when they're bled, because of the ABS pump, so gravity bleeding them may not have worked. Or I could be talking out of my §§§§.

I used a venturi vacuum to bleed mine and graham's brakes with no trouble (clutch was a different story tho)

[V70 Graham]

Ok chaps, thanks for your thoughts, bleed and braided hoses, think I can get these for around £60 iirc, master cylinder gonna be a bit more !

[oblark]

Didn't someone at one of the southern meets comment on the paint peeling off of the servo under the master ?

[V70 Graham]

Didn't someone at one of the southern meets comment on the paint peeling off of the servo under the master ?

Yeah but that was there when I bought the car, never got wet since then, think maybe the cylinder was replaced before I bought it.

[oblark]

It was just a thought :)

[LiamT4]

Have a look, or even better change your flexi's, they could be balloning, perfect reason to upgrade to braided hoses

Sounds like that could be the issue.

[Harvey]

Sounds like the master clyinder could leaking past a seal back to tank.
Try to get it pressure bleed first.

[V70 Graham]

Sounds like the master clyinder could leaking past a seal back to tank.
Try to get it pressure bleed first.

Will do, don't think there's a repair kit for my master cylinder.

[nobananas]

Had a similar problem once before. Checked all the brakes, replaced master cylinder and bled brakes god knows how many times but the fault remained. In the end I stripped all the brakes and removed the anti-squeal shims which cured it. Found out that some of the shims were acting like a weak spring and slowly pushing the caliper pistons into the calipers very slightly. First press of the pedal would go to the floor and then it would be fine unless the brakes weren't used for ten minutes or so (like on the motorway) then you'd get a long travel again, not saying it's causing you're problem but it certainly caused mine !

[JUDGENINJA]

Rather than just bleeding, have you completely changed your fluid?
Flexi pipes would be a good idea if they are the originals from new.
Never heard of shims making a lot of difference.
When I change my pads I do spend a bit of time cleaning and polishing the pins and sliders to ensure the pads can move freely.
then the last thing could be Master cylinder/servo.. It's been a while since I looked under my 850 bonnet are there any Vacuum lines that could be perished with a small air leak?

[Saaamon]

As above you need to completely flush the fluid out of every pipe which will require quite abit of fluid, also you need to start with the furthest away.

[V70 Graham]

Right, braided hoses ordered, gonna try them along with a proper bleed/fluid change.

[V70 Graham]

*Update*

Right, I had the brakes bled and fitted new flexi hoses, result was a better pedal.....till today !
It's back to as it was, pedal travels a bit further down but not to the floor, if I release it and reapply pedal is great, lovely and firm.
The only other addition to my previous comments is that last time I drove the car, I was pushing along a bit and was using the brakes fairly hard (for me anyway).
Surely brakes don't need bleeding every 2 Months (I know they don't).
I'm now at a loss as to what to look at next, callipers (car doesn't pull under braking) or master cylinder, or could it be the servo ?

Any comments as always appreciated.

[M-R-P]

It's odd that a bleed cures it for a while. Maybe something's letting air into the system. There's definitely no fluid seeping from the master cylinder?

[V70 Graham]

It's odd that a bleed cures it for a while. Maybe something's letting air into the system. There's definitely no fluid seeping from the master cylinder?

Nope, dry as a bone, each time seems to happen after I have been braking hard.

[Kingsford G]

So u have brakes on the 2nd pump of pedal.If u do 2nd pump and hold it does the pedal go down slowly?

[V70 Graham]

So u have brakes on the 2nd pump of pedal.If u do 2nd pump and hold it does the pedal go down slowly?

No, it stays firm.

[M-R-P]

Weird...

[stribo]

Weird...

Enough about Graham, what about the car? Definitely sounds like air's getting in somewhere. Has the fluid level dropped at all?

[V70 Graham]

Enough about Graham, what about the car? Definitely sounds like air's getting in somewhere. Has the fluid level dropped at all?

Not a bit, just wondering if Harvey was onto something with the seals in the master cylinder ?

[V70 Graham]

Just off the phone to a Volvo 'Guru' he recons it's 80% master cylinder 20% a sticking calliper.....

[nobananas]

Have you checked for brake fluid in the servo ? Easiest way is to pull the vac hose off and dip a cable tie into the bottom of the servo, any fluid and it's bye bye master cylinder. Another tip would be to clamp off each flexi pipe until the excessive travel stops though obviously this will only help if the fault is constant and you can't drive the vehicle like this.

[M-R-P]

I can see how a sticky caliper could cause that.

[oblark]

Just off the phone to a Volvo 'Guru' he recons it's 80% master cylinder 20% a sticking calliper.....

I`ve got a fully working master cylinder if you go down that route :)

[Kingsford G]

To change the master cylinder is an easy job.When was your brake fluid changed last?Do a quick master cylinder change,don`t have to bleed the whole system,just the 2 pipes that go to abs unit by undoing them on the pump will do the job.All gonna take 30-40 min max.

[V70 Graham]

Going to have it looked at on Thursday, fingers crossed it's found/fixed cheaply.

[Kingsford G]

Going to have it looked at on Thursday, fingers crossed it's found/fixed cheaply.
If u were near I have a good master cylinder and could sort it out whatever it is.

[960kg]

Only trying to help......

So many people when changing pads etc. don`t open the bleed nipple when pushing back the caliper piston, this can make the valves in the ABS unit get £££££e in them as well as forcing fluid the wrong way it was designed for in the Master Cylinder!

This results in MAYBE dirt from the old brake fluid blocking the ABS valves and also reversed lips on the master cylinder seals.

Although these things are possible they don`t often happen but one should always take precautions and do things the fail proof way.

To check the master cylinder get someone to look in the reservoir with the top off when another pushes the brake pedal on the FIRST stroke and if faulty you will see the brake fluid stirring
because of the backward flow of the fluid.

Because these things are pretty rare i would first look at the caliper pistons as i would bet one or more is sticking with a rusty ring around cylinder bore.

Squirt some WD40 onto the piston seal and passed the seal to see if it solves the problem then you will know more where your at.

[Brett855tdi]

I wonder if you have a bleed nipple sucking air when its hot? just a thought...

When you bleed it again and get your temporary fix... do you get any air out?

[V70 Graham]

When you bleed it again and get your temporary fix... do you get any air out?

Last time I bled them was after the braided hoses were fitted so not really ideal to check.

[Harvey]

When the pedal goes soft does the car stop in a straight line or does it pull to one side a bit (which is not normal for it).
If so then its a good chance it the master clyinder or

If you drive along with the windows open and turn left or right at low speeds near full lock can you hear the pads dubbing on the discs,this would be a pad sticking in a caliper,or a worn wheel bearing,or
(:splat:if you have had a couple of track days warped discs from high speed stops :splat:)

If the pedal is getting soft all the time,get the brakes tested on a brake rollers MOT type then that would show up any problems.

[V70 Graham]

It does stop in a straight line, though if it was a rear calliper it should still stop without wandering.
Wheel bearings were replaced last Autumn, did TRAX and MAYBE a disk is warped, but.....it still wouldn't explain why after bleeding the pedal firms up and after using the brakes hard pedal travel is longer and will stay that way till I bleed again !

[Harvey]

It does stop in a straight line, though if it was a rear calliper it should still stop without wandering.
Wheel bearings were replaced last Autumn, did TRAX and MAYBE a disk is warped, but.....it still wouldn't explain why after bleeding the pedal firms up and after using the brakes hard pedal travel is longer and will stay that way till I bleed again !

No i was only jokeing about the warped disc as you would feel it in the steering wheel.
It does sound like a master if you brake hard the seals in the master would take the brunt of the force.
see if you garage would do a brake test I think it would show up the part at fault.

If the master is at fault the n/s to o/s would be way off on locking force.

[V70 Graham]

Still no further forward, was going to go for the master cylinder but the place I was at yesterday was sent the wrong one :mad111:

Will let a few of the guy's have a look at the meet tomorrow, see if they have any ideas.