Problem with brakes ?

[maston]

Hi All,
Sorry if this is a really basic question but every now and then (completely at random) the brake pedal will become very slack with it travelling nearly to the floor when I try and brake. Very disconcerting whilst trying to stop !!!
Do you think the brakes need bleeding and if so do all 4 need to be done or can just the front brakes be bled ?
Many Thanks
Ian

[njhucker]

If it happens after a few miles, then it is likely to be a sticky rear caliper. I have had this on 2 wedges

[vampire222]

I'd have the fluid replaced and see if they don't stick or have worn out. Safety is a serious matter! If you end up replacing the fluid i can highly recommend steel brake lines btw!

[keatsie]

Air getting into the system or seal gone on the master cylinder - check carefully, brakes are so..... important

[adam quantrill]

Try going for a few miles drive without using the brakes at all if you can - safety first of course. Best to pick a quiet day and use the gears to slow down etc.

THen go round each brake to see how warm it is - any binding brakes will be much warmer than the others.

[TVRleigh_BBWR]

When was the Fluid changed, if you don't know or more than 3 years, change it and do a full bleed. but also do the checks posted above.

[jeff m2]

I would think the odds are, a problem with the master.
Even with really bad brakes the master should always "refill" from the res.

To get "nothing" on the pedal, ie less than bleeding pressure with an open bleeder, tells you a lot.

[bradderztvr]

Agree with above, I had this happen several years ago and was fluid passing the seals in the master cylinder.
In any case, check free movement of the caliper pistons, bleed the system, if still a prob, it's the master cyl.

[RCK974X]

If you get pressure if you repeatedly pump the pedal, then it's probably master cylinder (just the seals if you're lucky...).

Try it cold in the garage before you fire it up. If you get pressure then, but not after driving for a while, consider the sticky or seized caliper more likely... the master cyl problem will show up even when stone cold.

Mine was fine even for quick stops, once I got into the habit of pumping the pedal, but it got a bit silly and probably dangerous..... New seals fixed it.

New brake fluid might help - you're supposed to change it regularly, but nobody does.(OK, a select few do) After it absorbs water, its boiling point drops very rapidly and you get gas bubbles....

Bleeding and new fluid - with any vehicle I typically do the shortest runs first (i.e. front), and then longer runs (rear). Wedges are a bugger because they have the inline pressure reducer for the rear, and the rear calipers have two (three ?) wonderful looped pipes which are perfect for gas bubbles, and it can take a lot of bleeding (and cursing) to get it all flushed out.

Edited by RCK974X on Wednesday 29th February 22:34

[maston]

Thank you everyone for your replies.
Have booked it in with my local garage and will get a new master cylinder fitted too.
Where is the best place to get one ?
Thanks again
Regards
Ian

[TVRleigh_BBWR]

RCK974X said:

Bleeding and new fluid - with any vehicle I typically do the shortest runs first (i.e. front), and then longer runs (rear). Wedges are a bugger because they have the inline pressure reducer for the rear, and the rear calipers have two (three ?) wonderful looped pipes which are perfect for gas bubbles, and it can take a lot of bleeding (and cursing) to get it all flushed out.

AFAIK you should always do the longest one 1st.

The auto pressure bleed systems are very handy and not that expensive.

[RCK974X]

Yeah, I think many manuals *DO* say longest first, but I never got that order to work with any vehicle that had a rear pressure reducer.....I reckon the bubbles in the front get in the way.

On cars without the valve had no problem doing longest first.

That's just my personal experience, so whatever works !

Brake pressure systems (Ezibleed etc) are good but waste a lot of brake fluid as I understand.

[adam quantrill]

Deffo do the longest one first on the wedge because that is invariably the one where the bleed nipple won't work and if you don't do that one first all the rest of the effort (and brake fluid) is wasted.

[Wedg1e]

RCK974X said:

Brake pressure systems (Ezibleed etc) are good but waste a lot of brake fluid as I understand.

They don't waste much.

[RCK974X]

Fair enough - perhaps I'll go and buy one and try it out !!!