Front brakes binding

[Barry]

Well - I haven’t made it to the cruise tonight. 

Sitting in my bay about to call NRMA. 
Seems my front brakes are binding tight. 

I’ll get a tow home. 
Before I take it to the mechanic any pointers?

Slowly felt the pedal loose travel. 
Rear brakes cool. 
Front seem hot. Both sides. 
Haven’t jacked it up at all to test.

[Andy.]

Binding brakes (front disc callipers?) can be a number of things:
Old brake hoses, the inner lining can swell and prevent pressure releasing and holding the brakes on
Rust on the pistons (in the calliper), again preventing the brakes releasing.

However, you mentioning you slowly loose pedal travel, is that you push the pedal in and it does not fully return? Or the pedal returns fully, and cannot push in as far each time?
Both could mean different things.
If the pedal is not returning fully after braking, it will not let pressure in the calliper release. Could be a broken return spring, binding pivot, or something draging on the operating lever.
If the pedal returns fully, but cannot push in far, the master cylinder seals could be collapsing, or the galleries in the master cylinder could be blocked, again not letting pressure release.

It would need some investigations. Quick initial checks can help out, remove one of the wheels where it is binding (ensure van is safely on stands), see if you can push the pistons back. If they do not, it could indicate corrosion on the pistons.
Apply the brakes, and release the pedal. Crack the brake line and see if there is trapped in pressure.

Also try bleeding the brakes, if some seals are collapsing the brake fluid will come out dark/black from the rubber. If it comes out dirty straing away, it's most likely calliper seals, if it's clean for a bit then dirty, it's more likely master cylinder seals.

[Barry]

Andy
Thanks for the reply. 

While sitting there, all seemed fine again. 
I thought, I wouldn’t bother with tow, and started to drive home. 
Almost home, and all fine. 
Decided to turn around and complete night. 

Drove to Liverpool and all good. 
Drove to Greystanes and all good. 
Driving home and went pear shaped. 

Pressure built up in pedal again and brakes came on. 
It’s as though there is no compression in the fluid. 
It’s not mechanically (as in pedal jammed)
The fronts got real hot. 
Got off M4 and pulled over. 
Called for tow. 
By the time he pulled up there was movement in pedal again and brakes off. 

Things were checked when motor was done. 
New lines were put in and new brake booster one way valve.

[Barry]

Just add that master cylinder and booster look original

[rstucke]

Just add that master cylinder and booster look original

could be 
brake pedal return spring - does the pedal arm hit the bump stop under the floor when released, if not the transfer port in the Master cylinder may be covered slightly stopping fluid returning. push on the pedal let it go listen for the thump under the floor

spring in the blind end of the master cylinder collapsed - same outcome as above. Would need dismantling

central valve in the booster intermitantly leaking allowing atmospheric pressure to one side of the diaphragm (they are vacuum suspended ie. vac on both sides when not in use) - unlikely but may be caused by push rod with not enough clearence, diaphragm spring busted or valve problem. unlikely because front and rear would bind.

Don't think it's hoses or callipers because unlikely both would go the same amount at the same time

I think Andy has covered all this and given you a number of things to try

[Andy.]

Certainly does sound like the pedal (or master cylinder) are not fully retracting. A failing booster would not apply the brakes.
Any luck with diagnosing this further?

[Barry]

I’m not that good with brakes so it’s in withe Julian next week. 

Just to be clear - the pedal stays up. It’s the travel that disappears. 
It’s as though it suddenly becomes over adjusted?

All brakes must be coming on at once.

[brujef]

i had this issue with a valiant once - the callipers needed re building. the seals have a tricky piston return ability built in and once they are old and tired they can loose it but do not necessarily leak. 
see if you can put a seal kit in them, you might find some corrosion in there too so probably a re sleeving while it is all pulled apart. 
made a HUGE difference to my valiant's breaking ability!

[Andy.]

I’m not that good with brakes so it’s in withe Julian next week. 

Just to be clear - the pedal stays up. It’s the travel that disappears. 
It’s as though it suddenly becomes over adjusted?

All brakes must be coming on at once.

Hmm, that is a strange one. Let us know what they find once it's fixed!!

[grumble]

Hmm, that is a strange one. Let us know what they find once it's fixed!!

Barry when the vehicle is stationary and the engine is stopped, does the brake pedal have free travel usually about 3-5mm. It sounds like it has closed up and the residual pressure is building up in the system and locking the brakes on, when the fluid cools down it releases and starts the procedure all over again. Another possibility is there is some gunk in the bleed back hole in the master cylinder preventing the fluid returning to the reservoir. The brake pedal free travel is most likely or the pedal return spring is broken.