No brakes...........

[shepster]

On the way to Deva Friday night I suffered a sudden loss of brake pedal feel, pumping them got me enough pedal to stop so got there ok.

Had a quick look over the weekend and no obvious signs of a leak and no loss of fluid from the reservoir?

Started up Sunday and all seems well, only about an hours drive from home and was ok all the way.

My question is this, does it sound feasible for the fluid to pass the master cylinder seals and give me a spongy pedal without any sign of a leak, and then appear ok again?

I've ordered a new Master cylinder just in case but curious to hear any other thoughts.

Cheers in advance.

[bigbadbob76]

If the brakes are dragging on the disks/drums the fluid can boil and you lose your brakes until it cools down again.
I've also had a brake pad material fall off it's backing plate giving the same symptoms as you had but with a horrible grinding noise as the plate is then working directly on the disk.
Hope that helps.
Good luck.

[itchyfeet]

Had a front caliper sieze recenly was getting very hot.

Was it spongy pedal or just no braking power?
The latter could be loss of servo.vacuum

[captain Byrne]

Could you have left your handbrake on?

[shepster]

All good suggestions, need to have a closer look at the weekend.

Pedal went soft with no brakes but when pumped they worked, like when air gets in, but can't understand why they seem ok now?

Handbrake wasn't on and as far as I can tell no sticking calliper, this is why I thought maybe master cylinder.

I'll swap the master cylinder out and have a better look at all the hoses, pipes etc and take it from there.

Cheers for responses.

[California Dreamin]

Vapor lock (the brake fluid in one or more brake components, wheel cylinder or caliper, is getting so hot that it starts to boil)
Gaseous bubbles form and basic science dictates that gasses compress where as fluid doesn't, resulting in spongy brake pedal or even complete failure.

There can be several reasons for this to happen, reasons include:
Old brake fluid (has to be changed every two years as the fluid is hygroscopic, which means is absorbs water from the air) just 3% water lowers the brake fluids boiling point by around 95C.
A binding brake: sticking caliper piston, partially seized handbrake cable (pulling on but not fully releasing) over adjusted rear brakes (basically binding causing overheating and boiling fluid)
The Master cylinder is a mechanical device and fails either totally or with a creeping pedal (under pressure)

Martin

[Theclash]

What California just said ......had the same problem and symptoms you describe after adjusting and unadjusting rear brakes it took me a good few trips in the van to suss out handbrake cable was sticking ,go for a long run and feel your hubs if they are red hot there's your problem I had no choice when it happened to me third time on motorway I took hub off and backed the handbrake off and didn't use it again all the trip with no problems replaced both cables when I got home set the shoes and handbrake and been fine ever since ,just need to change the fluid next

[blakeys80]

I've had the same thing happen twice, scary both times! Once last summer, once last week. No obvious leaks.
I've had a good look @ the back brakes and all seems ok, but after a good run recently, I noticed both front callipers were Very hot, jacked it up and one now seems to be totally seized, the other only slightly less so. The fluid also looks horrible so will be changed along with two new callipers,pads,discs, hoses and bearings.

If you're out and about near Brierley Hill next weekend and you see someone drowning in brake parts, it's me!

[dave friday]

Check the rear brake cylinders for leaks (pull back the rubber dust seals)

[shepster]

Over adjusted handbrake/rear brakes could be a possibility as I recently changed rear shoes and a leaky cylinder and adjusted brakes ready for MOT, this was the first longish outing so might release them off a bit.

Cheers for all the suggestions.

[itchyfeet]

Over adjusted handbrake/rear brakes could be a possibility as I recently changed rear shoes and a leaky cylinder and adjusted brakes ready for MOT, this was the first longish outing so might release them off a bit.

Cheers for all the suggestions.

in my experience under adjusted causes this, you loose alot of travel while the shoes move second pump and you have solid brakes again.
New shoes wil have settled

[shepster]

I was thinking if I had over adjusted them and the brake fluid had gotten hot then this may have caused the brake fade?

[itchyfeet]

I was thinking if I had over adjusted them and the brake fluid had gotten hot then this may have caused the brake fade?

Maybe but I doubt rears would do this so easily
I once drove a powerful car with my handbrake on for miles when I realised the wheels were so hot the paint was bubling any yet I had no fade.

[shepster]

Fair play.

[captain Byrne]

I was thinking if I had over adjusted them and the brake fluid had gotten hot then this may have caused the brake fade?

Maybe but I doubt rears would do this so easily
I once drove a powerful car with my handbrake on for miles when I realised the wheels were so hot the paint was bubling any yet I had no fade.

Not wanting to disagree but somewhile back I had a similar problem. I couldn't do more than 20 miles without one of my rear brakes overheating. The pedal became spongy & brakes pretty ineffective.
I eventually figured I had a bent back plate which caused one edge of shoe to rub on the drum, much the same as having the handbrake on.