Weird braking problem that solved itself…

[Mottie]

The Golf hadn’t been used for a week as we were away and was left on the drive. When we were going out to pick up the dog, I pulled the Golf off while Mrs Mottie parked the A3 on there. As I was waiting for her, I noticed the brake pedal wound creep. Thought no more of it as on some cars with ABS this can happen. Driving it though, it got steadily worse until the pedal dropped alarmingly and I was hitting the secondary part of the system before the brakes kicked in (diagonally, it felt like). My first thoughts were the master cylinder but when I saw the price, almost £300, I started looking at repair kits for less than a tenner - which I am obviously capable of doing. Anyway, I thought that would be a job for tomorrow but when I went outside to move it, all was good! I took it for a bloody good drive and could not replicate the fault at all. I hate these faults that sort themselves out, Anyone had anything like this before?

 

[RandomGrinch]

Not that I know anything at all, but could a small air bubble(/s) expand in this heat to create a temporary air-lock. With agitation/cooling, the bubble(/s) then works its way out?

 

[Burnerman]

Have you checked out the rear calipers and pads lately? Any scraping noise, does the handbrake pull evenly on both sides?
John

 

[Lower]

The Golf hadn’t been used for a week as we were away and was left on the drive. When we were going out to pick up the dog, I pulled the Golf off while Mrs Mottie parked the A3 on there. As I was waiting for her, I noticed the brake pedal wound creep. Thought no more of it as on some cars with ABS this can happen. Driving it though, it got steadily worse until the pedal dropped alarmingly and I was hitting the secondary part of the system before the brakes kicked in (diagonally, it felt like). My first thoughts were the master cylinder but when I saw the price, almost £300, I started looking at repair kits for less than a tenner - which I am obviously capable of doing. Anyway, I thought that would be a job for tomorrow but when I went outside to move it, all was good! I took it for a bloody good drive and could not replicate the fault at all. I hate these faults that sort themselves out, Anyone had anything like this before?

When was the brake fluid last changed? Could have beeen a stickly caliper causing the pads to stick on and overheat a caliper, boiling the brake fluid and causing a vapour lock which you noticed as you had your foot on the brake pedal but has gone now the fluid has cooled again.

 

[carmanmemoranda]

Sounds like a master cylinder issue.

Seal sitting on a certain area or not, or lifting/twisting

 

[Mottie]

When was the brake fluid last changed? Could have beeen a stickly caliper causing the pads to stick on and overheat a caliper, boiling the brake fluid and causing a vapour lock which you noticed as you had your foot on the brake pedal but has gone now the fluid has cooled again.

"Have you checked out the rear calipers and pads lately? Any scraping noise, does the handbrake pull evenly on both sides?
John "


Hmm, a possibility as I did have a slightly binding rear caliper that was advised on the last MOT which I am going to change before this years test - didn’t want to do it last year as I might have had to get rid of it due to ULEZ but I overcame that problem. Thing was, the pedal was creeping from the moment I got in the car as it had been standing for a week. I‘ll have to take it to work next week, recheck that caliper and bleed the brakes right through.

 

[Old Salt]

I wouldn’t trust any brake fault that fixed itself

 

[Mottie]

I wouldn’t trust any brake fault that fixed itself

Neither would I - that’s why I’ll be investigating further.

 

[Mottie]

Have you checked out the rear calipers and pads lately? Any scraping noise, does the handbrake pull evenly on both sides?
John

When was the brake fluid last changed? Could have beeen a stickly caliper causing the pads to stick on and overheat a caliper, boiling the brake fluid and causing a vapour lock which you noticed as you had your foot on the brake pedal but has gone now the fluid has cooled again.

Hmm, a possibility as I did have a slightly binding rear caliper that was advised on the last MOT which I am going to change before this years test - didn’t want to do it last year as I might have had to get rid of it due to ULEZ but I overcame that problem.

Pretty sure that's what it is now. Brought the car up to the workshop this morning, all fine until I was nearly here when the pedal started to drop alarmingly leaving just the second circuit to stop me. Got to work, felt the rear wheels. Offside normal, nearside (the one that was binding last year) was stinking hot. Got other stuff to get on with at the moment so when they have cooled, I'll check that out before I go home and pick up another caliper tomorrow.

 

[Mottie]

Replaced the calliper, just waiting for a set of rear pads to be delivered- I think I’ve had the most out of these!

 

[Nozzle]

Shouldn't that brake pad, thin though it is, actually have shined/flat surface as it's in contact with the disc. The fact it's NOT shined/flat indicates it's not in contact with the disc. Same as the one in the far-ground of the image

Nozzle

 

[Burnerman]

What are the discs like Mottie? I bet they’ve seen better days!
John

 

[Mottie]

What are the discs like Mottie? I bet they’ve seen better days!
John

Discs are perfect. I only changed the pads and discs in June 2021, about 8,000 miles ago. Still waiting for the f'cking pads to arrive. They've sent the driver to the Isle of Dogs on another delivery but the idiot drove straight past me and is supposed to be dropping them off on his way back.

 

[Burnerman]

Those pads look a lot older than 8000 miles, matey!
John

 

[Mottie]

Those pads look a lot older than 8000 miles, matey!
John

Definitely not - maybe even less! Heres the pad from the n/s (sticky calliper) alongside the pad from the o/s against one of the new pads. Hardly any difference from the 2 year old pad and the new one. When I was fitting new pads in the other side, I thought for a moment that that caliper was siezed too - I could only get half a turn at most on the wind back tool. When I looked closer, it was almost fully back anyway!

Brakes worked fine on the way home and both rear wheels were just warm to the touch after my journey.