Boiled brake fluid - twice
Discussion
Had a track day at Oulton Park in the week and suffered almost complete brake failure after about 5 hot laps, was a bit of a bum clencher I can tell you.
Needless to say, I only had regular dot4 fluid in the car and it had boiled. I bought some higher boiling point fluid from the shop on site and had a go at bleeding it through the system, unfortunately i couldn't free off one rounded bleed nipple but decided to carry on but go easier on the brakes, which was fine for a while until i got in a tussle with a Noble and started brakeing later an harder again. This time I recognised the signs earlier and backed off before the peddle went completely soft, then called it a day.
My question is, if i completely bleed and replace the fluid with quality racing fluid, like the Carbon Loraine stuff (i have cl5 pads), will that be enough to avoid the problem in the future?
Needless to say, I only had regular dot4 fluid in the car and it had boiled. I bought some higher boiling point fluid from the shop on site and had a go at bleeding it through the system, unfortunately i couldn't free off one rounded bleed nipple but decided to carry on but go easier on the brakes, which was fine for a while until i got in a tussle with a Noble and started brakeing later an harder again. This time I recognised the signs earlier and backed off before the peddle went completely soft, then called it a day.
My question is, if i completely bleed and replace the fluid with quality racing fluid, like the Carbon Loraine stuff (i have cl5 pads), will that be enough to avoid the problem in the future?
ridds said:
Brummie and I both suffered from this. I tried 3 lots of fluid, more expensive each time! With no improvement. I could barely do 1 lap of the ring or 3 of Spa and neither of these are heavy brake circuits.
Fluid, ducts etc will not work. You have a sticky piston somewhere I'm afraid.
At least the seal kits are cheap.Fluid, ducts etc will not work. You have a sticky piston somewhere I'm afraid.
I have a sticky piston at the moment, will be refurbing as soon as the rest of the fleet stops breaking down.
Ridds, what do you think caused your piston to go sticky?
ridds said:
Brummie and I both suffered from this. I tried 3 lots of fluid, more expensive each time! With no improvement. I could barely do 1 lap of the ring or 3 of Spa and neither of these are heavy brake circuits.
Fluid, ducts etc will not work. You have a sticky piston somewhere I'm afraid.
Don't like the sound of that, changing brake fluid is just about within my capabilities, anything else is a stretch. How do you confirm that this is definitely the problem and which piston is sticking, using the temp strips mentioned earlier?Fluid, ducts etc will not work. You have a sticky piston somewhere I'm afraid.
The temp strips will tell you which calliper is getting hot,
However if you can change the Pads, it’s easy to see which piston is sticking.
Take out the pads, get a couple of 1/2 " wood packers and put them in place of the pads. This will stop the piston popping out of the bore.
Press the brake pedal half down, and then check the pistons. They should have moved the one which is stuck or sticky won't have moved much. It may need a little bit of refinement, but thats it. Caliper wind back tool helps moving them back in.
I found my n/s lower inner piston is sticky, it moved 5mm whereas all the others moved 10mm out. To be honest they were all sluggish!
Hope this helps
However if you can change the Pads, it’s easy to see which piston is sticking.
Take out the pads, get a couple of 1/2 " wood packers and put them in place of the pads. This will stop the piston popping out of the bore.
Press the brake pedal half down, and then check the pistons. They should have moved the one which is stuck or sticky won't have moved much. It may need a little bit of refinement, but thats it. Caliper wind back tool helps moving them back in.
I found my n/s lower inner piston is sticky, it moved 5mm whereas all the others moved 10mm out. To be honest they were all sluggish!
Hope this helps
Brummie found the problem.
I was starting to investigate my issues when he found a stuck piston. Think he changed he calipers out in the end. I suspect I cocked one up when I refurbed mine a couple of years ago.
The pistons are a very close fit in the bores.
I started with the Halfords stuff, then something racey and finished with Carbon Lorraine stuff and boiled each one after a similare amount of time.
Nothing obvious on the brake caliper front to show which one was hot but the pedal was on the floor within 3 laps at Spa. 20 minutes later it was back to normal.
I was starting to investigate my issues when he found a stuck piston. Think he changed he calipers out in the end. I suspect I cocked one up when I refurbed mine a couple of years ago.
The pistons are a very close fit in the bores.I started with the Halfords stuff, then something racey and finished with Carbon Lorraine stuff and boiled each one after a similare amount of time.
Nothing obvious on the brake caliper front to show which one was hot but the pedal was on the floor within 3 laps at Spa. 20 minutes later it was back to normal.
Hi moonmonkey,
Yeah, I was a bit paranoid about noise at OP as they have a rep for overreading on the noise test.
I have a decatted sports exhaust with 3.5" tails and i measured it at about 112db myself earlier in the year. That was prior to a TD at Anglesey and I had bought some Decibel Devil inserts to cut the noise but i reckon they only take about 5db off. As it turned out, they didn't even bother to test there.
I didn't think the Devils would cut it for Oulton so bought some ACT track cans to fit my tails, designed to drop about 10db. In the end I measured 100 db with the ACT cans, but the car sounded awful and was being strangled over 6000 revs.
I wish i'd taken and tried the Devils first as I reckon I may have scraped through whilst retaining a decent sound and almost full power.
Yeah, I was a bit paranoid about noise at OP as they have a rep for overreading on the noise test.
I have a decatted sports exhaust with 3.5" tails and i measured it at about 112db myself earlier in the year. That was prior to a TD at Anglesey and I had bought some Decibel Devil inserts to cut the noise but i reckon they only take about 5db off. As it turned out, they didn't even bother to test there.
I didn't think the Devils would cut it for Oulton so bought some ACT track cans to fit my tails, designed to drop about 10db. In the end I measured 100 db with the ACT cans, but the car sounded awful and was being strangled over 6000 revs.
I wish i'd taken and tried the Devils first as I reckon I may have scraped through whilst retaining a decent sound and almost full power.
MoonMonkey said:
Thanks FW
I'm having the same debate and was thinking about the ACT track silencers but not good if they throttle the engine over 6000rpm.
Don't know if it may be better getting the full ACT big bore exhaust with 6 silencers and changing over full exhausts for TD's if necessary
MM
I have the full ACT big bore exhaust with the balanced headers and use the track cans as well.I'm having the same debate and was thinking about the ACT track silencers but not good if they throttle the engine over 6000rpm.
Don't know if it may be better getting the full ACT big bore exhaust with 6 silencers and changing over full exhausts for TD's if necessary
MM
The track cans do not make much difference really and what you lose above 6000RPM you gain a little low to mid range torque.
Only just get on 105dB days even with the track cans on.
firewallguy said:
Had a track day at Oulton Park in the week and suffered almost complete brake failure after about 5 hot laps, was a bit of a bum clencher I can tell you.
Needless to say, I only had regular dot4 fluid in the car and it had boiled. I bought some higher boiling point fluid from the shop on site and had a go at bleeding it through the system, unfortunately i couldn't free off one rounded bleed nipple but decided to carry on but go easier on the brakes, which was fine for a while until i got in a tussle with a Noble and started brakeing later an harder again. This time I recognised the signs earlier and backed off before the peddle went completely soft, then called it a day.
My question is, if i completely bleed and replace the fluid with quality racing fluid, like the Carbon Loraine stuff (i have cl5 pads), will that be enough to avoid the problem in the future?
Yes is the answer but only so long as you don't have a stuck caliper. I run Pagid RS14 pads and the CL Fluid and can run all day with no problems.Needless to say, I only had regular dot4 fluid in the car and it had boiled. I bought some higher boiling point fluid from the shop on site and had a go at bleeding it through the system, unfortunately i couldn't free off one rounded bleed nipple but decided to carry on but go easier on the brakes, which was fine for a while until i got in a tussle with a Noble and started brakeing later an harder again. This time I recognised the signs earlier and backed off before the peddle went completely soft, then called it a day.
My question is, if i completely bleed and replace the fluid with quality racing fluid, like the Carbon Loraine stuff (i have cl5 pads), will that be enough to avoid the problem in the future?
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