Radical brake fluid?
Discussion
What sort of quantity is needed to change the fluid? I've no idea how old the fluid is in my car so thought it would be a good idea to change it as I know the car has been laid up for over a year before I bought it.
Never having done a complete fluid change I take it it's case of loosening the nipples off each caliper in turn and pushing the fluid through with the brake pedal in turn? Any tips or things to watch?
Anybody used Silicone brake fluid that claims not to need to be replaced and is DOT5 standard, Tweeks catalog page 321? Will this cause any problems if I empty the existing fluid as best I can and then re-fill with this, i.e. will the mix of the old fluid residue and the new be ok if the old is standard non-silicone fluid?
Thanks
Nick
Never having done a complete fluid change I take it it's case of loosening the nipples off each caliper in turn and pushing the fluid through with the brake pedal in turn? Any tips or things to watch?
Anybody used Silicone brake fluid that claims not to need to be replaced and is DOT5 standard, Tweeks catalog page 321? Will this cause any problems if I empty the existing fluid as best I can and then re-fill with this, i.e. will the mix of the old fluid residue and the new be ok if the old is standard non-silicone fluid?
Thanks
Nick
nick997 said:
Anybody used Silicone brake fluid that claims not to need to be replaced and is DOT5 standard, Tweeks catalog page 321? Will this cause any problems if I empty the existing fluid as best I can and then re-fill with this, i.e. will the mix of the old fluid residue and the new be ok if the old is standard non-silicone fluid?
Good thing with silicone fluid is that it does not attack paintwork (but can be a problem when re-spraying due to the silicone).Silicone fluids sometimes feel a bit spongey on the pedal (don't know why).
Also if the brakes are not used for a while, the seals tend to stick in the bores.
I would just use DOT 4.
Silicone brake fluid is hygroscopic which is why you get a spongy pedal after a period of time, it performance can also degrade at an alarming rate once it is gets some use. Moving from a glycol to silicon requires the whole system to be flushed as the two fluids do not mix. IMHO I'd stick to a decent DOT4, you'll need no more than a litre to flush the old stuff out. Flushing process is as you describe.
I think it's the other way around Rob. Dot5 does not absorb water hence the water accumulates at low points and can rust. Dot5 inherently is more comressible hence spongy and it has a lower BP that Dot4. It doesn't mix with Dot4 and has been known to swell rubber components (eek!). So apart from not destroying the paint it's not that useful!
I used halfrauds dot5.1 which is not silicone, just a higher BP that dot4. No idea if that's of any use in the application, but hey it's a race car innit?
Dot3, 4, 5.1 are all hygroscopic which is why they need changing regularly.
Yep, I used less than a litre for my flush. I found the wilwood nipples to be a bit of a pita. Once you open them wide enough to flush air/fluid out they tend to leak from the threads and make a mess.
I couldn't find an easi-bleed top for the fluid reservoirs, so I used the peddle pumping method. Two man job but it works ok. I put a clear pipe with a rubber end on the nipple with the other end in a jar of fluid.
The (two person) process is apply a little brake pressure.
Open the nipple.
Press the pedal down in a smooth firm action.
Close nipple.
Pedal up.
You inspect the "output" for bubbles. Repeat the process until clear.
You can lightly tap the calipers with a metal hammer to dislodge bubbles.
You can leave overnight and then do the whole thing again.
You have 4 nipples per caliper, but don't bother with the lower ones, just do the top.
Don't forget to keep an eye on the master cylinder. If you run it out of fluid, you pump bubbles into the system and have to start again!
I thought that with two M/Cs and a brake balance bar it would be awkward, but it was no problem.
Sorry for any "teaching grannies..."
HTH
Bert
I used halfrauds dot5.1 which is not silicone, just a higher BP that dot4. No idea if that's of any use in the application, but hey it's a race car innit?
Dot3, 4, 5.1 are all hygroscopic which is why they need changing regularly.
Yep, I used less than a litre for my flush. I found the wilwood nipples to be a bit of a pita. Once you open them wide enough to flush air/fluid out they tend to leak from the threads and make a mess.
I couldn't find an easi-bleed top for the fluid reservoirs, so I used the peddle pumping method. Two man job but it works ok. I put a clear pipe with a rubber end on the nipple with the other end in a jar of fluid.
The (two person) process is apply a little brake pressure.
Open the nipple.
Press the pedal down in a smooth firm action.
Close nipple.
Pedal up.
You inspect the "output" for bubbles. Repeat the process until clear.
You can lightly tap the calipers with a metal hammer to dislodge bubbles.
You can leave overnight and then do the whole thing again.
You have 4 nipples per caliper, but don't bother with the lower ones, just do the top.
Don't forget to keep an eye on the master cylinder. If you run it out of fluid, you pump bubbles into the system and have to start again!
I thought that with two M/Cs and a brake balance bar it would be awkward, but it was no problem.
Sorry for any "teaching grannies..."
HTH
Bert
Edited by BertBert on Tuesday 15th January 20:47
Gassing Station | Radical | Top of Page | What's New | My Stuff