Has anyone had problems with using synthetic brake fluid with the stock clutch master/ slave & brake master cylinders? I only ask this cuz when I rebuilt all mine a while back, only my slave is not leaking. I guess it has to do with the properties of the synthetic fluid swelling the seals & causing the leaks
My experience with syn. brake fluid and silicone brake fluid has been bad. for motorcycles and cars alike. It's hard to find good quality dot 3 and 4 fluid at parts houses anymore.
I found the syn. gave a bit less response as far as pedal. The silicone is ok for antique autos that sit for a long time as it is supposed to NOT absorb moisture as quickly, however it does not give the responsive pedal that a good dot 3 or 4 hydualic fluid does.
I put all new brakes in my '76 (everything brand new) and used silicone fluid (DOT 5) and am happy so far, also used it in the clutch. The brakes are very strong, no spongy feel and the clutch feels fine too. No leaks or anything, I would do it again. I only have about 4 months and 3k miles on it though so who knows what might happen. I also used stainless lines everywhere with permatex sealant on the threads. Just my $.02
DOT 5 brake fluid will eventually cause the FJ40 seals to fail as they are not compatable with DOT 5 fluid. If you read the can it will tell you to only use DOT 5 fluid in a system that was designed for it. Synthetic DOT 3/4 fluid works fine in a FJ40 brake system and will not cause seal failure.
dot 3, 4 and 5.1 are all glycol based fluids the differance between them is their boiling points. DOT 5 is silicon based which + a system that is surposed to be running glycol based = bad news for the seals very quickly......DOT 5 is generaly found in race cars
I've read that too but I thought it was more of a concern if you mix silcone with regular and I had a new system that never had fluid in it. Looks like I don't have much of an option now but to keep an eye on it for leaks and see what happens. I still think I am alright, mabey have to change my fluid on a regular basis... which we all should be doing anyway, right?
What is the difference between synthetic fluids and any of the ones we are talking about? I've only heard of silicone and glycol.
synthetic has a higher dry boiling point, has a higher moisture resistance, can be used in all brake systems - ABS, drum and disk, and being Dot 3 or 4 rated must be able to "mix" with glycol fluid, and extended service intervils.
I wouldent be running silicone fluid in a glycol system (only because the fluid manufactures say not to), if everythings fine for you, you may have DOT 5 rated seals in the system, apparently DOT 3 + 4 rated seals will swell quite quickly......but if everythings good you have done something right
I have been running DOT 5 silicone brake fluid for over a year. Good pedal feel and no issues. I'm guessing that all brake manufacturers upgraded their seal material long ago to be compatible.
That said, I have all new Toyota parts. I wouldn't recommend switching an older system over to DOT 5 fluid.
Eddy, how about an update? I just loaded silicone in my fj45. Cleaned the system all out, washed the components down, dried them all off, then loaded the silicone in. The seals were all replaced about four years ago, so no idea how well this will work. Guess I should make sure the e-brake is working VERY well before I can fully test it out.
