BRAKE FLUID

[thos25]

I recently lost the brakes on COMET. Thank heaven I spotted the puddle on the garage floor before I took the old girl out for a spin. I could see the fluid was seeping out from inside the left front hub so I proceeded to disassemble that wheel and what I found was an unsightly mess inside the wheel cylinder. My mechanic friend told me it was the DOT 3 brake fluid. I have always believed that we could not use the newer Silicone fluids such as DOT 5 which I understand prevents that gunk and rust since it is not water absorbent.
If anyone has used DOT 5 or can give me some pointers on whether or not it is compatible with older systems I would be very grateful.
Thanks and Kind Regards, TOM

[popscomet]

WAY WAY back in the 90's we built wifes 56 ford show car,,,it has dot 5,,,but the entire system was brand new,,,fresh from the gitgo,,you can not mix 3and 5 they jell up or something....the brake pedal on 5 always seems to feel just a tad spongy,but it never fells....we have never had a brake problem non what so ever,,,,it has as good as brakes today as it did back in the 90;s..you need to start with a freshly new system if your going from 3to5 or the other way....her 56 has stock on the rear and disc on the front.....the reason we went with 5 is cause if you have a leak...it don't eat up paint....but after all these yrs we have never had a leak or a problem...they are as good today as they ever have been....but if I had it to do over,,,I'd stay with 3...not everybody has 5,,,,,3 is on any street cornor,,,keep it simple !! pop,,,,JMO…..but your gonna have a few forum readers on here that may dis agree....so be it !! pop has been there ….they just read about it....but you do what ever you feel good with....good luck I have a brand new brake system on my cobra replica,,,,I went with 3,,,,POP

[lavron]

your gonna have a few forum readers on here that may dis agree

Certainly we would never have a disagreement here

I filled my new system with DOT3 and I am not sure I have ever seen 5 anywhere, so like Pops said everyone has 3 and if someone accidentally adds it to a 5 system it would be bad, besides my master cylinders all call for 3 right on the lid.

I think people have been running 3 for a long time with no issues.

See Ya,
Mike

[vicegrip]

DOT 5 will work in your car but it definitely does not mix with 3. The 5 is desirable if everything is detailed and you still want the paint to be there when you're done. Everything should be new if you switch to 5 but we have successfully rinsed the old 3 out of a system by pumping it out and adding mineral spirits to the mc and pumping it through each bleeder till it was clear solvent. We added an air hose nipple to an extra cap and blew out all the solvent with low air pressure.Worked fine and is still working after several years. If you stick with 3,I would suggest changing the fluid.Empty the mc by pumping the old fluid out through the bleeders or sucking it out with a vacuum device.Get a piece of clear vinyl tubing to fit over the bleeder and stick in a container.add new fluid to the mc and pump till the fluid is clear in the tubing. Start at the rear right,rl,fr,fl. Don't let the mc go dry.

[lavron]

I used a HF power bleeder to fill my system, worked great, will also work to replace the fluid but I would have a lot of fluid on hand, I went through a quart in nothing flat getting all the air out. I actually strained it back through a paint filter and reused it but my system is totally new so I wouldn't do that on an old system.

See Ya,
Mike

[poboyjo65]

I have dot 5 in my 65 comet & in a 76 ford truck that doesn't get driven much. it was all new systems on both when I started using it. had it in the comet for 5-6 years & in the truck about 16-17 years. never a problem with either. It seemed just a tad spongy at first but you get use to that. I got no complaints about it. but I probably wouldn't go thru the trouble of flushing the system just to switch over, because you need to >as mentioned above ,,it dont mix with dot3. but it does have advantages , higher boiling point, it don't hurt paint ,& wont absorb moisture=rust. Expensive but it seems like it lasts longer.