*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Bad brake fluid From: Andy Dingley Article: 83939 of rec.autos.tech Date: Tue, 04 Jul 1995 00:05:15 GMT In article: <3t5592$nqd@newsbf02.news.aol.com> bbartch@aol.com (BBartch) writes: > I've replaced master cylinders in my 74 Chevy truck twice now in the last > 4 years. Each time they failed, I found what looked like old black motor > oil in the reservoirs You should change brake fluid every 2-3 years. The black fluid is worrying though, that's nearly always due to ground-up rubber seals in the master cylinder. Over time (50K+) any cylinder will do this and changing the rubber components cures it. In such a short time though, it sounds like your master cylinder bores are chewed up. They should be the smoothest honed cylinders on the car, even better than the engine cylinders. Piston rings are pretty hard & resistant, but the slightest machining marks will destroy rubber brake seals. Another possibility is an "Andromeda Strain". A simple cause of this would be contaminated brake fluid; many automotive fluids will soften rubber seals. Could you have traces of ATF or something in there ? I would regard this as a good time to do a 20-year brake service. Change *all* the fixed pipes to copper alloy and *all* the flexies. Strip wheel calipers/cylinders & master cylinder and either replace the seals (if the piston/cylinder surfaces are OK) or replace the whole units if there is any doubt. Don't split caliper halves unless you're sure they can be re-assembled (it's not recommended for Lockheed front calipers, as the seals are hard to obtain) Metal brake components should be cleaned thoroughly with your favourite degreaser and then washed again with methylated spirit or Everclear. Try not to handle them after this point. Re-assemble them with the minimum of lubrication needed, using only clean brake fluid from a fresh can. Refit everything, refill the reservoir and bleed the system. Now would be a good time to switch to silicone DOT 5 brake fluid. It isn't hygroscopic like glycol, so it avoids many water absorption problems. If you do use it, make sure the reservoir cap is *wired* *down* with a warning placard on it, and always carry a spare, sealed, can. Garages just *love* to top up your silicone brake fluid with the wrong stuff. -- Andy Dingley dingbat@codesmth.demon.co.uk If Pte. Clegg is released without a similar gesture towards Republican prisoners *immediately*, we can kiss the whole peace process goodbye. *=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Bad brake fluid From: lockhart@vpihe1.phys.vt.edu (Rob Lockhart) Article: 84035 of rec.autos.tech Date: 4 Jul 1995 16:13:08 GMT Marv Miller (ae722@lafn.org) wrote: > In a previous article, bbartch@aol.com (BBartch) says: > >I've replaced master cylinders in my 74 Chevy truck twice now in the last > >4 years. Each time they failed, I found what looked like old black motor > >oil in the reservoirs (yeah, I know, I should have looked sooner). > >Anyway, I've used DOT 4, usually Castrol. Is there some kind of > >rubber-eating bacteria (a la Andromeda strain?) that also thrives on the > >alcohol/glycol in brake fluid?? Somehow the clear brake fluid is > >accumulating black sludge so my guess is the O-rings disintegrated. These > >are Raybestos re-manufactured cylinders. My neighbor's Ford truck has > >fluid doing the same thing and he keeps siphoning it out and replacing it. > > No failure for him yet, but in my case, my pedal went to the floor. > >Appreciate any info. I usually get that as well. I believe it is the brake fluid absorbing water, since it has the consistency of water (that muddy muck). I've flushed the brake fluid every other year for 10 years on my old car and I still had the OEM master cylinder. If the muck had part of my rubber seals, surely by now they would have been deteroirated. BTW, I sold the car and the owner still has excellent brakes (OEM master cyl). > Any reason why you couldn't use DOT-5, silicone fluid. I love it! > It might solve your problem, (or even kill Andromeda). ABSOLUTELY NOT!!!! You can only use DOT-5 on master cylinders that have the proper seals! I once replaced my master cylinder (on a car I later sold) and explicit instructions came with it telling me NOT to use DOT-5 because that required different seals. DOT-3 and DOT-4 are compatible, but DOT-5 is not. From what I read about it, DOT-5 is to a DOT 3 / DOT 4 system as R-134a is to an R-12 system. But, if your system is virgin, no problem (I guess?). -- Rob Lockhart lock3rd@vt.edu Virginia Tech Physics Department *=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Brake fluids and fade From: jcupples@iphase.com (Jerry Cupples) Article: 84062 of rec.autos.tech Date: Tue, 04 Jul 1995 00:11:24 -0500 In article <3svn2a$gaf@acmex.gatech.edu>, gt7518a@prism.gatech.edu (Seong Hoon Son) wrote: > In article <3suj34$fal@charm.magnus.acs.ohio-state.edu> dheister@magnus.acs.ohio-state.edu (David J Heisterberg) writes: > >In article <3st8d8$96q@acmex.gatech.edu>, > >Seong Hoon Son wrote: > >>here do i get one of those brake-bleeding hose??? should the local > >>pep boys have them??? > > > >Wouldn't it be easier to call Pep Boys and ask them? The telephone > >is a wonderful invention. > > > >I don't even bother with a check valve. A piece of tubing going > >straight up, then looping over the strut mount makes a nice seal > >in my case. But maybe I'm living dangerously. > > > > yup, i realized it as soon as i pressed that send button...;) > > > now, can you explain how does tubing looping over the strut mount make a seal?? > i don't quite get the picture... > > > -- > Seong Hoon Son > Georgia Institute of Technology, Atlanta Georgia, 30332 Not sure I do , either, but generally to assure that you don't pull any air back into the lines when you bleed. Pour some fresh brake fluid into a small glass container like a baby food jar. When you open your bleed tap, pump the fluid out through the line into the container. Watch for bubbles in the line. Keep topping level fluid in the master cylinder reservoir, and pump until you see clear fluid going into your jar. Close the tap when you have it bled, then pull the line off the tap. Whenever you release the pressure on your brake master cylinder, you will tend to pull a little fluid back up the line into the slave cylinders. Just make sure you don't break the surface of the jar with your length of tubing. It takes two people to do this. One to pump the brakes, one to hold the rig and close the bleed tap. Perhaps the check valve idea is good... myself, if Pep Boys sells it I wouldn't have much confidence. I've done the above for 30 years, it works if you are careful - basic shade tree technique. Good shops have a pressure mechnism that flushes a high volume of fluid through your lines and keeps constant positve pressure. You just open up the taps in series, starting at the farthest point from the master cylinder. Maybe you could rig that up as a rambling wreck, eh? Note that brake fluid is very hygroscopic and gets old fast. Use brand new stuff, and a clean jar. cheers, Jerry *=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Brake fluids and fade From: grep@cris.com (George B) Article: 84081 of rec.autos.tech Date: 4 Jul 1995 23:53:38 GMT In article , jcupples@iphase.com (Jerry Cupples) wrote: > if Pep Boys sells it I >wouldn't have much confidence. Amen! The store of last resort for me! BTW, another cause of brake fade is folks not using their parking brake if they have automatic transmissions. The parking brake is what keeps the rear brakes adjusted with both disk and drum brakes. If you don't use it, the rear brakes no longer offer any braking causing the front brakes to overheat and the pads to glaze over. This is also a contributing factor in front brake rotor warpage resulting in rotors being replaced more often than they otherwise might be. George Bonser grep@cris.com *=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Bad brake fluid From: smarties@helix.net (Ed Smart) Article: 84104 of rec.autos.tech Date: 5 Jul 1995 03:07:42 GMT In article <1995Jul4.041736.18934@lafn.org>, ae722@lafn.org (Marv Miller) says: > > >In a previous article, bbartch@aol.com (BBartch) says: > >>I've replaced master cylinders in my 74 Chevy truck twice now in the last >>4 years. Each time they failed, I found what looked like old black motor >>oil in the reservoirs (yeah, I know, I should have looked sooner). >>Anyway, I've used DOT 4, > >Any reason why you couldn't use DOT-5, silicone fluid. I love it! >It might solve your problem, (or even kill Andromeda). Do be careful about DOT5 fluid it may not be hygroscopic, but that doesn't mean water can't be a problem. Here in the North We_t I've seen a few cases of water collecting in bubbles in the fluid. If it boils, no brakes. Also it seems to defy the laws of physics that a liquid is not compressible. Pedals get spongier as the fluid gets hotter. Not a great thing in a heavier vehicle like a pickup. I've seen a few of my racing buddies try to knock down the fence after a few minutes of hot soaking (EG red flag after a lot of laps.) I think it's great stuff for show cars and other low use vehicles, but have had ample reason to very leary of it in real life. *=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= Subject: Re: Bad brake fluid From: lockhart@vpihe1.phys.vt.edu (Rob Lockhart) Article: 85399 of rec.autos.tech Date: 4 Jul 1995 16:13:08 GMT Marv Miller (ae722@lafn.org) wrote: > In a previous article, bbartch@aol.com (BBartch) says: > >I've replaced master cylinders in my 74 Chevy truck twice now in the last > >4 years. Each time they failed, I found what looked like old black motor > >oil in the reservoirs (yeah, I know, I should have looked sooner). > >Anyway, I've used DOT 4, usually Castrol. Is there some kind of > >rubber-eating bacteria (a la Andromeda strain?) that also thrives on the > >alcohol/glycol in brake fluid?? Somehow the clear brake fluid is > >accumulating black sludge so my guess is the O-rings disintegrated. These > >are Raybestos re-manufactured cylinders. My neighbor's Ford truck has > >fluid doing the same thing and he keeps siphoning it out and replacing it. > > No failure for him yet, but in my case, my pedal went to the floor. > >Appreciate any info. I usually get that as well. I believe it is the brake fluid absorbing water, since it has the consistency of water (that muddy muck). I've flushed the brake fluid every other year for 10 years on my old car and I still had the OEM master cylinder. If the muck had part of my rubber seals, surely by now they would have been deteroirated. BTW, I sold the car and the owner still has excellent brakes (OEM master cyl). > Any reason why you couldn't use DOT-5, silicone fluid. I love it! > It might solve your problem, (or even kill Andromeda). ABSOLUTELY NOT!!!! You can only use DOT-5 on master cylinders that have the proper seals! I once replaced my master cylinder (on a car I later sold) and explicit instructions came with it telling me NOT to use DOT-5 because that required different seals. DOT-3 and DOT-4 are compatible, but DOT-5 is not. From what I read about it, DOT-5 is to a DOT 3 / DOT 4 system as R-134a is to an R-12 system. But, if your system is virgin, no problem (I guess?). -- Rob Lockhart lock3rd@vt.edu Virginia Tech Physics Department