Another tech showed me that to replace brake fluid, he puts a tank on the fluid reservoir to avoid depleting the master cylinder, then cracks the furthest brake bleeder and lets the fluid slowly drain out.
I would think you would have to do this at each corner of the car and wonder if air could get in this way or does the exiting fluid really prevent this from happening?
To make the fluid as fully re-freshed as possible without letting air into the system before starting I suck as much fluid as possible out the resevoir then I push the pads back (if the nipples will open letting the fluid out via the nipples) and again suck fluid from the resevoir. Then put fresh fluid in the resevoir and use my pressure bleeder to push fresh fluid through the system and out through the nipples. If any of the bleed nippess won't open it it is no big deal at lest some fresh fluid will fill the calliper as the pads are pumped back out.. Of course always pump the pedal a few times before handing over to the customer.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Eh, it'd work. *shrug* It probably also takes forever? You'd definitely have to do it at all four corners for it to be a complete service, IMO.
I dunno that I'd let it go without manual bleeding each corner (that got opened) at least once. It shouldn't let air in? But it can, and I don't wanna deal with that comeback. :lol:
I wouldn't worry to much about method as long as you get fluid through the system.
With a brake fluid flush the main object is to reduce the water content of the fluid, brake fluid is so hydroscopic that even if you don't get all the fluid out of the system that the moisture any fluid you can't flush out will be dispersed through all the fluid in the system in a day or so. Because of this the % water content in the parts where in matters the calipers will be reduced to a level that is not significant.
Although it would be good to also get all the black rubber dust that accumulates in the system from normal wear it tends to sediment in places where it won't flush out.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
No kidding about the rubber stuff. :lol: I dunno if any European makes are this way, but GM's are HORRIBLE about blackening their fluid in a hurry. Definitely flush those more often than any other.
Tyler wrote: Eh, it'd work. *shrug* It probably also takes forever? You'd definitely have to do it at all four corners for it to be a complete service, IMO.
I dunno that I'd let it go without manual bleeding each corner (that got opened) at least once. It shouldn't let air in? But it can, and I don't wanna deal with that comeback. :lol:
What do you mean "manually bleeding each corner that got opened"?
If you keep the reservoir full while the bleeders are open you're not going to get air in the system.
bruce.oliver wrote: What do you mean "manually bleeding each corner that got opened"?
If you keep the reservoir full while the bleeders are open you're not going to get air in the system.
It shouldn't let air in, I agree. I just saw enough spongy pedal comebacks from other techs at a previous job to make me lose faith in the method.
Just my experience. If it works for you or others, flush away!
The whole secret of old style manual bleeding is to take it slowly, the person pumping the pedal must raise the pedal slowly at the end of each stroke. Some european models with ATE mastercylinders can be almost impossible to bleed without a pressure bleeder. Although vacuum bleeding should in theory get air out more effectively than pressure bleeding in my experience this isn't the case. I became a convert to pressure bleeding when I first had to deal with the old 1970's French Chrysler (Simca) models and haven't used anything else since.
One trick with any bleeding method is rather than having to rush to close the nipple to use a hose pinch to control the flow.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Andy.MacFadyen wrote: Simple low cost pen style device that estimates moisture content by conductivity
How well does that work? The way I understand it, moisture isn't the most important check. Copper content causes corrosion in the system, so testing for copper is most important. Or so they say
bruce.oliver wrote: How well does that work? The way I understand it, moisture isn't the most important check. Copper content causes corrosion in the system, so testing for copper is most important. Or so they say
I've always heard the same? I know the test strip is the only method accepted by MAP standards, anyway. I honestly think they both have merit? Like battery conductance testers and carbon piles.
I have one of the motive pressure bleeders but haven't bought the right adapter for the applications I would use it on yet. I'm waiting for someone to grab a cap from work to make something out of it.
I had one of those pen style fluid testers but it broke on me a couple of days ago. It seemed accurate, jusginf by results from new fluid, to 20k, to high mileage. I only paid like $10 for it, but it was brittle as hell. I just took the cap off the other day and the tool come off in the cap. Maybe I don't clean the fluid off well last time I put it away and it ate it up?
I use the bottle that keeps the reservoir full, after removing old fluid first from reservoir first. Then I have a vacuum bleed setup that I bought on flea bay. I also have a mighty vac setup. My rule of thumb is if the fluid is dirty I use the vacuum suction (with air pressure) to suck the fluid at each wheel location furthest from the pressure bleeder as you would do when manually bleeding the wheels. One point to remember is to keep the refill bottle full and let the suction go until you have clear fluid at each wheel location. IF the pressure bleeders weren't so darn expensive I would've got one years ago but the suction method works just as fast.
