Brake Fluid Flush

[ED.]

Took the 98 in for a free 32 point and one of the services needed was a fluid flush. I've done this on a few cars so I'm ready to go this weekend but wanted to see if you all had a particular brake fluid you used or Lexus recommend?

[billydpowell]

just read your manual, mine says DOT 3

[TA in KC]

Here is a tutorial on how to flush the brake fluid on a first-generation LS400. Some steps might be slightly different for your 98 but I would think this would still be helpful.

http://www.lexls.com/tutorials/brake/bleeding.html

[ED.]

Cool, thanks guys. I'll probably do a Mobil or Valvoline synthetic DOT-3.

P/S pump needs a reseal plus the ATF fluid is dirty. Projects for the next couple of months

[landar]

I believe the brake fluid flush is fairly straight-forward. You just NEVER want to let the master cylinder get so low that it sucks air. That would literally really suck! Then the ABS modulator might need special purging. So, just a precautionary note. You probably already know this but just in case...

[prix]

Yes, I am aware the last post was made on this thread in August. :-)

I started looking into the options for a brake fluid fiush, because I want to ensure the person I hire to do this does it 'right'.

I found this statement by a company called Motive (they sell reasonably priced pressure bleeders, the kind of equipment that is easily affordable to the DIYer):

"Also the typical method of pumping the brake pedal while a helper opens and closed

the bleeder valve can actually damage your master cylinder. By pushing the pedal

past the normal travel distance the master cylinder seals on the piston can be ripped

or gouged by areas in the master cylinder bore that are rusted or worn. "

I would be interested in knowing whether any of the real mechanics (experienced DIY-ers or other) in this forum agree that the pumper helper method can cause damage.

I've already ruled out using the Motive pressure bleeder (someone pointed out the design does not separate air from the fluids that are being pressurized, and thus could introduce air into the system... the exact opposite of what one wants). Should I also rule out the 'old fashioned way' of flushing the brake fluids? The 'pumper helper' method is also the method used in the lexls.com tutorial.

If true, then that means the only safe way to flush the system would be to go to the stealership, where (presumably) they have the expensive pressure bleeders, the kind that separate air from fluids during pressurization with a rubber diaphragm of some sort.

I find it hard to believe that a brake flushing method that people have been using forever (pumper helper method) can damage parts.

[SRK]

It is entirely true that pumping a master cylinder can damage the seals and destroy it. Brake fluid absorbs moisture, and that moisture will cause rust in cast iron master cylinders ( used for many years, even by Toyota) and as the pistons and seals travel a short distance only, that area remains clean. Further along the cylinder the rust occurs. When you open a bleeder screw, and depress the pedal all the way, the seals over-run the acculmulated rust, and very quickly destroy themselves. Lexus, and many other cars, now use aluminum master cylinders which don't accumulate rust, but can have aluminum oxide corrosion nonetheless.

I've bled my LS and GS by pumping the pedal - no harm done. Which is good considering the GS cylinder is hugely expensive. But I would not do it on an iron cylinder. I made a pressure bleeder for the German cars I used to work on when I had my shop, and never pushed the pedal to the floor to bleed them.

So it is a concern, even with these cars. But you shouldn't have any trouble. Open the bleeder wide, and use as little foot pressure as possible to move the pedal down. Do it slowly in both directions.

I wouldn't rule out the Motive bleeder just because it applys air directly to the fluid. My invention did just that, using about 15 psi on the resevoir. Never mixed air. People make far too much about "tiny bubbles" in brake fluid. Even if they appear, they will find their way to the ports in the master and vent out themselves harmlessly.

[prix]

Ok, sound slike he can use either one of those DIY pressure bleeders or the pump method, as long as we are craeful. I kind of thought the concern about the Motive design verged on paranoia, but really, it's just better to ask. An ounce of prevention is worth ...etc. Thanks.

It is entirely true that pumping a master cylinder can damage the seals and destroy it. Brake fluid absorbs moisture, and that moisture will cause rust in cast iron master cylinders ( used for many years, even by Toyota) and as the pistons and seals travel a short distance only, that area remains clean. Further along the cylinder the rust occurs. When you open a bleeder screw, and depress the pedal all the way, the seals over-run the acculmulated rust, and very quickly destroy themselves. Lexus, and many other cars, now use aluminum master cylinders which don't accumulate rust, but can have aluminum oxide corrosion nonetheless.

I've bled my LS and GS by pumping the pedal - no harm done. Which is good considering the GS cylinder is hugely expensive. But I would not do it on an iron cylinder. I made a pressure bleeder for the German cars I used to work on when I had my shop, and never pushed the pedal to the floor to bleed them.

So it is a concern, even with these cars. But you shouldn't have any trouble. Open the bleeder wide, and use as little foot pressure as possible to move the pedal down. Do it slowly in both directions.

I wouldn't rule out the Motive bleeder just because it applys air directly to the fluid. My invention did just that, using about 15 psi on the resevoir. Never mixed air. People make far too much about "tiny bubbles" in brake fluid. Even if they appear, they will find their way to the ports in the master and vent out themselves harmlessly.

[prix]

btw, the dealer quoted me $180 + tax for a brake fluid flush. So would be close to $200. Not going that route, of course. Seems awfully high...

[SRK]

That seems a bit high for a simple flush. Once on the hoist, 30 min. tops. A litre or two of fluid. Did they break down the labour and materials?