Exactly what I did. Replace the fluid with Motul RBF 600 and after you pressurized the reservoir with a motive bleeder or other tool available you will see the color of the fluid changing when opening the bleed port (in sequence of course...)....I also redone it with my PST2 to activate the booster pump and no change. The system was properly bleed without using the PST2....As per Loren on Renntech if there is no major part remove like the master cylinder there is no need to activate the pump for bleeding....Two years now and no problem with brakes.....

 

Thanks jp. But are the properties of Motul different from those of SRF that would not concern you regarding mixing of new and old fluid? While the amount in the ABS reservoir may be minute, as I understand it, mixing any fluid other than SRF with SRF should not be done.

 

I believe the bleeding is recomended because of the water that gets into the brake fluid and it is subject to vaporizing in the caliper when braking hard. Since the high temp is experianced in the caliper and the bleed screw is at the top, how does the contamiated fluid leave the caliper. It seems that all that has been done with the method described is to replace the fluid " up stream " from the caliper and the contaminated fluid will be untouched. Thus the high heat and vaporizion problems remain in the caliper. Perhaps if the caliper was removed and turned up side down it could be cleared properly. Anything else is entertainment.

 

Sorry for the dumb question in advance. I have never bled brakes, but planning to do so with the help of these awesome posts.

In this comment, does it mean to put on the motive bleeder cap to the resevoir, pressurize, bleed, then before the levels go to "MIN", reopen the resevoir cap, refill to MAX, then resume bleeding?

If this is the case, would opening the resevoir cap cause any pressure issues before resuming bleeding? Not sure if my question makes sense, but i want to make sure i do this correctly.

Thanks in advance for any insight.

wolf

 

Not a dumb question at all. You can open the cap anytime and repressurized after filling the reservoir. This air on top of the fluid will not enter the line. Like you mention be sure the level is not going below the minimum and you should be able to bleed properly.

 

I miss that one...Sorry...You make me thinking now because I was not aware of that. Of course There was a color difference between the old one and the new one and I open up the further bleed screw (right aft) until the fluid was clear like the new one and did the same thing for the other three... I need to do some research about your statement. Thanks for the heads up!

 

Nice product... Just ordered a Power Probe BA05 for $24 shipped.

The Motiv might be a great tool as well, but honestly I just have no more storage room for something the size of a small garden sprayer that will get used at most a few times a year.

I already have the compressor in both garages with quick release couplings (looks like that is what the power probe has on top), and this looks like a great little tool. Whatever additional time it takes to monitor/refill the master I'm sure will be made up by not dealing with filling/cleaning a motiv type power bleeder. Will flush/fill with Ate Typ 200 when it arrives.

I'm not overly worried about air line moisture, but I could also pick up an in-line desiccant filter for about $8 at Harbor Freight. You are just pressurizing the air in the master cylinder, as long as you aren't actually spitting water out of your hose (unlikely) it should be no problem at all.

 

None of the methods mentioned deal with the water in the bottom of the caliper, the lowest point of the system. Since water and oil dont mix and water is heavier than oil, the water will work its way to the bottom of the caliper and the bleed screw is at the top. All the discusion about pressure device and suction at the bleed screw dont remove the water in the caliper. Removing the water is necessary to prevent boiling and interfering with the pressure . Bleeding from the top of the caliper is entertainment!

 

The flow of brake fluid during the bleeding process has enough momentum to carry any water (even though its a higher specific gravity than oil) and sediment trapped in the low point of the caliper. The only time it wouldn't is if you blead the brakes super slow. That's why it helps to hook up the motive bleeder at about 20-25 psi and at the same time pump the brake several times while bleeding each caliper. Also it's super important to bleed the outer part of the caliper first, than the inner and not the other way around..

 

I see, the laws of physics have been repealed. Water and dirt will jump to the top of the caliper when the bleed screw is opened

All of the methods mention clean out the lines and resevoir and the contaiminated oil below the bleed screw will climb out by itself. When in fact the whole purpose is to get the water out of the hot caliper area so it wont boil.

 

Very interesting that according to you we can't get rid of the water in our calipers by bleeding yet I'm measuring my caliper temps at the track at upwards of 400F and miraculously not boiling fluid. Must be very special boil resistant water...Thats why I love this forum. You always get to learn some new valuable info. Thank you for your input..

 

Perhaps a bit more chemistry than physics...

Brake fluid is hydrophilic. Over time, it absorbs moisture from the air. The water molecules are interspersed in the brake fluid, not collected into a puddle of water settled down to the bottom of the caliper. Pressure bleed devices allow you to quickly and easily replace (almost) all of the contaminated fluid out with fresh fluid.

I've seen some guys reset the calipers all the way back into the bore and temporarily shim them fully in when bleeding to get a bit more fluid flushed, but unless you are working on a top level competition car (which probably is rebuilding calipers on a relatively frequent schedule anyway), I don't think you will ever notice a difference.

I've never seen a caliper with a puddle of water sitting in the bottom of it...

 

Exactly. Thank you..

 

I have found that on cars with ferrous alloy calipers and aluminium pistons that corrosion is a problem if the cars are not driven often. This is cause from the water in contact with the dissimilar metals and causing a galvanic reaction. Many of the cars today have aluminium calipers and pistons so this problem is greatly reduced, not because of bleeding. Boiling is still the risk and many drivers dont work the brakes hard enough to reach the boiling temperatures . Anyone driving on the race track should avoid this risk.

There are a number of principles at work here. The hygroscopic ( attraction ) and colloidal ( suspension ). Both of these account for the water presents but they dont explain any kinematics (motion ).

Over time the water in the brake fluid will migrate to the lowest point. If you use a bottle to catch the old fluid from the caliper bleed screw and allow it to set on the bench long enough you can see this effect. I think that over the years to many people who bleed brakes dont look for this condition and feel they have solved the problem. If bleeding is done "frequently" the contaminated fluid " above " the bleed screw will have very little water to settle out. That doesnt reflect the fluid below the screw.

If you put some dirt in a water bottle and shake it up there will be a homogeneous suspension for a brief period and the heaviest particle will settle to the bottom. There will be some colloidal suspension of the lighter particals for a longer period. If a hole is made in the side of the bottle, above the heaviest particles, they will not run out with those above the hole.

Any steps to reduce the water in the space below the bleed screw is helpful but any water that remains will still be able to boil.

Conventional brake bleeding is entertainment.

 

For those who have bled the brakes. What is the size of the beeding nipple screw on 09C2S?

Thanks