Bleeding brakes

[arnebret]

Hi,

This is the first time i'm going to bleed, or actually flush my brakefluid on a '88 ABS 951. The fluid needs replacement soon. I got the Haynes manual, but maybe you guys have a few more tips on how to completly replace the fluid. I don't have speed bleeders or pressure bleeders, but i do have an assistent that can operate the brake pedal. What are the steps to be taken and what are the DO's and DONT's? By the way, does it matter if it has ABS or not?

Thanks!!

[Bob's944]

All I can tell u is that doin my non-abs brakes with an assistant took over 24 hrs to get the bleeding finished without a bleeder. It was frustrating and required alot of time sitting with the reservoire full to allow fluid to seep down with gravity. I would get a bleeder or borrow one if you can, unless you have the time and patience.

[Magnus_944]

It does not take 24 hours to bleed the brakes. The clutch takes some time (and fluid, and patience..) to get it done.
Do like this:
http://porsche-944-garage.tripod.com/shop-manual/brake-01.htm

//Magnus

[divezic]

I use a Mity-Vac Brake bleeder. The vacuum system is relatively quick; it takes me about 45 min solo to flush all 4 brakes and the clutch. Just make sure the reservoir never runs out of fluid or you'll start all over again.

The only problem is its impossible to tell if all the air is out of the line--the vacuum draws air from around the threads of the bleed valve and you always get bubbly waste fluid out. It does NOT allow air into the system though. This has never given me a problem but if there is an air leak in the system, I'll never notice it.

[Bob's944]

oooops, magnus is right, i had clutch on my mind and brakes got spit out.... I'll shut up now... but i hear brakes are easier.

[Obin Robinson]

some helpful tips for you:

1) i have used both the Mityvac, and the Russel Performance speed bleeders. i was so pleased by the Speed Bleeders, i put them on all of my cars. bleeding the brakes takes about 40 minutes if i do it all by myself! brakes stay nice and stiff and all the old fluid is removed! i still use the Mityvac in some instances.

2) use a ratty old towel and surround the master cylinder opening when you take the master cylinder cap off. this way if you spill some brake fluid, it won't strip the paint off of anything it spills on. remember that brake fluid can rip the paint off of a surface REALLY fast! be careful with it!

3) you'll know when you have the new fluid through the lines when it goes from being dark to being very light and doesn't have "fizz" or "froth" in it.

4) do the longest lines first, and the shortest lines last. go in this order: right rear, left rear, right front, left front.

5) for what it's worth, I use Valvoline Synpower brake fluid in DOT3. DO NOT use the silicone-based stuff under any circumstances!!! i've tried many brands and the Valvoline stuff is what i've stuck with. works awesome!

http://www.valvoline.com/pages/products/product_detail.asp?Product=51

good luck!

obin

[arnebret]

I bought me a bit of Castrol DOT4 Synthetic, it seemed about the only good fluid they had at the stores here. Any experience with the Castrol?

[Lawrence Coppari]

I used to have trouble bleeding the brakes on my cars. So, I now pressure bleed them.

Since all my European cars use the same screw on cap for the master cylinder reservoir, I bought a spare cap and washer and drilled a 1/4 inch hole in the center. Then I cut a piece of copper sheet to the size of the inside of the cap. I drilled a hole in the disk and inserted the copper tube and soldered it. Brass tubing can also be used here. A good source of a brass stub end is a rubber tire valve stem with the rubber burned off. The copper disk must be as large as the gasket so it will seal.

So what you do is fill the reservoir and replace the original top with the new one with the copper disk. The gasket must be between the disk and the reservoir. Screw on firmly enough so it will not leak and attach a compressor line with the pressure turned down to about 8-10 psig. Then you just go around the vehicle and open the caliper bleed valves one at a time until the fluid comes out clean. Needless to say, if you go too far and drain the reservoir, you need to start over. If the new cap leaks a little air, that is no problem because the positive pressure will be maintained by the compressor tank.

You can buy a fancy one that pressurizes the reservoir with brake fluid if you want to spend the money. I have used this home made rig for years.