Gravity bleed help

[Timothy B.]

I have been reading past posts about bleeding brakes, use of silicone fluid, etc. and have a couple of questions. I just installed a complete new brake system in my 67 with PB and opted for DOT-5 since this was my opportunity (no old fluid to mix with). My initial bleed was the old fashion manual style preceded by a bench bleed of the MC, but I likely need further bleeding to get ALL the air out.

I understand the concept of gravity bleeding, but how do you do it without getting fluid all over the calipers and everything else? The bleeder valves tend to leak around the threads in addition to the nipple, so connection a hose to the bleeder doesn't help.

Also, has anyone used "Speed Bleeders" and how well do they work? Is there a cheaper place to get them, since a Vette has so many of them?

Or, should I instead spend the money and buy a Motive Products pressure bleeder? Has anyone used that product with silicone fluid?

Thanks folks!!

[Joe L.]

Re: Gravity bleed help

Tim-----

If you apply silicone grease to the bleeder threads, that will seal them from fluid leaking out (and, from air leaking IN while the bleeder is open and confounding the bleeding operation). Besides that, you need to install tight fitting PVC tubing to the bleeder nipple. A little duct tape or electrical tape at the junction will help prevent the tubing from falling off. These things will solve the mess problem. Immerse the lower end of the tubing in small jars of brake fluid.

I've not used the Motive Products pressure bleeder YET, but I intend to. I've heard very good reports about it. It WILL work with silicone brake fluid.

[Roy B.]

Re: Gravity bleed help

I use a vacuum pull unit.You suck the fluid out into a bottle from each bleeder.

[Scott Marshall]

Possible Mixing Fluids

Tim, I don't mean to scare you but, I have heard that even when you have installed ALL new brake components (calipers,lines,master cylinder), that you still need basically rebiuld the calipers and master cylinders because during the manufacturing they use DOT 3 or 4 to assemble them. Anybody have thoughts on this?
Scott

[Timothy B.]

Re: Possible Mixing Fluids

I had heard that too, so I disassembled the MC first and cleaned it. I talked to the brake caliper rebuilder in advance and they told me that they could assemble and test the units with silicone compatible materials. If they did what they said they would do I am hoping I should be OK on that front.

[Duke W.]

Re: Possible Mixing Fluids

Yes, that's correct. Most commercially available master and wheel cylinders are assembled with conventional glycol brake fluid. Unless you are absolutely positive that a component was assembled with silicon fluid due to special arrangements with a vendor, then you should disassemble the component, thoroughly wash everything with denatured alcohol to remove all traces of the glycol fluid, then reassemble the components with silicone fluid.

Due to some basic imcompatibilities between glycol and silicone base brake fluids, your best bet of success with a silicone conversion is to be absolutely positively assured that there is not even a trace residue of glycol fluid left in the system.

Duke

[Rob A.]

Re: Gravity bleed help

I used an inexpensive bleeder kit that came with a small bottle that had a magnet to hold it in place on the rotor while I gravity bled my calipers. It worked pretty well and took quite awhile to fill. I was glad I used silicone based fluid, because as you say there will always be some leaking around the bleeder screws, but the fluid did not harm the paint at all. I actually found this small $6 kit easier to use than the more expensive suction, or vacuum bleeder kit.