Brake Bleeding

I had some people ask me about this so I will elaborate on some things.

The pump is a vacuum pump. It was originally used for medical but appears to be a Badger air compressor with the ports reversed. It pulls 25" of vacuum. There are several pumps available through ebay and different sources. It is key that it can pull at least 20" of vacuum but it does not need much volume.

The vacuum pump is just hooked to a tank to catch the fluids so they do not go through the pump. I made sure the top hose is clear so I can watch for bubbles. the black hoses are sized for the bleed ports.

One problem I had with vacuum bleeding was air getting around the threads so I make sure there is thread sealant on the threads AND I put thread sealant around the base of the bleeder. This works well to prevent air from coming through the threads.

With both bleeders on the Wilwood calipers hooked up you can really go through some fluid so make sure you keep the reservoir topped off. This is good for getting difficult air bubbles out as you can really pull some volume.

I like to tap on the calipers as it flows to release bubbles stuck on the caliper wall.

Gary

Thanks for the pics and the explaination.

As an "armchair" mechanic, I just had a wild thought. would it be possible to pull a vacuum above the resevoir with the bleeds closed so that the fluid in the calipers is at the reduced pressure and any micro air bubbles expand and hopefully return to the resevoir.
I don't have a good grasp on the master cylinder to know if a path would be available

as I say, just my wild thought this morning

I was trouble shooting a problem during this process. In desperation I tired that. I made a lid with a port and pulled a vacuum in the reservoir. It really did not seem to do much. I think good flow through the system seems to be best but that's just me.

The darn mechanic on this build (me) needs to have his licensed checked. I could not get a good pedal and pulled my hair our running lots of fluid through the system, pumping brakes, etc.

Turns out the dumbass (me) who swapped the plungers in the master cyl forgot to put the plunger caps back on.

I did learn one thing I would do the next time I do a *new* brake system and that is lightly pressurize the system dry.

An air leak can make you pull your hair out trying to find. It is hard to find pumping brakes or pulling a vacuum as it pulls the air in.

Next time I am going to lightly pressurize the reservoir cap (20psi or so, not much) and spray all connections with soapy water.

I had one leaky fitting. The way I found it was pulling 25psi at the tank then shutting off any noise in the shop, radio fan, etc, then shutting off the pump. The tank would still pull pressure for a while. I moved around and heard it sucking in through a fitting in one of the calipers.

I freaking hate bleeding brakes.....Doesn't everyone?

JFB, nothing is that simple in this life. I've tried such a scheme and found that the seals are one-way; if you pull a strong vacuum on the 'wrong' side of either the clutch or brake master, instead of pulling bubbles up to the reservoir from 10 feet away, it will often pull air INTO the system at the master cylinder piston. Some guys do pressurize the master cylinder cap(s) to help push bubbles out the bleeder nozzles.

quote:

Some guys do pressurize the master cylinder cap(s) to help push bubbles out the bleeder nozzles.

We made a tool from an old hand held Hudson sprayer that fits on the reservoir and pressurizes it. This pushes the fluid out the bleeds when you open them. If it wasn't for this homemade tool we would no have been able to bleed the clutch.

I set up and tried a pressurized system but I emptied the reservoir too fast and it was harder to fill.

I did the clutch with the vac and it was a 5 min job.

The problem as I see it with pulling a vacuum right on the bleeder is air bypassing that can occur through the open bleeder threads.

The most effective way is to bleed across the entire brake system i.e. Master cylinder reservoir to caliper. I have on of the Motive Power bleeders, they are not very expensive and make brake and clutch bleeding a simple one man task with no fear of bleeding dry the master cylinder reservoir.

Julian

In some ways it's all about the details. Air is an issue around the threads but I put a fair amount of thread sealant around the threads to where no air leaks; problem solved.

It's nice because if you need to run a gallon of fluid through you can flow as much fluid as you like.

One issue that constantly comes up is, if you bleed brakes using fast fluid flow- as in pumping the brake pedal very fast or with a pressure bleeder, be aware the brake shuttle valvein your front trunk WILL travel to one end of the valve body and probably stick there. The Pantera, unlike almost every other car that has such a valve, does NOT have return springs so the shuttle will remain at one end of its travel, virtually disconnecting that caliper from the system. A hard pedal but poor braking follows.

The vendors have gotten many cars in for brake work in which the shuttle has been jammed in one end of its valve for an unknown period, and have gotten good at freeing them up with judicious use of air pressure in the bleed valve. But IMHO the real fix is to take the assembly off and put it on a shelf where it can't cause trouble.

All it does is light up a red warning light on the dash when brake pads get too thin- or a line blows off. The same light comes on when the e-brake handle is pulled so you never really know what its warning you of... And any driver worth the name will glance at the fluid levels and pad thicknesses every now 'n then, sort of pre-flighting their car. Trust me- you won't miss this troublesome assembly.

I've got this guy ...

Vacula Bleeder:


I've had it for years and am quite satisfied. Sometimes I still have one of the kids get in for the final manual bleed, but for filling or changing fluid...works great.

I think what I like about my tank/pump set up is that it is multi use. I have drained a lot of other things with it like power steering pumps before removal, oil in lawn mowers, etc.