cj68

I have been using the GM Motive cap that came with the bleeder, but it does not seal completely airtight, especially over 12 psi. It hisses slightly and I did have large, tightly grouped bubbles coming out in the middle of my bleed on the first caliper (rear pass).

I bought a GM cap and gasket and put a fitting on it and hooked it to my power bleeder, but it did not seal well at all. What do you guys do to get a good airtight seal on the MC cap, in order to use more than 12 psi?

Also, can those bubbles I am seeing be coming from that air leak at the cap or the bleed tubing/bottle while bleeding (I use a drinking water bottle with a hole drilled in the cap and a piece of tubing running through it... and the tubing fits tight on the nipple)? I am not getting a mushy pedal at all or experiencing any braking problems, and I only see bubbles in that caliper, about 1/2 way through my bleed (espescially if it is leaking slightly). I always go back and check that caliper and there are no bubbles in it once I am done.

Thanks,

cj

sothpaw2

I shove some paper towel in there to make a better seal.

Miaugi

Call Motive and tell them about your problem, I have read here that they had some units go out with the wrong gaskets (too thin) and they will/should send you the correct gaskets to fix the leak you're having.

MySR71

I have the same trouble. I use two clamps to put modest pressure on the cap to prevent it from leaking. I clamp between the cap and underside of the master cylinder and keep the clamps about 180 degees from each other. Otherwise, one clamp will push down on one side and the other side will go up.

Last C5

I had the same problem with the factory cap on the MC. I removed the rubber seal and put a couple layers/round discs of plastic I cut out of some milk jugs behind the rubber seal when I reinstalled it and it fixed the problem.

rustyguns

God I luv American Know! I fix stuff like this all the time

AU N EGL

I got tired of the poor seal so I made my own cap

94ZR1#444

I got an old truck tire inner tube and cut out circular gaskets. The truck inner tube is pretty thick and seals the cap fairly well. You can still have a small amount of leakage as long as the pressure stays up you're OK.

I'm guessing the bubbles are happening when you move the tubing that is attached to the bleeder valve on the caliper. If so, I'd say that the bubbles are not from inside the brake lines, but from the air getting into the tubing when it's moved. That's what I sometime see when I'm bleeding my system. Just make sure your Master Cylinder fluid level is UP and doesn't start to suck air.

rbl

I finally figured out that if I try to make it too tight it leaks. I just get it fairly tight with the chain and wing nuts making sure it is centered ... workd great. If it is overtightened it warps it just a little.

cj68

That's what I did too (minus the valve), but the GM cap sealed way worse than the Motive cap. .. it didn't hold any pressure. Did you use washers to put underneath the gasket... If so, what kind?

Thanks,

cj

The Spark

cj68 - are you putting the brake fluid in the Motive bleeder?
Most people (I think) just use the bleeder to pressure the MC.

Just a thought.

On my Motive, the pressure guage was not working when I got. They replaced it under warranty. The cap blows off the reservoir when I pressure up. So I went back to the Mity Vac to bleed my brakes last time.

While messing with the cap, the nipple broke off so I need to rig up a new cap.

cj68

No fluid... just for pressure.

yakisoba

I called Motive, and they knew about the problem instantly! I had a new washer from them in the mail at their expense in about a week. Good service, fixing that issue.

trumper Z06

Try Kent-Moore P/N J35589-A , Adapter, compact Brake Bleeder.

This tool is substituted in place of the reservoir cap when bleeding a brake system...

You will need to rig-up a flow valve and a vent valve using common air-line brass fittings.

We've used this & the Motive Power bleeder since 2002. I got the info from the Watts brothers @ VIR when I had a brake issue.

Not "Cheap"... but it does solve the problem.

Kent-Moore's phone # 1-800-468-6657

Cya @ the track,

Trumper

Hardcorvette

My Motive Bleeder w/GM cap came with 2 washers. With the thicker one installed, I have had no problems with pressure up to 15-18lbs. Once it gets close to 20lbs the cap pops loose.

cj68

I think I have the thicker washer, as it sits tight up against the tabs on the cap. I tried the GM cap with an additional washer in it and it still leaked. I will call motive.

cj