Vacuum the Clutch Master Cylinder?

[Cudajon]

They are having the National Street Rod Association meet here in OKC this weekend. I stopped by the TREMEC tent to ask a few questions and in the discussion I mentioned the difficulty of purging the air out of out master/slave cylinders and asked the best way. The TREMEC expert proceeded to tell me I had been doing it all wrong and to completely purge the system. The absolute best was is to apply a vacuum to the master cylinder. The guys there were busy trying to sell trannys to the Hot Rodders and got tied up so I got a very brief how to. OK, has anybody else ever heard of this before? Exactly what are the steps to this process? It sure sounds like a lot less effort than laying underneath the truck working the purge line.

 

[VENOMOUS1 RACING]

You go buy a mightyvac handheld vacuum pump. You stick the tip end in the hole in master reservoir and apply around 12 in/vac
You should see bubbles purge. After that, You can disconnect line and press ckutch pedal. If it's solid it's air free. I'd it depresses, air is in line or bad master.

 

[10-1=9]

Many vehicle manufacturers use this method. Years ago I seen it done at the Harley Davidson plant in York PA. They clamp a device on the master cylinder minus the lid or cap. It's a flat plate with rubber on the side that touches the master cylinder opening. It has 2 hoses going to it. One for vacum and one to supply fluid. A vacuum pump pulls a vacuum on the sealed system. Then it holds it for a specific time to check for leakage. If that passes it then shoots the brake fluid in. Seeing the system is under vacum (absolutely nothing inside especially air/like outer space) the fluid flows to the back of the system regardless of bends or length.

It is kind of like changing an air conditioner with freon.

The external hydraulic clutch system on my Jeep TJ & the regular Ram trucks also have something similar. The whole system comes as one piece m/c, hose & slave. It's pre filled the same way from the factory. The slave cylinder doesn't even have a bleeder fitting on it.

 

[Cudajon]

You're never to old to learn something new. Thank you.