It would be interesting to read the text to see just what they are testing for. I tried rebuilding one of these units by putting it back in the truck to test and that just is not really practical. I was working from the standard CMP MB-C2 manual. Set up to test it on the bench with a vacuum pump and it was a lot easier. Issues I ran in to were as follows:
- Leaks between the base plate and barrel
- Leak at the one way check valve
- No problem with the piston shaft
- No problem with the actuator valve
- No problem with main piston seal
Using the vacuum pump with and a ball valve I was able to test each component for leak down. As the number of leaks was narrowed down listening with a stethoscope became useful. When all the leaks are tracked down an minimized the brake booster will hold vacuum up to over night. Though even with a booster that will not hold charge once the engine is shut down the boost in braking power is significant.
Keeping the air that is going into the unit clean seems to be the biggest issue. Which means finding a replacement for the bellows boot, fortunately off road shock absorber boots can be found that are a very good size match.
But as I said it would be very interesting to hear what the major test the Bendix Book is recommending.
Cheers Phil