1st gen vacuum over hydraulic questions

[draymorris]

At work, we use a 91 to pull a GN that has vacuum over hydraulic drum brakes on it. I have installed a vacuum gauge and 2 new vacuum pumps. But even when I have full vacuum(23in/Hg) I may or may not have trailer brakes.

Do I need more vacuum?

Do I need to do something to the trailer brakes? The trailer is a 72 Kalyn King Goose.

Should we scrap the whole rig?



Thanks

 

[PToombs]

Did you check vacuum at the trailer? Maybe there is a collapsed line, or an obstruction. Are the trailer brakes any good? In adjustment?

If the trailer is in decent shape, put on electric brakes.

 

[draymorris]

Thanks for the reply.

Yestersday I loaned the trailer to a man that did not have vacuum brakes. When he started to leave, the brake on the trailer were engaged- not locked but close. That isn't normal is it?

I could not find any adjusters on the brakes. I had to bleed off pressure to release them yesterday.

 

[PToombs]

I'm not exactly positive how they work. The vacuum runs a regular master cylinder right? Some medium trucks had a remote booster/ cylinder, gotta be almost the same. If the brakes are dragging, it has to be either adjusted too close, or, my bet, the master cylinder has a plugged port internally, holding fluid on the wheel cylinders. I think this because you had to bleed it to release them.

Hope this helps,

pete

 

[draymorris]

Yes it is a booster/master cylinder on the trailer. When I get the chance I am going to bleed the entire system. For now, just don't get in front of me and stop quickly.



Thanks again,



I will reply on here as I learn.

 

[PToombs]

I don't think bleeding it will help. Good luck though!

Maybe remove the cap on the reservoir, look and see how much gunk is in the bottom.