Posted in the Offroad section of this forum.
A few times while wheeling I have had situations where the engine wasn't available and I was on a hill. One time I lost oil pressure and turned it off myself and had to back down a pretty steep grade. Another time the fuel pump gave out at a very inconvenient time. The thing with vacuum assist brakes is you get one more pump (maybe two) and then it's done. With no vacuum assist the brakes are very stiff and not so good, even worse with all of the weight I have added to my rig.
So, I got the idea to add a vacuum pump to the brake system. It's a popular modification for over cammed street cars with low vacuum. They use the pump to provide enough vacuum for decent power assist in normal driving.
Normally I have enough vacuum but on those rare situations where I am on a hill and the engine isn't cooperating or I am being drug out of a trail for some other reason I didn't have the advantage of vacuum assist.
I started with a vacuum canister, that got me a couple more brake pumps. Later I added a vacuum pump to the system. My vacuum setup is a bit different compared to what the manufactures show in their installation manuals. They normally show the pump between the engine vacuum and the tank with a check valve between the engine and the pump. I found the inline check valve was really restrictive and limited how well the normal engine vacuum worked so I put the pump between the tank and the booster. This works great. The tank has its own check valve so when I turn on the pump it creates vacuum in the booster and the tank.
Currently it's wired with a manual switch to work even if the ignition is off. This means it will operate while normally parked and the ignition in the 'off' position. This could drain the battery if I forget to turn it off. I am thinking of changing so it only operates if the ignition is in the 'on' position.
I normally leave it turned off and will just turn it on if I am approaching a big hill or have had an engine problem.
What do you all think of this idea? I haven't seen it used much for offroading. Any thoughts on alternatives to how I installed it?