An idea I had for the brakes

[will e]

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?

[Stuka]

I think thats a great idea. Not having power assist to hold a heavy vehicle with big tires can really suck. Almost all newer vehicles use vacuum pumps for the brakes since most new vehicles are turbo charged. So you really only get vacuum at idle. The difference is they are often mechanically driven. But some are electric.

[SJTD]

My Nissan motor had it mounted on the back of the alternator.

[letank]

Very good idea, diesel cars had electrical vacuum pump -but, I only worked on a Peugeot years ago, ah, ah, a 1/4 century ago-

Yes, it is really chilling, the engine dies on a cold morning and you are barreling down a steep SF hill... put shifter in neutral while stomping on the brake pedal and turning the ignition switch while pumping for gas to dump gas down the carb throat.

Can you share any refs on the vacuum pump and the vacuum canister?

Thank you for such a very useful idea

[SJTD]

25 Years? That's when I started my project. One reason I've got shuch an archaic motor.

I've gone to hydroboost but that too gives you nuttin if the engine's off.

[Pablo]

25 Years? That's when I started my project. One reason I've got shuch an archaic motor.

I've gone to hydroboost but that too gives you nuttin if the engine's off.

It feels like my project is taking me 25 years, but only 8 so far.

To the main topic, maybe a good reason for a line lock? If your power goes out, pump the brake and throw the line lock to lock at least half the brakes on?

[Yeller]

I can get 3 good solid pumps out of my hydro boost. After that you still have brakes but may need to source your in inner green Hulk to have much power. You have the same issue with a vacuum booster unless you have an electric vacuum pump. Even that is limited to battery power.

[will e]

The line lock is a good idea but the main reason I installed the vacuum pump is if I lose engine power while wheeling. I remember one time I was climbing a pretty steep hill out by box canyon. My oil pressure dropped so I killed the engine and had to back down with no power brakes.

[devildog80]

That sounds like a lifesaver idea for sure.

As I am just starting rebuild on my '84 Grand Wagoneer, will keep that in mind after getting it back to normal, and considering worthwhile mods to think about.

[michaelbennett902]

Thanks for sharing

[j10builder]

I really like this. Thanks

[sierrablue]

Or you could put the non-power brake pedal on and give yourself lots of leverage--and at that point, you could eliminate the power entirely and not lose any brake when the engine dies

Yes, I'm mostly joking, but at the same time, the '71 has never had power brakes (yes, it has discs in the front now), and I can lock up the tires on dry pavement. Sure, they're 225/75r15s, but I can lock them up at 60 mph.

[will e]

I had no idea non-power brakes were ever available.

I've got 37's and do a 'lot' of off roading. Plus, I have added a lot of weight to my rig too! But I like your idea.

[sierrablue]

I'm not sure they were with the discs from the factory. I think if you got the very base model J10 (and maybe Cherokee?) post-'74 for a few years you maybe could get non-power, but I'm pretty sure they were drums on the open knuckle axle. The '62-'73s though, never had disc brakes in the front (and had the closed-knuckle front end), and I'm 100% sure you could get non power on those.

I would probably be ok off road with the non-power; my concern would be at speed, those 37s are going to have a super high moment of inertia, as they're not only heavy but also move the tire out farther, causing it to take a much larger quantity of force for the same amount of braking, assuming the same weight. Now, the plus side is, with the lift required to run 37s, the wind will be working in your favor for stopping

You could still get the pedal for the non-power brakes if you're really worried about it (BTW that pedal is the same between the manuals and the automatics); it might be kind of irritating if it's already heavily boosted, but then at least if the engine died you'd have the extra leverage...

[will e]

Now, the plus side is, with the lift required to run 37s, the wind will be working in your favor for stopping

Air Brakes!

I am going to stick with what I have. The pump is working out great, I've tested it a few times off road and so far the engine hasn't died on a hill yet. (Truck Avenger).

[sierrablue]

Now, the plus side is, with the lift required to run 37s, the wind will be working in your favor for stopping

Air Brakes!

I am going to stick with what I have. The pump is working out great, I've tested it a few times off road and so far the engine hasn't died on a hill yet. (Truck Avenger).

Cool! If you wanna use aero to slow you down, you could always use flaps like airplanes use; that'd stop you in a hurry