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I was thinking of hooking up a gage to monitor my brake vacuum. Any suggestions? Where and how would I hook this gage up? What gage should I use?

Thanks for your help.

Well, I found a gage and kit online. Looks to be easy to hook up. Now I just need to know where, such as before the brake booster or after in order to best monitor the vacuum.

Hy Iron Clad, you will be actually monitoring engine vacuum, so any port below the throttle on the intake manifold or carb will be a good place to connect to, hope that helps.

Thanks 3B, I really appreciate the reply. So, by monitoring the engine vacuum, this will give me a good indication of what's happening with the brakes? I know this brake system is based off of the engine vacuum, but do I need to monitor vacuum after the booster? This gage kit I'm looking at has a 3 way tee that hooks right into a vacuum line and goes to a gage that can be bolted to the dash board.

I don't mean to ask these seemingly stupid questions but I have never owned a truck with vacuum brakes before, even after having owned at least 70 vehicles in the last 30 years!!

Iron Clad,

Your barke system is Hydraulic with vacuum assist, just like the cars.

If you want to monitor the vacuum for the brake system I'd install the gauge tee near the vacuum tank. Under normal conditions if the engine stops running you'll have 2 or 3 pushes on the brake pedal before your tank is empty (providing the check valve between the engine and tank is working).

Mike B

Thanks Mike. Well, I did know it was hydraulic with vacuum assist, LOL......I should have written my last post a little differently......LOL...

Anyway, this is just the kind of information I wanted to know. Once I shut the engine off it seems the tank emptys immediately. Otherwise, under normal driving conditions, the brakes work well. I was thinking of installing the tee behind the tank going to the brakes this way I can monitor actual vacuum to the brakes. Any thoughts?? I don't know if any of this makes any difference.....

Oh, what should the vacuum be, 18" ?????

Hy Iron Clad, if you have no vacuum reserve after the engine is shut off, then you probably have a leaking check valve or other leak. Does your engine run alright, consistant at idle? I'm not sure if you understand how the vacuum assist works, so I'll give you a brief explanation, under normal driving conditions there will be vacuum on both sides of the booster diaphragm, when you apply your brakes an atmosphere valve is opened on the apply side of the diaphragm, this allows air under atmospheric pressure to enter, this air is higher pressure than the vacuum on the other side of the diapragm, so the diaphragm and the piston attached to it will move, pushing brake fluid out to the wheel cylinders or brake calipers. The more you press on the pedal the more air is admitted through the atmosphere valve, and the more brake apply "power" you get. So monitoring vacuum will only give you limited information. A quick test to see if your vacuum assist booster is functioning correctly is, with the engine off pump the brake pedal a few times to make sure all the reserve is gone, now press and hold the brake pedal down, and start the engine, when the engine starts the pedal should go a little closer to the floor if the booster is functioning correctly, hope that helps.

Put a factory-correct VAC gauge, which was available on the Medium-duty & Heavy-duty trucks, in 1964-1966, with factory power brakes.

Thanks 3B and 4-5-6.......3B, the engine runs very well. I will inspect the check valve. Also, I will run the test you described. Thanks for the great information.

4-5-6, will do. I found a good source for a VAC gage. Unfortunately my truck doesn't have a gage, not that it didn't at one time, I'm not sure.

Okay 3B, I tried the test you described and the brake pedal did go down a bit, perhaps not quite a quarter of the distance from the floor. More like 1/8th. So it should be good to go then......I did notice that when the engine is running and I step on the brake pedal the engine rpm picks up a bit and seems to smooth out, not that it runs bad either way.

Hy Iron Clad, I'm glad your brake booster passed the test, a lot of the old trucks I've been involved with experience a slight change in idle when the brake pedal is depressed, I'm not sure if it's actually a temporary leak in the system, or because of the distance the vacuum signals have to travel. At any rate if the booster passed the starting the engine with your foot on the brake pedal test it should be functioning as it should.

Thanks again 3B for your comments and help. You are an indespensible truck expert......