Brake Booster Question

[dnoda]

I recently bought a '68 Mustang coupe with a 302, auto trans, power brakes / steering.

According to the previous owner, the brake booster either needs a new check valve replaced altogether. The shop manual I have shows on an auto transmission car, the the check valve has two hoses connected. Of course it doesn't say where they go... obviously one goes to the manifold vacuum port.

Where does this other hose go? It wasn't hooked up to the booster when I bought car -- maybe this is the problem (engine stalls when the booster is hooked up and I press the brake pedal)?

Thanks!

[Gearhead999]

Does the check valve have two ports?? One should have a cap on it. I've never seen anything hooked up to the vacume line or check valve, except the supply vacume line from the manifold "T".

If the car stalls when you step on the brakes, the booster is bad.

[dnoda]

The check valve does have two ports, one is capped.

As far as I ever knew, all that should be hooked up is the one port to the manifold, but in the 68 repair guide it has a pic of the booster with an inset showing one hose connected for manual trans and then another inset showing two hoses for auto trans. Doesn't say a word as to what that second hose is about. This is why I am confused.

[Gearhead999]

I recently sold a 68 Mustang 289 C-4 automatic transmission. It had two ports. The smaller one was capped. The transmission modulator hose came off the vacume port on the rear of the intake manifold.

I presently have a 68 Cougar 302 C-4 automatic transmission. It also has two ports. Smaller one capped. The modulator comes off the same vacume tee port as the Mustang did.

I wouldn't worry about it. I'll look at my shop manual and see if I can see what you're talking about.

[Gearhead999]

I looked at my shop manual this morning and see what you're talking about.

I've never seen one hooked up like that. I wouldn't worry about it.

It was probably the way they were going to route it in the beginning and then made a change before production or shortly after it started.

If the valve was bad the engine would stall all the times, because the valve has vacume all the time, not just when you step on the brake pedal. Sounds like the diaphram is leaking in the booster.

[dnoda]

Just recieved my replacement booster. Now I just need to find time to install it!

It is reassuring to know that only one port on the check valve is all that is needed.

Thanks for the advice!!

--Don