Okay WTH? Now my Power Brakes are not working!

[Dodge Don]

I had my valve lash tightened up and had a new set of mufflers installed...drove 2 miles home no problems. Go to back it out of garage and no power brakes. All the hoses are hooked up and good on brake fluid. Any ideas?

Not good with only a couple of weeks before Carlisle.

[b5blue]

Check the vacuum hose, nipple, booster grommet the valve that plugs into it first. The vacuum nipple on mine had extra smaller nipples on it and one time one cap leaked from age/heat. 

[Finn]

Agreed. Your booster might have gone out, mine did.

[Chryco Psycho]

Do you have anything else tied into power brake vacuum hose ?
If the PCV is connected into the same hose it may not supply enough vacuum .

[Dodge Don]

I depressed the brake pedal and released several times with engine off. I didn't notice any increased resistance each time and the pedal felt very firm the whole time. I kept foot pressure on the brake pedal and started the engine. The pedal did not sink slowly but remained firm.

I'll be testing the vacuum to the booster and will advise.

[resq302]

I would think if there is no increased pedal resistance, then you arent losing vacuum like mine does when you press down on the pedal.  To me that means that you have a leak when the engine is off which would indicate that your booster is bad. 

I seem to recall booster Dewey having about a 1 week turn around time.   

[green69rt]

Here's something to think about, look around the area that you had to get into (to do the valve lash check.)  I think there is a good chance that something was bumped, moved or knocked loose (like a vacuum line) maybe even moved a small amount so that vibration did the rest of the job.  Even the nipple on the booster could be busted or something.   Anyway take a little time before you go on a big repair job to make sure that all is ok.

[Dodge Don]

I disconnected the hose at the power brake booster (the one that provides vacuum off the intake manifold). I inserted the vacuum gauge into the end of that hose and fired up the engine.

At idle (bouncing around 700-800RPM) the gauge jumped around between 8" and 17" of vacuum at the extremes however seemed to center off of around 12" of vacuum. When I stepped on the gas and held at 1500 RPM the gauge was steady at around 15" of vacuum and when I stepped it up to 2,000 RPM the gauge was steady at around 20" of vacuum.

I disconnected the gauge and hooked the hose back up to the brake booster and held RPM at 2,000 RPM and still had no power assist on brakes. Just a firm pedal.

[b5blue]

If the booster has crapped out that car will be a beast to stop! Be careful! 

[resq302]

did you check the check valve in the booster?

[Just 6T9 CHGR]

Don the tests you ran seem to point to the booster being bad.....look on the bright side....you wont have to drive much in Carlisle

[Dodge Don]

Don the tests you ran seem to point to the booster being bad.....look on the bright side....you wont have to drive much in Carlisle

This is true. If it is indeed the booster I may very well wait until after Carlisle to replace it since it will just drive off the trailer into building T and then back onto trailer when done.

[Dodge Don]

I disconnected the intake to booster hose from the booster check valve and installed a seperate hose on the booster check valve to test it.

Midland Ross power brake booster with a check valve with two ports (one blocked off with a plug...the other connects to the intake hose)

With cap on secondary unused port and new test hose on intake hose port:
- When I blow into the hose it will not allow air to pass through booster check valve
- When I suck on the hose it will not allow air to pass through booster check valve ( I think it should allow air to be sucked out shouldn't it??)

With cap removed from secondary unused port and new test hose on intake hose port:
- When I blow into the hose it will allow air to pass through booster check valve
- When I suck on the hose it will allow air to pass through booster check valve

Based on this I'm thinking it may be the booster check valve that is the issue. Thoughts??

[Dodge Don]

Pulled the check valve out of the booster and performed same test with hose. This time I could not blow into the valve but could suck out of the valve.

So I think I just blew my previous hypothesis and perhaps it is indeed the booster itself.

[A383Wing]

I agree, bad booster

Bryan