Powermaster issues

[IL KIM]

Oh boy.  Thanks Steve. How go I test test the booster or check valve?  Could the issue be not enough vacuum with the tee hose teed off the pvc hose? 

When this is fixed, what would I see - will the force or speed of depressing the pedal be less and quicker?

[Steve Wood]

The vacuum in the pcv valve line should be the same as if measured anywhere else...  First I would be sure that the vacuum at warm idle is up around 18 inches/hg in Park.  It should be obvious that it takes a good vacuum to make the brakes work normally.

Second, here is a link to testing the booster   https://m.roadkillcustoms.com/test-power-brake-booster/

The check valve that is inserted into the booster should maintain a vacuum in the booster.  If you run the engine, then turn it off, and remove the check valve a few minutes later, you should be able to hear air rush into the booster.  Or, if you remove the check valve, then connect a mitey-mite and pump away on it, it should draw a vacuum and then hold it after you quit pumping.

If I recall correctly, my vacuum brake conversions always felt a bit more sensitive to applied brakes and seemed to stop more easily (less pedal pressure) than the powermaster.  On the other hand, I have seen some cars with the powermaster that stopped very well and others that did not so my experiences are subjective.  Never had any problem locking the tires at low speed.

I also wonder how far down the pedal did you end up drilling the hole?

[IL KIM]

Thanks Steve. The saga continues. I’ll find a vacuum gage and also test out the booster.
I drilled the hole 1” below the EOM pin.

[nocooler]

It looks like you have the dual-diaphragm booster - so you should be good with a clean vacuum signal. 
Are the bleeders on the top side of the calipers?

[IL KIM]

Are the bleeders on the top side of the calipers?

Yes the bleeders are at the top rear of the calipers. Why do you ask?

[nocooler]

If they are on the bottom it’ll make them impossible to bleed

[IL KIM]

Hope everyone had a Merry Christmas.

Thanks for the link Steve. Good article and video link.   I pasted in the Booster tests and what the results were below.

Brake Booster Test 1
With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4″, this indicates that the booster is working properly.
Result: The pedal drops way more than 1/4”; maybe all the way to the floor. Test 1 passed as 1/4” is a minimum?

Brake Booster Test 2
Run the engine a couple of minutes.
Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.
Result: The 1st pump does go low easily. The 2nd pump is firm from beginning of stroke and pedal remains fairly high. 3rd is same as 2nd. I think test 2 passed with 1 stroke of assisted pedal?

Brake Booster Test 3
Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.
Result: after a couple seconds, the pedal starts Rising instead of holding.  It pushes back on my foot with firm/pressure raising pedal to nondepressed position.  Test 3 failed; air entering mc side of booster while booster valve is closed. Maybe check valve is bad?

Inspect the Check Valve
Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.
Results:  Not sure if I do this test after engine off and pumping brake a few times to remove residual air or not. First test: I could blow into the hose and the booster indicating bad check valve. I cannot seem to repeat this result. Subsequent trials: I can suck (hard to do) a little bit of air and then when I cover the hole with my tongue - the suction from the booster side will keep my tongue stuck there. When I remove my tongue the booster sucks air in. I heard a moan twice. Test failed.

I then took the check valve out of the booster and left the hose on it. I can easily blow through the rear (pedal) side of the valve or suck through the hose; That’s good. However I can also suck air from the rear of the valve if I suck lightly or blow air through the hose lightly.  Confirms bad check valve.

So do you guys think is the check valve bad and what about the booster itself? 

Note: Engine vacuum was checked with a gage is steady 15 at warm idle.

[Steve Wood]

Normally, you would check the valve after running the engine and turning it off....no pumping of the pedal.

Based on what you wrote, I would try a different check valve since that is a cheap option.

[IL KIM]

My thoughts as well. Hope the booster is good.
Now I gotta figure out what car and year this check valve is for.....  maybe they will be on a parts help rack.

[Steve Wood]

86 buick regal with a V8 engine should work.  I think they were the same for me 30 years

[IL KIM]

Thanks Steve. Can’t find one for 86 Regal V8 online at Advanced but an AC Delco part is $27.00. I was surprised they run that much. Time to contact my eBay seller for advice. Hope he comes through.

[ULYCYC]

Dorman "help" Power Brake Booster Check Valves 80190 will work.  All the major parts stores including Amazon and Summit carries it. Cost around $5.00 us

[IL KIM]

Ed Baker!  Great to see you are still actively engaged. Trust all is well.  Thank you.

[IL KIM]

Update: I ordered an $27 AC Delco booster check valve with a 2 year warranty. Tired of bad parts out of the box. It finally came and it flows real easy when I blow through it but the hose end is too large in diameter for the hose.

SO I then bought a Dorman off the help shelve carried at Advanced and Autozone. t’s hard to blow through the valve - nothing close to the AC Delco.  Doesn’t feel right when installed, or the booster is bad; feels lethargic on subsequent brake pedal applies.  I hope the booster is good but can’t drive the car with all this snow.

I keep thinking it woulda been so much easier just getting a rebuilt Powermaster but wanted to put an end to brake issues. It’s not a difficult conversion if parts were all good. Oh, The 89 Pontiac Turbo Trans Am check valve also has a larger nipple and 86 Regal V8 check valve does not show up at Advanced. The saga continues and I’m done venting. Thanks for listening.

[Steve Wood]

I am not sure what you are saying.  You should not be able to blow thru the check valve from the engine side but you should be able to suck thru it from the engine side.

I have always bought check valves off the Help display.  There is a grommet in the booster where the check valve plugs in and it should not be cracked so leaks can occur around the outside of the valve.

If you take a vacuum pump and draw vacuum thru the check valve and pump long enuf to build up a decent vacuum, when you stop pumping, the gauge on the pump should indicate the vacuum is not going away but is holding steady for awhile.

If you cannot pull a vacuum on the gauge on the pump, then there is leak in the booster.

All the cars I have installed vacuum brakes on used parts that I bought from the wrecking yard and were used.  They still work.  I replaced the check valve just for the heck of it but I think I have only found one bad valve in the last 30 years.

I think we posted a few links on checking the set up but there are many more if you were confused.  In recent years, I have seen more problems with master cylinders right out of the box than anything and these are usually easy to figure out because the cylinder will not bench bleed correctly.

Some of the newer boosters have had adjustable push rods on them and/or spacers that may be needed to get the proper throw on the master cylinder piston.  I ran into this when I decided to install new brakes on my '69 Camaro when I was getting it ready to sell.

The '89 TTA had vacuum brakes which puts the lie to those that claim one cannot safely use vacuum brakes on a Regal.  There were not magic or different parts on the TTA.

I believe some of the later cars used a metric hose on the line to the booster which is slightly different from the 3/8's hose that was typically used.