Braking issues

[Dsl_Dog_Treat]

Well got a good load in the pants tonight on the way back with the little butts.
In Goldie, rolling up to the stop sign at the intersection by my fire department and stepped on the brake pedal. All was good, let off and stepped on them again and almost got t-boned by an oncomming car. Bad intersection as others have bought it previous at the same place.
I didn't really step on the brakes that hard or for more than 4 seconds first time. Second time the pedal was hard as a rock and no stopping power whatsoever as engine was at an idle and trans in neutral.
Master cylinder was replaced with a new 1 1/8" roughly 20,000 miles ago and the vacuum pump was replaced at the same time by the PO. All the vacuum lines looked good and reservoir was full and all lines are dry. The RABS sensor has been separated by MI weather and has not been repaired yet but sensor light was on before and haven't had time to troubleshoot the system with Scotts info he forwarded.
I could make it happen again by the same actions but the truck would stop fine if I stood on the brakes like normal and no release. During this operation the pedal would remain constant and wouldn't fall. During the hard pedal simulation with truck running of course, the pedal would fall slightly at idle but fall a little faster when the rpms were brought up.
Is this normal operations for this particular braking system or is the need for a vacuum canister in order for more vacuum storage. I am in the process of acquiring a fiver over 30' length as a project rebuild and don't really want any issues with that or for normal driving. I really had never encountered this before so I am a bit concerned.

 

[Dsl_Dog_Treat]

Will be checking vacuum pressure tonight. Anybody have vacuum specs as to what the pump should pull?
Might be looking at a bad booster?

 

[towcat]

DOT specs are three pumps on the brake pedal before the vac supply in the booster is emptied. If you have a vac gauge hooked up, the Hg's should be 21" by the vac pump.

 

[82fordtruck]

I have the same problem when my adjusters are acting up on the rear brakes. It uses a lot of vacuum when those aren't right, but I think calvin is on the right track there.

 

[soulpatchfr]

c'mon, Ron... you know Peter The Great has the vac test & specs in his gallery over at [censored]


glad you & the kiddies are OK, BTW.

 

[Dsl_Dog_Treat]

Well I had a few minutes to tinker before the little butts showed up. I grabbed the vacuum gauge and tied in at the manifold by the heater box as was the closest to the pump for time being and couldn't find the adapters, but it registered 20 in HG @ idle.
Hmmm
Will finish testing tomorrow as is my short day and will see if'n I get a pressure drop when brakes applied.

Mike... Never thought of that. New brakes this summer, maybe they are not adjusting. Will check that too.
I can get 2 good pumps on the pedal and that's all. Hopefully just the brakes need a little snugging up.

Thanks

Frank ya know better than to go there....... Thanks

 

[Agnem]

Ron, a bad pump will usually pull 21 inches at sea level, just like a good one, but it's not the amount so much as it is the speed at which it does it. In general, I find a failing pump will not build vacuum fast enough, and it drops too low with the foot on the pedal. At idle, you should get 21 inches in about 3 seconds from zero, and when you step on the brake, it shouldn't drop to much below 13 or so, and then come right back up real quick when you let off.

 

[93turbo_animal]

I'd say your vac pump is getting weak sound like the symptoms of low to no vac

 

[82fordtruck]

I wonder if there is a way using a fixed orifice in the line to test the volume from the pump?

I only posted what I did because it's what happened to me, but it seems that others have not had the same problem as me.

 

[Dsl_Dog_Treat]

I'd say your vac pump is getting weak sound like the symptoms of low to no vac

Was thinking that at first but digging thru all the paperwork the PO gave me, it is only bout 2 years old. Doesn;t mean much tho. Starter replaced at the same time.
Just for giggles I pulled the line off the booster and stuck my thumb over it and let go acouple of times. It seemed to pick up a vacuum fairly quick.
As far as the brakes go. I know yer supposed to use the brakes backing up and is what adjusts them. Well with the 5 speed, I really have a bad habbit of not doing that often enough. The brake tech for may patrol vehicle said the same thing cause they were not adjusting enough and was smoking thru front pads every 10,000 miles.
BAD driving habits when eating doughnuts and drinkin' coffee.
Will give it the run down tomorrow with the troubleshooting guide that Frank had to bring over here. Will post results afterwards.

Mel, Thanks for that info, was needing that. Also answer yer phone next time.

 

[Agnem]

Sorry Ron. With the job hunt going full speed, things are not as they normally are. I should also say that my company cell phone might disappear at any moment, but I'll let you all know if that happens.

 

[Dsl_Dog_Treat]

Sorry Ron. With the job hunt going full speed, things are not as they normally are. I should also say that my company cell phone might disappear at any moment, but I'll let you all know if that happens.

Was just gonna give ya a hard time anywho.

Well here's tonights findings..............

Photo 1 shows that the vacuum pressure at curb idle was 20 in Hg.

Photo 2 shows that the vacuum pressure dropped to 13-14 in Hg-needle was dancing abit.

Photo 3 showed that the vacuum pressure after brake release also dropped the pressure to 5 in Hg- needle dancing abit.

According to the test procedure that I was directed to by the purple gloved exercise boy Frank, it states to replace the brake booster. Test procedures attached also.

I had an extra vacuum pump from my van donor motor and swapped it real quick like and had the same results.

With the entire vacuum system operational, it took the pump 10 seconds to return to 20 in Hg when the idle was run up to 2000 rpms.
It took all of the 30 seconds to charge up the system at idle.
So it looks like the ole and hollar booster replacement will have to commence.
AFTER I replace the ignition actuator that broke in town tonight.
Thank goodness for the screw driver to start the truck from the solenoid trick.


NEXT problem any suggestions on a friendly wager.

 

[Dsl_Dog_Treat]

AHHHHH

1 hour and soaked underwear, the gay truck is back to braking like a big pig should.

You must be registered for see images

Only issues were the nuts retaining the master cylinder.
I ran some vacuum tests to verify things and was quite suprised to the findings.
Depressing the brake pedal after the system was charged, the gauge only dropped to 16 inHg, while holding the pedal down and constant the vacuum began to increase.

You must be registered for see images

Let off the pedal and it only dropped to 11 inHg
did this several times and took her for a spin round the block and

You must be registered for see images

she put me into the windshield she stopped so good. No sagging pedal, just nice firm brakes.
Just wished it wouldn't have been raining so hard. Shop is out of commission for a rearanging.
Well I'm done.

 

[icanfixall]

Glad to hear you have brakes again. Now check the rears for proper adjustment. If you brake peddle goes half way or more towards the floor, you need to manually adjust the rears. If your emergancy brake peddle engages more than half way down, then your rear brakes need adjustment. -Deadhorse

 

[Dsl_Dog_Treat]

Not again

Cruising up to drill this am brakes worked good.
Backed out of the gas station parking lot and pedal went hard again.
Same symptoms as befor but not able to check vacuum pressurees until late tonight.

A bad brake booster?
Or do I have something else going on?