The check valve on the power booster broke off where the line connects to it the other day. I've replaced the power booster and the master cylinder since they were both old and it looked like there was a leak were the came together. I did the bench bleeding and assembled them onto the truck. The pedal was very stiff. I bled the lines and started the truck and the pedal goes to the floor before the brakes grab like crazy. I'm assuming there is still air in the lines or I got a bad part. Ive done this job before on other trucks and havent had this problem before. I'm going to rebleed the lines as soon as I can get an extra foot to help. which brings me to a question for you guys & gals. I bought one of those one man brake bleeder pumps ($43). Read the entire direction book (3 times) for assembly and use and I got nothing from it. Anybody ever have any luck with one of these one man deals? If you did let me know what you used. I got this one at NAPA with no gauge for $43 then saw the exact same one same brand at Harbour Freight for $28 with a gauge. I think this would be a great tool to have if it worked like its supposed to. BTW this is the F150 4x4 shortbed.

 

I have one of those hand pumps with the inline bottle to catch the brake fluid. Works well, and makes more sense that having someone pump the brakes. Just make sure that you are getting a good seal on the brake bleeder and apply pressure, then open slowly and close. Pump and repeat.

I've often considered making one that pushes from the master cyl, using a spare master cyl cap/cover with a couple of valves screwed into it. Then pressure could be applied via a pump of some sort, maybe like a plastic pump bug sprayer.

 

I have one as well. I use mine for checking all kinds of vaccumm operated parts.
Have tried it with the brakes and found that if you put a little bit of thread sealing tape on the brake bleeder fittings, it will work better.
You know the drill, start at the farthest wheel from the master cylinder and work your way in.
Hook up the hose, crack the bleeder open and and start pumping. You should stop getting bubbles into the tube after a while.
Hope that helps some. Also, keep your eyes on the fluid level or you will have to start over.

 

Are you bleeding the brakes with the vehicle running?

 

Are you supposed to? I've never heard of doing so.

 

Working 4-12 this week sorry so late. No the trucks not running when I bled the brakes. And yes I started with the rear passenger side even tho the pump book says to start @ wheel closest to MC. Didnt understand that at all. Ive always started at the back. I had my brother pump the brakes and did it the old fashion way and they seemed to bleed just fine. When I started truck to test them, pedal went to the floor. The pump kit I got is a Mightypump brand with the little plastic jar to catch the fluid. If its not raining tomorow and the wife is up to it I'll bleed them again. If that doesn't work I think Im taking the MC back.

 

Well with power brakes the vehicle should be running this has been argued in the past. Some say it makes no difference others do because the vacum boster or hydro boster. Yeah I have always been taught to start from the wheel furtherest away from the master cylinder.
Try it with the vehicle running I have never had an issue after replacing M/C brake boster or calipers or any thing else. Always that chance you got a bad part.

 

Well I got the wife to come join me in truck maintenance today. Rebled the lines (the old fashioned way) and still got a sloppy pedal. Ive got brakes but also alot of travel before they start to slow you down. Took it around the block and it stops, but I do alot of travelling on the highway and I wouldnt trust it to stop if I had to at higher speeds. Im going to pull the MC off again tomorow and double check the push rod travel. I adjusted it out before installing but it may need to come out more. Theres about 3/8" of threads showing now. How long are the threads on that. Never taken one all the way out before.

 

watch screwing it out to far It can cause the problem your having.

 

can someone please describe this MC adjustment. I need to remove mine and re-bleed it and would like to know what tweaking I can do to improve braking.

 

Was the MC level when you bench bled it? Did you wait 20-30 seconds between each push while you bench bled it?

Can you guys give some details on the booster pushrod adjustment? I wasn't aware of a pushrod adjustment on power brakes, only manual brakes.

 

Yes the MC was level when I bled it and I dont think I waited that long in between pushes. It wasnt real fast but it wasnt 20-30 seconds. I actually put it on, bled the lines and took it off and redid it, thinking I didnt get right the first time. Maybe I didnt get right the second time either. Creedog and fmc400 on the power booster pushrod there is a acorn nut attached to a threaded rod that screws into the pushrod on the end. Hold the rod lightly with pliers and turn the nut in or out. This adjust it for contact inside the MC "valve". (How many times did I say rod?) 77explorer you might be onto something. I thought it seemed to be out kind of far. Im going to pull it off again tomorow(today) and check out.

 

Stupid question/observation from personal experience. When was the last time you adjusted your rear shoes? If they are out of adjustment, the master cylinder will do exactly like you are describing, the pedal will go way down before the brakes engage. When I bench bleed a master cylinder, I do it level first, and once I think the air is out, I angle it nose down and try again a few more pumps to give any trapped air a chance to untrap itself, and a few more pumps in the level position, and a few smart whacks with a hammer for good measure..

I would adjust your rear brakes just to say you did it, it will eliminate one more frustration on why your brakes are not working properly.

Something I do when bleeding brakes, I take the bleeder screws out, put some pipe dope on the threads, put a piece of hose on the nipple, and put the end into a jar, or a water bottle with a hole just big enough for the hose to squeeze into. When bleeding, the fluid will go into the bottle, and the air bubbles will not have a chance to somehow get back into the system because it will draw fluid not air, and also the threads on the bleeder screw are sealed, so air wont get back in that way either. I also have a power bleeder, that pressurizes the mastercylinder. It has worked for me on several occasions, but sometimes its a pain to adapt it to the vehicle I am working on. Also, they sell one way bleeder screws. They let fluid out, but wont let air in. I think they are about $10 for two of them, look in the help section at Napa.

 

If this isnt your issue you could had also got a defective master cylinder I cant count the times Ive got remanufactured and even new units through work and had to R&R some units as many as 4 times before I get a good one.

 

Had a problem with only one -new- master cylinder so far but every
"re-manufactured" master cylinder is suspect right from the start! :/

Don't waste your time on "re-manufactured" ("cleaned up" is more
like it) parts (when you don't have to) but especially on something
as important as brake parts! :/

Ok? :)

I worked with a guy in Sacramento that had worked for a fuel pump
"rebuilding" place. He said... "when the pumps came in, the first thing
done was to test them and those that tested good, were cleaned up
and re-boxed, just like that :)".

He didn't buy "re-manufactured" parts he didn't have to either (and
just like me) even went over brand new parts before installing them.

YMMV

Alvin in AZ