Ok guys, Im having brake issues and I am in need of some expertise.The truck is a 73 F250 hiboy 4wd. 360 eng and an auto tranny with power drums on all 4 corners. I adjusted the brakes last weekend to barely scrub when turned. When I apply the brakes they slow me down but the pedal is on the floor. On the 3rd or 4th pump Im slow enuff to stop. Well I bled them off at the wheels cloudy fluid but still no air or pedal. While checking the fluid level I thot to press the pedal w/ lid off to see if I can see any air come up. The fluid hit the bottom of the hood.I read that this is a sign of bad seals.Truck has set for at least 18mo b4 I bought it so its a possibility.Tonite I put on a reman MC and the replacement has a third more fluid volume. I start to flush system and bleed. I did bench bleed it. Filled MC and installed cap. Pumped the brake pedal to pressurize the system. Got cloudy fluid and pedal about an inch off the floor board. finally got clear fluid at a 4 corners but still pedal in same position from floor. When I start the truck I loose eveything and have to pump but Im only a hard push from the floor. I dont get it? I can hear the shoes hitting the drums but no pedal. I have looked for leaks but the drums and lines are dry. If I could get some input on this I would greatly appreciate it.

 

I'd check the brake hoses, even though may appear ok they can deteriorate from the inside out allowing them to expand when pressure is applied, in turn allowing your pedal to sink, it's cheap insurance just to replace them before one bursts.

 

18 months...That's about my own warning signs for rubber hoses and wheel cylinders. I'd also go as far to check the drums for any cracks or severe wear.

S-

 

Also it seems like the parts store sold me a MC for front disc brakes. DOH

 

Yeah...that won't help matters given the internal action could be different.

S-

 

Drum brakes are supposed to have equal sized chambers if what ive read is right. Its what came off of it too. Thats why it slipped by me about the chamber size

 

Ive put on alot of "bad" new master cylinders over the years grab another from the parts store and try again sometimes you have to go through a few to get a good one.

 

Does anyone know anything about a threaded shaft between the Power brake diaphram and the master cylinder plunger?

 

The reason I ask is between the MC and Diaphram my plunger looks to have threads in it. After a little measuring, somewhere along the way The truck has lost 2in of stroke before the diaphram plunger hits the MC piston. I found a bolt that threaded into the plunger and cut the head off leaving the bolt threads 2in long. I rounded the cut section with a grinder and threaded it into the plunger shaft. Installed MC and bled the brakes. Instant pedal and all 4 wheels lock up. The pedal is up on the brake switch like its supposed to be also. I dont get it? Could a previous owner not remove the MC and cut the shaft? Any info on the shaft would be extremely helpful.

 

Oh well I guess Ill figure it out

 

don't be suprised at anything you find, or don't find
most people know just enough to be dangerous, especially when it comes to "fixing" things

 

The pushrod coming out of the vacuum booster is designed to be adjusted. Normally what you should have (again...most cases) is a threaded rod coming out of the vacuum booster, kinda on the short side, but it probably has a retaining nut to keep the rod from spinning once correctly set. This is used to compensate for changing master cylinders from brand 'a' to brand 'b' where there might be a slight difference with the piston design within the master cylinder--and also with different designs with vacuum boosters where the throw might be either to long or to short.

S-

 

340 6pack

are you talking about this part ?

 

YES YES YES !!!!!! That is it. Now the only problem is finding one @ some point down the road. As of right now the brakes are doing great. My wife and I drove it into town tonite and got some cement for the postholes for my building and everything worked great. Now, the only MC I can get has different size reservoirs.This is from Oreilys who also has the cardone parts. the part # is 101388 that is now superceded by the part I have now. Everything seems to work fine tho. Thank you all for the help,Im gonna change gear oil in both rears tomorrow. Someones put some chocolate puddin in the housings. LOL LOL Gotta find the additive too.

 

I'm kinda puzzled by this comment, what do you mean BOTH rears?

It's one axle, pull the cover then refill. And you knly need to worry about LS additive if you actually do have a limited slip differential.

Just use a good 80w90 or a synthetic 75w140.

Josh