Brakes

[S-west]

Well like an idiot I have been driving with horrible brakes, when driving slow (5-10) it stops fine but feels spongy, any faster I can stand on the pedal and it feels like I'm ddriving a compact car with the brakes on and a trailer truck pushing me down the road (takes forever to stop). I have bleed the brakes numerous times and have replaced the fluid, the rear brakes are entirely new. However the master cylinder pumps fluid from the front resiovior to the back one.. If I fill the front resiovior and leave the back one half empty, by the end of the week the back one will be full and the front almost empty. Anyway it's time to get this figured out as I rear ended a minivan yesterday, it was a slow speed impact at about 10 mph and the only damage to my truck is one headlight stoped working and theheadlight adjuster fell off the same light. The other guy needs a new hatch door and bumper

 

[OLDBULL8]

New master cylinder before you injure someone.

 

[chris142]

Master cylinders are cheap and easy. Why have you not replaced it?

 

[S-west]

Ya. I actually bought one for it a few months ago and haven't put it on because of the damn weather, Ive never actually driven a vehicle until very recently with good brakes so I thought(stupidly) that I was used to it and could stop fine. But when the person in front of you decides last second to pull in the gas station on the other side of the street... Well I can't downshift that fast haha. But I guess I've learned my lesson I'm going to go through the whole thing. And that car that I drove with good brakes, the first time I touched them my head almost hot the steering wheel haha

 

[ToughOldFord]

Wow, glad no one was hurt. X3 on starting with the new MC.

 

[lotzagoodstuff]

However the master cylinder pumps fluid from the front resiovior to the back one.. If I fill the front resiovior and leave the back one half empty, by the end of the week the back one will be full and the front almost empty.

You have an issue with the length of the master cylinder rod. When you pull your master cylinder off, you will see that there's a plunger that actually pushes on the cylinder. If it's too far out, it doesn't allow the cylinder to return far enough to release the line pressure and every time you push the brake pedal you will essentially keep pumping up your brakes until they are rock hard. If the cylinder rod is too far in, you will pump fluid from the front section of the master cylinder to the rear. Pull the lid off your master cylinder and have a buddy SLOWLY push the brake pedal and you should see this phenomenon of "boiling" fluid out of the front reservoir in the master cylinder.

Pull off your master cylinder and lengthen the rod via the adjuster. You should be able to find a spec with tolerance somewhere.

In any event, get it fixed before you make a bigger mess for yourself.

Good luck

 

[franklin2]

You have an issue with the length of the master cylinder rod. When you pull your master cylinder off, you will see that there's a plunger that actually pushes on the cylinder. If it's too far out, it doesn't allow the cylinder to return far enough to release the line pressure and every time you push the brake pedal you will essentially keep pumping up your brakes until they are rock hard. If the cylinder rod is too far in, you will pump fluid from the front section of the master cylinder to the rear. Pull the lid off your master cylinder and have a buddy SLOWLY push the brake pedal and you should see this phenomenon of "boiling" fluid out of the front reservoir in the master cylinder.

Pull off your master cylinder and lengthen the rod via the adjuster. You should be able to find a spec with tolerance somewhere.

In any event, get it fixed before you make a bigger mess for yourself.

Good luck

Make sure you look that spec up before you mess with the length. If you get it too long and slightly push on the master all the time, it will cover up the compensation ports, and you will get a couple miles down the road and the brakes will start applying by themselves. The compensation ports are the little holes in the bottom the reservoir. You should see a geyser from each one when the pedal is pressed.

 

[lotzagoodstuff]

.......If you get it too long and slightly push on the master all the time, it will cover up the compensation ports, and you will get a couple miles down the road and the brakes will start applying by themselves......

That would be the pumping up the brakes part I warned of in my post. This pic should help you figure out the dimension that you are looking for (NOTE: this is a generic pic). I can tell you from my own personal experience that it needs to be lengthened, franklin2 is correct that too much length will result in a "check valve" effect on the master cylinder, so my suggestion would be to make small adjustments if you can't find or effectively measure the push rod distance, and just as a final check, I would apply the brakes with your truck in park several times, and then crack a bleeder on one of your front calipers to see if there's a lot of build up pressure.

Ask me how I know this test procedure

You must be registered for see images attach

 

[lotzagoodstuff]

FYI, looks like according to this link the distance should be .931-.946". I don't trust everything I read on the internet, but maybe somebody with an '86 F350 manual can confirm this.

Good luck

http://www.ford-trucks.com/forums/595533-power-brake-booster-rod-adjustment.html

 

[S-west]

My manual for 80-96 f-series sais .995 and tells me to make or buy a guage for it but I'm just going to use a caliper with a depth guage because I don't see why that won't work. Thanks for the help guys I'm gonna go ahead and replace the master cylinder and check the length right now

 

[S-west]

I don't have it together yet but it was infancy shorter than the Manuel states it should be. So I set it to the proper spec. It was .95 now it's .995 so we will see.