Brake troubles

[rockyroad217]

Ive been working on trying to get the brakes going on my truck. After gathering up necessary tools I thought I needed and then some, I ended up only getting the front wheel cylinders and shoes replaced. While I was under there, I noticed fluid around the master cylinder and pulled the boot back, sure enough alot of fluid dripped out. So now I am in need of a master cylinder too. I'm replacing the entire brake assembly at the wheels with brand new because it was included with the truck, but now I'm assuming I need a master cylinder too. I really don't want to rebuild it. Another question, I'm trying to learn what I can about the brakes, but it's more complicated than what I'm used to..So, if I apply the brakes and the brakes aren't bled and I'm low on brake fluid, should the airpack still make the air blow off noise? It isnt, and I wasn't sure if brake pressure is what activated the air part of the braking system or not..I'm really not wanting to have to drop the money for an airpack haha and the rebuild isn't really that cheap either.

 

[steelandcanvas]

Nothing wrong with rebuilding the MC, and alot cheaper than a new unit.

 

[rockyroad217]

I'm just worried that it will be a rusted/pitted mess and I will end up having to buy a new one anyway. And I'm impatient and would rather bolt and go haha. But I really want to know about the airpack question so I can stop worring about it.

 

[fsearls92]

Mine wasn't making the air blow off noise so I checked the fluid. It was empty, and I filled it up and it started blowing off air again(not sure why fluid makes it blow off air, but it did). Went for a drive and the brakes didn't work at all! After jamming into low gears at a stop sign I went right home and bled the brakes. Tried another drive went great for about twenty minutes and then again no brakes. I replaced the air pack that I got from boyce, install took about an hour and it was the best thing I have done; and rebled the brakes(people made sure to tell me to use DOT 5, its expensive but everything on these trucks are). Brakes work awesome and now I have peace of mind. I would definately replace since it is a week point of the truck. Yeah its expensive, but hitting someone because your brakes don't work costs a whole lot more!

 

[rockyroad217]

Mine wasn't making the air blow off noise so I checked the fluid. It was empty, and I filled it up and it started blowing off air again(not sure why fluid makes it blow off air, but it did). Went for a drive and the brakes didn't work at all! After jamming into low gears at a stop sign I went right home and bled the brakes. Tried another drive went great for about twenty minutes and then again no brakes. I replaced the air pack that I got from boyce, install took about an hour and it was the best thing I have done; and rebled the brakes(people made sure to tell me to use DOT 5, its expensive but everything on these trucks are). Brakes work awesome and now I have peace of mind. I would definately replace since it is a week point of the truck. Yeah its expensive, but hitting someone because your brakes don't work costs a whole lot more!

Thanks..I was hoping that not having pressure in the line had something to do with it...That may explain my brake lights not working too haha. I have 3 gallons of DOT 5 fluid, so I have that covered

 

[doghead]

The hydraulic fluid pressure coming out of the master cylinder, goes into the airpack/brake booster. It moves the piston in the airpack, which operates an air valve that applies air to the back side of the air cylinder, there by boosting the force to the piston. This is the same principle as power brakes. The air valve also actuate proportionately, the air brake line to the rear for use with an air actuated trailer brake.

The original brake light switch is a simple pressure switch. it needs brake fluid pressure to function.

There was a MWO to change out that brake light switch to an air actuated brake light switch. That way, if the switch fails(leaks), you don't loose 100% of the braking function(just loose the boost function).

 

[Heavysteven]

[media]http://www.youtube.com/watch?v=-q74Hkk0m4g&feature=youtube_gdata_player[/media]

 

[rockyroad217]

I got the new master cylinder ordered last night, so today I figured I would try some more wheel cylinders. I started attacking the furthest rear axle and was going to replace the entire assembly (when I bought the truck he included 4 brand new complete brake assemblies) but found that it was riveted on unlike the front. I also found the bearings and all the grease filled with gear oil. I'm not real up on these axles, and thought it could be that rottten piece of cork causing it in that little keyway, so I used some rtv in the keyway and repacked the bearings and cleaned all the grease out and filled with new. Am I right in my thinking about the keyway causing gear oil to get in there?

 

[Scrounge41]

subscribed

 

[Seth_O]

Am I right in my thinking about the keyway causing gear oil to get in there?

Gear oil in the knuckle is usually caused by a bad axle shaft seal. If you're tearing it down to the cork key, I would just do the job all the way and replace the shaft seal as well.

The cork (or lack thereof) can cause leakage, but that little piece of cork is actually the original factory design. Every time I have opened mine up I have used RTV to reseal it, and with good results.

 

[Heavysteven]

Don't forget the spring vent needs to be cleaned.

 

[rockyroad217]

Gear oil in the knuckle is usually caused by a bad axle shaft seal. If you're tearing it down to the cork key, I would just do the job all the way and replace the shaft seal as well.

The cork (or lack thereof) can cause leakage, but that little piece of cork is actually the original factory design. Every time I have opened mine up I have used RTV to reseal it, and with good results.

When you say knuckle..Are you talking about in the front axle? I'm talking about the rear axle at the moment. I was aware of it being the factory way of doing it, but there wasn't much left of it haha.

 

[rockyroad217]

Don't forget the spring vent needs to be cleaned.

Where is the spring vent? I'm new at all this

Edit- Oh for the axle vent??

 

[Heavysteven]

Center of the photo

 

[rockyroad217]

Center of the photo

Thanks I will definitely check them all before I take it out on it's maiden voyage! (with me driving it anyway haha)

Well that and after I get all of the brake components replaced...Got a lead on a used airpack for extra cheap. I have to take it off the truck though. At the price, I may get them off all 6 trucks he has. Can't hurt to have extras

 

[DeucesWild11]

How loud is the brake blow off noise? Not sure if mine is doing it correctly or if I am just missing it.. Does it sound similar to when you disengage the front wheels or is it louder? Going to replace some brake lines the weekend and bleed, hopefully that is all of my problems.. probably not..

 

[Keith_J]

Gear oil in the knuckle is usually caused by a bad axle shaft seal. If you're tearing it down to the cork key, I would just do the job all the way and replace the shaft seal as well.

The cork (or lack thereof) can cause leakage, but that little piece of cork is actually the original factory design. Every time I have opened mine up I have used RTV to reseal it, and with good results.

Yes, this keyed, washer-looking seal is the problem, it leaks through the threads and ID of the seal. A bit of RTV here works fine.

You can tell if the lip of the seal is working, if so and rubber isn't cracked, reuse it. Don't pack grease in the hub (where it does NOTHING!!!) because this keeps oil from the inner bearings and seal which keeps gear oil from the brakes if the weep holes clog.

Like I always preach, rebuild wheel cylinders with proper expander-ended springs. The government got cheap wheel cylinders which will leak. The kits can be obtained from NAPA or Rock Auto. It is a generic kit so you have to find the Dorman cross-reference number for the wheel cylinder diameter.