M35A2 LOTS of Brake questions - HELP!

[AZDeuce]

My daily driver is a M1009, it blew the flexplate so that will be this weekends project....DOH! So i needed to drive my Deuce today (M35A2), when I went to stop at a 4-way stop, the pedal was HARD, and would not move, I downshifted and made a right hand turn and coasted right through the stop sign.

SCARED the crap out of me, but fortunately it was a 2 lane road and everybody was in the left lane, so no harm no foul - THIS TIME!

I made it to work, and the brakes worked fine the rest of the way, but I can't trust them now! I'll be taking all the backroads home and downshifting WAY in advance so I can stop it with the parking brake if I have to.

I have all the parts on hand, to replace all the wheel seals, the wheel cylinders, and the master cylinder, as I planned on doing that the third week of this month, then going camping on the fourth week.

So the parts are in hand, my question is what would cause the pedal to be fully up and hard? It was like the time I blew an under the dash flexible air line and lost all air pressure, hard pedal, but no stopping action.

But thismorning my air pressure was fine, I had just looked at it a few seconds before the "incident". I'm thinking the truck may have corrosion in the master cylinder and /or wheel cylinders, and occasionally it jams them up.

What do you all think?

Also what would be the best thing to use to flush the brake lines with?

And while I'm talking brake lines, I bought all new flexible lines, but the only ones I could replace were on both front wheels, all three "frame to axle" flex hoses would NOT break free......even after copious amounts of Kroil.

My plan of attack is to CUT all three lines and get closed end wrenches on the fittings and muscle them into submission! Is this the correct thing to do? I have no torch to heat up the fittings so Kroil and muscle is my solution for now, unless some of you post a better way.

So basically what I need to find out from you all is:

1. What do think caused the hard pedal?
2. What can I flush the brake lines with?
3. what is the best way to remove rusted/stuck brake hoses?

Thanks!

 

[REO 54]

First of determine what type of brake fluid you have in your system.Dot 3 or Dot 5 or...The two are NOT compatible.Then,bleed accordingly.Also,check out your air pack.Has it been serviced and lubed lately?

 

[AZDeuce]

Airpack? Not by me! What needs to be done there?

Running Dot 5 synthetic, but added some new stuff, DOT 3 SYNTHETIC, as I needed brake fluid right now and that was all that was available. Never heard of DOT 3 Synthetic, but I "figured" since it was synthetic it was probably compatible.

But it won't be the last time I made a"command decision" and got it wrong. Anyway, when I figure out how to purge the brake lines, i'll run straight DOT 5.

But I am interested to know what I should have been PMing on the Airpack?

 

[REO 54]

I just learned all this.Dot 3 is glycol based,and Dot 5 is silicone based.Mixing the two could potentially compromise your seals.As far as the airpack maintence,just put in that term into "search forum" and you should get alot of good info relating to it.

 

[Heavysteven]

DOT 3 and DOT 5 not the same. DO NOT MIX

 

[kastein]

X3 on that! I know that DOT 5 in a DOT 3 system will ruin all the seals because they are dissolved by oil based fluids, don't know if putting DOT 3 in a DOT 5 system will do the same thing though. Anyone know for sure?

 

[AZDeuce]

I understand that DOT 3 and DOT 5 are not compatible but thought it was because one is synthetic and one isn't. BOTH the DOT 5 and the DOT 3 I used ARE SYNTHETIC so why is there an issue?

Curious minds want to know.......so they don't screw up and do the same thing twice!

 

[kastein]

Synthetic just tells how the chemical was made - if it was man created instead of distilled from some naturally occurring source, it is synthetic. Think of synthetic vs non synthetic as electric vs non electric musical instruments - you can have an electric or non electric guitar and you can play the same songs on em, but you can't easily play a guitar song on a violin, electric or not.

DOT 3 is glycol based while DOT 5 is silicone based - silicone oils will dissolve/foul the kinds of rubber used for seals in DOT 3 brake systems. I'm not sure if DOT 3 will damage the kinds of rubber used in DOT 5 brake systems, though.

 

[AZDeuce]

Yes, but the DOT 3 I used was some new stuff from Prestone (I believe) and it is clearly marked SYNTHETIC, this is not your normal DOT 3 that's why I'm questioning this.

I know better than adding "old school" DOT 3 to DOT5.

But it the DOT 3 and DOT 5 are BOTH synthetic......and THEY ARE......then why is there an issue?

 

[kastein]

Because DOT 3 and DOT 5 are not the same chemical. Synthetic or not it will not change the fact that they are different chemically and will not behave well when mixed.

Figure it's like oil and water... doesn't matter if you boil or filter the water, it still aint mixing with the oil.

 

[AZDeuce]

Awww....I got it now (finally).....thanks for being patient!

Ok now to the next question.....what is the best substance to use to purge my brake lines of this hideous concoction?

 

[kastein]

That, I'm not sure of. I've always been extremely careful to avoid mixing the two - nearly put the wrong one in my first jeep when I rebuilt the brakes though!

I'm still not sure if you need to replace all the rubber seals in your brake system or not. Hopefully DOT 3 doesn't damage DOT 5 systems, only the other way around. If DOT 3 doesn't damage DOT 5 systems you may be able to just drain everything out, flush with DOT 5, then fill and bleed with more DOT 5, but I am not sure.

 

[AZDeuce]

I have all new brake parts, master cylinder and 6 wheel cylinders I plan on installing in a couple of weeks, I just want to purge the lines before I install the new parts. The only thing I don't have new is an air pack.

I've been reading in the search area on airpacks, but still haven't found where I need to add the oil. I did find that I should use machine tool oil.......is that correct?

 

[G-Force]

Some interesting reading is here:
D.O.T. 5 Brake Fluid
The problem you experienced is the air pack not functioning when you applied the brakes. I would get an airpack rebuild kit and rebuild it. Then blow all your lines out with air (nitrogen would be the ideal thing to use since it won't contain moisture) and then refill and bleed with fresh fluid of your choice (DOT 5 since this is what is recommended by the manufacturer). As the article in the link above states, when you mix DOT 3 and DOT 5 it causes the brake fluid to change into a sludge the consistency of salad dressing.

 

[G-Force]

Another good one......

brake fluids

Gee......i guess when they put the incomatability of DOT 5 and the others in bold type it must mean something.....

 

[REO 54]

Indeed!Read the labels.I feel like I,m truck class 101 most of the time.So go slow,learn as much as possible.I am truly grateful for this forum.

 

[jeffhuey1n]

One of the brake threads discusses using alcohol (no not that kind, the stuff you CAN"T drink) to flush it out, then use clean DRY air to get the alcohol out. Do not use straight from an air compressor air, it has oil in it. To a certain degree, if you use a compressor, you'll contaminate the lines. There were some really cool looking pump rigs set up to flush out the lines. Sorry you'll need to do some searches to find the specifics.

 

[jeffhuey1n]

One other point...oil based lubricants, syntheitic or otherwise, eat silicone seals. Silicone usually leaves seals alone. If DOT 3, (oil based) went in the system, best bet is to replace every seal in the system. Better safe than "OH CRAP!!!"

 

[m16ty]

At the risk of being flammed, I'll admit that I've added DOT3 to a DOT5 system before without ill effects. That was about 3 years ago and the brakes still work. It's a truck I only use off road so I'm not too worried about it.

 

[G-Force]

FLAME, FLAME, FLAME........