Thread: Brake Bleeding

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I know there's a lot of info on this site regarding this subject, but I have
run into one I haven't experienced before. Have 1980 Chev pk up trk, been
sitting for two yrs. Replaced front calipers, and rear drums. Also replace
the tee and hose feeding the rear breaks. Noticed no fluid when I disconnected old Tee. Tried bleeding brakes the old way with two people.
only got fluid in one caliper. Put on new primed master cylinder, still no
luck. No fluid at one caliper and none at all in the rear. Is it possible that
I just need to put in new lines all the way around, or maybe trying to blow
them out real good. I've never seen this before, just sounds like lines are
stopped up...What do you guys think?

The flexible rubber hoses will deteriorate internally and plug up. See if you have fluid down to the juncture where the hard lines enter the rubber hoses.

Don

Brake fluid is hygroscopic - it attracts moisture from the air. Sitting for two years you probably rusted your lines solid. I suspect you may need to replace all of your brake lines, but you may get by with blowing them out and being sure that they are clear.

Both good ideas guys..I will give that a look at..thanks

Might also want to take a look at the distribution block/proportioning valve--old brake fluid and moisture can really mess them up!

Originally Posted by Dave Severson

Might also want to take a look at the distribution block/proportioning valve--old brake fluid and moisture can really mess them up!

yep distribution block valve could be off side s and bad hose crack the line a head of the hose and see if any thing will come out if so hose is bad

Replaced both front brake hoses. One was completely stopped up. Replaced
both rear hyrdaluic cylinders as they were stuck. The Port valve is a big
pain in the rear. I did blow it out and did some cleaning, but the local parts
store said he could not get one due to age of trk....I was just wondering if
I would have a problem bypassing the Port valve all-together and just use
tees?

Originally Posted by rdobbs

Replaced both front brake hoses. One was completely stopped up. Replaced
both rear hyrdaluic cylinders as they were stuck. The Port valve is a big
pain in the rear. I did blow it out and did some cleaning, but the local parts
store said he could not get one due to age of trk....I was just wondering if
I would have a problem bypassing the Port valve all-together and just use
tees?

Did you open it and clean it? or did you just cleaned the outside and try to blow air through it?
It is basic, just open it up and clean the inside, remove the switch pin from the front, if you think it's dirty inside. Carefull and you will not need any new seals. odds are you don't need a new one.

It is most likely just off center and locking the flow. and don't need to be opened up, just recentered.

BEFORE OPENING!!!! remove the switch terminal, or else you will break the end off. If you didn't already by blowing air through it. You can buy just the treminal if you do break it off.

Pat

Thanks for the info and diagram. Back to one of my questions. Can you
operate the breaks without the valve?

You could but I wouldn't.
The front where the 2 separate front lines goes to, makes it so your front brakes don't pull to one side before the pressure equals out, and it also sets pressure on to the rear brakes lightly before it sends the pressure to the fronts, and then applies the rear brakes so that you don't get the rear to lock before the fronts start to work. Cause it takes a lot less pressure to lock the rears, than it take to make the front work.

You could use a manual adjustable one, but it doesn't work as good or the same as using the one you have factory. Plus you have a trip light on the factory one. I would keep it.

Pat.

Originally Posted by HemiTCoupe

You could but I wouldn't.
The front where the 2 separate front lines goes to, makes it so your front brakes don't pull to one side before the pressure equals out, and it also sets pressure on to the rear brakes lightly before it sends the pressure to the fronts, and then applies the rear brakes so that you don't get the rear to lock before the fronts start to work. Cause it takes a lot less pressure to lock the rears, than it take to make the front work.

You could use a manual adjustable one, but it doesn't work as good or the same as using the one you have factory. Plus you have a trip light on the factory one. I would keep it.

Pat.

Pat,
I was thinking the same thing - you can, but why? The valve also warns you if you lose 1/2 of the master cylinder by lighting the e-brake light while you're braking. A person could go for weeks with a failing MC, not knowing it was less than 100% until a panic stop situation. I'd fix it.

Well, I only blew the valve out. Did not take it apart. Put it back together
and front brakes work fine, but not enough pressure at rear to expand brake
linings. I think valve is bad..Truck is farm use only and not worth what I have
already spent on it. Think I will leave valve hooked up for front brakes, plug
valve openings that operate the rears, and run a direct line to rear bypassing
valve. As for as warning light, it was never hooked up to begin with. I guess the
worst that can happen is I run thru a fence. Trk is in good shape including motor,
but trying to sell it would not be worth what I have invested..

What you did was jammed the piston to the back (rear brakes), when you blow air into it, with the other side open (line off). and it is shutting off the flow to the rears. Normally it would self recenter it's self, when you open (release) the pressure to the side that works. Try this, remove the terminal switch, releasing the pressure to the fronts, and tapping on it's sides and see if it's just stuck lightly. Find the light brown (tan) wire hanging around and rehook it to the switch. Light on dash should be off when centered.

Or you can try to have someone open a front bleeder, and then jam on the brake peddle, (First remove the terminal switch) but don't let up on it or you'll get air in and have to re-bleed the fronts. Try it a couple of times, checking after each time to see if you have flow to the rears.

If you hook it up the way you say, the rears may always lock up.

Pat