brake problem

[cherokeechief79]

this is not mine but it looks similar.
when it rains and my 86 monte has been sitting ,the rear brakes lock up violently for the 1st couple of low speed stops.its been doing this for about a year now.ive replaced just about everything except the proportioning valve which is still stock.i did not really suspect this because this only happens if its been sitting and it rains.for the life of me I cant explain this.
I think I would break every hose going into this trying to remove them.
is there any way of safely just removing the large hex fittings to look if there is anything funny going on inside?
the brake light is not on so I assume its sitting in the right position.there is a pin sticking out of the left side just like the pic.I can pull it out with piliers and it seems to go back to where it was but it doesn't seem to want to go inward.
is there any way this valve could be causing my problems?
is there any way to test it?

 

[pontiacgp]

water is getting on the shoes from the rain or the humidity in the air

 

[cherokeechief79]

I did not replace the shoes yet but I did put brand new drums on which didn't help.
the shoes are duralast from autozone.
a few yrs ago we resealed the ford 9-3/8 rear in the car.at the time my friend who builds rears said it would be a good time to upgrade to 9 inch drums and brakes which we did.
from the first stop the rears locks up if anything more than just a lite tap was applied.
I was on a 4 lane highway and had to suddenly slow down because I saw brakelights up ahead.
the car immediately locked up in the rear and before I could do anything the car did a 180 at 65 mph and I hit a guardrail that finally stopped me.
fortunately I just creased the quarter a little.it was probably the scariest experience ive ever had.
after this I changed the rear cyls to the largest dia thinking they would act slower .it helped but it was still bad.then I put a adj prop valve inline after the metering block to the rear.this still didn't completely stop the problem so I went back to 7 inch brakes.
these seem fine except for this problem after it rains.

 

[pontiacgp]

if you were travelling straight the rear brakes locking up first would not cause you to spin. It might be a good idea for you to take a course in a skid school

 

[cherokeechief79]

I was actually going into the other lane at the time and was not straight.

 

[Wageslave]

Are you using metallic type brake pads? I had a set of those on a Dodge Dakota that would about send you through the windshield the first two times you used them for the day. I ended up going with a ceramic set that got rid of the issue.

Rust on pad + rust on disc/drum = extremely grabby

 

[ed1948]

I had a 3/4T Chev pickup that would lock with the first stop. Would get better the more you stopped. Turned out to be a small brake cylinder leak that was misting brake fluid.

 

[1STLATIGERDIVISON]

Hi ur problem as I have experiences within last month the proportioning valve is a POS GM design ur lucky the back even engage. I didn't realize mine has not been working the rear drums and brake shoes look OEM new only the front disc were working and stopping the care. SO I researched didn't find a OEM valve because our great designers at GM didn't make the valve any longer as I said no fecal matter! So I went to classic auto got an after market POS PP valve worked until one day on I-20 cruising bout 80 mph went to exit at my usual place it decided to fail great feeling by the way pedal went slam to floor. My a-hole sucked the seat God was my co-pilot no doubt. Couldn't leave the SS there because it would be gone due to certain segments of the population that are no good SOB's would have stolen the car. A death sentence in my book to the culprit!! So I drove my SS another 25 miles praying all the way eventually got her home as we have been together 25 yrs!. The relief valve blew out and fluid went every where what a junker. More research thru MikesMontes & he quit handling the crappers because of failures & complaints as well as liability issue. Got another from Classic that POS would work but the back brakes would lock slam up so went to Wilwood manual PP valve screw type manual adjusting and with re pluming brake lines woo-la it works no more probs got thru Summit... guys at Summit are magnificent but u be the judge not promoting them just stating fact. in my opinion, OK? I had 2 responses from the guys here one was able to find a OEM PP valve that works that was great the other used an after market not the Classic POS. They didn't seem to give a rats *ss bout it failing I am sure due to civil liability issue. So stay away from those butt heads. Wilwood again in my opinion only sir is Wilwood. Also the after market POS requires a center tool with a one time use its 15 bucks plastic so use wisely if u go that way.

I am very anal bout my car since we been together that long and my grandson will be the recipient of the car when I am gone hopefully he will appreciate it as much as I have. I apologize for being so long winded but I thought u should no the problems u potentially face if u change the OEM PP valve out. its a rotten design! Then again u may not have the problems I have experienced but good luck thought it would be worth mentioning hope it helps but if not so its there for u sir.

Gary

 

[cherokeechief79]

mine has close to 400k on it!
maybe ill look for a lower milage one.
is it possible to take the fittings out of mine mounted on the frame to clean or reseal it without removing the brakelines?

 

[1STLATIGERDIVISON]

Not that I no of but never tried that. I don't trust the PP valve old or aftermarket, the brass one.