Proportioning Valve

[sonicbluezx3]

I replaced the brake lines, calipers, brake houses, drums, and proportioning valve last February. The truck has been mostly sitting in a garage since then while I finished fixing it up on the inside.

During the whole time, I never noticed any brake fluid leaks. Recently, I took it out for a spin and had it running for a little while. Came back, parked it, everything was fine. Didn't go back out to the garage for about a week or so and noticed fluid under the truck. Brake fluid. So I got under the truck and noticed it was coming from the newly installed proportioning valve.

Any ideas as to why this would happen? I tried tightening the connectors but they were pretty much as tight as possible.

This is the one I replaced the stock one with:

http://www.carolinaclassictrucks.com/81-87-GM-FS-Truck-Prop-Valve.html

 

[HotRodPC]

I"ve never heard of such a thing and wouldn't know to suggest other than try to find where the leak coming from.

Do keep in mind, tight may not matter. Is it possible you got one overtight and split the end the of the flare? If that happened, no matter how tight you get it, it'll leak. Also, is it possible the valve is defective?

 

[sonicbluezx3]

If it was over tight, then why would it just all of a sudden start leaking after 9 months of just sitting?

I am going to have someone go out there with me this week and hit the pedal while I look at the valve to see if it is leaking more when the pedal is pushed or if it is just while sitting. It's a slow leak, but I still want to fix it.

 

[sonicbluezx3]

Since it's a safety issue, I am thinking about just taking it to a shop to have them look at it. The whole system was replaced about a year ago (lines, hoses, etc.) and it was bled, and then I moved. I did not do the install... my more knowledgeable mechanically inclined friends did. I know how it all works, but I would feel more confident having a shop check it all out. Fortunately though I hooked up the parking brake (which the previous owner decided to remove) so I will feel a bit safer now.

 

[HotRodPC]

Since it's a safety issue, I am thinking about just taking it to a shop to have them look at it. The whole system was replaced about a year ago (lines, hoses, etc.) and it was bled, and then I moved. I did not do the install... my more knowledgeable mechanically inclined friends did. I know how it all works, but I would feel more confident having a shop check it all out. Fortunately though I hooked up the parking brake (which the previous owner decided to remove) so I will feel a bit safer now.

I think you're making the right decision. If you don't feel 100% confident with doing that work to deal with brakes, then yes, get it to someone who is. Anyone can make one go, but not everyone can make one stop.

 

[chengny]

Check the o-ring that seals the electrical (prop) switch to the valve body and the plastic plug itself for tightness.

It appears that this also serves as the bleeder fitting - it may be left loose on purpose.