Proportioning Valve - Help?! (Long)
Thread Starter
Intermediate
Joined: Aug 2011
Posts: 36
Likes: 0
Proportioning Valve - Help?! (Long)
Hi all!
I have a '75 Stingray that's been giving me quite a pain in the rear end with the brakes.
A little history on my problem child:
About 3 months ago I started having some issues with the brake pedal feeling a little soft.. took her in and little by little had the rotors, both front calipers, brake pads, and brake booster switched out for new. About a week after all repairs were done, I got in, tried pulling out of my parking spot, and the brake pedal just went down to the floor - AGAIN
Needless to say, I was freaked out and extremely concerned with the quality of work / parts that were put into my car. I then took it to another mechanic who was referred to me by a friend who has a C7 'vette. Also because the previous "mechanic" tried to sell me on a conspiracy theory saying that someone had it out for me and was cutting my brakes at night - mind you - while the car is securely garage parked each night..
Anyway - before taking it to the new guy, I checked out the master cylinder and noticed it was bone dry on the right side. I made note of it and explained it to the new mechanic. He put new brake fluid and pumped it a few times then raised the car and noticed a leak.. he said my proportioning valve was damaged and had a leak. This is the first time I had heard of a proportioning valve so, naturally, I began to research. He advised that the part is extremely difficult to find but he had a guy that could REBUILD my old valve and guarantee it for 6 months at $144 + $130 labor.
After doing some research, I was able to find GM Part # 339780 here for a much better price:
https://www.paragoncorvette.com/p-35...ing-valve.aspx
My question now is this.. Do I take his advice and let him rebuild my original valve OR do I move forward with the reproduction?? Which would be the better buy and what would last longer? Also, am I in the right direction with Part # 339780?? Is this the right part for what I need?
Please advise.. Any help advice on this would be greatly appreciated. This is my first classic / restoration project and I'm taking it day by day, piece by piece. Thanks in advance!
I have a '75 Stingray that's been giving me quite a pain in the rear end with the brakes.
A little history on my problem child:
About 3 months ago I started having some issues with the brake pedal feeling a little soft.. took her in and little by little had the rotors, both front calipers, brake pads, and brake booster switched out for new. About a week after all repairs were done, I got in, tried pulling out of my parking spot, and the brake pedal just went down to the floor - AGAIN
Needless to say, I was freaked out and extremely concerned with the quality of work / parts that were put into my car. I then took it to another mechanic who was referred to me by a friend who has a C7 'vette. Also because the previous "mechanic" tried to sell me on a conspiracy theory saying that someone had it out for me and was cutting my brakes at night - mind you - while the car is securely garage parked each night..
Anyway - before taking it to the new guy, I checked out the master cylinder and noticed it was bone dry on the right side. I made note of it and explained it to the new mechanic. He put new brake fluid and pumped it a few times then raised the car and noticed a leak.. he said my proportioning valve was damaged and had a leak. This is the first time I had heard of a proportioning valve so, naturally, I began to research. He advised that the part is extremely difficult to find but he had a guy that could REBUILD my old valve and guarantee it for 6 months at $144 + $130 labor.
After doing some research, I was able to find GM Part # 339780 here for a much better price:
https://www.paragoncorvette.com/p-35...ing-valve.aspx
My question now is this.. Do I take his advice and let him rebuild my original valve OR do I move forward with the reproduction?? Which would be the better buy and what would last longer? Also, am I in the right direction with Part # 339780?? Is this the right part for what I need?
Please advise.. Any help advice on this would be greatly appreciated. This is my first classic / restoration project and I'm taking it day by day, piece by piece. Thanks in advance!
Burning Brakes
Joined: Feb 2011
Posts: 849
Likes: 0
From: Woodland California
Where was it leaking from on the valve?
There isn't to much to these valves.
I did my brakes a year and a half ago, and looked into these valves.
Mine didn't leak but I had to reset it by pumping up the brakes and purging a front and rear slave cylinder at the same time.
Ralph
There isn't to much to these valves.
I did my brakes a year and a half ago, and looked into these valves.
Mine didn't leak but I had to reset it by pumping up the brakes and purging a front and rear slave cylinder at the same time.
Ralph
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
New ones are available for around $100.00.
Here is an older thread with a 75 valve pictured.
http://forums.corvetteforum.com/c3-t...ake-screw.html
Here is an older thread with a 75 valve pictured.
http://forums.corvetteforum.com/c3-t...ake-screw.html
Race Director
Joined: Oct 2000
Posts: 12,680
Likes: 3,134
From: Shamong, NJ
The 339780 proportioning valve is the correct one for your car. They were used on all 74-77 Corvettes.
For the $90-$100 that the repro valve sells for, it's not worth screwing around with the old one.
For the $90-$100 that the repro valve sells for, it's not worth screwing around with the old one.
