Q: Metering Valves Causing Brake Problem
I keep having brake falure but it appears that the master cylinder is fine and the problem is maybe with the metering valve. I have bypassed the valve and the pedal appears to be firmer. I’ll know in the next couple days if it is still working though (I’ll know when I go through the stop sign!).
If it turns out to be this valve, it’ll be the 4th one I’ve put on it. I bought it from a company in NH that sells them, rebuilt. The problems I’ve had are leaking fluid from the rear and sucking air into the system. Although the company has been supportive in sending me replacements, I’m tired of the failures!
Has anyone else had issues with the metering valve? Now that it’s bypassed, any issues? (The metering valve is a round cylinder – 3″ long, 1″ diameter – mounted under the left rear of the master cylinder. Used on 1969 AC cars. Lines run from the front of the master cylinder to the valve, then to the porportioning valve assembly)
A: Yes, I had problems with mine. Since I wasn’t ready to put it on the street but wanted the brakes to work when I moved it around, I, too, bypassed the valve. I made several test runs on the streets around my house and the system seemed to work fine without it.
There has been some F-List talk on this subject in the past. Some point to safety issues (i.e., if the engineers thought it was necessary then who are we to argue?) while others just mention originality. Personally, unless the car was placed on a very sensitive brake machine that would measure brake engagement times and pressures, I think you would be hard pressed to tell the difference when bypassed.
Something that I thought was a bit ironic… The engineers installed the metering valve in the front system be reduce the braking pressures and prevent the front brakes from locking before the rear brakes. But, if the car came with factory A/C, they had to install a second metering valve in the rear lines (it is located on the driver’s side frame rail, about the middle of the driver’s door) to keep the rear brakes from locking first. This was necessary because the A/C added about 200 pounds to the front of the car.
What does this mean?? Well… if you’ve moved the battery to the trunk, installed an aluminum intake, and a fiberglass hood, you just messed up your braking system because you just change the weight bias of the car by about 200 pounds… at least according to the engineers.
Now, take into account the hundreds of drum-to-disc conversions that I’ve heard about using Chevelle and Camaro parts and have never heard of any REAL problems AND, combined that with my Seat-O-Pants-O-Meter, I think the valves add little to the system. If anything, it’s just another thing to go wrong when you can least afford it.
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Content last modified: January 23, 2014 at 9:40 pm