Thread: Brake Combi valve leaking through weep hole for rear line?

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When it rains it pours.....brake fluid.

Dustin's 65 El Camino. Disc/Disc. CPP Combi Valve. 8" booster. Corvette style master cylinder.

Decided before I turned my son loose with the car we would try some panic stops. And it didnt work. In fact I was only able to lock up the front right (5" bicycle tires) tire once. Yikes!!!! The pedal seems stiff with little or no brake. We have good vacuum (added vacuum pump). I proceed to check for air in lines. Starting at rear I notice the caliper had a slight leak at the shaft (Cadillac Seville calipers with ebrake). I happened to have a spare and replaced. Bled caliper until all air was gone and my son had good pedal. Then I notice all of a sudden it sprung a leak in the weep hole in the combi valve (for the rear brake lines). I still have good pressure to the rear brakes but realize that with that leak the resevoir will be empty in no time. After disassembly, the front valve is seperate from the rear valve. I imagine it has a bad o-ring on the valve assembly allowing fluid to pass to weep hole. Could master cylinder build to much pressure to rear? The car has sat for extended periods of time but was moved in and out of the shop so its not like it sat for ever. Or could this be our DOT 4 mistake just now coming back to haunt us as a few folks mentioned quite some time back?

Is it worth my time trying to replace the o-rings on the rear valve (combi) or should I just buy a new one? It doesnt appear to be like a shuttle valve, where one valve would affect the other so I dont feel like a reset is necessary like the Ford units?

I was thinking I may just start from scratch and buy a whole new master/booster/combi valve kit from CPP or somewhere. Really dont want to spend the money. Not sure if my trouble is the valve or the master cylinder. Absolutely bummed about this whole mess. We finally get the car painted and now he cant drive it. I miss my 36!

Any thoughts?

David

I'd get the new valve, and maybe also consider a brake pressure gauge and test connections, being able to check the brake pressure at each wheel can eliminate a lot of guesswork.....

Thanks Dave. I'm going to go with the Wilwood combi valve with the built in prop adjust. I'm surprised how hard it was to find a 3/8"-24 IFM to 7/16"-24 IFF adapter. Need to go from the 3/8" port on the valve to 1/4" line for rear brakes.

David

best way I found for finding those type fittings--go to Napa, Carquest, etc, get them to take you to the tubing rack display and find a short piece of tubing with the fitting you need on it----otherwise, the drawers are all mixed up, none of the fittings in the right bin and they are replenished by a contarctor who comes around and does the order/resupply-------

Dave,

Thanks for the tip with the pressure gauge. Sometimes the simplest things are overlooked. We found the prop valve to be the culprit. Went ahead and changed the MC anyway in favor of a alum vete MC for aesthetic reasons. Now with the new Wilwood valve adjusted so the rears lock up just after the front skinny's, it'll throw you through the windshield in a panic stop. My son is very impressed.

Jerry,

I actually found the fitting at Autozone. I was shocked. But the I opted to convert the rear line to 3/16" instead since it's disc all around and we're running the small D154's on all four corners. Seems to make it a little more responsive (we don't have to have the adj prop valve cranked in as much).

Funny how someone else's engineering can mess you up. Previous owner had installed an 8" single diaphram booster, 1 1/8" MC disc/drum, combi valve for disc/drum (PA-4). We changed over to 9" dual diaphram, 1" MC disc/disc, and the adjustable Wilwood prop valve. Works great. Now prior to turning it over to my son, I decide to do a safety check. Had him bouncing on the back of the car.....found the frame was hitting the rear drivers side caliper. Not good. Today he is cutting off the caliper mounts. Previous owner had them clocked at 12 o clock. We're going to clock them at 3 o clock. It'll give him 2.5-3"s of compression travel.

David

With the new mounts he has good suspension travel now. Actually rides good down the road.

We did have some difficulty with both rear calipers dragging on the rotors. Was getting very hot. I was worried I was sent the wrong MC, with internal residual valve, but we verified the calipers were retracting slightly after pumping brakes with car on jack stands. Now I wonder if the pads were too thick because after a few trips into town, with extended cool down periods, they are no longer dragging.

I feel much better knowing he has good brakes.

David

sometimes living too close to town is a problem with new brakes

Thats funny Jerry. I live 1 block from my office. Fortunately it's my dads shop where we work on the cruck, a 15 minute drive to town. I have a feeling I may not have the caliper brackets square with the rotors even though they float. Dustin said they are acting fine now and rotors are now bright and shiny instead of blue.

David