Dustin's El Camino brake woes.....

I posted this earlier on different thread and should've started a new one since we seem to have soo many problems with the El Camino brakes.

65 El Camino 9" dual diaphragm booster, aluminum vette style master cylinder from Speedway, Wilwood adjustable prop valve only, 3/16" lines all the way around, and D154 calipers at all four corners.

Dustin's rear disc brakes just aren't backing off after releasing pedal. Dragging slightly all the time. I have the Wilwoood prop valve backed off all of the way. No other combi valve. Using an aluminum vette style mc from Speedway (you know...the one with the stainless valve) and the tech fella assured me it was for rear discs, but now I'm having my doubts. If it was a true vette style it wouldn't have any residual valve built in....correct? We're using the D154 style calipers in the rear. All new hoses. No crimps. I just see no reason that pressure wouldn't be released back to the mc. Oh, and I've triple checked pedal free play and rod length. Pedal doesn't move the rod on outside of booster until after a 1/4" of pedal travel.

How can I test rear portion of mc to make sure fluid returns? I was thinking about using some clear hose to a baby food jar but did figure it would move enough fluid to tell if what was going in was going back.

David

Yeah, that's a weird one. The only thing I've seen cause that is when an old hose collapses inside but it sounds like you have that covered. Unless your new hose going from the hard line to the rearend is bad. I know that's a longshot.

Put a set of pressure gauges on the calipers . front and rear . The kind that screw into the bleeder screw hole .

David,
Isn't this the car that inadvertently got the mixture of Dot 3 (or 4) fluid with Dot 5 (or 5.1)? Is it possible you're seeing the affects of that on your hoses, or your caliper seals? Sorry to bring it up if it's a sore subject...

Quote:

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Originally Posted by rspears

David,
Isn't this the car that inadvertently got the mixture of Dot 3 (or 4) fluid with Dot 5 (or 5.1)? Is it possible you're seeing the affects of that on your hoses, or your caliper seals? Sorry to bring it up if it's a sore subject...

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Lols. Yes it's the same car. :D You've got a heck of a good memory Roger. Everything has been changed though. New everything.

David

We're going to hook up the pressure gauge in the next night or two. Maybe we can sectionalize the problem to one area.

David

A little embarrassed to admit but I missed something simple. First Imagine the brake pedal not hooked up, we mount the master cylinder and notice resistance about 3/16" from being seated. I did have pedal free play adjusted correctly (1/4") but never thought about the rod in the booster itself being too long. Pulled it out, did sme measuring and found, sure enough, it was pushing the valve in 3/16 when mounted. The booster wasn't adjustable like some I've noticed so pulled the rod out and ground 3/16" off the end. Remounted and bled brakes. The rears don't seem to be dragging anymore. Dustin made his way back home and said his wheels are no longer hot.

But I did notice while using the brake pressure guage (with the prop all the way out.....least amount of rear bias) that at best he only gets 600 psi. But under driving conditions with a panic brake it still tries to lock up the rears with the fronts. Starting to think my new gauge is bad. Going to hook it up on my 04 truck and see if it's still low.


Thanks everyone for inspiring me! :)

David,
That's one of the easiest things to miss! That 3/16" was likely just enough to keep the very back return port in the MC covered, trapping fluid in the lines. Glad you found the problem and that Dustin has brakes, and won't be keeping the local parts house rich replacing pads monthly. Another benefit - Dustin learned to not simply give up and take the problem to somebody else, but to keep at it and not give up. I predict that this brake lesson is one that he will be telling his kids & grand kids about one day, "Yeah, I remember once when my Dad and me were chasing this problem on an El Camino....." Good job, Dad!!

No embarrassment in finding and correcting a problem!!!! Congrats on taking the time to check your own work!!!!

theres nothing wrong with locking both the fronts and rears---just that the rears should not lock first so you still have some steering, but eventially all four should be able to be locked--after that its in the drivers finnist????????????


however------------on an truck (el cameo) the absence of some load or the addition of some cargo will effect rear/total braking conditions-----

my truck likes to spin a wheel or slide a rear one when empty on the paint stripes when wet-------

Funny you had that problem on a Camino, my '72 Elky was the same way. I shimmed the cylinder with a 1/8" plate and fixed it. The rear brakes never worked for years!

Now two days later, brakes are doing great.

Roger, the booster is the type with non adjustable rod so I was surprised to find it off by that much. I'm enjoying the father son time. I know that soon he'll be starting his own family. I'll have some great stories for my grand babies some day. :)

Dave, thanks again for reminding me to get the gauge. It has already paid for itself.

Jerry, all four lock up, front skinny's first. Thats with all the rear bias out of the Wilwood prop valve. I'm surprised how easy the big rear tires lock up. All the more reason I'm liking the rear discs. I doubt he'll ever have much in the bed. Maybe a dirt bike.

Pope (don't know your first name), if your booster has the non adjustable rod, it can be ground down if it's like mine.

Honestly guys, I just couldn't stand to let someoneelse do something I should be able to figure out. :LOL::LOL:

Thanks again guys,
David

First name's Rich. Ironically, my Camino went into the rear end of a coyote hunter's truck after I fixed the brakes. Glare ice, downhill, and the other guy was backing across the road to check some tracks. Totaled both vehicles off! 540 thou miles on it.