Dragging front factory disc brakes and metering valve.

[AR67GTX]

Helping a friend sort out his 69 Hemi Roadrunner with factory, power disc brakes. This is a rotisserie restoration and everything is new. Suddenly started having problems with front disc brakes staying on after pedal is released. It takes about 10 seconds after pedal is released before the tire can start to be turned again. At first only seemed to affect the right side so he installed a new rubber line on it in case the other one somehow got crimped. No change and now we noticed the left one is sticking too. Next he quickly cracked the bleeder valve on a caliper as the pedal was released. That released the brake immediately so ruled out sticking caliper. Next I loosened the bolts on the master cylinder in case the PB rod was adjusted a little too long. No change other than a bit more free play at the top of pedal - brakes still stay locked for about 10 seconds. Climbed under dash to check his pushrod to the pedal and found it's the correct Hemi setup and booster - no toggle linkage and a rectangular section push rod that appears to have no adjustment. Matched up to the shop manual exactly.

Rear brakes are fine.

So that left us looking at the factory metering valve for the front brake lines. Not sure I fully understand this valve but apparently it delays activation of the disc brakes until the rear drum have had a split second to get to the drums. With pedal released we can push the little rod on the bottom up about 1/16". Step on the brakes and it stays hard and cannot be pushed up at all. Release the brake pedal and push up on the rod and I get some fluid leaking down - I guess from the diaphragm and it seems that the brakes release. So that has us looking at maybe this valve is somehow defective and at fault. All his lines, calipers, blocks, distribution and metering valves were provided by In Line Tube I believe.

Car is all newly re-done. Factory power brake booster and MC provided by a noted rebuilder to be correct for a Hemi car. Not more than a couple hundred miles - still trying to shake out all the bugs. This just started a couple weeks ago. Anyone run into a similar issue?

 

[Johnpat]

Still sounds like m/c problem

 

[AR67GTX]

Well that's still in contention. Watching it's action with the lid off looks like it's working OK. Loosening the bolts and pulling it out from the booster about 1/8 - 3/16" didn't help any. The piston was fully retracting at the rear. We actually tried to get a rebuilt one at O'Riellys but all they had in stock was a drum brake one and the PB/disc one he said he didn't think they could get it anymore. He will probably have to get one from a Mopar Restoration Parts place. Hate to just tell him to throw more money at it.

 

[PurpleBeeper]

My 2-cents? Throw that highly dangerous Inline Tube metering/hold-off valve in the trash and find a decent factory one to clean up. I put the same setup on my '70 Roadrunner with the stainless lines & 2-piece metering/hold-off & I had my front brakes working intermittently and caused me to rear end a Lexus...change them out & no more problems.

O

 

[dadsbee]

Metering valve for the Kelsey/Hayes front discs allows pressure to go to the REAR brakes momentarily before it goes to the fronts. First post says he has Factory metering valve.. next one fogs it up to say it may be Inlines..

 

[miller]

Suddenly started having problems with front disc brakes staying on after pedal is released.

Basic question...are you sure the front caliper piston isn't hanging up?

 

[AR67GTX]

Probably guilty of "fogging" up the metering valve description - it is Inline but I assumed it was a duplicate of the factory one. I was just trying to describe this is as much as possible a factory style installation and not an aftermarket disc brake adaptor kit.

I did say I wasn't completely clear on the purpose of the valve. My 67 GTX has all 11" drum brakes so I hadn't run into one of these before. But, it delays application of the front I see. Operationally, does it make sense it could mal-function and delay/slow the release of the front brakes when the pedal is released? It's basically a piston moving past an orifice inside so it seems that if it is dragging when the pedal is released then that would cause the lockup until it finally crept by the inlet line orifice to relieve pressure(???)

Not completely sure it isn't a dragging caliper piston but we cracked the bleeder on one simultaneously with releasing the brake and the wheel released immediately rather than 10 seconds later - so we assumed the caliper pistons were releasing OK. And we figure it would be a real unlikely that both would be suffering the same issue. But again - not 100% sure.

 

[miller]

Probably guilty of "fogging" up the metering valve description - it is Inline but I assumed it was a duplicate of the factory one.

Yeah, like you, I would question the metering valve. But, past that...

I'm no 'expert', so don't get me wrong. Sure don't have any experience on Hemi cars, or front/rear disc brake set-ups.
One thing that does come to mind, something I've been told is, the various MCs are designed for each brake set-up. Meaning, as far as the 'delay' stuff, have been told some of that is built into the MC itself. Internal metering valves, springs/pistons/and bleed ports, all inside the MC. And, I'll toss in, even with the right parts and pieces, doesn't mean it wasn't put together right.

I'll assume the MC is the right one, and has the right 'guts'.
(The answer will probably be a simple one!)

 

[Officer Higgins]

I had very similar situation with my 67 R/T four wheel drum with power brakes. That turned out to be the power brake booster that was supposedly rebuilt by booster Dewey. From guy i bought car from. I took the booster to local guy in Cincinnati, he rebuild it and correctly zinc dichromated the housing. That was 20 years ago, and it still works today. You could disable the booster vacuum signal and see if it still hangs manually.

 

[AR67GTX]

The master cylinder is a question mark to me. It was supplied with the brake booster by the supplier he bought it from. It's a bailing wire cap type with larger rear reservoir than the front - so looks suitable for a front disc/rear drum brake system. We wondered about residual pressure valves - no external ones but not really sure how to identify an internal one. Not sure much can be told from this engine compartment picture I attached. I don't have a good close up of it.

The brakes stay locked up whether pushing down on the pedal with the engine running or the engine off. Also, the rear brakes are not being affected by this so we didn't think the booster was an issue. It holds a hard pedal with engine on or off.

 

[Officer Higgins]

Nice car man good luck

 

[miller]

The master cylinder is a question mark to me.

Yeah, I'd have to do some research on it. Stock disc/disc brake set-up...any chance you've got a manual on the car? It would have the correct brake parts and pieces in it.
That master looks the same as on mine, disc/drum, larger pot feeds the disc brakes. But, putting them side-by-side, can't tell the difference. Bore size, and the internal parts, make them do what they do.
If the master IS correct, easily something mechanical, holding up the release. All disc brakes run with small clearance at the pads, anyway.

 

[AR67GTX]

The MC would seem correct but I'm basing that on the two different size reservoirs and that it was set up and sold by a specialty rebuilder as a set. But as you said - hard to tell. The MC on my power drum GTX system (replacement) is not to dissimilar.

He decided to try the metering valve first and it's on order from Megaparts. But their guy there said they supply Inline Tube so if they are an inferior valve may only be a temporary fix. Problem with going with an original, used metering valve is he said they are about double in price from Tonys and because the metering valve mounts in a different position than the replica proportioning/metering valve arrangement, he would have to make up new lines or find someone who replicates the exact original OEM lines between the two valves and running to the front brakes. It sounded like the Megaparts guy was pretty familiar with the system. He told him the description of the problem did sound like the valve and knew it was going to be a bitch changing it out and suggested he pull the torsion bar back to gain room and talked to him about some other details.

 

[miller]

The MC would seem correct but I'm basing that on the two different size reservoirs and that it was set up and sold by a specialty rebuilder as a set. But as you said - hard to tell.

Yep.
Just for kicks, forgot I have a copy of the 69 Plymouth manual, for my engine. Looked up brakes, master cylinder, and for the 4 wheel disc. Master is different, calls it a tandem . Kinda sorta stuff. Pots are about the same, one bigger than the other, cap different, no part number.
Combination of the master, and the other valves in the system. All in the book, if you have one.

Did a quick search, but no tango, finding one like in the book.
Good luck on it! Drool once on that Hemi, for me!!

 

[AR67GTX]

I've sweated on it a lot more than drooled on it lately. I was up in the car on the lift operating the brakes the other day while he watching things below. As he let us down he commented "You know you look good in that car", a running joke between us - How would you like to take this cantankerous thing off my hands?

But no can do - I've nicknamed it Christine.

 

[AR67GTX]

Metering valve change out was painful and also a bust. Trying to find a correct master cylinder now. I'm not 100% confident that is the issue but higher on the list than odds that both calipers are sticking or proportioning valve is bad.

Noticed what I thought was strange - after refilling and bleeding the front brakes we confirmed they remain locked up for 4++ (sometimes as much as 10) seconds after releasing pedal with the engine off and just stroking the pedal. But when I went around and tried the rear brakes out of curiosity, pushing the pedal to the floor would not apply the rear brakes in the least with the engine off. Further, the parking brake - which we just adjusted 2 weeks ago, would not apply. I had him start up the engine and then the rear brakes worked as did the parking brake. I thought that was extremely odd as last week and before when the rear brakes were blead, we did it with the engine off?? That may point to some issue with the MC - don't know.

 

[miller]

But when I went around and tried the rear brakes out of curiosity, pushing the pedal to the floor would not apply the rear brakes in the least with the engine off.

That does sound odd. Even with no booster applied, the MC should move enough fluid to engage the brakes.
Drum brake cylinders okay, brake lines to the rear clear? Enough to question. If they are good, yeah, I'd be looking at the master. Too easy for something inside it to be worn out, clogged, or installed wrong.
Years ago, I used to rebuild my own.

 

[69b3rt]

Some times old brake hoses act like one way check valves when the inner lining deteriorates.

 

[AR67GTX]

That does sound odd. Even with no booster applied, the MC should move enough fluid to engage the brakes.
Drum brake cylinders okay, brake lines to the rear clear? Enough to question. If they are good, yeah, I'd be looking at the master. Too easy for something inside it to be worn out, clogged, or installed wrong.
Years ago, I used to rebuild my own.

I'm glad I'm not the only one who found that odd. About 2 or 3 weeks ago he had a rear brake dragging but when we pulled the drums I found a lower shoe retraction spring was reversed and wasn't clearing the adjuster spool which pushed it loose. After fixing that we tested those drums several times to check they were applying and releasing and then adjusted the parking brake. We did a bunch of checking and never started the engine??

Now that I think about it, he thought it was a rear brake dragging a couple of weeks ago but I bet it was actually the fronts acting up - and we just happened to find the spring popped off on the rear drum.

 

[AR67GTX]

Some times old brake hoses act like one way check valves when the inner lining deteriorates.

All brand new brake components throughout. But we still replaced one front hose just in case the hose somehow got kinked by dropping a caliper with it attached. No change.