67 Brake Pedal Super Hard - No Brakes

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67 Brake Pedal Super Hard - No Brakes

Post by MikeinNP »

Hi All - still working through all the kinks in my 1967 restore project and now coming to the issue of why does the brake pedal feel so hard and the brakes not engaging. I've rebuilt the brakes on all 4 wheels - beautifully professionally rebuilt calipers, new rotors, pads, etc up front and new everything in the back - drums, shoes, slave cylinders, springs, etc.

The master cylinders is new, but the booster was not replaced. With the engine out of the car I decided to give it a wait and see on the booster.

During the brake bleeding I remember thinking how hard the pedal was to push to get fluid to come out of the calipers and the rear slaves, but at the time thought it was because the engine wasn't running and the booster engaged. The pedal never bottomed to the floor like I would expect during normal brake bleeding and I thought that was pretty weird. I've bled brakes before with boosters and never had this problem but thought there might be something unusual about the Lincoln.

With the engine now running and vacuum getting to the booster I'm still getting the same symptoms - hard brake pedal and the brakes not engaging. To say it a different way, with the engine running, foot hard on the brake, the wheels still turn. No pressure getting to any of the brakes.

My initial thinking is that the pressure differential valve and/or the pressure control valve may be clogged, stuck or something. In reading through the manual one thing I didn't notice before is that the pressure control valve for the front brakes has a push button on the bottom of it apparently for bleeding, though I'm not sure why that's critical given the symptoms. Maybe I never got enough fluid to the front calipers starting from a completely dry system?

Thanks again for everyone's help as I continue on this journey. If it was an old Mustang, I'd have it all figure out. :)

Mike - Seattle, WA
Mike Bishoff - Normandy Park, WA
1967 Lincoln Continental - WIP :)
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Dan Szwarc »

Answer these questions:
1. Did you install an o-ring on the back of the MC to seal it against the booster?
2. With the car off, do the brakes “pump up” after multiple presses and is the pedal “high and hard” with no squishiness (indicating an air-free bleed)?
3. Did you bench bleed the MC before installing it to the car?
4. Did you bleed the rears first starting with the right rear?
5. Did you bleed the fronts last starting with the right front?

Number 1 is the most likely. Get an o-ring kit if you don’t have one or bring your core to size.

In general, it has been said that the metering valve does not need the button pushed to perform a bleed in spite of what it says in the manual. A bad metering valve may never properly bleed. Many are seized inside due to rust and that button cannot be pushed.

I’m going to assume that you know everything else about bleeding brakes because you seem to be experienced. In general, the 67 is no different from other vacuum-boosted brake systems.

Good luck. If you work on 60s Mustangs, then you a]should already know what you need to know.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Solid »

If the pedal isn’t moving without excessive force with the engine running then I’d be looking at the booster/master o-ring like Dan suggests. A vacuum leak there will give you a hard pedal and little brake engagement since it will take hundreds of pounds of force on the pedal to actuate the brakes that way. If the booster has failed, the same holds.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by TonyC »

In general, it has been said that the metering valve does not need the button pushed to perform a bleed in spite of what it says in the manual
Those who have said the metering valve's button need not be pushed in are correct in only one regard: The '67 valve's pin (it's a pin in that year, not a button) doesn't need to be pushed in. It needs to be pulled out and held in the pulled-out position while bleeding takes place. But they are wrong when they say it is not necessary. To get a proper bleed for the front brakes, it is necessary to pull the metering valve's pin out and keep it in that position until bleeding is complete. It can be pulled with a pair of needle-nose pliers, and a second pair of vise-pliers can be clamped on to hold it in that position. Just don't forget that they are there when you're done.

With your engine out of the car, naturally there will be no way to test the booster for proper function. On the other hand, bleeding and resetting the brakes must be done with no booster power applied. Keep in mind that the pedal is supposed to feel hard once bleeding and resetting is correctly done. It will feel spongy at first, but after several pumps—which may be as few as 7 or as many as 37, depending on each individual situation—it will become hard, which is what it's supposed to do.

(Actually, a man could take that two ways... :smt017 ...perhaps I could have worded that differently.)

ANYWAY, make certain that you do the bleeding properly, and that means factoring in the metering valve as well. As a matter of fact, when you replace pads down the road (metaphorically-speaking), you need to pull that pin to its outward position, or you will not be able to reset the caliper pistons properly.

---Tony
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Dan Szwarc »

The '67 valve's pin (it's a pin in that year, not a button) doesn't need to be pushed in. It needs to be pulled out and held in the pulled-out position while bleeding takes place...
Well, you don’t pull on a button, so that would be accurate. But are you absolutely sure you aren’t mixing up 67 with 68? Didn’t 68 move to the smaller brass metering valve mounted on the cross-member sub-frame, or was that 69? [Edit: Nope. Tony is correct!]

My 70 Marquis had this valve, but I could have sworn 67 had the same setup as 66 and 68 got the new prop-valve and metering setup. [Edit: Nope. Tony is correct!]

Shop manuals are very inaccurate. I’d have to check the MPC to see what part numbers come up. I might even have pics from a 67.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by TonyC »

I'm certain; I know this not only from the shop manual of that year, but also from organ donors I checked trying to find one years ago, to retrofit on Frankenstein when I realized I had missed that in his conversion to the dual-tub M/C. '67 was the year they first employed that metering block with the pin, at least on the Lincolns.

---Tony
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by MikeinNP »

Replying in sequence:

Dan - I frankly don't recall an o-ring on the MC between it and the booster. I may need to take off the new MC to check and I also don't recall bench bleeding the MC so that might be even more reason to take it off. Regarding the pump-up, I don't believe the pedal pumped up like I have experience with other cars. I've bled a lot of brakes over the years (but never a MC) and follow the usual routine of open the bleeder valve, push the brake pedal to the floor, close bleeder valve, pump up and repeat until no air appears. For the Lincoln this didn't seem to happen as I would expect. The pedal never went to the floor and it was quite an effort to get fluid to come out of the calipers at all. On sequence, yes, farthest first, closest last. As I mentioned in the original post, applying a lot of pressure on the pedal does not even slow the front wheels from turning. Clearly something is wrong and the reason for thinking maybe it was a stuck valve.

Solid - I'll be looking at the booster more closely.

Tony - I would agree. I've bled brakes with power boosters before and I don't recall changing the process to bleed from non power brake systems. I don't recall anyone ever suggestion you bleed the brakes with the engine running. :) On the metering valve, the 67 Manual says in BOLD "Be sure to keep the bleeder button on the metering valve depressed while bleeding the primary (front brake) system." I tried with a reasonable amount of effort to push the valve in using a screw driver against the frame and it didn't budge. It's either stuck or as suggested it might actually be a pull and I'll go out to the garage to see what's going on there and report back.

At this point I plan to drain the MC, remove it to check on the o-ring and bench bleed it. While it's off I plan to remove the Pressure Differential Valve just below the MC and disassemble it to make sure nothing is stuck in there. I'll check on the Pressure Metering Valve to see if it's a Button or a Pin. If I can't get it to move in either direction I'll remove it for further inspection.

Appreciate all the comments!

Mike
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Lincoln Brake Valve.jpg
Lincoln Bleeding Instructions.jpg
Mike Bishoff - Normandy Park, WA
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Dan Szwarc »

Thanks for the pictures Mike. Tony's post is correct. The shop manual is incorrect. You have the 67-70 metering valve system.

1. You must bench bleed the MC. You can google instructions, but they should have also come with the new MC. I find the block the ports and push repeatedy until no more bubble come out method to be the easiest as long you have plugs for the ports.
2. That metering valve requires the pin to be pulled out. Here's a shot of it from the 1969 Manual.
metering.jpg
If you have some spring steel around, maybe you can fashion your own "tool" like they show. Try making sure yours even moves using needle nose pliers. It should move in and out freely.
3. Once you've confirmed the valve is OK, and the MC is bled, you should rebleed the system.

Make sure the booster is attached to the intake manifold by the 1/2" vacuum hose. However, even a totally dead booster won't prevent manual pressure from stopping the brakes. You may have to stand on it with significant force, but it still should stop.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by MikeinNP »

Yup, Dan. Turns out the "button" is not a button at all and moves when pulled not pushed. I grabbed it with some angled needle nosed pliers and it pulled out of the valve about 1/8". Not sure if that's a full pull or it needs to move more for bleeding. Of interest on this 69 diagram, the pin on mine doesn't appear to have the little nub at the end of it to secure that cool looking tool. Maybe they finally figured out by 69 that pulling and holding the pin was a pain in the butt. ;)

Dang, yes, looks like I need to pull the MC off and start over. In the scheme of things, that's not painful, more annoying. It should be at least partially bled since I did get fluid from the rear slaves and front calipers. What I really want to see is the brake pedal going to the floor when bleeder valves are opened.

Still, I'm wondering why the brake pedal is so hard and never went to the floor when bleeding. The rear brakes don't have this metering valve with a pin/button as far as I can see in the 67 diagram.

Mike
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Solid »

I don’t think a master that has not been bench bled will give you a hard pedal, it’ll likely have air in it depending on how the system was bled, so a soft pedal with poor brake engagement. In my experience the vacuum leak from not having an O ring on the master to seal to the booster is noticeably loud. I’m a big fan of the quad ring design for safety systems.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by MikeinNP »

Solid wrote:I don’t think a master that has not been bench bled will give you a hard pedal, it’ll likely have air in it depending on how the system was bled, so a soft pedal with poor brake engagement.

Couldn't agree more. Still left with the mystery of why the pedal is so hard. :( I'll be going through it one component at a time this week.

BTW, if it wasn't clear from any of my posts, the engine is now running and the 1/2" line to the brake booster is attached. I was hoping with the engine running the booster would kick in and do its job, but the symptoms remain the same.

Mike
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by Mike »

You shouldn't have engine running to bleed brakes even with power booster. Other then the feel of power brakes vs non the booster shouldn't make the pedal hard. It sounds more like there is something wrong with the master cylinder or one of the other parts is locked up and preventing things from moving properly.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by frasern »

If you haven't already checked, see if the pedal moves smoothly with the cylinder removed. this could be an interference issue.
I had a weird problem with mine, where a cowl leak had let water run down the bracket to the pedal pivot, causing it to rust enough to become stiff. This held the pedal from seating, causing the brake lights to stay on. Removing the load on the pedal, allowed me to trace the resistance.
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by MikeinNP »

frasern wrote:If you haven't already checked, see if the pedal moves smoothly with the cylinder removed. this could be an interference issue.
I had a weird problem with mine, where a cowl leak had let water run down the bracket to the pedal pivot, causing it to rust enough to become stiff. This held the pedal from seating, causing the brake lights to stay on. Removing the load on the pedal, allowed me to trace the resistance.
Makes sense. Starting from square one. I opened up the bleeder valve on the MC to see what happens to the brake pedal when pushed. It goes down further, but never bottoms to the floor. It hard stops maybe 2" from hitting the floor. I have to pull it back up to return and like you in order for the brake lights to go off. So there's something right there I need to look at. I put on a replacement MC and I'm not suspicious that it's not allowing the pedal to hit the floor, but maybe it's not supposed to? And then why isn't it returning all the way back up on its own. It seems to move without obvious resistance and I think along with a spring somewhere underneath somewhere, the MC is supposed to add a bit of spring to push the pedal back up??

I feel like I need to take the MC off to see how far the pedal moves on its own as you suggested.

Do you know if the pedal should hit the floor when bleeding?

Mike
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Re: 67 Brake Pedal Super Hard - No Brakes

Post by TonyC »

Here's a suggestion, Mike. The shop manual in Chapter 15 details how to remove the brake-light switch. Study it, and remove the switch from its placement. When you do, that will completely separate the pedal from the booster-M/C assembly. Hold the input rod to the booster out of the way, and swing the pedal back and forth by hand; that will help you check whether the pedal may have seizure in its hinging. It should move freely with no resistance; if it doesn't, then Fraser's suggestion is what you need to concern yourself with. I'm pretty sure that's what he meant by "removing the load on the pedal."

If it does move freely, then there is something wonky with the booster or the M/C—probably the booster, as the M/C you have is new; although a defective new part could occur, it isn't very likely. Maybe, just maybe, a spring inside the booster may have broken.

---Tony
"Don't believe everything you read on the Internet, just because there is a picture with a quote next to it." (Abraham Lincoln, 1866)
"Question Authority!"

1966 Continental Sedan, affectionately known as "Frankenstein" until body restoration is done (to be renamed "General Sherman" on that event)
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