[jnorwich]

I have a 1967 xr-7 289 with the midland booster.
I think the brake booster is not working. Last year
I had to have the master cylinder replaced along with
new brakes front and back. The car stops ok but the pedal
has a very hard feel to it. I had a guy at a local shop test
drive it, without telling him about what I had done to the
brake system. When he came back his first words were your brakes are bad. After I told him all that I had done he said it
must be the brake booster. I check it after driving it for awhile
by pulling the hose off the check valve. I did here some air
when I did that, so does that mean the booster is ok?

Is it possible to change the booster without having to bleed
the brakes? I have never done any brake work before,
however I think I could change the booster on my own....

Thanks,

Jim

 

[jnorwich]

that was: "who knows brakes"

I hate when I do that!

 

[DaveK]

Here's my guess...

I'm going to say you can't do it without bleeding the brakes again. It takes some space to get the booster out so I would guess that your best bet is to bite the bullet and remove the master cylinder.

Good luck.

 

[itow]

Check the booster first. An easy way to check it is: With the engine off, set in the seat and pump the brake pedal about 20 times (push it down and the let clear off and do it over and over about 20 times to make sure its empty). Then push down on the brake pedal pretty stiffly (hard but dont blow out the wheel cylinders!) and start the engine. If the booster is good you should feel the brake pedal pull down/get softer from the vacuum filling the booster and assisting you push it. If you feel a difference then the boosters probably good, if not its shot for sure. Also if you push the brakes with it running and hear a hissing noise inside the car then the boosters bad also. The vacuum checkvalve may be bad also. If the booster checks ok then let your foot off of the brake pedal and go out under the hood. Pull the vacuum line off of the check valve (while leaving the check valve in the booster sealed up still) then after the line is off, when you pull the check valve out of the booster you shoule hear air escape. Do this after checking the booster because if the booster is bad you wont hear any air either but if the booster checks out and the check valve does not then it may just be the valve (much cheaper and way easier to replace!)
As for replacing the booster yourself, lots of times you can replace it without disconnecting any lines. To give a little extra room, you can remove the bolt that holds the distribution block (the brass colored part with the electrical switch in the top below the M.cylinder mounted to the fender apron) then un bolt the M.cylinder and sorta pull everything forward and tilt it away from the booster. This wont always work but Id try it first.
Good Luck!
Scott

 

[Royce Peterson]

Did you check the pushrod length when installing the new booster? if the pushrod is not adjusted properly you can have hard brakes.

Another common problem affecting power brakes on Cougars is vacuum leaks. Do your headlight doors close by themselves? If not you have a massive vacuum leak when the headlights are off. Also, if you have access to a vacuum guage be sure you have at least 13" of vacuum at idle.

Finally, the boosters commonly available at auto part stores are often not rebuilt properly. Get one from Booster Dewey - see the vendor section.

 

[jnorwich]

itow, Royce,

the booster I have in the car now is not new looks like a stock part.
My headlight doors close just fine by themselfs.
So I guess there is no vacuum leak.
As far as the pushrod what do i check? That is also stock.
Advance auto here in Pittsburgh sells a booster for my car
for $112 plus a $50 core. not sure if it's a new booster or a rebuilt one.
I will try the test that you suggested first.
my check valve is white is that a new part or is that the color
that came from the factory? Who sells a check valve for a 67 xr-7?
The ones i saw in MU and Autokrafters looks different.

Thanks for your insite...

Jim

 

[Royce Peterson]

Jim,
The factory shop manual has the dimension to measure. If you don't have one, they are about $35 from the vendors. It tells you all about troubleshooting brake problems and is generally great to have around.

 

[jnorwich]

Royce,
How do I find Booster Dewey?
I looked in the vendor section, but
could not find a link.

Jim

 

[Royce Peterson]

Booster Dewey:
503 238-8882

I thought he was in the links section, I am probably thinking of the Cascade Cougar club site.

 

[jnorwich]

Well I just now got around to doing the test that itow suggested.
When I did it the first time I could feel the pedal start to go down after I started the car. I then took off both vacuum lines from the check valve and removed the check valve from the booster.
Nothing....no sound of air coming out.
Tonight I tried it again with a new check valve. This time I did not feel the pedal go down after I started the car. Then with the engine off I left the two vacuum lines on the check valve and then removed the check valve from the booster. Big sound of air!!!

Also while I was looking around by the master cylinder I found this wire hanging by itself. Turns out the wire is for the brake light on the dash. I re-connected the wire to the distribution block
and started the car. Now I have a warning light on my dash that says "brakes"! The light just stays on all the time now! Looking in the owners manual under "brake system pressure warning light"
it reads like this:The word "brakes" will be illuminated on application of the brakes if the system has sustained a loss of brake fluid or hydraulic pressure to either the front or rear brakes.
I checked the fluid and it's about 1/2" from the top on the larger side and about 3/4" from the top on the small side...which I think might be a bit low. Will adding brake fluid help at all?

The brakes are still have a very hard feel to them. No grinding,just hard to stop going down a steep hill.
Should i just disconnect the wire again or is the warning light a good thing to have? Is it a accurate indication of a brake problem?

Thanks,
Jim

 

[cougarshaman]

Try replacing the sensor the plug fit in to on the prop valve. It's only a couple of bucks.
Don't rule out your brakes being bad either. New brake job or not. Especially if you buy your brake parts at Advance Auto. Not that I'm dissing you, mind you. I used their parts for a while, but now I go for better stuff... Your brake job could have gone bad. That's all.
The brake booster:
Mine made a weird noise when it went out that you could hear every time you hit the pedal. Like a duck call holding a steady note...
Don't buy the cheapest booster you can get. Especially if you like to drive fast. Booster Dewey or an independant parts store like the Bumper to Bumper network will stock a new or quality rebuild part.

 

[TheRktmn]

The brakes light will go on if there is a significant difference in pressures between front and rear. Basically there is a piston in the distribution block taht can slide back and forth to the low pressure side. Once this happenes there is away to re-center the piston to make the light go out. This has been discussed on these forums.

http://www.mercurycougar.net/forums/showthread.php?s=&threadid=3511
http://www.mercurycougar.net/forums/showthread.php?s=&threadid=4629
http://www.mercurycougar.net/forums/showthread.php?s=&threadid=6012

Do not replace "the sensor the plug fit in to on the prop valve" until you are sure that the valve is centered.

 

[cougarshaman]

Nah. Center the valve AND replace the plug. 30something year old sensors aren't to be trusted to not leak and read true. One more FoMoCo part just waiting to fail. In fact, you can just put on a new and improved prop block that can be had from summit and do away with the idiot light. Factory gauges exist to let you know just how bad the damage is. And idiot lights are worse.
"Hey my brakes are screwed up! And now a light is illuminated on the dash to let me know!"
And buy yourself a shop manual too. If you are a visual learner, a textual walkthrough can be worse than nothing.

 

[TheRktmn]

Yeah. Good point. Replace everything, then you'll have no worries.