F500 brake failure...

[tsherry]

I have one of the oddest trucks of the Fordification website, I'm fairly sure....This is a 1971 F500 with a monstrous straight 6, 1bbl, 4 speed. It has a hydraulic ladder on the back that I used to paint the house and now have lots of new friends who like me for my truck.....

On to the problem.

It has a large master cylinder on the firewall, with a vacuum booster and what looks like a secondary hydraulic fluid reservoir mounted on the booster, complete with bleeder valve. Schematically, the MC has a fairly large diameter single line feeding into the second hydraulic cylinder, which looks like it boosts up pressure before splitting into the individual wheel cylinders. An odd system. Don't get me started on the parking brake setup....

On occasion over the past several years I've owned it, after sitting, the MC is all but dry, but I cannot find any leak. The pedal of course goes to the floor when this has happened. Put fluid back in the MC, everything's fine again.

Today, same deal, but when filling the MC up, the pedal still goes to the floor. Bled the lower unit on the booster, got some air out of it, nothing. Started the truck up, creating vacuum in the booster, which usually stiffens up the pedal...nothing.

Is the MC finally gone? Sure feels like it to me....

Tom S.

[kaptnkaos]

Hey Tom....

You are not alone with the mystery vanishing brake fluid problem.
My Bus Olde Skool is a '68 B-500 essentually an F-500 with a Bluebird short bus body.
You can click the blue link below to check it out.
I have been collecting tools to be able to go through the brake system.
I have been wondering of there was away to change the brake system to something more modern without having to do the wheels and hubs.
Possibly using an MS and power unit from something else.

You probably have the hand pull lever that engages the drum brake on the back of the tranny that brakes the driveline...

I have the '68 Ford service manuals with diagrams and stuff for my pickup and bus.
I bet Hawkrod has everything you'd ever wanna know about yer truck in his huge Ford reference library..
I think he's got the largest private collection in the world.

KaptnKA S

[BRUTUS_T_HOG]

you know its possible for the MC to leak into the vacuum booster?

just unbolt the MC and check for wetness... there also might be bubbled paint underneath

[kaptnkaos]

Yeah... BRUTUS_T_HOG

I do know about that...

The vacuum booster on these things is mounted on the frame and is about the size of a 5 gal bucket... so they could hold lots of brake fluid.
that might be a slight exaggeration, but not much.
They are a PITB to get bled out completely cause they have a master cylinder on the fire wall, a slave cylinder mounted on the vacuum booster, then, each wheel has 2 cylinders...
Getting these babies bled only to have the fluid disappear in the MS the next time ya wanna drive it really sucks.
I don't know if they improved the systems after '68 or not.
There was a recall on them for brake failure on the '68 models...
Didn't learn that until after I had mine.
That's why I am wondering if there is a way to upgrade the system to some like a '73-'79 or something that's a little different...
Like upgrading a bump pickup from manual brakes to vacuum assist using parts from a dent side truck,
No one seems to know if parts from a 73-79 F-600 are interchangeable on 67-68 F/B 500's or not.
I've only seen one other B/F-500, but have seen a couple of dent side F-600's which is what I am hoping that the MS, booster and slave cylinder's would be interchangeable with mine.

KaptnKA S

[tsherry]

I have one of the oddest trucks of the Fordification website, I'm fairly sure....This is a 1971 F500 with a monstrous straight 6, 1bbl, 4 speed. It has a hydraulic ladder on the back that I used to paint the house and now have lots of new friends who like me for my truck.....

On to the problem.

It has a large master cylinder on the firewall, with a vacuum booster and what looks like a secondary hydraulic fluid reservoir mounted on the booster, complete with bleeder valve. Schematically, the MC has a fairly large diameter single line feeding into the second hydraulic cylinder, which looks like it boosts up pressure before splitting into the individual wheel cylinders. An odd system. Don't get me started on the parking brake setup....

On occasion over the past several years I've owned it, after sitting, the MC is all but dry, but I cannot find any leak. The pedal of course goes to the floor when this has happened. Put fluid back in the MC, everything's fine again.

Today, same deal, but when filling the MC up, the pedal still goes to the floor. Bled the lower unit on the booster, got some air out of it, nothing. Started the truck up, creating vacuum in the booster, which usually stiffens up the pedal...nothing.

Is the MC finally gone? Sure feels like it to me....

Tom S.

Pulled apart the MC, cleaned and honed the slightly rusted cylinder (wasn't too bad), and put it back together. A rebuild kit for the cylinder was not immediately available, and there were several listed in the catalog at he parts store.....Anyway: Filled the MC with fluid and bled it back into itself with a tube from the outlet port back into the reservoir. Then, plugged the outlet port with a threaded plug.

At this point, when the pedal is applied, I think the pedal should be hard as a rock. Instead, it traveled to the floor.

Sounds like it's a goner.

I'll dig into it again tomorrow.

But for tonight, I do have front tires that aren't bald...that's another story.

Tom S.

[fomocoguy]

Sure would like to see a picture of this ladder truck.....

[tsherry]

Sure would like to see a picture of this ladder truck.....

Let's see if this'll work.

Meanwhile, I bought a rebuilt MC yesterday, bled it and the slave cylinder, and the wheel cylinders this morning. It stops like wool on velcro now.....

[kaptnkaos]

Very cool truck tsherry...

May I ask where you got yer MC ??? And approximate cost?
I've not been able to find one.
NAPA was supposed to order a rebuild kit for mine...
They showed that there was one in the data base in the Georgia, but it never showed up.
I figured that's where I'd start.

KaptnKA S

[fomocoguy]

That truck is cool! I wish you were closer; I sure could use some help takin a tree down....

I bet you get a lot of that!

[tsherry]

Very cool truck tsherry...

May I ask where you got yer MC ??? And approximate cost?
I've not been able to find one.
NAPA was supposed to order a rebuild kit for mine...
They showed that there was one in the data base in the Georgia, but it never showed up.
I figured that's where I'd start.

KaptnKA S

First, it's best to take your old one in with you, and match it up with their catalog and stock.

But NAPA had five of them for my truck, with a couple other types for at least three other applications. The rebuilt one (limited lifetime warranty) was $51. A new one was $103. Rebuild with that kind of warranty was fine with me.

I was smiling all the way home. I figured that I was gonna be out of luck for days, ordering it in from somewhere....

It was a good day...

If you need the NAPA part number that I bought, let me know and I'll track it down. (Also, the secret to getting one 'right now' for me is to go straight to the regional warehouse. I don't even bother with the neighborhood storefronts anymore.)

[kaptnkaos]

Do you do that online???
If not, where is the regional warehouse?

I figured I just replace mine before doing anything else...
and a rebuilt one sounds just fine to me too...

KaptnKA S

[tsherry]

Do you do that online???
If not, where is the regional warehouse?

I figured I just replace mine before doing anything else...
and a rebuilt one sounds just fine to me too...

KaptnKA S

I'm in Spokane. Our regional warehouse is way too conveniently located on my way to work every day....I'm not sure how big a radius this one serves, but I get the feeling that it must serve this side of the state.

[tsherry]

Here's one that looks promising in Kent:

8441 S 180th St
Kent, WA 98032
(425) 656-8980‎

I always look for "NAPA Main Store" and end up happy, and lighter in the wallet.

[kaptnkaos]

Thanks for that info tsherry

Kent is a little over 100 miles from me so I can't imagine saving enough over the local store to make the trip worth while...
unless of course I was gonna be there for some reason anyway

KaptnKA S

[71PA_Highboy]

Kap'n,

Though there is it least 1 harbor freight between you and the Napa warehouse, there is an HF 1 or 2 exits down.

While there, there are a couple of JYs that had some bumps, so you might wanna check those.

Just trying to give you more excuses.... if you needed them


Eric