I see a spot for a light switch in the ebrake foot pedal system but cannot imagine how it would fit something in there. None of the parts houses seem to have the switch and it is not shown in the manual. Does anyone have a photo or could take a photo of the switch, its location and how it is installed so I can fix mine. My light is on 100% of the time and I do not see a switch anywhere.

Thanks,

M

 

If you're referring to the brake warning light on the dash, that isn't for a parking brake engaged indicator. That is to alert you if there is a loss of pressure in the brake system. Follow the brake lines coming out of your master cylinder, they should connect to what looks like a junction block. That is your pressure differential aka proportioning valve. You should see the two lines in from the m/c and two or three lines out. Should be a line to the rear rear and there will be one or two coming out for the front brakes. You should see two wires going to that valve as well, those wires route back to your brake warning switch.

This one of those valves from my '79 but the valve on yours should look similar. The green arrow points to the brake light switch.

 

Thank you so much, this makes a lot of sense! I reset it just as the instructions stated. It took quite a bit of pedal force but it did finally reset the shuttle and the brake light did go out but now the brakes feel funky. So I have to figure out what happened.

Thanks!

M

 

The only time I've had that brake light come on and stay on is when I had a front brake hose failure, it was quite obvious there was a problem when that happened though. You might check for slow leaks at the brake hose fittings and at the wheel cylinders (calipers if you have done a disc conversion of any sort). If still running drum brakes, you might want to pop the drums off and see if any of the wheel cylinders are leaking which may not be visible from the outside unless it is leaking badly. That pin moves when you have unequal pressure between front and rear brakes which triggers the light to come on as a warning. The general idea is to limit brake fluid going to the end with low pressure as that loss of pressure usually indicates a leak in the system. Kind of a limp home mode so you still have some brakes for a couple more stops until you can safely get off the road. There may also be a fitting along the frame rail just behind the cab for the main hard line to the rear end. Look the rubber hoses over really well too, there might be a small crack in the line that will soon turn into total failure, especially if you have to make a panic stop and slam on the brakes.

Another place the system can leak is at the master cylinder, where the m/c bolts to the booster (or firewall if you do not have power brakes), look at the area below m/c on the booster and if it looks damp, the seal on the m/c has gone bad.

 

I should add, If you don't find any cracks in the rubber hoses or any areas that appear damp near wheel or master cylinders or any other fitting in the system then there might just be air in the system and it needs to be bled.

 

When I got the truck the brake lines were shot - rusted. I replaced them including all the rubber hoses. Bled the system and the brakes have worked wonderful all drum. The PO rebuilt all the brakes, new cylinders and master. I have been driving the truck for a couple of weeks around town and up on the highways. Brakes fine, doesn't lose fluid. Then per the instructions I mashed the pedal and it dropped quite a bit and the light went out. But now the brakes push down half way. So I have some work to do the figure this out. Thanks for your assistance, I will figure this one out. Appreciate it!!!

 

I would start with the master to make sure it is full.
Being you have all drums adjust them so they just start to drag. If they are out of adjustment the pedal will be funky / low.
If still not right time to bleed the system starting at the farthest wheel then next closer and so on.
If you have a helper pump the pedal tell them to take their time when pumping. If too fast fluid dose not have time to fill behind the piston to get pumped.
Also note that valve may move again.
Dave ----

 

Well, it turns out you guys may have saved my life. In the instructions above it says mash the brakes and the shuttle will center again. When I mashed the brakes, the only brake line I did not replace exploded right there in the garage. The line looked good but the rust was between the frame and the brake line unseen. So I replaced it but could not get the shuttle to center again so I just removed the bulb for now and am back on the road.

Thanks everyone!

 

Even though not correct, removing the bulb has been the tried and true method of making the light on the dash go away, for 50 years or more.

After a certain age, which isn’t very old, most of them failed to recenter, no matter how hard you try.
You have to physically go in and reset the shuttle manually.
Sometimes it involves disassembling the whole block and cleaning the chamber and putting it back together.
It’s a real shame, but that seems to be the only way sometimes.
Pulling the bulb works too. Just have to remember to carefully check the brake system visually now and then. For the next 40 years!

 

If you don't center the shuttle, is there a chance that the brake fluid flow would be restricted and the performance of that circuit diminished?

 

No, I'm pretty sure it's not.
It's been debated almost as long as we've been talking about these. Still both schools of thought, but I lean towards the not-blocking side of things.
Many people I consider more expert in such things as I, say it does not impede flow. And this would seem to be borne out by the diagrams.
If you look at the ends of the shuttle, you can see that they are smaller than the cavities that they slip into when tripped by a leak. This tells me that fluid can still pass no matter what position the shuttle is in.

And this would be consistent, I believe, with safety concerns. It only takes a tiny imbalance to trip the light fantastic on the dash. Not even enough to cause a loss of braking power. I've had that happen myself, when my rear hose started to just seep on my Bronco.
The light came on long before any pressure loss from the tiny leak, and certainly before my fluid was even showing signs of going low in the master cylinder.
Another way I think about it is this. If the fluid flow was blocked to the first leak, what if a second, more catastrophic leak occurred? You would be left with no brakes, even though one end was still functioning.
So the light is just a warning. Hopefully a very early warning, rather than telling you that you're currently screwed!

Paul

 

Paul,
That makes sense and is reassuring.