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If you've been following my "'78 Toro gains a stablemate" thread (and it's ok if you haven't), you know my history with this car. 1977 Toro XS bought in late March, and I've been working on it ever since.
I completely redid the rear brakes. After removing the drums, which was an effort in itself, the rears looked like they might never have been serviced in the 44 years since the car was built. It now shows just over 80,000 on the odometer. The shoes were worn to nearly nothing, everything was coated in thick crud, one of the return springs on the driver's side was broken, and yet the car showed no outward signs of brake issues. I only looked at the rears because I wanted to know their condition.
Here's the left rear as it appeared when I finally got the drum off. Does this look like it was last exposed to the light of day when Jimmy Carter was president? Note the missing return spring for the front shoe (toward the left in the photo). The broken spring was rattling around in the bottom of the drum (but I never heard anything while driving). The adjusting rod and star wheel at the bottom were frozen solid on both sides, not that there was any shoe thickness left to adjust for. Note how thin the linings are.
Anyway, I've replaced everything on both sides, including drums, shoes, wheel cylinders, and hold-down hardware. I did not touch the front brakes other than to inspect them because the seller provided service receipts for new rotors and pads dated June of last year, and my inspection confirmed this. The front brakes look to be in good shape.
I also replaced the vacuum booster and master cylinder because both of those looked original (and quite rusty) as well.
I bench-bled the master cylinder just like the book says. No problems. I bled the brakes just like the books says, starting at the right rear and finishing at the left front. Everything went just as expected. Flushed out the air bubbles until nothing but fluid came out. Never let reservoirs drop below 3/4.
I test drove the car, and the brakes work fine. Pedal is firm (comparable to my '78 Toro), car stops quickly with no pulling in any direction. No strange noises. No fluid leaks. Reservoirs stay at full level. I have no complaints, but the brake warning light came on pretty much as soon as I started the car for the test drive and has not gone out. I thought it might be the parking brake warning light switch, but I never touched the parking brake pedal, and I made sure it was fully released. If it weren't for the warning light, I would have no reason not to declare the brake job complete and a success and move on to the next big thing.
The car does have a combination valve with a piston that activates the warning light that is supposed to recenter once any pressure difference is eliminated, and I can see how bleeding the brakes might have caused a pressure difference and caused the piston to move. I did not replace the combo valve, but I do have a new one and could do it. I just didn't do it because I had no reason to suspect a problem with the original one other than the fact that's also 44 years old. Is it possible the piston moved and now won't move back? I'm guessing it is. Any way to push it back?
Please help me make my brake warning light go off. I could put tape over it (red electrical tape would blend right in), but that seems less than satisfactory. I'm thinking the next step is replacing the combo valve, but I'm interested in other opinions as to what might be the cause.
If it's of any help, here's the figure out of the CSM showing a schematic of the combo valve.
Thanks.
Last edited by jaunty75; Jun 11, 2021 at 02:57 PM.
You're supposed to stab the brake pedal (with foot) with a bleeder open at the opposite end that you think the valve is stuck at or vice versa?
Joe provided pics of a fancy tool that is inserted into the valve where the switch goes in.
Putting tape over the light does not solve the lack of fluid due to the shuttle being to one side, if that is the problem. If you remove the wire from the valve and the light goes out, then it's the valve causing it.
I don't know which way the valve is stuck, assuming it is. But since I bled the rear brakes first, I would guess that the piston moved that way (toward the right in the above figure) as the rear was the side with the open bleeder valve and thus presumably under less pressure..
Where does Mr. P. reference this tool? Yes, as he always says, "search is your friend," but sometimes searching can be quite time-consuming as you try various search terms.
What did the brake fluid look like? If it was very grungy I'd try flushing the entire system again in hopes that another flush will get any remaining crud out of the hydraulic lines.
Did you flush and bleed using the brake pedal, a pressure bleeder, or a vacuum pump/gravity bleed?
May take a few attempts to recenter the pin and turn the light off.
Joe provided pics of a fancy tool that is inserted into the valve where the switch goes in.
If it's the tool I'm thinking of, it's used to depress the pin (under the rubber protector) on the metering section of the combination valve and allow a higher pressure flush thru the calipers.
Last edited by rocketraider; Jun 11, 2021 at 03:35 PM.
It was the piston in the combo valve. It was displaced toward the rear brakes side, as I thought it might be.
I first did what oldcutlass suggested and removed the wire connector from the combo valve. Dash light went out. So it's not the parking brake switch.
Then I removed the switch from the valve. It is threaded and takes a 5/8" wrench. It loosened easily and came right out. I checked the little plunger that sticks out the bottom, thinking it might be stuck in the UP position. But no, it moved freely. so no problem there.
Then I looked down inside where the switch is screwed in, and the piston that moves back and forth with the narrowed center part was displaced to one side. It if were properly centered, I should see the thinnest part in the middle of the bore. But it was not. The thinnest part was toward the rear brake side. I took a very small screwdriver and reached in and attempted to slide the piston back to the center. It moved very easily. (So why didn't it move back on its own? I don't know). I put everything back together and started the car. Brake light is off. Took it for a five-minute test drive using the brakes extensively. They worked fine, and the light stayed off. Hooray! Replacing the combo valve would have solved the problem, but I'm glad I don't have to do that.
To answer rocketraider's questions.
The brake fluid actually looked quite good right from the start. Everything coming out during the bleeding process was as clear as the new stuff going in. I'm guessing this is because of the front brake work done a year ago. They would have had to bleed brakes at that time, so any old fluid would have been pushed out then. I'm guessing the fluid that was in the lines was no more than a year old. Now it's only a few hours old!
I used the brake pedal to bleed the brakes. I actually followed the process in this video. I made a reservoir and tube setup using a water bottle just like his for single-person brake bleeding.
No, it is the tool that you remove the switch from the valve and then insert the TOOL before doing brake stuff. It locks the valve from any movement whatsoever until you are finished playing with your brakes system.
No, it is the tool that you remove the switch from the valve and then insert the TOOL before doing brake stuff. It locks the valve from any movement whatsoever until you are finished playing with your brakes system.
Ah, I don't have this tool, but I can see how it would be helpful.
Now you just need to get the valve centered. Since you bled the rears, have you tried the fronts? Usually when the valve shifts to one side or the other, it blocks the side that was leaking.
Now you just need to get the valve centered. Since you bled the rears, have you tried the fronts? Usually when the valve shifts to one side or the other, it blocks the side that was leaking.
I thought I did center it with my screwdriver. I assumed that, if the piston is centered enough to make the light go out, then it's centered enough, period. Not true? The portion of the piston in the center that is narrowed is very short. It doesn't take much movement to cause the switch to close and the light the light, which is what you want. But like I say, my assumption is that, if the light IS off, then the piston is as centered as it can be.
I did bleed all four wheels originally. I did not have any problems getting fluid to come out of the bleeder valves. The diagram does seem to indicate that, if the piston is moved to the right (toward the rear brakes), the tip of the piston would block the flow of fluid to the rear brakes. But I didn't experience this. Maybe the piston moved some point later? Maybe the combo valve is not working right, and I should replace it, anyway?
No, it is the tool that you remove the switch from the valve and then insert the TOOL before doing brake stuff. It locks the valve from any movement whatsoever until you are finished playing with your brakes system.
That sounds intriguing, but how do you avoid brake fluid loss and having to re-bleed the system while doing this? Inquiring minds wanna know!😎 as well as where to find that tool!
That sounds intriguing, but how do you avoid brake fluid loss and having to re-bleed the system while doing this?
If I'm understanding correctly, the switch is removed and the tool is inserted in its place. It locks the piston in place so it can't move due to a pressure difference. The switch is isolated from the front and rear sections of the combo valve, so it never comes into contact with brake fluid. There is no fluid loss with the switch removed, so brake bleeding is unaffected.
That sounds intriguing, but how do you avoid brake fluid loss and having to re-bleed the system while doing this? Inquiring minds wanna know!😎 as well as where to find that tool!
Glenn, if brake fluid comes out when you remove the switch from the distribution block or combo valve, the unit is junk. There should be no fluid in that space.
Looking close at the cutaway I see how it works. There are seals on the shuttle piston that keep it dry in the switch area. I'm lucky I've never had any combination valve problems.
Now where did you get that marvelous toy?!😎 I may never need to use it, but that never slowed me down buying tools! Though I sometimes have to think to remember what the tool was for...
Looking close at the cutaway I see how it works. There are seals on the shuttle piston that keep it dry in the switch area. I'm lucky I've never had any combination valve problems.
Now where did you get that marvelous toy?!😎 I may never need to use it, but that never slowed me down buying tools! Though I sometimes have to think to remember what the tool was for...
It was the piston in the combo valve. It was displaced toward the rear brakes side, as I thought it might be.
I first did what oldcutlass suggested and removed the wire connector from the combo valve. Dash light went out. So it's not the parking brake switch.
Then I removed the switch from the valve. It is threaded and takes a 5/8" wrench. It loosened easily and came right out. I checked the little plunger that sticks out the bottom, thinking it might be stuck in the UP position. But no, it moved freely. so no problem there.
Then I looked down inside where the switch is screwed in, and the piston that moves back and forth with the narrowed center part was displaced to one side. It if were properly centered, I should see the thinnest part in the middle of the bore. But it was not. The thinnest part was toward the rear brake side. I took a very small screwdriver and reached in and attempted to slide the piston back to the center. It moved very easily. (So why didn't it move back on its own? I don't know). I put everything back together and started the car. Brake light is off. Took it for a five-minute test drive using the brakes extensively. They worked fine, and the light stayed off. Hooray! Replacing the combo valve would have solved the problem, but I'm glad I don't have to do that.
To answer rocketraider's questions.
The brake fluid actually looked quite good right from the start. Everything coming out during the bleeding process was as clear as the new stuff going in. I'm guessing this is because of the front brake work done a year ago. They would have had to bleed brakes at that time, so any old fluid would have been pushed out then. I'm guessing the fluid that was in the lines was no more than a year old. Now it's only a few hours old!
I used the brake pedal to bleed the brakes. I actually followed the process in this video. I made a reservoir and tube setup using a water bottle just like his for single-person brake bleeding.
It's attached to the frame about 6 inches directly below the master cylinder. It's situated just perfectly to destroy my back if I had to bend over to reach it for any length of time, which I would have to do to remove the five brake line connections, one of which is underneath and not so easy to get to. This is why I'm content to leave the old one there. If it ever becomes unusable, then I'll hire someone with a better back to replace it!
