1970 1200 Pickup Build-Resto-Mod

[MrCypress]

For anyone following this thread, the rear drum rebuild is complete, new bearings and seals. I put the refurbished wheels on and have been driving the truck around this summer.

A new problem developed. The “brake failure” light came on after a couple days but I didn’t experience any problem braking. I was a little more careful with driving but it took me a few more weeks to try to trouble shoot it.

Yesterday I bled the rear brakes and got a little air out. But the light stayed. Actually when I unplugged the sensor the light went off which was not what I was expecting. But maybe that’s how it was wired back then (today a wire break should register an error, in my opinion).

The last easy thing to do is replace that pressure switch. Does anyone have other suggestions?

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[Jeff Jamison]

Take the part that has the wire attached out,then press the brake peddle a couple of times,reinstall the piece you took out(switch) sometimes they need pulled out to reset.Yes when you unhook the light will go out,that wire grounds out when the switch is triggered to set off the light.If you look in the hole there should be a piece that slides that the pin on the switch rides on.

 

[MrCypress]

Thanks for the tip. I guess I'll have to re-bleed too right? That pin is looking at hydraulic fluid isn't it?

Take the part that has the wire attached out,then press the brake peddle a couple of times,reinstall the piece you took out(switch) sometimes they need pulled out to reset.Yes when you unhook the light will go out,that wire grounds out when the switch is triggered to set off the light.If you look in the hole there should be a piece that slides that the pin on the switch rides on.

 

[MrCypress]

Answered my own question I hope. Found this image in a search. This isn't my metering block but probably it's a common IH arrangement. The switch works off a cam action with another little shifting cylinder. Might get a little air in there but not much.

 

[MrCypress]

I took the switch out, cycled the pedal and the switch a few times. Reinstalled. When I turned on the ignition the light was off. When I pressed the brake pedal to put it In drive the light came on and stayed on.

Now what?

 

[Jeff Jamison]

one of 3 things,one you still have air in the system some where,the switch is broken,or your mastercylinder is going bad.

 

[1975IH200]

Valve looks like this.....

The Pin in the switch is retracted when the brakes are 'normal' as it rides on the large diameter of the two pistons in the center.
When there is a pressure imbalance between the front & rear brake hydraulic circuit, the pistons shift to the lower pressure side and the pin in the switch extends down into the recess in the high side piston.
If you do not remove the switch before bleeding, you can shear the pin if the pistons shift in the other direction.

 

[MrCypress]

This afternoon I took the switch out again. Put some oil down in it and worked it around. The spring action works smoothly. Then I took the front piston out of the distribution block, looked it over with the spring and the little pusher cap thingy. No corrosion or gummy stuff there. I put those parts back in. Then I bled the back brakes again and the front brakes again.

No change in the brake feeling. They work but they seem looser than they were before I started working on the rear drums. It's like there's slack in the system somewhere. Or the booster is doing anything for me anymore. I checked the vacuum connection and that's all good still.

And the red light was still on.

I have 3 working theories.
a. The switch is bad.
b. When I rebuilt the rear drum brakes I messed something up. Maybe the self-adjustment screw is *really* loose. Maybe something I though was secured has come loose.
c. there's something wrong with the booster or master cylinder (new, installed last year) that didn't present itself until recently.

I'm sorta running out of time to fool with this stuff. I might have to bring it to a shop and let them inspect it.

 

[Greg R]

Put some oil down in it and worked it around.

NEVER put oil in ANY part of a brake system that uses glycol based brake fluid. It will ruin the rubber parts. Go around to all the wheels and make sure all the shoe adjustments are the same and tight. It is possible, I did it once, that 2 adjusters got swapped side for side. The warning light is a nice to have, not critical. As long as the brakes work, do not leak, and there's no pulling to any side when braking hard, you'll be okay.

 

[MrCypress]

You're right. I maybe need to flush that little bit of oil out or reap the consequences. I brought the truck to a shop near home because I was running out of patience and time for it. They called me today and said the brakes appear to be great and in their opinion the switch is just wonky, stuck in th triggered state. They say if it start pulling to some side or the pedal goes to the floor then obiviously there's a failure somewhere. So the light isn't really needed...Replace it or disconnect it. I'll call Coonrods and try to get a couple spares. Install one. If it works I'll leave it wired. If not then I might just leave it disconnected.

 

[Alex]

Mr. C:
You've certainly done justice to that pickup.
You'll figure out that brake light problem.
Good work.

 

[MrCypress]

My kid has been driving the truck to school and back for the last month without much of an issue. He left the lights on once and had to get a jump.
In the fuse panel I patched in an RL45 automotive relay and a 12v buzzer per this schematic : and

Tested it out and works great. He won’t forget that again.
I noticed the horn was weak sounding and I’m tinkering with that now.


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[Randall Barringer]

Perfect!
Nicely done.

 

[supercrouton]

You're right. I maybe need to flush that little bit of oil out or reap the consequences. I brought the truck to a shop near home because I was running out of patience and time for it. They called me today and said the brakes appear to be great and in their opinion the switch is just wonky, stuck in th triggered state. They say if it start pulling to some side or the pedal goes to the floor then obiviously there's a failure somewhere. So the light isn't really needed...Replace it or disconnect it. I'll call Coonrods and try to get a couple spares. Install one. If it works I'll leave it wired. If not then I might just leave it disconnected.

I had a similar problem with my '73 S2. But I didn't actually know it because the PO disconnected the switch at the master . The reason I started investigating the braking system was the brakes were too heavily biased toward the rear. It was eating rear brake shoes and the rears were locking up prematurely. If the switch itself goes from open to closed it is likely good. The slide that has shifted does more than just operate the failure switch, it also diverts brake pressure when a brake circuit looses pressure or when a moderate differential of pressure between the front and rear circuits is detected (usually because of air in the system). My issue turned out to be a small amount of air in one of the front brake lines. After bleeding the brakes and resetting the slide with a pick, all is well and the truck stops as it should. That warning/bypass system is an important safety feature, and may be all that stands between life and death if you actually have a brake failure, or have to make an emergency stop. I would advise bleeding all four corners starting with the furthest from the master and working back to the closest, reset the slide and see what happens. Good luck!

 

[MrKenmore]

My brake combo vale on the Travelall is acting up right now. Light won't go off. It was like this when I got it (wire off terminal actually). I have serviced all the brakes and bled them. I removed the sensor and looked down in the hole and saw brake fluid. Per the service manual, that's a no no. Indicative of fluid making it's way past the o rings of the slider. I have a new combo valve from Scout connection I will be installing. Here's the combo valve now:

 

[MrCypress]

I need to give Coonrod another call. I agree I'd like to have that switch working. Been very busy with work and from all other accounts the breaks are working properly so I haven't worried much about it.

This weekend me and my dad made a useful choke adjustment. "Rolled into the shop" with a sticking choke reported by my son. Oiled it up. I think it was just getting too much friction when it takes the first 90 under the dash. Also looked at the low idle speed and decided that it was over-choked on most startups. Adjusted to idle a fraction faster and use less choke. Very happy with results. Rerouted the fuel line behind the carburetor instead of over the distributor next to the thermostat. Found and fixed a small vacuum leak where it plugs into the transmission.

 

[MrCypress]

Might not have been needed but I replaced the oil pump. What she did need was a new gasket and rtv. Part from Rock auto fit fine. Crank case looked really nice IMO, for ~57k miles.

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[MrKenmore]

Sweet!!! I do notice you are now missing the IH rust preventative measures! A leaky engine. LOL. Nice to see you back in the build forum!