Hey everyone, i have replaced the break pressure sensors two times on my 78 fj40. I keep buying them from Cruiser Corps. Has anyone else had this same issue?
1978 FJ40 break pressure switch issues (Keep going bad)
- Thread starter Landlover12
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New parts aren't always good - but I doubt they are all bad. I'd be looking elsewhere. Wiring and the master cylinder come to mind.
Have consulted the manual?
Have consulted the manual?
- Thread starter
- #3
the master cylinder is new. i have not looked in the manual yet but thats a great idea
I think those switches detect a difference in pressure - some sort of small air bubble in one of the chambers on the piston my cause enough pressure difference to trigger the light. But that's why there are manuals.
Did you bench bleed the master?
Did you bench bleed the master?
What senders are you referring to? The 2 on the master are there to warn of a low pressure fault in either circuit, they have nothing to do if all is well. Brake lights are powered thru the double contact switch on the pedal.
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The ones on the my master cylinder run the brake light warning one the dash.
Is the problem that dash light staying on or not lighting? Do your brakes work well? Disconnect 1 sender at a time and see what happens.
I bought a 78 new so remember that light. As I recall, it lit when I had the parking brake on. I remember this because I was 18 and this was my first
"car". I had a street bike before a Land Cruiser. I drove all the way home from the dealer with the e-brake partially engaged not understanding that stupid
light. Somewhere in the 80s one or both of those wires broke or became disconnected. It never affected braking so I never reconnected them.
"car". I had a street bike before a Land Cruiser. I drove all the way home from the dealer with the e-brake partially engaged not understanding that stupid
light. Somewhere in the 80s one or both of those wires broke or became disconnected. It never affected braking so I never reconnected them.
Yes, the dash light goes when handbrake is on and also if you apply the foot brakes and 1 or both of your brake circuits don't develop pressure. Or did when everything was 50 years younger.
like my Land Cruiser, I too worked better when I was 50 years younger
In an attempt to condense the info contained in the above posts for the OP...
First off you didn't list any symptoms. What makes you "think" that they're bad?
The dash panel brake light will come on if 1) you have the hand brake on, 2) there's a pressure drop in the circuit when the handbrake is off, 3) you have a faulty handbrake switch, 4) the handbrake switch is mis-adjusted or 5) there's a wiring fault. With the handbrake set the light should go out if you apply the foot brake - unless the brake pedal switch or wiring is mis-adjusted or faulty.
I've never seen brake warning switch go bad on a dual circuit '78 master cylinder that was in good repair. If you have badly contaminated fluid or air in the master circuit (did you bench bleed the master? was asked above) then things can go wrong. It's possible you're buying from a bad batch so picking up a used set would be a way to test that out once you have everything adjusted correctly. HTH
First off you didn't list any symptoms. What makes you "think" that they're bad?
The dash panel brake light will come on if 1) you have the hand brake on, 2) there's a pressure drop in the circuit when the handbrake is off, 3) you have a faulty handbrake switch, 4) the handbrake switch is mis-adjusted or 5) there's a wiring fault. With the handbrake set the light should go out if you apply the foot brake - unless the brake pedal switch or wiring is mis-adjusted or faulty.
I've never seen brake warning switch go bad on a dual circuit '78 master cylinder that was in good repair. If you have badly contaminated fluid or air in the master circuit (did you bench bleed the master? was asked above) then things can go wrong. It's possible you're buying from a bad batch so picking up a used set would be a way to test that out once you have everything adjusted correctly. HTH
This is a timely post.
I’m trying to chase down a fault in my brake system. I think it might be one or both of the pressure sensors. How does one test them to see if they are bad or not?
(My light on the dash is on and goes out when I apply pressure to the brakes)
I’m trying to chase down a fault in my brake system. I think it might be one or both of the pressure sensors. How does one test them to see if they are bad or not?
(My light on the dash is on and goes out when I apply pressure to the brakes)
Have you looked in the manual? free downloads Land Cruiser Factory Service Manuals (FSMs) - https://www.cruisercult.com/factory-service-manuals
Pull the wires off the 2 sensors on the mc and use a test light hooked to your battery. It should light if you touch it to the sensor terminal. Now get someone to jump on the brakes and the test light should go out. I'm guessing Slapshot has an issue with the double pole switch on the brake pedal - do your brake lights work?
Thank you. I’ll try that.
My brake lights do work. I’ve replaced the switch on the pedal and tested the parking brake switch.
Master cylinder sensor wire isn't connected to handbrake switch? That would give issue you describe
Did you get this figured out?
Even if the parking brake switch tested good, the system will behave as you describe if it's misadjusted and isn't triggered correctly by the park brake actuator. If there are no leaks in your system (including internally in the master) then it's likely a switch or wiring issue.
Thanks for the advice. I’ve been busy lately and haven’t tested anything. I’ll report back when I get a chance to look into it
