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240 Cause of brake failure light?

Joined
Nov 22, 2017
Location
California
So I was driving back from school earlier today, when out of nowhere, the brake failure light came on. It stayed on all the way back home, whether I was pressing on the brakes or not. My brakes feel fine and when I parked, I shut the car off and put the key in again. All the dash lights turned on as usual, once turning on the car, the lights went out except for the brake failure light. Just hoping it's nothing serious since it's the middle of the week and my daily driver to college.
 
What year is your 240? You either have a switch on the octopus (brake warning valve) or on the brake fluid reservoir that will turn on the light.

The warning valve on the octopus indicates a failure of one of the circuits in the master cylinder. The switch on the reservoir indicates a low fluid level.

If you have the octopus, make sure the wire didn't come off and touch ground somewhere.
 
What year is your 240? You either have a switch on the octopus (brake warning valve) or on the brake fluid reservoir that will turn on the light.

The warning valve on the octopus indicates a failure of one of the circuits in the master cylinder. The switch on the reservoir indicates a low fluid level.

If you have the octopus, make sure the wire didn't come off and touch ground somewhere.

1987 240 DL. Where would the octopus be?
 
Down on the frame rail on the drivers side, just above the suspension control arm.

Follow the brake lines down and you will find it
 
Now I'm even more confused. I didn't check the wire on the octopus yet, but on my drive to college, the light faded away. Like right when I started the car, the light was on, but not as bright as my others like the parking brake light. And while I was driving, the brake failure light faded until it was practically off when I arrive at the college.
 
The light seems to go off every five years or so in my '82 244 Turbo; it too has the "octopus" switch.

I've been able to clear / reset it every time so it does not recur by removing the wire from its spade connection on the switch then unscrewing and removing the threaded piece that holds the spade connector; this exposes a spring and another piece which I remove, exposing the interior.

I then use a small, narrow tool such a a small phillips screw driver or the like and push fairly lightly into the guts of the octopus (there's a recess there), then put it all back together.

This seems to reset it / restore balance in the octopus.
 
The light seems to go off every five years or so in my '82 244 Turbo; it too has the "octopus" switch.

I've been able to clear / reset it every time so it does not recur by removing the wire from its spade connection on the switch then unscrewing and removing the threaded piece that holds the spade connector; this exposes a spring and another piece which I remove, exposing the interior.

I then use a small, narrow tool such a a small phillips screw driver or the like and push fairly lightly into the guts of the octopus (there's a recess there), then put it all back together.

This seems to reset it / restore balance in the octopus.

Would that require bleeding the brakes after? Or is there no chance of any brake fluid leaking from taking out the threaded piece?
 
If there's brake fluid coming out of the switch, the octopus is bad. You can take it apart and replace the leaking o-rings or replace it with a new one. You can also use the octopus without a warning valve but you'll lose the warning light feature unless you get a cap with a fluid level switch and wire it into the system.

octopus6.jpg
 
No, the proportioning valves are under the car by the fuel pump.

ProportioningValves.jpg


The warning valve is also a distribution manifold. Actually, 2 separate manifolds with the failure switch in between.

BrakeWarningValveLate.jpg
 
The warning valve is also a distribution manifold. Actually, 2 separate manifolds with the failure switch in between.

BrakeWarningValveLate.jpg
So I unplug and unscrew the threaded spade connector, poke around the inside with a small flathead screwdriver, screw the connector back in, plug it in, and hope it works?
 
I wouldn't mess with it unless it's leaking and you're going to pull it off to reseal it. The switch assembly will come apart when removed and it's no fun trying to piece it back together in situ.
 
No.

After you remove the threaded piece that holds the spade connector you must then remove a couple loose pieces, a spring and a piece the spring fits onto.

Only then can you use a tool to poke inside at the very bottom: don't use a flathead, use a phillips or something similar.

No need to bleed the brakes, as it only seems to restore the balance to the proportioning valve.
 
Are you low on brake fluid? When my distribution block failed, I lost a bunch of fluid and ended up with an imbalance between the two circuits, which triggered the light on the dash.

I didn't see any brake fluid leaking out of any lines or calipers because it was leaking out of the switch on the distribution block and was slowly filling up the driver's side control arm.
 
Are you low on brake fluid? When my distribution block failed, I lost a bunch of fluid and ended up with an imbalance between the two circuits, which triggered the light on the dash.

I didn't see any brake fluid leaking out of any lines or calipers because it was leaking out of the switch on the distribution block and was slowly filling up the driver's side control arm.

Not low on fluid, checked this morning and half an hour ago after parking, just under the max line.
 
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