93 F250
When I sit at a traffic light with my foot on the brake pedal, after about a minute, my red "brake" indicator light comes on. As soon as I release the pedal, the light goes out. I suspect the balance switch for the front/rear brakes is not centered. Can someone tell me where it is located? Or can I have someone press the brake and loosen one or other line coming out of the master cylinder

 

I know there is a sensor that's supposed to illuminate that light if the system gets low on vacuum to run the booster, no clue on the proportion valve, should be on the frame below the master, also should be an antilock valve for the rear somewhere. Iirc most were around the rear end.

 

on the 93 there are 3 ways to trigger that Brake light Normally .... low fluid sensor under the Master Cylinder Reservoir, Low Vacuum sensor located near the Driver's side battery, and the parking brake switch.

Ok 4 ways for a normal trigger .. it should also turn on and do a Bulb Test when the Ignition switch is in the Start Position,

as suggested by DOC it is probably a Low Vacuum Warning.

there is no proportional valve on this truck, that is all handled by the Master Cylinder and the RABS any RABS failure sets the ABS Lamp not the Brake warn Lamp however the RABS computer does watch the Brake Warn Lamp signal.

 

inspect the Booster Check Valve for a leak.... I've posted on this before....



NOTE the small crack on the RH side at 3 Oclock

 

Thank you DOC and lonewolf for your input. I will check it out and let you know.
I posted my truck for sale. Surprised you had no comment lonewolf. You have spent so much research time on it, it's almost a part of you

 

I knew you wanted to sell it some time back, doesn't change my willingness to help

 

well I certainly thank you for your help.
Would you please reply to my other post concerning my fuel problem?
Thanks

 

Done ...

I really thought everything was pretty much covered.....


and BTW you might not have a Cracked Check Valve on the Booster but I have seen that and it causes low Vacuum....

More than likely either the Pod on the Vacuum pump is weak or maybe the Brake booster is leaking .... BUT as long as you don't have low Fluid and the Brakes work fine don't worry too much about it.

BUT you can always put your Vacuum Gauge on that Vacuum Manifold mounted on the driver's side fender well and see what is happening... you know it could be you are loosing Vacuum from one of the HVAC lines too.

 

Yes, you are correct. For some reason I did not receive your fuel problems answers before reading this.
As usual, I thank you for your assistance

 

Not sure what I did and what the part is called but I followed the vacuum line from the manifold to a round thing sitting next to the steering pump. Don't know if I did something to that or to the manifold but after disconnecting that line from the manifold, installing vac gauge, then re- connecting that line, the problem went away.
I sure wish my problem with the IP was as simple
Thanks again lonewolf

 

that Round thing is the Vacuum Sensor.

 

I had my brake light come on a few months back. I would depress the pedal once, and then if I needed to brake again in short succession the pedal would be solid and the light would come on. Ended up being my Vac Pump. Easy enough to swap out and I didn't even have to bug Lonewolf

Have you noticed any change in your brakes or is it simply the light? If you have vac issues I would suspect you would be loosing some pressure on the booster. If it's just the light I would suspect the sensor. Just my 2 cents as a novice. Good luck!