I hope somebody can help me out with this problem(s). A few weeks back I started noticing that my cruise control didn't want to cancel unless I got down on the brake pretty hard. At about the same time, it got to where it was VERY hard to get the truck out of park every now and then (you know, you have to hold the brake down to take it out of park). I suspected the master clyinder was going bad because when holding steady pressure on the brake pedal, it would slowly ease on down toward the floorboad (truck idling, in or out of gear). I figured the little pressure switch on the end of the master cylinder is probably what allows the shift lever to be moved out of park when it senses that the pedal has been depressed. I also assumed that this same switch probably tells the cruise to cancel. Well, I replaced the master cylinder today and I still have the classic symptoms of a bad master cylinder. The pedal slowly inches toward the floor under steady pressure but I'm not losing fluid anywhere. The cruise is still acting the same way ie hard to cancel via the brake. So far it has not refused to come out of park like it was doing but I have only tried it a few times. Am I making some bad assumptions here?

 

freddie

there is a switch i believe down by the pedal. it may need to be adjusted or bent to engage quicker. it should be the only switch down at the brake pedal. as far as your master cylinder what year truck do you have. if you have a mid 90's to late 90's this is a very common problem recognized by ford. i am a mechanic and also drive a 95 f-250. when i got the truck it had a low pedal that slowly dropped with steady pressure. i proceeded to replace the rear brakes that were shot. helped. then replaced the abs valve. another common problem. didn't help. flushed and bleed about 2 gallons of brake fluid through the system. didn't help. replaced the master cylinder with one from a 96 that had a 1/8 inch bigger bore. this was fords fix and it helped a little. i keep the rear brakes adjusted up really good and live with the low and mushy pedal. every ford truck and van i have driven which is quite a few have the same problem. i hope this helps. if you have more question just post them.

good luck
tjbeggs

 

Thanks for the reply TJ. Sorry, I forgot to mention that it is a 1995 F-350 dually. Does the switch that you are talking about control the canceling of the cruise and the "park release" on the gear shift?

 

The switch on the master cyl. is used to cancel the cruise control.They are bad about leaking they will usually fry the wire connection at the switch also.

 

freddie go with the last post for the switch i wasn't sure where the switch was. but yes the switch probably does work with the cruise, brake lights, and shift interlock. i will try to check a wiring diagram today at work and see.

tjbeggs

 

Again, thanks for the replies. The pressure switch is not leaking and the conection appears to be fine. Maybe the pressure switch is bad? Sure would appreciate you checking that wiring diagram.....

 

FYI all.....On a 95 PSD dually, the brake light switch that is on the brake pedal plays a part in more than the turning the brake lights on and off. It must also be functioning properly in order to get the cruise control to cancel as it should and it if it malfunctios it will lock the gearshift lever in park (auto trans of course). I learned this little lesson after changing out the master cylinder and the pressure switch on the master cylinder at a cost around $100. The brake light switch was $6.31. Also, you can't necessarily determine if your old switch is working properly through observation and/or testing with a multi-meter. The compression resistance of the spring in the switch must be correct. Hope this saves someone some time and $$$.