On my 96 f350 I'll be driving down the road and the parking brake light will pop on, then go off when ever it wants too. I've even seen it kinda fade in and out on it. I have tried several different things as far as pulling up on the peddle when it comes on and what not but it doesn't do any good.

Its not all the bothersome unless I'm trying to run cruise. Then if it comes on it kills my cruise. First time it happened I didn't know what was going on but after a few times I finally realized what was happening.

Anyone ever have this happen to them?

 

sounds like your vacuum pump is on its way out

 

Dies it pop on when you hit a big bump?

 

It's not a parking brake light. That's always a misconception. =)


Check the wire on the Parking break under the dash, if it's loose, it will give you some wierd issues.

Then check the vacuum on your vacuum system if that doesn't fix it.

Another thing to check would be the sensor on the end of the master cylinder.

 

Having the same issue. Talyn, whats the best way to test the vacuum pump?

 

I'm not sure when it comes on the most. I know for a fact that it doesn't always happen on a bump, but then again you hit a small bump and it feels like a big one. But I think I've seen it come on even when sitting at a red light.

I have checked the wire on the parking brake even while it was on, I pretty sure I even unplugged it and the light didn't do anything.

We just replaced the master cylinder back in December, come to think about it, it might have started happening after that.

If its not a parking brake light.........Then what is it?

 

William (Talyn) is splitting hairs a bit. He is a stickler for semantics (nomenclature).

The light is a "brake system light" of sorts that can illuminate for a number of reasons, one of which being that the parking brake is engaged. Does the light go out if you rev the engine slightly? One of the other things that can make the light come on is a low vacuum level in the system. I am betting that pumping the brake pedal a couple times will make your light come on and then it will go off a couple seconds after the pedal is released. If that's the case, you're probably due for a vacuum pump. The only way for sure is to put a vacuum gauge on the system and see what it is running.

 

OK OK OK. I get the light joke now.

I know the passenger rear brake is messed up. The adjuster cable broke on me and I've still yet to fix it. Could this be causing a vacuum issue?

It all started back end of the year. I went to stop at a stop sign one day and the truck wouldn't stop. Luckily it was a sign town and no one around for miles, so I was able to roll right through it. Then it all worked just fine after that.

I went to leave for my camp one day after work and pulled out of the parking lot and the truck wouldn't stop. So I had to slowly limp my truck home with no brakes. Well come to find out the master cylinder went out on it and thats when we replaced it. And ever since is when I've started noticing the "brake system light" coming and going.

I've tried pumping the brakes before with out the light doing anything. And I'm not sure about the reving of the engine.

 

If the light is off and you pump the brakes and it comes ON, then I would tend to think you need to look at the vacuum pump or the booster.

This is probably a stupid question, but is the fluid level in the reservoir full?

 

I'm pretty sure it is. I'll be honest I haven't looked in a while though. I know it was when we changed the MC out though. I'll have to play around with it later when I get off work and see what all sorts of things I can make it come on and maybe even off.

 

A vacuum gauge is the easiest way to test the vacuum.

But if your hitting the brakes or pumping on them and the light is coming on, then your vacuum pump is probably ded.

If it usually comes on sitting at a light, its prolly the vacuum pump.

The system will usually build up a vacuum and shut the light off when driving down the road and not using the air system, if its coming on driving down the road, I'd suspect a vacuum leak.


Yes, I was splitting hairs, sorta. =)
Thanks for making it funny DIY.

It's really an idiot light to signify a brake or vacuum issue/alert.

Think about the check engine light. How often does it actually have to do with the engine? =)
Why isn't a "check sensor" light? hehe.

 

Good tell on the booster, even with a low loss booster, is that the pedal will die easily.


IIRC, the light wont come on if your booster is bad, it will just let the pedal fall easily and be squishy.
Low vacuum will be a hard hard pedal while the light is on.


Hmm. I wonder if the leak was in the booster how the booster would act.
Probably act like a bad booster.

I still find it amazing how 15 lbs of air suction can make while applying brakes.

 

Ok so I didn't get off work untill 10 last night. I live .9 miles from work so I didn't even think about it last night.

This morning. I climbed in the truck and turned it on. The light came on. I played with the parking brake and nothing happened. I bumped the brakes and nothing happened. I reved the engine and nothing happened. Driving down the road and about 2 miles into it, the light went off, 5 miles later and the light never came back on.

Still have yet to pop the hood though to check the fluid level.

 

When you hit the brakes its not coming back on?

If its staying on like that and going off eventually, its probably a pump issue or leak issue.

When my pump went bad, that's how it acted.
But every time I stopped, I mean stop, not slow down for 4 miles before the stopsign and then stopping, it would come back on.

 

When my pump went bad, I could stop just fine the first time, but if I had to pump the brakes again I was in trouble. The pedal would be rock hard if i had to hit it more than once.