Brake Light is On!!!!!
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Freshman User
Joined: Dec 2010
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Brake Light is On!!!!!
Okay....just got the truck back on the road....finished rewiring the valve cover connectors and things were great. Drove about 23 miles and all of the sudden the brake light goes on.....brakes seem to be working fine and did not appear to be leaking anything.....any suggestions.....
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
First thing to check is the parking brake pedal. Sometimes it won't open the switch when it's up all the way, and the light will stay on.
So the truck stops normally, pedal is neither unusually soft OR unusually hard?
Do the HVAC controls work?
So the truck stops normally, pedal is neither unusually soft OR unusually hard?
Do the HVAC controls work?
Hotshot
Joined: Oct 2003
Posts: 17,799
Likes: 103
From: Ashland City, TN
the light signifies a few different things.
Check the vacuum on one of the vacuum lines.
If you have a vacuum leak, the brake light will come on.
HVAC controlls is the easiest way to check, but you can have them work and still have the light come on. It starts throwing the light at like 12PSI I think, I didn't write it down when I was checking mine last time.
Check the vacuum on one of the vacuum lines.
If you have a vacuum leak, the brake light will come on.
HVAC controlls is the easiest way to check, but you can have them work and still have the light come on. It starts throwing the light at like 12PSI I think, I didn't write it down when I was checking mine last time.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Most likely a sign the vacuum pump is getting weak.
Mine has started coming on when the engine temp is very cold, but goes out when it is warm.
Heater controls are still working, just a little slower than when it is warm.
Given the temps and snow outside, it is just going to be on for a while unless it gets a lot worse.
Comes on at 10 or 12 inches of mercury though (vacuum), not PSI (pressure).
Mine has started coming on when the engine temp is very cold, but goes out when it is warm.
Heater controls are still working, just a little slower than when it is warm.
Given the temps and snow outside, it is just going to be on for a while unless it gets a lot worse.
Comes on at 10 or 12 inches of mercury though (vacuum), not PSI (pressure).
Fleet Owner
Joined: Aug 2004
Posts: 20,419
Likes: 197
From: AZ
My emer brake release sometimes will not release all the way. It will hang up right at the top just before the botton is release. I pull on the release handle again and it comes all the way up, light is out.
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Cargo Master
Joined: Feb 2010
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From: College Station, TX
My p brake pedal seems to have no bearing on the light function but when I hold the brake pedal down a while it comes on and flickers out when I release it. Significant of vacuum pump too?
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Logistics Pro
Joined: Oct 2004
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From: FL
Mine was doing exactly that when the vac pump was going
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
That's actually not good; it should go on when you apply the parking brake. Doesn't directly affect the main brakes, of course; only if you leave it on (that's why it lights the light), and most of us are grownups and know when we've left it on...
If the pedal goes real soft while you're holding it, I'd be more suspicious that it's a hydraulic issue. If it doesn't, or it feels like you need more foot effort, then yeah, that's vacuum. If not the pump, maybe a line leak.
but when I hold the brake pedal down a while it comes on and flickers out when I release it. Significant of vacuum pump too?
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Freshman User
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Well, I thinks its the vac pump...I heard a weird noise coming from the engine and pointed it to the pump.....guess thats the next thing to get changed......Oh but there is more...that will be my next post!!!! Thanks for all the info
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Vacuum pumps get weak over such a long period of time, that you don't notice the brakes take more pressure to stop until it fails completely.
Then when you put a new pump on, you suddenly realize how much better the brakes work.
Then when you put a new pump on, you suddenly realize how much better the brakes work.
Post Fiend
Joined: Feb 2009
Posts: 8,773
Likes: 1
From: Texas Coast
Thought I'd jump in here. Found my third brake light out the other day so pulled it open and glad I did had a little rust starting and some water was getting in there a shorting across the polls. Looks like it was really taking some heavy voltage there too. Bulb got so hot that it distorted. Reconditioned the seal and doctored the rust up. If the light would not have went out I may not have caught the rust in time like I did.
Anyhow back on topic, Vacuum leak or pump croaking sounds like the issue here.
Anyhow back on topic, Vacuum leak or pump croaking sounds like the issue here.