marko
Registered Member
What would cause the brake light to stay on in my blazer? The dash light.Its an 89 k5 350 700r 241
CK5
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brake light
- Thread starter marko
- Start date
NewUser
1/2 ton status
brake light on dash or actual taillights?
bad master cylinder would cause dash light to stay on.....bad brake light switch would cause taillights to stay on
bad master cylinder would cause dash light to stay on.....bad brake light switch would cause taillights to stay on
marko
Registered Member
Is there a way to test the mc?
got brake fluid? is the ebrake switch stuck?
Two things will do that.
There's a switch on the parking brake pedal that could be loose or misadjusted or the wiring could be bad. You can unplug the connector from the switch and jump across it with a bit of wire, see if the light goes out. If so, fix the switch or wiring as appropriate.
More likely is an issue with the hydraulic part of your brake system. If the combination valve detects a major difference in brake pressure between the front and rear circuits, a switch trips and the light comes on.
If you don't know much about brakes, seriously consider taking the truck to a shop. I'm the king of doing it myself, believe me, and I've completely redone brake systems on my trucks ... but brakes are not a good place to start learning. Alternately, especially if it's not your primary vehicle, get to your Chilton's and read up.
There are some simple checks to do -- first, make sure the fluid level is correct. If the fluid level got too low, the system like swallowed some air, which is A Bad Thing for hydraulic systems, but you can luck out and just top it off.
Then, locate the combo valve. It's located on the back of the crossmember, basically under the fan, towards the driver's side. It's a metal box maybe 4" wide and about an inch, inch and a half tall, with five metal tubes going in and out if (these are the brake lines.) You can also follow the brake lines down to it from the master cylinder.
On the far driver's side of the fitting should be a rubber button, maybe 1/2" or so in diameter. (I've seen a few without the button, like maybe the button fell off or deteriorated over the years.) In any event there's a metal plunger under there -- fairly small, like 1/8" in diameter. You should be able to push it in with your finger. Doing so will reset the trip switch mentioned above.
The light should now go out. It is possible that resetting the switch is all that was needed and you can go on your merry way. More likely is that, sooner or later, the light will go back on, meaning that you've got a leak somewhere, and it'll need to be fixed.
Especially if there's any change in the brake pedal travel, like you have to push it farther than you used to ... fix it or get it fixed.
Could be the master cylinder is leaky; they're relatively easy to replace, but any time you play with the hydraulic system you have to bleed the brakes. Could also be a leaky or old brake hose (the rubber ones will eventually swell, when they get old, and so they don't transmit pressure very well.) Could be a leaky wheel cylinder (in the rear) or caliper (up front.)
Ain't brakes fun?
-- A
