Brake light below fuel guage says I have a problem....

[4bogginchevys]

I'm curious if anyone has had a similar issue, the brake indicator light below the fuel guage started blinking tonight when I was backing into my driveway. It blinks when I hit the brakes, staying on sometimes until I pump the brakes a little, it will stay off for a few more pumps and then come back on. I had just come from helping my buddy get his blazer put back together, we were a few parts short(if anybody see's "murphy" I wanna talk about his law)lol. We decided to go play in the 1008 instead of running around the woods in his truck. We went through lots of deep puttles, some the size of ponds. The deepest crossing was probably 20-25". Of course I had to pump the brake pedal some to get the water out when we entered the highway to go back to his house.....no light at this time. The light didn't come on at all during the 15+ mile journey home. As I said I was backing in and it just started blinking with use of the pedal, since I was home I started pushing hard on the pedal sometimes to see if the pedal would firm up anymore/see if I could get it to stay off. During one push of the pedal it did go down maybe 1.5" further than normal...and then it was back to good. tonight and since I've had the truck the brake pedal has always been good and firm and responsive so this issue definately indicates a change. This heavy duty brake booster setup is maybe the thing about the truck I know least about, hydraulic vs. vaccuum changes things abit so I thought it best to ask a veteran or two, (no pun intended)....thanks again

 

[Sgt Hulka]

Hmmm. Check the brake fluid level. You may have a slow leak somewhere...

 

[SPECIALTYLC]

Leak in system has allowed the pedal to travel enough that the sensor in the proportioning valve set off the light. Could be low fluid, bad master cylinder piston seals, leaking wheel cylinder.

 

[scooter01922]

You do realize that not like a check engine light you can ignore and hope it goes away That light means that your truck just might not even think of slowing next time you hit the brakes. PLEASE look into that, like at least check your fluid. Fluid that i'm suspecting is very low.

 

[AN/ARC186]

The way I see it you have 2 choices, stop driving the thing and check your braking system or go buy a really good drag chute.....

 

[CDN-CUCV]

I had the same issue. I ended up bleeding all the brakes and replacing my fluid with silicone fluid with a machine, this way I could do a leak-down test and check for pressure. My braking system ended up having excellent pressure (around 23 psi.) and the old fluid was contaminated with moisture.

You don't necessarily have to go with silicone, this was a route I took because I have a bunch. Check your fluid levels, but even then, you may want to bleed your brakes and check for air, water etc.

As soon as I changed mine, the problem went away.

I hope this helps.

 

[PorscheTech911]

Please heed the warnings, get it fixed ASAP! Check brake fluid level, check caliper seals, check your lines, master cyclinder, proportioning valve, ect. Don't use my family to slow yourself down! Don't drive it till its fixed! Bad Idea

 

[CDN-CUCV]

The way I see it you have 2 choices, stop driving the thing and check your braking system or go buy a really good drag chute.....

lol!

 

[4bogginchevys]

thanks for the input, and I will look into fixing it immediately of course. I have owned the truck about 3 months, a couple of weeks ago I checked the fluid for the first time and it was perfectly full(it was previously owned by a civilian, not right out of a gl yard). I will check fluid level tomarrow in am if it's not raining, tonight when the truck acted up it was dark/raining and I dont have a garage. we'll see.......

 

[CDN-CUCV]

Just a head's up, When I had that problem, the fluid level was good. Try not to assume that everything will be fine once you top your levels up if yours is down. Time to do a full check it seems.

Good luck

 

[doghead]

I had this same issue when I first started driving my M1008A1.

I did the same thing as CDN-CUCV, in post # 6. My level was good also.

Never been an issue since.


I would do a thorough bleeding of the brakes with new DOT5 and see if that takes care of it. Don't be stingy and run atleast, a quart of BFS through it

 

[niferous]

The way I see it you have 2 choices, stop driving the thing and check your braking system or go buy a really good drag chute.....

Come on now you know none of these trucks really builds up enough speed to make one of those deploy! At the scene of the accident people would say something like "This big green truck just didn't stop and then a bunch of bed sheet looking stuff with string attached came out the back and just started dragging along the ground. Then he hit that tree....."

 

[4bogginchevys]

I had this same issue when I first started driving my M1008A1.

I did the same thing as CDN-CUCV, in post # 6. My level was good also.

Never been an issue since.


I would do a thorough bleeding of the brakes with new DOT5 and see if that takes care of it. Don't be stingy and run atleast, a quart of BFS through it

WHATS bfs.....?

 

[4bogginchevys]

ok, the level in the master was low in the front...that's the rear brakes if memory serves. it was not very low, .5" below normal. I looked around underneath and could not locate where fluid maybe going. Its wet underneath still from the wet air and driving it yesterday so i'll have to wait for warmer/drier weather to locate the leak.

What is that thingy: it appears to be a junction block where 2 metal lines go to 1, just before the flexible brake line in the rear, it has a pivot arm hooked to the block, looks like it might actuate line pressure for some reason when diff goes up and down....anybody had to change/eliminate this. It doesn't look like it does anything, my 3/4 ton doesn't have one and the brakes on it work fine.

 

[TyJustice]

By the "Brake Light" are you talking about the emergency brake light that is comes on when you apply the e-brake?

Or is there another brake light I dont know about on the cucv?

 

[4bogginchevys]

By the "Brake Light" are you talking about the emergency brake light that is comes on when you apply the e-brake?

Or is there another brake light I dont know about on the cucv?

I think it's the e-brake light

 

[4bogginchevys]

ok, I went to napa to get a quart or 2 of dot 5 syn......WHOA, 28.00 a quart. We did some research to find out the difference between the syn/glycol, dot 3,4, and 5 and the differences were syn-glycol based and the boiling point of each accordingly, think what you will but that's a little pricy for my tastes. Why cant I run dot 3 syn......it's only 7.00 a quart,(lol) I've never had any trouble in my 3/4 ton with dot 3 glycol.....i'm just asking so that I can get a reason better than (thats what the book says). BTW, i do know you cant mix different dot rated fluids so I would do a whole system flush if I were able to run dot 3 syn. thanks again

 

[doghead]

BFS, brake fluid silicone, DOT5

 

[4bogginchevys]

ok, i found out what that thingy is, it controls how well the back brakes work according to the load on the suspension. Just a simple proportioning valve, and yes I will keep it unless thats where my leak is.

 

[SPECIALTYLC]

The light was set off by the proportining valve that is mounted on the front cross member under the radiator. Thats where the light gets its signal from. If part of the system stops working the valve moves and sets off the dash light. The proportiong valve will reset itself. DONT waste your money on DOT 5 fluid and is not compatable with dot 3. That stuff is for race cars that generate way more heat than you will in that old cucv.