So my 98 Yukon has been acting up. At some point, the parking brake light came on and stayed on, with the parking brake completely off, checked. Then, the brakes were soft with reduced stopping power. I checked the fluid. The large,rear,shallow reservoir is full, the smaller, front, deep reservoir is very low. (No idea if they both should have the same level). Got the car up on jacks. The parking brake works, stops the wheels quick. When i press the brake pedal, the rear wheels keep going as if unburdened. Do I have a leak, or a failure in the booster/cylinder/valve? The computer had no codes.

Thanks in advance!

Well, both reservoirs should approx be at the same height.....

Since one is low, it'* one of two things.....the rear brakes are worn so low it has caused a drop in fluid, or you have a leak and there is air in the system......

You saw no external leaks under the vehicle?

Drums or calipers? If drums, remove them and look for leaking wheel cylinders...

Ahh. So the same fill level. That makes sense. I should have mentioned the rear brakes are totally done, maximum drum diameter, shoes are worn. Should I refill the reservoir and then replace the brakes first? I'm still Curtis why the light is on? Leak? If the parking break works, that make me think fluid pressure is low...

Also, I could not find any obvious leaks. I will check the wheel cylinders tonight. Thanks.

the red light is for "brake problem". more likely a leak. most of them get the first one driverside under frame where the tank lines go up. its hard to see, i would look along the frame there for fluid. i ended up just replacing all the lines, the abs is hard to bleed and you dont want to do it a bunch of times. you have to fix the rear, make sure the adjusters are free, and bleed everything a few times to get a decent petal. might as well start new.

Found it. Really just forward of the driver side rear brake, next to the gas tank. Looks like I am replacing the lines. Should I use stainless? I have done the double flare, which sucks. The extra money for the SS may save my sanity. Thanks.

i didnt bother with stainless, its too expensive. i just got a couple coils of regular and painted it once i was done. some are metric bubble flair. you have to bleed it with the key on, go out on a dirt road and activate the abs a couple times , then bleed it again, then if you fixed up the rear you should have a half way decent petal and the rest will work in over time. if there are no other leaks.

I like to bleed the system with my manual vacuum pump setup....

i have one of those, but i dont think it makes a difference. the late 90s truck abs just seems to get bubbles and i dont have a two way scanner to command it on. i have heard some have success bleeding it with the engine on, but i havent really found that necessary.

Ok, quick question. About how long is the 1/4 inch line running from the engine compartment to the rear axle? I just want to make sure i know for fabrication, as i have no plans to take the old one out (heard its not worth it).