- This topic has 30 replies, 4 voices, and was last updated 12 years, 8 months ago by
.
-
Topic
-
Hi everyone, recently I got a 1976 K20 Scottsdale with the 400 engine. When I first got the truck I noticed the brakes were very soft but still able to stop the truck. The brake warning light was also constantly on With help from my Dad we bled the system and replaced the master cylinder and for awhile it seemed to work. Then about a week later the brakes started to feel soft again. The brake light would come on but when Id pumop the brakes itd go off. I adjusted the back drum brakes and again this seemed to correct the problem. Its been a few days and the brakes are getting soft again and the brake warning light is almost constantly on. I do still have brakes. I have been watching the brake fluid levels and havnt seen any losses. I checked the brake lines and havnt seen any leaks, the calipers look good. I havnt been able to get the drums off to inspect the wheel cylinders because they are the hub/drum assembly which I dont think I have the right tools to pull them. My question is without a loss of brake fluid do I have a bad component or do I just need to re-bleed the brakes? My dad is questioning weather or not the hydro-booster in bad although from my reading if that fails then the pedal becomes very hard due to loss of power brakes essentially.
-
Replies
-
From what I can read its part of the master cylinder but ill take a better peek when I have more daylight
In order to properly bleed those brakes you need the special tool for the proportioning valve, it has a valve on the inside that when there is a brake fluid loss it closes off to prevent a complete loss of braking. It’s a very cheep tool as all it does is hold the prop valve open to allow fluid to pass through it freely. I would recommend getting this tool and bleeding the brakes again to make sure you got all the air out.
http://www.amazon.com/OTC-OTC7853-Propo … B000K1FVLW
Normally it’s on the firewall or on the frame rail just below the master just follow the brake lines from the master as the prop valve is the next stop on those systems. I don’t think I’ve seen the prop valve as part of the master on something of that vintage.
Well its been about a week. My brakes are still functioning with no warning light, to me it feels like theres still a little bit of air in the lines but not an alarming amount. My question is in my research Ive noticed on my truck if the light comes on it means either the valve is off center (proportining valve) or theres an excessive amount of air in the lines So does no light mean the valve is ok? Also Im trying to figure out where the pin would be on the valve that i need to adjust to hold the valve center
Thats where I was finding what caused my question dreamer. Im not sure if the lack of a warning light means my brakes are ok or if I should finish bleeding them,. The last few times Ive driven it actually feels like normal brakes. Of course it has been very cold out too
If the brake warning light is not on, then the hydraulic system should be working correctly. Those light will illuminate if there is a hydraulic imbalance in the braking system (as well as using the emergency brake and electrical issues with the wiring).
If the pedal feels firm and you are able to do emergency stops, then you should be good to go.
If the brake pedal still feels spongy, you still may have air lingering.
I would forget about the warning light and just bleed the brakes out with the prop valve held open, it really is the procedure for those systems and it doesn’t take much to do for that kind of piece of mind of making sure you have all the air out. If you feel they are good however then move on and call it a win.
Thanks Eric, just the correlation between the light and valve were throwing me off. Im waiting for a warmer day after payday to try again.
Oh and Eric that trick on Hondas works on GM products too I think. A couple of times I inadvertantly locked the brakes on ice/dry pavement areas and it seems to stiffen up the pedal
Well final update on the brakes guys. Ive bled them again this time ensuring the pin remained center didnt have too much effect on the brakes. They still respond but the pedal hasnt gotten any firmer from this last round so I guess Ive bled them as much as I can.
Do you feel safe driving the vehicle? Will the brakes lock up in an emergency stop? (Not that that’s a good thing) If you know anyone that has a similar era truck, give it a ride, and see if the pedal feels the same. I’ve always thought Chevy trucks had a squishy pedal no matter what you did. (Older ones, like the crap I usually own and drive)
Mornioing Beefy. I do feel safe driving the truck, Its hard to get the brakes to lock up but you can if youre on dry pavement. Its on a lift and a heavier truck so its braking ability is less than say a smaller truck. So I just follow my cardinal rule dont drive the truck to the point where you think you’re gonna have to lock the brakes up. Most trucks and K5s Ive driven of that era had the same squishy funny brake feel with about the same braking.
- You must be logged in to reply to this topic.