I did it now. I replaced the rear drum brakes on my truck. I went ahead and replaced the shoes, wheel cylinders, all the hardware, and the drums. I adjusted them until there was a slight drag, them backed it off a few more clicks. Anyways, I'm having a heck of a time bleeding them. I've been through 2 quarts of fluid, and they are still mushy. I hooked up my mityvac 7201, put a vacuum on the bleeder valve, opened the valve. I did let the master cylinder run dry once. My fault - wasn't paying attention. But, I've kept it topped up, and still can't get the air out. I've been all the way around the truck twice. Where is the air at? And why can't I get it out? And how do I get it out!!?!?! The rear drum brakes are ABS, and am wondering if I got air in it somehow. Any help would be greatly appreciated. And I will buy anyone a beer who can help. Thanks guys.
Brake bleeding problems -- 93 Silverado
- Thread starter Bamboooo
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I just blew a rear break line on my 93 chevy truck and im having the same issues as you are having but i have not tried the traditional method yet just the mighty vac. Maybe this post will shed some light on the subject. After a qt of fluid i felt like i was just wasting my time and quit.
Do these trucks have RWAL? Sometimes you have to lift these things at funky angles to get the brakes bled right. I remember having to do that on some trucks, like lifting the back up high while bleeding. Hydraulic clutches are the same way.
I think, if you have a bubble, it wants to go up. It's not going to go down and out the bottom. I've seen some YouTube videos that demonstrate a reverse bleed for a hydraulic clutch. The idea is to push the fluid up from the slave cylinder, (or the brake) up toward the master cylinder.
I had a similar situation with the clutch on my BMW 2002... I was never able to get it "good" until one day I think the bubble must have worked it's way out on it's own. The trouble is there doesn't seem to be any good tools out there for doing a reverse bleed, on your back, and not getting a shower of brake fluid at the same time.
I had a similar situation with the clutch on my BMW 2002... I was never able to get it "good" until one day I think the bubble must have worked it's way out on it's own. The trouble is there doesn't seem to be any good tools out there for doing a reverse bleed, on your back, and not getting a shower of brake fluid at the same time.
Try one more time to see if these steps will help:
Fill up master cylinder to the rim.
Connect main tube to Mityvac 7201 tight, connect bleeder hose to main tube tight.
Pump Mityvac 7201 3-4 times to create a vacuum at bleeder valve
Crack open bleeder valve 1 full turn.
Pump Mityvac 7201 5-6 more times.
Keep master cylinder full, remember that the brake fluid is coming out very fast now along with air bubble in the system.
Close bleeder valve after 0.5-0.6 pints had been suck out from rear wheels, 0.3-0.4 pints for front wheels.
Test the brake system by starting engine and do 4-5 quick pumps on the brake pedal, it should firm up now.
Fill up master cylinder to the rim.
Connect main tube to Mityvac 7201 tight, connect bleeder hose to main tube tight.
Pump Mityvac 7201 3-4 times to create a vacuum at bleeder valve
Crack open bleeder valve 1 full turn.
Pump Mityvac 7201 5-6 more times.
Keep master cylinder full, remember that the brake fluid is coming out very fast now along with air bubble in the system.
Close bleeder valve after 0.5-0.6 pints had been suck out from rear wheels, 0.3-0.4 pints for front wheels.
Test the brake system by starting engine and do 4-5 quick pumps on the brake pedal, it should firm up now.
IMO...after the above steps....go back to the master cylinder and make sure that the brake fluid reservoir is filled to the max.
Then drive off......
Then drive off......
Thanks. And it did this last night, and I also put grease around the bleeder, and the bleeder-to-tube connection, so I wouldn't be sucking in air anywhere.
I just got done bleeding it the "ol fashioned way". My son pumped the brakes, and I bled them at each wheel. Got quite a bit of air at the 2 rear wheels. Hardly any at the front. Took it for a test drive, the "brake" light went out, and the brakes feel good.
I don't know why, but for some reason the mityvac didn't seem to get all of it out. I don't knw if air was trapped in the new brake cyliders, and they had to be "pumped", or what. But it seems all good now. Thank you all.
I just got done bleeding it the "ol fashioned way". My son pumped the brakes, and I bled them at each wheel. Got quite a bit of air at the 2 rear wheels. Hardly any at the front. Took it for a test drive, the "brake" light went out, and the brakes feel good.
I don't know why, but for some reason the mityvac didn't seem to get all of it out. I don't knw if air was trapped in the new brake cyliders, and they had to be "pumped", or what. But it seems all good now. Thank you all.
It may be bled OK.
Rear drum brakes need a long time to seat - that very well could be the mushiness you feel.
Rear drum brakes need a long time to seat - that very well could be the mushiness you feel.
Some GM trucks with ABS have a bad habit of trapping air in the ABS unit, we always bled these troublesome buggers with the truck running. With it it running, it allows the air out of the ABS unit. Make sure the truck is in park if auto, neutral with handbrake on if manual. Safety first eh.
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Originally Posted By: bigmike
I always like the 2man method to bleed brakes. The problem is finding a good partner for it.
Thanks Mike. That's what I ended up doing. Got quite a bit of air out, and had a good pedal. Besides, it's not as boring!
I always like the 2man method to bleed brakes. The problem is finding a good partner for it.
Thanks Mike. That's what I ended up doing. Got quite a bit of air out, and had a good pedal. Besides, it's not as boring!
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