Bleeding Brakes

[JTodd]

I replaced a bad caliper and decided it was time to do a complete brake system flush. After purging the air from the new front caliper, I went to the back. Using a 1 person bleeder (small cup with a lid and hose) I filled one cup, emptied it and went back for more. After the first cup, the brake pedal goes more than 3/4 of the way to the floor before any pressure and it is very slow to return to the top, and the insturment panel brake system light is on. I made sure the whole time that there was more than enough fluid in the master cylinder resevoir. I get the same pedal issues with engine running or off.

Any suggestions? Have I introduced air into the system somewhere and need to just struggle through getting it out, or is there some other reason? When bleeding I have pushed the pedal slowly all the way to the bottom and let it return. At some point I began to push it with my hand and pulling it back up to quicken the processes.

[JTodd]

Somehow air got in, but I finally got it out and things seem fine. A question for those that consider their brakes good - How firm is your pedal? My Sub brakes fine and straight, but it seems like the pedal is spongy and a little low.

[gmenor]

I've always bleed the brakes starting from the furtherest brakes away from the master cylinder. I've never had any problems doing that way (RR, LR, RF, LF).

[NH2112]

I've had good luck gravity-bleeding one wheel at a time when doing a complete flush. Fill the reservoir, crack 1 bleeder at a time (in the RR, LR, RF, LF order) and let fluid work its way there and drip for a while then close up and move to the next wheel. If you ran the master cylinder dry at all, you have to bleed it before the wheel cylinders or calipers, too. You can either keep the plastic hoses that come with a new MC and use those, or make a set out of steel tube and flare nuts. Just pump the pedal till no more bubbles appear in the fluid, then bleed the brakes in the normal manner.

[dieselbegreat]

I hope you were keeping the reservoir filled with fluid while you were bleeding. That's why it's really a two person job. Otherwise you'll have do just do it all over again. Gravity doesn't really do enough of a job dislodging and shooting the tiny air bubbles out. Replacing all the old fluid every spring will give a harder pedal. Also, all the brake hoses, hard lines and hardware (calipers, pad shims, slide pins, adjusters) must be in good shape and wheel bearings must be tight for a hard high pedal. All you need is one sloppy wheel and you'll have a low pedal.

[trbankii]

I've been using one of these for a few years:
http://static.summitracing.com/global/images/prod/large/mvp-0250_w.jpg

I bought it from Summit Racing:http://store.summitracing.com/partdetail.asp?autofilter=1&part=MVP%2D0250&N=115&autoview=sku

There are a couple different versions with different adapters depending on what vehicles you own.

I had tried to use the MityVac setup a few times, but always ended up with air in the lines. The old two person standby of one person pressing the brake and one opening the valve works well when you can collar a second person and also remember to check the reservior every now and then. But for single person work the Motive Power unit is the way to go!

[HowieE]

Trbankii

What pressure can you apply to this bleeder without running the risk of setting the safty in the proportioning valve and stopping the flow to the brake you are bleeding?
Even though my proportioning valve did not work when I lost a brake line I still ask because maybe something GM designed would work when you did not want it to.

[trbankii]

Hmmm... Never considered this and haven't actually bled the brakes on the K2500 yet - it's on my list of things to do, though.

The Toyota only has a LSPV (load sensing proportioning valve) - as you add load to the bed the valve allows more flow to the rear brakes. I'm not aware of a safety valve in the system.

Are you sure there is a safety valve? It would seem that the pressure built up by stomping the brake pedal to the floor would be much greater than what I'm applying with the little hand pump on this unit.

[stingthieves]

What pressure can you apply to this bleeder without running the risk of setting the safty in the proportioning valve and stopping the flow to the brake you are bleeding?

The equipment I have used (similar to the picture) will only force fluid at 8 to 15 psi. - Far less than normal pressures. Unless you violently open and close a bleeder valve you will not disturb the proportion valve. Kind Regards Rick