The Stovebolt Site Forums The Parking Lot Big Bolts 58 2-ton brake bleeding question

Sorry for the long post, my question is at the bottom, but the top part is the history of what I have done so far. Also, let me say that I have been in the garage since I was 3 yrs old and have done lots of brakes but this one has me baffled.

ok, I'm working on a new to me 1958 2-ton. First off, it had no brakes so, I added fluid to the master cyl, pumped it up and got a pedal. A few days later, I still had brakes but I noticed some fluid leaking from the left rear wheel. I rebuilt the rear wheel cylinders, cleaned everything up, adjusted up the rear shoes and proceeded to bleed the hydravac and then all 4 wheels. I have to pump the pedal 3 or 4 times to get a firm pedal so, I figured I still had air in there.... re-read manual a bit, discovered it says to loosen adjuster for top shoe on both sides on the rear brakes (assuming that should squeeze air out of that cylinder). So, I did that and then re-bled hydravac and all 4 wheels. SAME ISSUE! I have now bled about 1/2 gallon through the system! I am using a mighty-vac pump (I know, not the best.) I came in and re-read the manual real slowly... and noticed the first section is for pressure bleeding then the manual bleeding part is for NON-Hydravac brakes.

So, my question is, can I manually bleed the brakes with the Hydravac or do I need to pressure bleed them? (manual says to pressurize 25-30# and not let it fall below 20# at any point during the process!) If the answer is pressure bleed, no problem, I will build a bleeder.

Are you sure you have ALL of the brake shoes adjusted (all 4 wheels)? They need to have heavy drag when turning the tire by hand.

Mike B

I did not touch the adjustment on the front, I did adjust the rears though, and I had a good pedal before I started so, I am thinking I still have air in there somewhere. I will bleed either manually (not using the mighty-vac) or build a pressure bleeder and do it that way tomorrow night. I will also lift the front off the ground and make sure they are adjusted as well.

My main question is, can you bleed them without a pressure bleeder, or is it best to use one?

Did you follow the Shop Manual sequence for bleeding the Hydrovac and the brake lines? The sequence is different for Hydrovac trucks' brakes.

My 54 GMC 2-ton's HydroVac brakes would pump up but loose pedal (before/after a full rebuild/bleed of the brake system). I replaced the hydrovac and they then worked fine. I bled the lines following the Shop Manual sequence - and, I did three times/rotations of bleeding. Nice brakes, when they are working right.

yes, I followed the manual, I also adjusted the front brakes this morning as Mike B suggested but still have the same issue. I am going to make a pressure pot and pressure bleed them tonight. I'll report back, hopefully that all is well!

These don't lose the pedal as long as I keep pressure on it. They also had a good pedal before I started, just leaky rear wheel cylinders.

UPDATE: bled brakes with pressure bleeder, and now have a brake pedal. Let it set for 30 minutes nad I have to pump it once, then have a pedal. Question, looking at the manual, it shows to do both bleeders on the hydrovac, then it looks like LR, RR LF, RF BUT, the RR is the farthest away, so, is it LR, RR or RR, LR ?

No, the procedure/sequence-order is different with a hydrovac.

I follow the procedure in the Shop Manual.

so, hydrovac bleeder 1, then 2, then LR, RR, LF, RF is correct?

Where is the brake line "TEE" on the rear axle? If the rubber line from the frame to the rear is on the passenger side than the LR is the farthest away.

Mike B

the "tee" is on the driver side.... BUT, all the manuals I have (55 and 58) tell you the first wheel to bleed is LR then RR so, I am assuming that is the proper sequence (even though RR is a tad farther away)