Bleeding brakes lines M37? still has bubbles

[scubaasteve]

I replaced pads and wheel cylinders all around a few months ago. I do have brakes now,,,but a very soft pedal. This weekend with holiday company I blead the system once around. Also starting at the drivers side rear wheel.

I still have air bubbles (quite a bit) esp. coming from both rear wheels. For some reason this doesn't seem to be happening from the front.

Is it possible I need a new maste. Previous owner says no.

Steve Maritn

'53 Dodge M37, stock brakes.

[Clint Dixon]

I replaced pads and wheel cylinders all around a few months ago. I do have brakes now,,,but a very soft pedal. This weekend with holiday company I blead the system once around. Also starting at the drivers side rear wheel.

I still have air bubbles (quite a bit) esp. coming from both rear wheels. For some reason this doesn't seem to be happening from the front.

Is it possible I need a new maste. Previous owner says no.

Steve Maritn

'53 Dodge M37, stock brakes.

Just as a personal observation, I have never been able to completely bleed brakes on ANY vehicle with just one lap around the circuit. I always do three or more laps - whatever it takes to get that last air bubble out. I waste a lot of brake fluid this way but it gives the system a good flush. Also, I recheck the level in the master cylinder after bleeding each wheel cylinder. Once the level gets too low and sucks air, you find yourself starting over.

[scubaasteve]

Yeah my post is'nt well written. I should have explain the system seem to be well bleed several month ago. Let me just try bleeding the crap out of it with a partner again. Yeah..I always top of the master after 3 or 4 valve releases at a given wheel cylinder.

I"ll give an update soon. Sorry about the poor post.

[Desoto61]

Are they adjusted properly? That can make the pedal seem soft.

How are you bleeding the brakes? Some of the vacuum systems will introduce air bubbles through the bleeders.

I'd also check all the connections. Could be sucking in air at one of the joints.

[Clint Dixon]

Yeah my post is'nt well written. I should have explain the system seem to be well bleed several month ago. Let me just try bleeding the crap out of it with a partner again. Yeah..I always top of the master after 3 or 4 valve releases at a given wheel cylinder.

I"ll give an update soon. Sorry about the poor post.

Not a poor post at all.

Did the system seem well bled immediately before or immeditely after you replaced the shoes?

I ask because I worked on a guys Power Wagon that did not have any apparent air left in the system, but he had an overwhelming spongy feel to the pedal after installing all new brake parts. I discovered that the lower adjusters were way out of spec and was causing only the heals of the shoes to contact the brake drums with a big gap remaining at the toes. All the sponginess that was felt was the shoes and drums flexing as the gap between the toe and drum decreased as additional pedal pressure was applied.

This, of course, would not cause air bubbles in the system, but is something to keep in mind when considering the big picture.

[Kaiser2boy]

If the person doing the pedal work is pumping rapidly it will make millions of bubbles that need quite a while to settle down. So you could bleed it and two days later get more out after the tiny bubbles gather together. Pump it up very slowly and smoothly.
This may sound stupid but have you seen any wet spots on your back plates or any sign of seepage?
You mentioned PADs, does the truck have disc brakes? Not that that matters but if it does and you did not do it you know some one has been doing a lot of work , hopfully right.

[scubaasteve]

thanks for the replys. truck has drums all around. yeah I was pretty careful that the new shoes contacted the drums top and bottom after installation.

as I recall yeah the thing was bubble free all around last august. anyhow, I'm going to try again. what I think I've learned:

1. pumping three strokes for each bleed to build up pressur is helpful. But perhaps don't pump fast as per the reply above.

2. Pumping via the master cylinder will give greater pressure and therefore velocity to remove bubbles. vs a pressure bleed kit.

3. I still intend to configure and use a pressure bleed kit. I used to own one that I used on 1980's mercedes diesel not that long ago and a pressure bleed system does avoid the sometime aggravation of troubling a variety of disinterested parties in pumping your brakes.

while I do believe all my wheel cylinders, being new, are intact, it is possible for whatever reason the master cylinder is damaged and somehow causing bubbles, but let me give it another good bleed.

steve, of Dallas texas