Motive Power Bleeder and DOT 5 Brake Fluid

[Paul S.]

I completed my standard to power brake conversion Friday night, and am pleased with the end result but not the brake bleeding process I had to go through. Hence this post.

I have a Motive Power Bleeder and used it successfully in the past to flush and refill with DOT 4 brake fluid when replacing the master cylinder 3 years ago.

On my power brake conversion I decided to go with DOT 5 since everything would be new. To bleed, after bench bleeding the master cylinder, I hooked up the Motive Power Bleeder and it got fluid throughout the brake system easily--first time in my life that I ever filled a completely dry, new brake system.

All the big air bubbles were gone per normal (my rule of thumb is to run at least a pint through each bleeder screw, intermittantly closing off the bleeder when it looks clear/no air and beating on the caliper with a rubber mallet to force more air up and out).

The problem was that each time I re-opened the bleeder screw, I kept seeing a very short burst of tiny, tiny air bubbles followed by clear with no air fluid. Close the bleeder, beat, repeat and tiny bubbles again and again. The Motive Power Bleeder was pressured at 5 psi down to zero, which is barely gravity bleeding flow.

No matter what I did, the tiny air bubbles on opening the bleeder never stopped while using the Motive Power Bleeder and I used a ton of brake fluid (4 liters). I used about 2 liters just on the right rear caliper alone before deciding to move on to the other 3, and then go back to the right rear where I started. Same thing everywhere--tiny bubbles (and if Don Ho were still alive, I'd like to shoot him dead ).

After using up the 4 liters of DOT 5 brake fluid I bought from CSSB and going to NAPA to buy more, I figured I had to do something else.

Having no better ideas, I switched to gravity bleeding and then finished with the two-man old fashioned way. It worked--saw the tiny bubbles at the start of the two-man cycle at each caliper and then none. I'm not happy it came to having to enlist the aid of my neighbor to get my brake system bled.

My question is this: Has anyone successfully used a Motive Power bleeder with DOT 5 brake fluid, and if yes, how did you do it differently than I?

I knew to leave the DOT 5 brake fluid sit unmolested--mine came mail order from CSSB, and I unpacked and it sat in the bottles for 3 weeks while I was tearing apart and re-installing all new brake lines, ect...

I then filled the Motive Power Bleeder pouring as slowly and smoothly as possible and let the fluid sit in the bottle unpressured for hours. Used low pressure--with DOT 4 I always start at 10 psi, and this time with DOT 5, I used less than 5 psi which basically was enough pressure to keep the the master cylinder filled and the outflow at the bleeders was about what gravity bleeding produced.

In case I have to do some additional bleeding if more air works its way out of suspension in the fluid, I'd like to do that with the Motive Power Bleeder so as to not inconvenience my neighbor any further (and he got paid a case of beer for helping me out with the two man bleeding to get my car back on the road--I just prefer not to bother my neighbors with my car projects).

Tips, tricks, and advice appreciated from those who have used the Motive Power bleeder successfully with DOT 5 brake fluid.

[Mike M.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

for a case of beer, i'll bring me and my neighbor. seriously, i've had similar troubles bleeding DOT5 with my Phoenix injector brake bleeding system> With my bleeder, one can either push the brake fluid out or suck it out under vacuum. seems the vacuum method produces less air bubbles.mike

[Terry M.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

I can't help you because I don't have a Motive Power Bleeder. I have always wanted one, but then I have successfully flushed my daily drivers every two years for decades (DOT 3 & 4) without one. Only one of my fleet has DOT 5 (the 1970) and I gravity bleed that way back when. No air bubbles there ever; and I have flushed that (gravity again) once in a fit of analism after the first batch of DOT 5 was in there for two decades.

[Joe L.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

I completed my standard to power brake conversion Friday night, and am pleased with the end result but not the brake bleeding process I had to go through. Hence this post.

I have a Motive Power Bleeder and used it successfully in the past to flush and refill with DOT 4 brake fluid when replacing the master cylinder 3 years ago.

On my power brake conversion I decided to go with DOT 5 since everything would be new. To bleed, after bench bleeding the master cylinder, I hooked up the Motive Power Bleeder and it got fluid throughout the brake system easily--first time in my life that I ever filled a completely dry, new brake system.

All the big air bubbles were gone per normal (my rule of thumb is to run at least a pint through each bleeder screw, intermittantly closing off the bleeder when it looks clear/no air and beating on the caliper with a rubber mallet to force more air up and out).

The problem was that each time I re-opened the bleeder screw, I kept seeing a very short burst of tiny, tiny air bubbles followed by clear with no air fluid. Close the bleeder, beat, repeat and tiny bubbles again and again. The Motive Power Bleeder was pressured at 5 psi down to zero, which is barely gravity bleeding flow.

No matter what I did, the tiny air bubbles on opening the bleeder never stopped while using the Motive Power Bleeder and I used a ton of brake fluid (4 liters). I used about 2 liters just on the right rear caliper alone before deciding to move on to the other 3, and then go back to the right rear where I started. Same thing everywhere--tiny bubbles (and if Don Ho were still alive, I'd like to shoot him dead ).

After using up the 4 liters of DOT 5 brake fluid I bought from CSSB and going to NAPA to buy more, I figured I had to do something else.

Having no better ideas, I switched to gravity bleeding and then finished with the two-man old fashioned way. It worked--saw the tiny bubbles at the start of the two-man cycle at each caliper and then none. I'm not happy it came to having to enlist the aid of my neighbor to get my brake system bled.

My question is this: Has anyone successfully used a Motive Power bleeder with DOT 5 brake fluid, and if yes, how did you do it differently than I?

I knew to leave the DOT 5 brake fluid sit unmolested--mine came mail order from CSSB, and I unpacked and it sat in the bottles for 3 weeks while I was tearing apart and re-installing all new brake lines, ect...

I then filled the Motive Power Bleeder pouring as slowly and smoothly as possible and let the fluid sit in the bottle unpressured for hours. Used low pressure--with DOT 4 I always start at 10 psi, and this time with DOT 5, I used less than 5 psi which basically was enough pressure to keep the the master cylinder filled and the outflow at the bleeders was about what gravity bleeding produced.

In case I have to do some additional bleeding if more air works its way out of suspension in the fluid, I'd like to do that with the Motive Power Bleeder so as to not inconvenience my neighbor any further (and he got paid a case of beer for helping me out with the two man bleeding to get my car back on the road--I just prefer not to bother my neighbors with my car projects).

Tips, tricks, and advice appreciated from those who have used the Motive Power bleeder successfully with DOT 5 brake fluid.

Paul------


The phenomenon you describe is usually caused by air being drawn in around the bleeder screw threads when you first open the bleeder valve. It can usually be cured by applying silicone grease to the bleeder screw threads. In any event, I don't think it has anything to do with the Motive Products bleeder or the DOT 5 fluid as I have experienced it using neither.

[Jim L.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

Paul,

Your tale of woe suggests that the power bleeder might not be the best choice when working on a system with DOT 5 fluid. I've never used one, always having to resort to either gravity bleeding or tricking my bride into working the brake pedal. I've gotten perfect results with these two methods and never had to use even as much as a quart of fluid.

The key thing with DOT 5 is to do everything at a glacial pace. You did the right thing letting the fluid sit for extended periods. I suspect, though, the power bleeder action may have been too aggressive. Just a hunch.

Jim

[Dave S.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

Paul,
I have had exactly the same experience that you experienced. Like you i have a Motive pressure bleeder. I has happened to me on 3 different cars and I always thought I was the problem. In each case I put my wife in the drivers seat and had her push the brake pedal the old fashioned way. Mike's point about pulling the fluid rather than pushing it may be a good option the next time. I have given up on the Motive pressure bleeder with DOT 5 fluid.

[Paul S.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

Paul,
I have had exactly the same experience that you experienced. Like you i have a Motive pressure bleeder. I has happened to me on 3 different cars and I always thought I was the problem. In each case I put my wife in the drivers seat and had her push the brake pedal the old fashioned way. Mike's point about pulling the fluid rather than pushing it may be a good option the next time. I have given up on the Motive pressure bleeder with DOT 5 fluid.

That's what I figured--as far as pulling the fluid, I tried a Mitivac (Sears had it on sale for $30) and it wasn't worth a hoot and I will return it. It wouldn't hold a vacuum long enough to be any better than gravity bleeding.

[Paul S.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

Paul,
I have had exactly the same experience that you experienced. Like you i have a Motive pressure bleeder. I has happened to me on 3 different cars and I always thought I was the problem. In each case I put my wife in the drivers seat and had her push the brake pedal the old fashioned way. Mike's point about pulling the fluid rather than pushing it may be a good option the next time. I have given up on the Motive pressure bleeder with DOT 5 fluid.

That's what I figured--as far as pushing the fluid, I tried a Mitivac (Sears had it on sale for $30) and it wasn't worth a hoot and I will return it. It wouldn't hold a vacuum long enough to be any better than gravity bleeding.

[Terry M.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

That's what I figured--as far as pulling the fluid, I tried a Mitivac (Sears had it on sale for $30) and it wasn't worth a hoot and I will return it. It wouldn't hold a vacuum long enough to be any better than gravity bleeding.

In my post above I failed to mention that I use a shop-made vacuum tank to draw and contain the old brake fluid when I flush the systems on the DOT 3/4 equipped cars. I once tried this suction method on the DOT5 when I first installed it on the 1970. All it succeeded in doing was to draw the pistons into the caliper bore. It would not pull the fluid through the empty lines to the calipers. I have several theories why, but I gave up and used gravity for the DOT5. However, suction works fine for the DOT 3/4 equipped vehicles.

[Jim D.]

Re: Motive Power Bleeder and DOT 5 Brake Fluid

Paul,

Your tale of woe suggests that the power bleeder might not be the best choice when working on a system with DOT 5 fluid. I've never used one, always having to resort to either gravity bleeding or tricking my bride into working the brake pedal. I've gotten perfect results with these two methods and never had to use even as much as a quart of fluid.

The key thing with DOT 5 is to do everything at a glacial pace. You did the right thing letting the fluid sit for extended periods. I suspect, though, the power bleeder action may have been too aggressive. Just a hunch.

Jim

I've used the same method and had the same results as Jim on every car I've converted to DOT 5 (10+ cars). It's never taken a full qt. and the pedal is always rock hard.