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Brake Fluid Bleeding....Vacuum vs Pressure?

SoCal Angler
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SoCal Angler Enthusiast

SoCal Angler

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I've decided that I need a brake bleeder that allows the bleeding to be performed solo.

 

I have read about the Mity Vac (vacuum) , Motive (pressure), and Speedi Bleeder (pressure that uses your tires for the pressure...or an air compressor if you chose).

 

I am leaning towards pressure bleeding as I believe the opportunity for air/vacuum leaks is minimized between pushing fluid (pressure) and sucking (vacuum) fluid. 

The Speedi uses vehicle specific alum master cylinder adaptors.  The others use universal adaptors....I have read several instances where they leak.'

 

Does anyone have any experience with these tools, especially the Speedi?

 

I'll be starting my bleeding on an upcoming brake job on my 2018 Toyota RAV4.  In the future I would like to try it on my '23 GMC 3500HD 6.6L Gas model when that time comes.  I would need to purchase specific adaptor for it.

 

Are there any precautions on the '23 GMC HD trucks that need to be taken (ABS module, EPB, etc.)?

 

Thanks!

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Another JR Senior Enthusiast

Another JR

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I have a Motive power bleeder I bought for bleeding and replacing the brake fluid in my old BMW e46. I bought the specific threaded reservoir cap for BMWs. All the parts seemed to be of good quality. 
 

The instructions are to partly fill the pressure tank with brake fluid, connect it to the top of the master cylinder reservoir, pump it up to about 10-15 psi, and open the wheel cylinder bleed valves one at a time until you see fresh fluid. 
 

“Are they nuts!?!” was my reaction. Brake fluid under pressure in silicone tubing with hose clamps with a pressurized air reservoir behind it?  If any of the connections lets go you will ruin the paint job of every car in that garage with sprayed brake fluid. Plus even if it all goes well your power bleeder system is still a brake fluid mess. 
 

I used it differently. I did not put any fluid in the power bleeder, and instead just used its air pressure to force the fluid in the reservoir out to the wheel cylinders. I was careful to monitor and fill the reservoir each time it got down to about the 1/3 full level so as not to drive any air into the master cylinder. I had to refill maybe 3 times. This worked well and allowed me to flush the fluid myself.  I think a lot of people use it this way. 

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SoCal Angler Enthusiast

SoCal Angler

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Interesting…. Never considered the possibility of hose bursting.  Although 10-15psi is not much pressure, I suppose it’s a possibility, an ugly one at that!!  I haven’t read of any such disasters.

 

I guess you could drape a large beach towel over the pressurized fluid container while performing this procedure.

 

The Speedi Bleed is the unit I am considering.  It uses EPDM for air hose to tire.  The hose construction(into reservoir) is not mentioned.  However, I have seen some bleeders that offer Oiteker style clamps.  Perhaps a mod could be made to these pressure bleeders where quality hose and Oiteker clamps are used.  I use Oiteker clamps when I make up fuel hoses for outboard motors.

 

 

Edited by SoCal Angler
SoCal Angler Enthusiast

SoCal Angler

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Now you have me wondering if a vacuum system, such as the Mity Vac is better solution for eliminating a fluid catastrophe!  
 

I’ve read that vacuum systems struggle eliminating air from the system, especially around bleed ports.  Some have used silicone based grease around bleed port bases (threads) to eliminate air intrusion.

Another JR Senior Enthusiast

Another JR

Posted
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Instinct tells me pressure bleeding is better for the reason you said in your first message, but I have not used a vacuum bleeder. I agree a system bursting is very unlikely, but the consequences would be pretty bad. The method I use works fine and is fast. 

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SoCal Angler Enthusiast

SoCal Angler

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This was the second part of my first post......

 

Are there any precautions on the '23 GMC HD trucks that need to be taken when bleeding brakes...(ABS module, EPB, etc.)?

 

Will GM or other software be needed to perform a brake fluid exchange, as I have read about ABS needing software to allow for it to be bled or perhaps other situations during bleeding process?

 

Thanks!

bruceb58 Enthusiast

bruceb58

Posted
Posted (edited)

I just use a Motive pressure bleeder. Have ZERO worries about vinyl tubing bursting at only 15PSI. I use 25 to 30PSI since that is what is specified in the OEM service manual.

 

You don't want to use a vacuum type bleeder. OEM service manual only specifies pressure bleeder.

 

Edited by bruceb58
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bruceb58 Enthusiast

bruceb58

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Posted (edited)
On 3/27/2025 at 2:26 PM, SoCal Angler said:

Will GM or other software be needed to perform a brake fluid exchange, as I have read about ABS needing software to allow for it to be bled or perhaps other situations during bleeding process?

 

Thanks!

Only if you opened up the ABS system and/or introduced air into the system. Scanner tool has an Automated Bleed Procedure. 

Edited by bruceb58
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newdude Senior Enthusiast

newdude

Posted
Posted
On 3/27/2025 at 5:26 PM, SoCal Angler said:

This was the second part of my first post......

 

Are there any precautions on the '23 GMC HD trucks that need to be taken when bleeding brakes...(ABS module, EPB, etc.)?

 

Will GM or other software be needed to perform a brake fluid exchange, as I have read about ABS needing software to allow for it to be bled or perhaps other situations during bleeding process?

 

Thanks!

 

 

Parking brake is on its own on the HD and not a part of the rear calipers like on the 1500s so nothing to worry about there.

 

You "might" need to do an ABS computer bleed.  

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SoCal Angler Enthusiast

SoCal Angler

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When “might” that be needed?  Would it be fir the reasons mentioned by bruce58?

 

Also, which recommend DIYer scanners are able to perform this Automated Bleed Procedure?  I’d hate to be bleeding brakes only to find out that a scanner is needed and not have one.  It’s not something I’ll be performing anytime soon, but will in the future.

Edited by SoCal Angler
revrnd Senior Enthusiast

revrnd

Posted
Posted (edited)
On 3/25/2025 at 10:07 PM, SoCal Angler said:

Interesting…. Never considered the possibility of hose bursting.  Although 10-15psi is not much pressure, I suppose it’s a possibility, an ugly one at that!!  I haven’t read of any such disasters.

 

I guess you could drape a large beach towel over the pressurized fluid container while performing this procedure.

 

The Speedi Bleed is the unit I am considering.  It uses EPDM for air hose to tire.  The hose construction(into reservoir) is not mentioned.  However, I have seen some bleeders that offer Oiteker style clamps.  Perhaps a mod could be made to these pressure bleeders where quality hose and Oiteker clamps are used.  I use Oiteker clamps when I make up fuel hoses for outboard motors.

 

 

I'm not sure about elsewhere in industry, but we used Oetiker clamps on 3/8" & 1/2" air hoses. The air pressure was 90 psi & proper barbed fittings were used. So for the most part I dont think there is a problem w/ them.

 

Now the 'spring clamps' the OEMs have used over the years to replace worm gear type clamps in assembly of vehicles, might be a different story.

Edited by revrnd
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Another JR Senior Enthusiast

Another JR

Posted
Posted

I recognize it’s very unlikely for a hose or factory hose connection to let go. The attachment to the top of the master cylinder is probably the weakest link. I just didn’t see the need to take any risk of a big brake fluid spray event or to get the bleeder gear all covered with brake fluid when just watching the reservoir and refilling it did the same job. I started full for the farthest rear wheel, topped off for the other rear, and then topped off one last time to do both fronts. So two extra disconnect/reconnects of the bleeder to the master cylinder reservoir. Doing the refilling probably took no more time than cleaning up the bleeder would have taken. 

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SoCal Angler Enthusiast

SoCal Angler

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On 4/5/2025 at 9:17 AM, Another JR said:

I recognize it’s very unlikely for a hose or factory hose connection to let go. The attachment to the top of the master cylinder is probably the weakest link. I just didn’t see the need to take any risk of a big brake fluid spray event or to get the bleeder gear all covered with brake fluid when just watching the reservoir and refilling it did the same job. I started full for the farthest rear wheel, topped off for the other rear, and then topped off one last time to do both fronts. So two extra disconnect/reconnects of the bleeder to the master cylinder reservoir. Doing the refilling probably took no more time than cleaning up the bleeder would have taken. 

I'll probably be doing the same....just using the compressed air to push fluid out at bleeder ports.  I like vehicle specific machined aluminum reservoir caps that SpeediBled uses so I will be purchasing a Speedi...if they still let me, as they are made in Canada!!!🤣

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