Brake Bleeding

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I've read that gravity bleeding is the safest way to bleed the brakes. However it may be time consuming and may not push out crap that is in the system.

So then there is pressure bleeding. Very effective and safe however it is limited to adapter sizes. Which does not work with all vehicles.

The old school pump and hold method, is bad for the master cylinder's seals because the plunger is required to travel further. Even putting a 2×4 wood block would still hurt the primary seals. One person method also falls in this situation.

Then we got the common vacuum bleeding with shop air connected to suck out the dirty fluid which sounds great. But some are saying it may be misleading because it sucks out air from the system however, if the bleeder screw of the fitting is too loose it may suck air around the bleeder screw. So what if we apply silicone grease around the fitting, make sure the hose has a tight connection, and crack the bleeder screw as little as possible, enough to suck the old fluid, would this method be effective enough to suck out all the air from the system? End results with firm hard pedal with no to little air left?

Any input on this?

Thank you for any constructive information.
 
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I've read that gravity bleeding is the safest way to bleed the brakes. However it may be time consuming and may not push out crap that is in the system.
Takes too long.
So then there is pressure bleeding. Very effective and safe however it is limited to adapter sizes. Which does not work with all vehicles.
Pricey to have the correct adapter for every application but is the best method, IMO.
The old school pump and hold method, is bad for the master cylinder's seals because the plunger is required to travel further. Even putting a 2×4 wood block would still hurt the primary seals. One person method also falls in this situation.
Does not hurt the seals as long as you do not allow the pedal to bottom out. Not sure where you heard this from, but it is the specified method in many factory service procedures. Also, the method is viable for removing air, but takes too long for fluid replacement.
Then we got the common vacuum bleeding with shop air connected to suck out the dirty fluid which sounds great. But some are saying it may be misleading because it sucks out air from the system however, if the bleeder screw of the fitting is too loose it may suck air around the bleeder screw. So what if we apply silicone grease around the fitting, make sure the hose has a tight connection, and crack the bleeder screw as little as possible, enough to suck the old fluid, would this method be effective enough to suck out all the air from the system? End results with firm hard pedal with no to little air left?
Hope you have a large enough compressor for vacuum bleeding. Those units use a lot of air. Also, you may need to allow the system to gravity bleed for a min (or do one manual bleed) in order to remove any air that may have been allowed in.
 

Luftmasse

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I appreciate this. Thank you.

As for where I got the information from pump and hold method is bad even with wood blocks underneath is from the internet searches. I feel that you can always learn new things everyday. So I got curious and searched.

I think I will stick with the suggestion you made about vacuum bleeding. 👍
 
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Yesterday I replaced brake hoses and two front calipers on a 2012 Forester. I let gravity and a clear hose do most of the bleeding, then followed up with the two man method, just to be sure. I put a block under the brake pedal to limit travel. No problems to report, and I've done it this way for a very long time. I think the master cylinder getting damaged by the two man method is because people ram the brake pedal to the floor, and to make matters worse don't use something to limit pedal travel.
 

pbm

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This thread is very timely for me because I just replaced the master cylinder and rear calipers on a recently purchased 2009 Rav4 and I'm having trouble getting a firm pedal despite a lot of bleeding. I did the 'bench bleeding' of the MC before installing it but the pedal is still softer than I'd like. I had my wife pumping the pedal so I'm not sure if it went to the floor but I'm hoping not since I'd hate to have damaged the new master cylinder seals. Any thoughts on why it's so hard to get this bleeding right? Any way of testing the MC to verify that the seals weren't damaged by my bleeding technique? Thanks

Will trapped air migrate toward the bleeder screw with use or does it stay put in the line?
 
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This thread is very timely for me because I just replaced the master cylinder and rear calipers on a recently purchased 2009 Rav4 and I'm having trouble getting a firm pedal despite a lot of bleeding. I did the 'bench bleeding' of the MC before installing it but the pedal is still softer than I'd like. I had my wife pumping the pedal so I'm not sure if it went to the floor but I'm hoping not since I'd hate to have damaged the new master cylinder seals. Any thoughts on why it's so hard to get this bleeding right? Any way of testing the MC to verify that the seals weren't damaged by my bleeding technique? Thanks
Has the car been driven?
 

pbm

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Has the car been driven?
Yes....and it's better than before the MC was changed but not perfect. We bought the car with the brake issue and I saw a 'Scotty Kilmer' Youtube saying that the MC was an issue on higher mileage Rav4's. I never drove the car before so I don't know how it felt when the brakes felt good.
 
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Yes....and it's better than before the MC was changed but not perfect. We bought the car with the brake issue and I saw a 'Scotty Kilmer' Youtube saying that the MC was an issue on higher mileage Rav4's. I never drove the car before so I don't know how it felt when the brakes felt good.
Is the pedal travel reasonable with the engine off?
 
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Yesterday I replaced brake hoses and two front calipers on a 2012 Forester. I let gravity and a clear hose do most of the bleeding, then followed up with the two man method, just to be sure. I put a block under the brake pedal to limit travel. No problems to report, and I've done it this way for a very long time. I think the master cylinder getting damaged by the two man method is because people ram the brake pedal to the floor, and to make matters worse don't use something to limit pedal travel.
Man that damage thing is a new one to me, I've been bleeding brakes since forever and I do change out the fluid every few years on all my cars. The person in the car is always my wife or one of my daughters and I wouldn't say they have been all that careful nor gentle with "down" when told to do so.

Wouldn't there be a mechanical stop on the pedal assembly to prevent damage to the master cylinder?
 

pbm

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Man that damage thing is a new one to me, I've been bleeding brakes since forever and I do change out the fluid every few years on all my cars. The person in the car is always my wife or one of my daughters and I wouldn't say they have been all that careful nor gentle with "down" when told to do so.

Wouldn't there be a mechanical stop on the pedal assembly to prevent damage to the master cylinder?

I'm glad to hear this....I don't have that much experience but the 'damage from pumping' without a 2x4 got me nervous...
 

Luftmasse

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+1 on the HF bleeder kit. If you have a compressor it works fast and no problems with bubbles from loose bleeder.

I always see bubbles when evacuating the brake fluid. You just feel like the bubbles will never go away. This is how this thread came about.
 
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I've read that gravity bleeding is the safest way to bleed the brakes. However it may be time consuming and may not push out crap that is in the system.

So then there is pressure bleeding. Very effective and safe however it is limited to adapter sizes. Which does not work with all vehicles.

The old school pump and hold method, is bad for the master cylinder's seals because the plunger is required to travel further. Even putting a 2×4 wood block would still hurt the primary seals. One person method also falls in this situation.

Then we got the common vacuum bleeding with shop air connected to suck out the dirty fluid which sounds great. But some are saying it may be misleading because it sucks out air from the system however, if the bleeder screw of the fitting is too loose it may suck air around the bleeder screw. So what if we apply silicone grease around the fitting, make sure the hose has a tight connection, and crack the bleeder screw as little as possible, enough to suck the old fluid, would this method be effective enough to suck out all the air from the system? End results with firm hard pedal with no to little air left?

Any input on this?

Thank you for any constructive information.
I've been using an OTC vacuum bleeder for years, and yes it doesn't matter if you are leaking a few bubbles around the threads of the bleeder screw. It's all about moving fluid through the system, and quickly is preferable. Some bleeder threads are too loose and pull more air, than fluid. So you just put some Teflon tape on the threads to make a better seal is all. Been bleeding brakes for years by myself, and have lots of other tips if anyone cared. I also have a pressure bleeder too, that is sometime necessary.
 
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I've read that gravity bleeding is the safest way to bleed the brakes. However it may be time consuming and may not push out crap that is in the system.

So then there is pressure bleeding. Very effective and safe however it is limited to adapter sizes. Which does not work with all vehicles.

The old school pump and hold method, is bad for the master cylinder's seals because the plunger is required to travel further. Even putting a 2×4 wood block would still hurt the primary seals. One person method also falls in this situation.

Then we got the common vacuum bleeding with shop air connected to suck out the dirty fluid which sounds great. But some are saying it may be misleading because it sucks out air from the system however, if the bleeder screw of the fitting is too loose it may suck air around the bleeder screw. So what if we apply silicone grease around the fitting, make sure the hose has a tight connection, and crack the bleeder screw as little as possible, enough to suck the old fluid, would this method be effective enough to suck out all the air from the system? End results with firm hard pedal with no to little air left?

Any input on this?

Thank you for any constructive information.
If the vehicle has ABS you may need to bleed the ABS unit, this is usually done with a scan tool although some (not many) ABS units have a bleeder screw on top.
No need to spend big money on OE scan tools for this job, this one will do the job and can be found online cheaper than the retail price.
Not to be confused this with an OE tool or high scanner it isnt but it is more than good enough for most DIY jobs.

 
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It can be done by a single person (I do it myself) and with no special tools in most cases, just use a long enough clear tubing and lift it above bleeding screw enough so when fluid goes back in there is no air going back. Chris Fix has a video on this.
Eric the car guy had a point in one of his videos where he bleeds closest to master cylinder caliper first to get most of old fluid out followed by farthest and the rest.
It's actually very easy to do.
 
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I always have a helper while bleeding so I don’t have to worry about doing it anyway other than the old school way. And I start furthest from the master cylinder like what is recommended and it works every time for me.
I've done it with and without a helper over the years. If my wife is around I have her step on the brake. The old school way hasn't let me down yet.
 
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