two person brake bleed question

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Hi all...I want to flush the brake fluid on my 95 Maxima. The factory service manual outlines the two-person brake bleed method. Of course, when the brake is pumped and held down, opening the valve will cause the pedal to go all the way to the floorboard. I have done this procedure a few times in the past on this car but have always wondered if this is really OK for master cylinder components etc. After all, you are pushing it well past where it normally stops. I have also read some folks place a block of wood or similar material under the brake to limit travel but not sure if this is because they had the same concerns and is there really a difference between then going perhaps halfway between normal stop point and the floorboard?. I also saw several youtube videos about the one person bottle method but never really understood why the old fluid that is pushed into the bottle filled with clean fluid doesn't also suck the mixture back into the brake lines. Finally, I really don't do this often enough to buy a MityVac. I would assume the Nissan engineers have thought all about this before describing the two-person method in the manual but thought I would get some thoughts here too. My other thought was perhaps to open the bleeder valve just a bit and then close before the pedal hits the floorboard.
 
The two person brake bleed put the most pressure on the system to force air out.

If they designed so that when the pedal went all the way down it somehow ruined the master cylinder by pushing it father than designed how would that look. You break a brake line, pedal goes to the floor and ruin master cylinder??
 
Motive Power Bleeder
1 person, quick, works every time.
I used to use ATE blue. You could easily tell when the line was flushed and all new fluid with the switch from amber to blue.
But someone caught on, got upset that brake fluid was blue, and put a stop to sales in the USA.
Even with amber fluids though, you can pretty much tell when new fluid has filled the line and caliper.
 
I use the one person, hose in bottle, push the pedal yourself method with no problems. YMMV. Chris Fix and others have YouTube examples.

The possible master cylinder damage is hypothesized as corrosion on the metal parts going past where they normally go and damaging rubber seals (what I read). The block under the pedal is an easy thing to do for "just in case".
 
Pressure is the key. That doesn't mean the brake pedal has to go all the way to the floor either. Use something to stop the pedal from going that far down (2x4, brick, etc).
 
I've heard of damaging MC from doing this, but always wondered if it was an old wife's tale, or if only possible on really old stuff. And if it's not correlating something unrelated--sometimes things just up and die, and there is no connection. For instance, the fact that you had the windshield changed the day before the MC failed doesn't mean the MC failure was caused by the new windshield. Just because you changed brake fluid and the MC failed a week later doesn't automatically mean you damaged the MC.

Heck, if you put new pads onto a car, one of the things you do is push the piston all the way in. Doesn't the pedal now go to the floor until the piston is pushed out to its new position?
 
No it's not an old wives tale. Master cylinders that have been in service for a long time can fail pushing the pedal all the way to the floor because the pedal does not normally go all the way to the floor board. Have ruined a couple myself over the years. If I do a two man bleed, I use a piece of 4x4 block under the pedal.
 
To change the fluid you can just open a bleeder one at a time and let the old fluid run out. Keep pouring new into the reservoir. No need to press the pedal at all.
 
Have always done the 2 person method with pedal to the floor. 0 issues. More vehicles than I can count and over many years.

Do what makes you comfortable though.
 
Originally Posted by BigD1
No it's not an old wives tale. Master cylinders that have been in service for a long time can fail pushing the pedal all the way to the floor because the pedal does not normally go all the way to the floor board. Have ruined a couple myself over the years. If I do a two man bleed, I use a piece of 4x4 block under the pedal.

If that is the case then why does a 4x4 work? Wouldn't it be any travel past what is normal thus catching the seal on the ridge that is formed?
 
Originally Posted by mk378
To change the fluid you can just open a bleeder one at a time and let the old fluid run out. Keep pouring new into the reservoir. No need to press the pedal at all.


If you're replacing a caliper that works great, but if your flushing out old fluid that would take a long time. I guess if you were by yourself it would be ok, but everybody knows one person that you can do the two person method. Took me approximately 20 minutes to do my S10 with a helper.
 
I always pushed right to floor or right to the throttle (motorcycles), never had a problem, but always opened the bleed vzlve before pushing, and closing it before releasing.

My brother uses the one man, hose in a bottle half filled method, but I had issues where air got back through the bleeder thread when releasing. So, I only do 2man from there.
 
Speed bleeders are awesome
smile.gif


I used Russell speed bleeders on my 96 I30 with great success
 
Originally Posted by NissanMaxima
I really don't do this often enough to buy a MityVac.


How much does a brake fluid change at the dealer cost? Probably more than the MityVac.
 
Been doing it like that since my dad's 1972 Dodge Dart back in the late 70's/early 80's and no damage to the MC or components.
 
I have the plastic MightyVac. I've had it for a lot of years and am surprised it's lasted this long. It worked better on my old Honda without ABS. You definitely have to do a lot of pumping to draw out enough fluid on vehicles with ABS for some reason, but it still gets the job done. My favorite method is still the two-person method. The kids always seemed to enjoy pushing the brake pedal while I turned the bleeder screws and said, "up...down...up...down."
 
FYI:
Changing brake fluid yourself is great, but it does NOT swap out the fluid in the ABS module.

For my hondas I go to the dealer, and they are supposed to have this super secret tool that opens up the ABS module.

Any after market tools to do so for DIYers?
 
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