Any master cylinder reservoir upgrades?

[Supercharged111]

Why is that? Is it a different dot fluid? Or are the lines just newer and different material?

Not sure really. My guess is that, because the truck once had 10+ year old fluid in it, there's enough crap sticking to the innards that it'll always be that way. Or maybe the reservoir lid doesn't seal as well as new?

 

[SUBURBAN5]

Could be. My wife buick brake fluid is clear. It's a 12.. always wondered that

 

[Schurkey]

It would be so much easier to build a pressure bleeder if it were a round screw on cap.

Huh?

1. Why are you "building" a pressure bleeder? You aren't thinking of using one of those crappy garden-sprayer things, are you?

2. Adapters are readily available for the open-top plastic reservoirs. They're intended to pressurize the master cylinder without pressurizing the fragile plastic reservoir. Branick 39CG, for example. (I have a somewhat different style, came off a Tool Truck, I don't know who made it. KD, perhaps.)

 

[LA2SD]

I haven't seen any adapter plates for bleeding the GMT400 that don't involve wing nuts and chains.

I looked up the Branick adapter, and it doesn't look any different.

 

[Schurkey]

Mine has a pair of rubber straps. Sorta-kinda tarp-strap stuff. And there's a single connection to the fluid tank, so I can bleed both sides of the master without having to re-connect the pressure hose.

Whoever made mine must have gone out of business. I can't find anything like it on the Web. I got it in the late 1980s.

Even with chains...how often are you going to connect the bleeder? Doesn't seem to me to be a real "deal-breaker".

I own a "real" pressure bleeder, and I haven't used it in three years, because I gravity-bleed most of the time. 'Bout the only time I use a pressure bleeder is when I'm flushing old brake fluid. Yes, I'm over-due for brake fluid flushes on all my vehicles. Probably have a Flush Party next spring.

 

[LA2SD]

Yeah, bleeding or flushing the system isn't something we do all that often.

But those adapter plates with the chains and wing nuts really do suck lol.

I have a motive pressure bleeder and it's version of the chain adapter plate. The most I can pressurize the system before the plate starts leaking is 13 PSI. It works, but ideal PSI would be between 15 and 20 IIRC.

I haven't tried gravity bleeding...

 

[Schurkey]

I have a motive pressure bleeder and it's version of the chain adapter plate. The most I can pressurize the system before the plate starts leaking is 13 PSI. It works, but ideal PSI would be between 15 and 20 IIRC.

I don't have much good to say about Motive garden-sprayers. They're inexpensive (good) but they don't separate the fluid from the air used to pressurize them (bad).

What really concerns me here is your mention of a "plate". I'd like to see a photo, or a link. I'm concerned that you're pressurizing the plastic reservoir, instead of pressurizing the metal body of the master cylinder. The plastic reservoir was not designed to be pressurized, which is why the proper adapters fit down inside the inlets to the master, not on top of the reservoir.

"Ideal pressure"? Enough to move fluid out the bleeder screws. I typically only use ten or twelve psi, and I can't remember ever using more than 20 deliberately--on ANY vehicle I've pressure-bled. Early in my career, I was warned about using too much pressure--the chances of spraying brake fluid all over paint are too great.

I haven't tried gravity bleeding...

Pressure bleeding involves a lot of set-up and take-down time--you've gotta find the pressure bleeder, haul it out of the garage to the vehicle, piss 'n' moan with those chains to strap the pressure lid on the master cylinder. Then pump up the bleeder tank. And then do all that in reverse to put the equipment away. But the actual bleed time is very fast; you can blow a LOT of fluid very quickly through all the bleeder screws. Heck, you can have more than one screw open at a time.

Gravity bleeding is just the opposite. You grab a wrench or socket-and-ratchet, collect a drain pan...open a bleeder screw, and wait for the fluid to dribble out. If you're replacing a wheel cylinder or brake hose--something towards the end of the brake hydraulic system--you're not going to need to bleed quarts of fluid, so the very short set-up and take-down time is nice, even if you have to wait for the fluid to flow enough to move the air out. Once in a while, you pop the cover off the master, and top off the fluid.

 

[Supercharged111]

I don't have much good to say about Motive garden-sprayers. They're inexpensive (good) but they don't separate the fluid from the air used to pressurize them (bad).

What really concerns me here is your mention of a "plate". I'd like to see a photo, or a link. I'm concerned that you're pressurizing the plastic reservoir, instead of pressurizing the metal body of the master cylinder. The plastic reservoir was not designed to be pressurized, which is why the proper adapters fit down inside the inlets to the master, not on top of the reservoir.

"Ideal pressure"? Enough to move fluid out the bleeder screws. I typically only use ten or twelve psi, and I can't remember ever using more than 20 deliberately--on ANY vehicle I've pressure-bled. Early in my career, I was warned about using too much pressure--the chances of spraying brake fluid all over paint are too great.



Pressure bleeding involves a lot of set-up and take-down time--you've gotta find the pressure bleeder, haul it out of the garage to the vehicle, piss 'n' moan with those chains to strap the pressure lid on the master cylinder. Then pump up the bleeder tank. And then do all that in reverse to put the equipment away. But the actual bleed time is very fast; you can blow a LOT of fluid very quickly through all the bleeder screws. Heck, you can have more than one screw open at a time.

Gravity bleeding is just the opposite. You grab a wrench or socket-and-ratchet, collect a drain pan...open a bleeder screw, and wait for the fluid to dribble out. If you're replacing a wheel cylinder or brake hose--something towards the end of the brake hydraulic system--you're not going to need to bleed quarts of fluid, so the very short set-up and take-down time is nice, even if you have to wait for the fluid to flow enough to move the air out. Once in a while, you pop the cover off the master, and top off the fluid.

I've had excellent luck with my Motive bleeder, but I only use it to pressurize the system because I don't want to aerate the system. I know there's still risk of aeration, but I only use 10psi and depressurize as slowly as possible. I've used it on both trucks, the Envoy, Camaro, and Corvette with good results. YMMV. The real bleeders like what you have are $$$$.

 

[LA2SD]

I don't have much good to say about Motive garden-sprayers. They're inexpensive (good) but they don't separate the fluid from the air used to pressurize them (bad).

What really concerns me here is your mention of a "plate". I'd like to see a photo, or a link. I'm concerned that you're pressurizing the plastic reservoir, instead of pressurizing the metal body of the master cylinder. The plastic reservoir was not designed to be pressurized, which is why the proper adapters fit down inside the inlets to the master, not on top of the reservoir.

"Ideal pressure"? Enough to move fluid out the bleeder screws. I typically only use ten or twelve psi, and I can't remember ever using more than 20 deliberately--on ANY vehicle I've pressure-bled. Early in my career, I was warned about using too much pressure--the chances of spraying brake fluid all over paint are too great.

Here's what I use on the OBS. When I referenced the ideal PSI, I was going off of memory. The factory shop manual must have been referring to a professional pressure bleeder, like what you have.

Aside from the universal adapter plate, the motive bleeder worked fine. Depressurizing takes a bit of finesse, so that you don't overfill the reservoir with fluid, but one can get the hang of it.

Good advice though. I need to replace the front calipers, so I won't pressurize the bleeder to 13 PSI next time, and see how that works out.

You must be registered for see images attach

 

[Schurkey]

1. That style pressure adapter shouldn't be used on the GMT400-style plastic reservoirs.

2. Doesn't the Motive bleeder have a shut-off valve in the pressure hose somewhere? If not, it shouldn't be too hard to add one. Shut off fluid flow, then release the pressure adapter. No over-filled reservoir.

3. The problem with "garden sprayer" bleeders is not that they don't "work". The problem is that they contaminate the new fluid by exposing it to the compressed air--and the humidity in that air. The fluid is wet before you even pump it into the master cylinder.