Bleeding the Master Cylinder

[ConfederateTyrant]

I was looking under my hood and noticed that my master cylinder has a covered screw, similar to the ones on calipers. Is this a bleed screw? If so, can I bleed it via gravity bleeding?

One more question. When gravity bleeding, air can't get in the system as long as the master cylinder does not run dry and as long as the brake pedal does not get pumped, correct?

Here's what I planned to do:
1. Open bleeder screw on master cylinder (if mine has one) and allow to drain, while adding clean fluid, until fluid draining is new looking.
2. Open passenger-rear bleeder screw, and allow to drain, while adding fluid to master cylinder, until fluid draining is new looking.
3. Repeat 2 for driver-rear wheel.
4. Repeat 2 for passenger-front wheel.
5. Repeat 2 for driver-front wheel.

All input is appreciated.

 

[labman]

Bear in mind, if you slip up and let the master cylinder go dry, you may create a real problem fixing something that wasn't broke.

 

[JAYCEE]

I have noticed that it is hard to start a gravity bleed sometimes. Harder if the fluid has been neglected. A good way to start the gravity bleed on neglected brakes is to do a 2-man bleed at first for each bleeder valve. That seems to blast the garbage out and allow for an easier gravity bleed.

If you have no possible way to do the 2-man method for each bleeder, you might try driving the vehicle to heat the fluid.

 

[ChrisW]

that screw is a 'stay' screw sorta like a set screw to prevent the bore/cyl from coming out when dissasembling the m/c. at least thats how they were in my brakes and susp class.

 

[Laminar Lou]

Tyrant:

I just did a brake bleed last weekend with this:

Motive Power Bleeder

It was a piece of cake. Someone from another forum suggested that I use ATE Super Blue racing fluid. Not because it is a great fluid (although it is), but more for the fact that it has a bright blue dye in it. It makes it easy to figure out when you get all the old fluid out. On the next brake flush I will just use regular fluid and alternate back and forth.

I had zero problems with the motive product and would recommend it. Just make sure that you get the right one. I had to get the "import" adapter to fit my Tundra. I think the whole process took 45 minutes, but the next time I think it will take half that time now that I know what I am doing.

I had 5 drain points so make sure you catch all of them!

 

[Laminar Lou]

quote:

---

Originally posted by ConfederateTyrant:

Here's what I planned to do:
1. Open bleeder screw on master cylinder (if mine has one) and allow to drain, while adding clean fluid, until fluid draining is new looking.
2. Open passenger-rear bleeder screw, and allow to drain, while adding fluid to master cylinder, until fluid draining is new looking.
3. Repeat 2 for driver-rear wheel.
4. Repeat 2 for passenger-front wheel.
5. Repeat 2 for driver-front wheel.

All input is appreciated.

---

I assume that your master cylinder is on the driver's side, right? If so your order is correct. The theory is farthest from master cylinder to closest (but it looks like you already knew that - just making sure)

 

[mechtech]

Gravity bleeding works well.
I would do the wheel cyls., and leave the master cyl. alone unless you have a definite problem there.

 

[kgb007stb]

Yup, that is my next project on my car, will be using ATE brake fluid, will be using motive products. Hey are you getting ready to flush you PS system???

 

[ConfederateTyrant]

Thanks for the responses everyone, I'll leave that screw on the master cylinder alone.

kgb007stb, I'm still in the early Auto-RX stage, but hopefully within the next month or so I will flush the power steering fluid. I just posted a response on that thread.

 

[bdcardinal]

certain cars, bleeding the master is par to fhte proper bleeding procedure. i know for my 98 mustang GT, the proper procedure is master, RR, LR, RF, LF, master, RR, LR, RF, LF. but on a lot of hte fords there are 2 bleeder screws on teh master. i just do it with a Vacula and a resivouir on top of the master that automatically refills.

i use the vacula on almost every car i work on and hardly ever have a problem.