Changing brake fluid

[Stallion]

I think it is about time I do this. How would you drain and put in new brake fluid? By what means would you accomplish this?

Thanks!!
TR

 

[pws69]

I think it is about time I do this. How would you drain and put in new brake fluid? By what means would you accomplish this?

Thanks!!
TR

Use a PRESSURE BLEEDER!

 

[Bob Chadwick]

TR,

Without a lift this is a PITA. I paid $70 to have it done for me. I tried first and concluded that this would be money well spent.

Bob

 

[Stallion]

What is a pressure bleeder and how does it work? And what exactly do you do with it?

 

[Bob Chadwick]

Three ways to bleed the brakes that I am aware of; gravity, pumping the pedal and using a pressure bleeder.

With gravity you let gravity drain the fluid from the system.

With pumping you have an assistant pump the pedal and hold it steady when you open the bleeder allowing the fluid to move through the system.

A pressure bleeded turns the pumping method into a one man job. I think most connect to the bleeder and suck the fluid out when you open the bleeder. I have read about those that fit on the top of the master cylinder and push the fluid through the system as well.

If you take it to a good shop, they will pressure bleed the system.

I bought a $20 pressure bleeder and was not happy with the job. That's why I took it to the shop.

 

[Stallion]

Wouldn't the gravity method be easiest and cheapest though? :confused

 

[pws69]

Three ways to bleed the brakes that I am aware of; gravity, pumping the pedal and using a pressure bleeder.

With gravity you let gravity drain the fluid from the system.

With pumping you have an assistant pump the pedal and hold it steady when you open the bleeder allowing the fluid to move through the system.

A pressure bleeded turns the pumping method into a one man job. I think most connect to the bleeder and suck the fluid out when you open the bleeder. I have read about those that fit on the top of the master cylinder and push the fluid through the system as well.

If you take it to a good shop, they will pressure bleed the system.

I bought a $20 pressure bleeder and was not happy with the job. That's why I took it to the shop.

Actually, you covered 4 ways. The method you mention that you connect a vacuum pump to a bleeder is NOT pressure bleeding. I have a couple of those and I hate them for bleeding!

Gravity certainly works to a degree, and it is very slow. It's cheap and handy when your system is in top shape. I like the pressure method because it FORCES the fluid (and any of the yukkies mixed in) out of the system under pressure. Gravity will NOT do this!

I have an ancient pressure tank which I updated with new hoses and adapter plates. It's sweet! You can build one out of a Nylene bottle (i.e. small pump sprayers, etc.) and a few parts.

 

[Bob Chadwick]

Gravity is not at efficient as getting all the gunk out of the lines either.

 

[MaineShark]

As the others have said, gravity is very slow, and does little to remove contaminants.

Vacuum works, but the maximum pressure you can develop is 1atm (14.7 psi). And, in reality, the vacuum pump is not perfect, so you won't develop that much.

Pressure allows you to force the fluid out with a much greater force.

Pumping the brakes will also achieve a similar effect, but be prepared for a major workout (try pushing your brake pedal with the vacuum booster empty, and then multiply by many pumps).

Also, if you do end up switching to silicone, remember that you will need to chemically flush the lines, before adding the new fluid.

Joe

 

[Steve Grodin]

You should remove all of the old fluid from the master cylinder before doing a brake fluid change. Use something like your wifes turkey baster.

 

[kenwa]

I'm with bobchad. I took mine to my mechanic and had it done for $65. My car has ABS and I didn't want to chance messing up the system. The ABS pump costs hundreds to replace. You probably don't have ABS on your C3 though.
The shop used a pressure bleeder attached to the master cylinder. The process gets brake fluid all over the wheels though, so they washed the whole car for me.
Ken

 

[Stallion]

You should remove all of the old fluid from the master cylinder before doing a brake fluid change. Use something like your wifes turkey baster.

Wouldn't that be part of the draining? Wouldn't you get everything out of the whole brake system, including the master cylinder? Why wouldn't those ways (like gravity) get the fluid out of the master cylinder?

 

[Steve Grodin]

Wouldn't that be part of the draining? Wouldn't you get everything out of the whole brake system, including the master cylinder? Why wouldn't those ways (like gravity) get the fluid out of the master cylinder?

You want to start the flushing of the brake system with FRESH brake fluid. I'm talking about DIY projects. I assume a professional shop wouldn't flush a brake system with old fluid in the MC.

 

[Stallion]

You want to start the flushing of the brake system with FRESH brake fluid. I'm talking about DIY projects. I assume a professional shop wouldn't flush a brake system with old fluid in the MC.

I don't think I'm understand. When you drain the brake system, I assume that you take all the fluid out of it. And this would be the previously used brake fluid. And then wouldn't you just fill it up with new fluid?

 

[kenwa]

The brake fluid is forced out through the bleeder valve at each wheel, with fluid refilled as necessary to keep the master cylinder from running out of fluid. This is to keep air out of the lines.

It's probably necessary to refill the master cylinder after each wheel is done.

 

[MaineShark]

I don't think I'm understand. When you drain the brake system, I assume that you take all the fluid out of it. And this would be the previously used brake fluid. And then wouldn't you just fill it up with new fluid?

Generally, you remove the fluid from the master cylinder resevoirs, then put in new fluid. You push the new fluid in, and it pushes the old fluid out, ahead of it.

Yes, there is some mixing, but it's not enough to matter - the fluid is thick and doesn't "swirl" much in the lines. Particularly not when it's under pressure.

Again, though, if you want to switch to silicone, you need to flush the old fluid out with a flushing agent, or the two fluids will mix and turn to goo.

Joe