Thread: Bleeding brakes

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I'm putting new brakes on my '32 in the front. How can I determine what fluid is in the car now so I can get compatible fluid?

Thanks in advance.

Don't try to match it. Purge it all and refill. Brake fluid is hygroscopic (absorbs water). Your current brake fluid probably has absorbed some water, so get rid of it. It's not expensive and you're putting on new brakes. Why not go all the way? I would use DOT 3. DOT 4 and DOT 5.1 have higher boiling points, but they may not be compatible with the rubber-like elastomers in your current system.

Thanks, I was thinking the same thing. I wasn't looking forward to draining the master cylinder and lines when it's so hard to get to. An under car master cylinder is great for a clean firewall, but...

Guess I'll put the time in and do it right.

Thanks again.

Ocezam, you can use a "turkey baster" to suck out the fluid in the MC (go get one at the Dollar Store or WallyWorld - don't use Mama's from the kitchen or you'll be buying HER a new one . Yes, lesson learned, in spades!). Then you can refill the MC with new DOT 3, and purge your lines, wheel cylinders & calipers. A vacuum bleeder is a neat way to do it, but my "old school" way is to get about 18" of vacuum hose that fits tight over the bleeder fitting, put about an inch of new, clean fluid in a clear jar or bottle, and starting at the wheel farthest away from the MC hook up the hose, let the hose hang into the bottle with the open end submerged and loosen your bleeder. Pump and release the pedal until the fluid coming out is clean. You may be surprised how nasty the old fluid is.... Just be sure that you keep that MC reservoir filled and you can simply close the bleeder and you're done.

Just one way to do it, and maybe not the best way.

Originally Posted by Henry Rifle

Brake fluid is hygroscopic (absorb water). Your current brake fluid probably has absorbed some water, so get rid of it.

I agree. I'm currently getting my old 46 Coupe ready for some serious cruising this summer and noticed the brakes felt a little soft. I flushed the system with new DOT 3 fluid and the pedal is now nice and tight. There didn't appear to be any air in the system, but the fluid must have degraded with time.

I use a home built pressure bleeder for my under car MC. I have a couple of high points in the plumbing that make it difficult to bleed any other way.

Mike

Originally Posted by rspears

Ocezam, you can use a "turkey baster" to suck out the fluid in the MC

This was/is my plan to drain the MC. However, there is only an inch to an inch and a half clearance between the MC and the floor. I doubt I can get a baster in there. It'll be a day or two before I'm ready to do this, but I'm thinking I'll have to get some tubing to clamp or glue to the baster to suck it out. I may need to fill the MC that way also, unless somebody has an alternate suggestion?

A quart mason jar, with two pieces of steel tube soldered into the lid.

One goes to the bleeder screw and the other a vacuum source.

I use a vacuum pump for refrigeration service, but I wonder if the intake manifold vacuum would be enough? You'd need about ten foot length of vacuum tubing, but it might work.

I'll try it next time I do brakes. Might be easier than grabbing that heavy a$$ vacuum pump

You might consider fabricating a new master cylinder lid or ordering one that already has remote fill capabilities, some pretty neat looking stuff out there.

Heres another easy way You could braze on a elbow on a old lid and put it on the master cylinder, get a old pump up sprayer and take off the wand and use hose clamps to clamp the hose to the elbow, fill the sprayer full of brake fluid and pump it up, put small hoses on the furthest bleeder first and crack it with the hose in a jar to collect the old fluid, the pressure will force the fluid all the way through (make sure sprayer always has plenty) and go through all the lines, unhook the sprayer and suck out a small amount so you can remove your modified lid and put your old lid back on, your done. Ok I wish I could take claim to this but I bought a power bleeder from Summtt and thats basically all it is, go to there web site and look it up if you want. best of luck Matthyj

I'd cut an access hole in the floor with enough room to remove the lid from the MC anytime you need to check/add fluid, especially if it's a glass car?

Originally Posted by rspears

I'd cut an access hole in the floor with enough room to remove the lid from the MC anytime you need to check/add fluid, especially if it's a glass car?

Roger, you read my mind as I was typing. I did that with my 1930 A-bone. It saved a lot of work.

Originally Posted by rspears

I'd cut an access hole in the floor with enough room to remove the lid from the MC anytime you need to check/add fluid, especially if it's a glass car?

Yeah, if I were building from scratch, definitely. And yeah, it's glass. But time is my enemy right now. Too many projects and not enough time. Heck, the Nationals are coming to Pueblo in a couple weeks, I don't want to miss it.