Bleeding 95 SC400 Brakes
 

Installing stainless braided hoses, started with the right rear and then went to bleed that corner. Using a hand vacuum pump at the caliper to extract fluid/air, but noticed that as soon as I loosen the bleeder screw enough to let fluid flow, it also starts to leak air around the thread, causing it to not bleed properly. Anyone else experience this?

Yes that’s a pain. That is why despite having good vaccum kits, I do brakes with either 1) two-person pressure system, or 2) gravity method. Or use the vaccum until you get clean fluid, then let it settle and let gravity finish it.

Gravity works just fine if you are not in a hurry. You can do them all at once as pressure is the same everywhere (Pascal’s Law). With any method, be really careful to not let the res. get low and get air into the ABS unit. That can be a nightmare to rectify depending upon the system.

That's what I'm doing now, letting them gravity bleed. How do you know how long you have to let them sit like that? How do you know it's done?

I went ahead and replaced the left rear hose as well. Have both rear bleeders open and they're both letting out a drop every 2 seconds or so.

when it’s clean. Tighten them up and pump the brakes, see if it feels firm and all air out. The bleed valve is at the very top of the cavity so if fluid is coming out, then all air should have been pushed out already.

Well, I let them drip for a while and then stuck a piece of clear tube onto the bleeder screws and saw just pure fluid coming out with no air bubbles. Tightened up both bleeders, got in the car and pumped up the brake pedal - feels good for now. Still need to do the fronts and a few other things before I can go for a test drive, but so far so good.

Good deal. Once you have the front done and all air out of the system, here’s a tip to keep from having to bleed them again for a LONG time:

Every summer, take the vacuum pump and suck out the contents of the fluid reservoir. Fill with clean fluid. Within a bit of driving, it will mix fully with the fluid all through the system. you will halve the water contamination and other contaminants and the pedal will firm right up. I’ve been doing this about 10 years and except for when I’ve broken open a system to put in SS lines or rebuild a caliper, all the brakes on all our vehicles are nice and responsive as they should be.

If draining/filling the reservoir doesn’t get you quite what you want, do it again. It’s a lot easier than bleeding and very effective.

I take the opposite approach. As long as you never open the reservoir, you pretty much never need to add or change brake fluid. Opening it to the atmosphere is what gets moisture in there...