Let sleeping dogs lie or prevent a problem?

[bkirk]

I have been slowly but consistently updating components on my 99 Z3 Coupe. At first it was typical service items, tires, air filter, oil change and filter, fuel filter, spark plugs, plug boots, and brake pads, etc. Then I got a bit more aggressive and replaced all the belts, hoses, cooling system pipes, CCV system, and radiator.

My plan now is to replace the rubber brake hoses and to flush the brakes lines with new brake fluid. I may replace or rebuild the wheel calipers, but I got to thinking about the master cylinder. It doesn't leak and doesn't appear to have any obvious problems, but then again neither did the cooling system and I replaced it out of an abundance of caution, given the chance of catastrophic engine failure. Should I consider replacing the master cylinder given that it is 21 years old too?

The job doesn't look all that difficult to swap in a new one. Given that I plan on rebuilding or replacing the calipers and bleeding the brake system, now seems to be the right time to consider this "while I'm at it" expansion of the to do list. Thoughts?

[gtwhimself]

Stainless steel brake lines

[ProductUser]

The brake system isn't a weak point (e.g., known failure) with the Z3 from time spent on this board. Unless there are signs of a failure, I would leave them alone.

[KBH22102]

I check to make sure the calipers are all still sliding smoothly when I inspect the brake pads. If they are sticky, then obviously they need to be serviced. I changed to braided lines when I recently refurbished the M roadster, but it was likely more out of vanity than need.

[bkirk]

I check to make sure the calipers are all still sliding smoothly when I inspect the brake pads. If they are sticky, then obviously they need to be serviced. I changed to braided lines when I recently refurbished the M roadster, but it was likely more out of vanity than need.

I've already ordered the stainless steel lines and that is also likely for vanity sake. Whatever I do with the calipers will likely be 1/2 for maintenance and 1/2 for appearance sake. I'm not dying to mess with the master cylinder, it was just a thought given that I have to bleed the brake lines regardless and I might as well tackle the whole system at one time....still not sure.

[Randy Forbes]

I've already ordered the stainless steel lines and that is also likely for vanity sake. Whatever I do with the calipers will likely be 1/2 for maintenance and 1/2 for appearance sake. I'm not dying to mess with the master cylinder, it was just a thought given that I have to bleed the brake lines regardless and I might as well tackle the whole system at one time....still not sure.

If you leave the m/cyl alone, it'll be a lot easier to bleed the circuits after reassembly. I'd avoid letting the entire system drain completely, by capping the steel pipes when you remove the rubber hoses (rubber caps are typically supplied with the better s/s-Teflon hose sets).

While bleeding a system that's had air introduced is not impossible, it can prove to be a challenge if you don't have the means to cycle the pump and valves. Why make the extra work for yourself?

[bkirk]

If you leave the m/cyl alone, it'll be a lot easier to bleed the circuits after reassembly. I'd avoid letting the entire system drain completely, by capping the steel pipes when you remove the rubber hoses (rubber caps are typically supplied with the better s/s-Teflon hose sets).

While bleeding a system that's had air introduced is not impossible, it can prove to be a challenge if you don't have the means to cycle the pump and valves. Why make the extra work for yourself?

Good input Randy, I have a Motive pressure system to aid in flushing the lines, but will take your advice about capping the lines when I remove them for replacement.

When I rebuild or replace the calipers, is there any way to pre-fill the caliper portion with brake fluid, or just bleed them as usual until air is out?

[Mr Bingley]

You install the calipers in the fully compressed position, so there is nothing to fill. To be clear, the concern, and the thing to avoid at all costs, is allowing the system to drain to the point that air is introduced into the ABS pump. If this happens, you will need to be able to cycle the pump through a bleed routine, which requires computer access to the controller. The power bleeder is a nice tool, but it will not address that problem.

[Randy Forbes]

Good input Randy, I have a Motive pressure system to aid in flushing the lines, but will take your advice about capping the lines when I remove them for replacement.

When I rebuild or replace the calipers, is there any way to pre-fill the caliper portion with brake fluid, or just bleed them as usual until air is out?

I suppose you could, but I've never bothered to try. As long as you don't forget about the fluid level in the reservoir, I'll leave the bleed screw open of the caliper I just mounted while I'm mounting the opposite side's caliper. Once I see the fluid start to drip out, close that one and move on to the next. Just remember to keep an eye on the reservoir...

It helps minimize the tension while waiting for the fluid to appear when you actually do go to bleed them (that was the entire extent of my entire bleeding procedure on an old Suburban I used to have)!

[bkirk]

I suppose you could, but I've never bothered to try. As long as you don't forget about the fluid level in the reservoir, I'll leave the bleed screw open of the caliper I just mounted while I'm mounting the opposite side's caliper. Once I see the fluid start to drip out, close that one and move on to the next. Just remember to keep an eye on the reservoir...

It helps minimize the tension while waiting for the fluid to appear when you actually do go to bleed them (that was the entire extent of my entire bleeding procedure on an old Suburban I used to have)!

The ABS is reason enough alone to not mess with the master cylinder. Working on the hoses and calipers sound straightforward and not a whole lot different than other cars I've worked on. I've wanted a Motive system for the tool cabinet for a while, this was just an excuse to get one.

[LannVouivre]

Doesn't the INPA setup via the electrical diag thread have the capability to bleed the ABS components? I haven't ever checked... I guess I do have my laptop right here, though.

[solimans]

Yes it does...it cycles through the process with instructions along the way....

“Press the peddle 80%”
“Release peddle”
And so on...

What is 80%? Don’t know


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