OK,

I have a 01 5spd with the BlehmCo BBK with 300Z calipers on it. Today the brake light would not come off pulling out of driveway. I do a quick check and ebrake is working ok.

I checked under the hood and the brake fluid is low. At the min line.

I cant seem to find any leaks at the calipers, either end of the "new" SS lines or in the engine bay. My car has left no fluid stains anywhere, so I topped off the fluid, light goes out.

Here is my question: Where in the heck did it go? It cant evaporate...so where did the fluid go? This is perplexing me...and a bit scarey.

 

Maybe it's getting into your vacuum booster.

 

Could you clarify how it could get in there and what possible steps necessary to see if I have fluid in an area it should not be?

I have no pedal problems, brakes are still VERY tight. I am at a loss here...

 

It could be seeping out of the bore of the master cylinder into the booster where it's bolted together. Sometimes the fluid is drawn into the vacuum side of the booster and burned in the engine. Look inside your brake booster vacuum hose for any dampness and check the bottom of the master cylinder where it attaches to the booster for any dampness.

 

clutch master cylinder...check for a leak down your clutch pedal and/or on your driver's carpeting. I had the same problem...CMC was leaking. You will have to bleed the brakes if the fluid level gets below the brake line feed in the master cylinder, so make sure you keep filling it up until you find the problem.

 

check your pad thickness too...

as your pads get thinner, more fluid is used to keep pushing them out....

 

I thought about that late tonight...but these pads only have like 2K on em...if they are worn..HOLY COW! Although I do have the 300Z calipers, so maybe it could be in there since there is way more caliper "area"? Maybe?

So, you had missing brake fluid, but it was your clutch that was leaking? Is the clutch and brake reseviour combined somehow? Not sure I follow how that could happen....? Perhaps a little more explaination for my feable mind...

BTW, I put fluid in right away...I only drove 100 yards or so. And the fluid still had about 1/2" when I put it back in the drive way.

 

oops...sorry not paying attention

though the brake master cylinder can leak the same way......

 

No problem dude...I have a feeling its going to be a weird thing thats the issue, and your suggestion followed that path. Ah well, back to the research. Although I will look to see if I see leaking in the footwell. You never know!

 

If the MC is leaking, usually you won't see it, since it will be inside the vacuum booster. you might be able to pull off the hose running from the booster to the engine and see if there's any fluid in there.. if it is, then you've got a bad seal in the MC.

If not, check the calipers again for leaks. the places that it would leak would be around the pistons themselves, and you might have to pull the calipers off or at least remove the pads to see that.. should be enough room if you just pull the pads off and check things out. look for any sign of fluid leakage there. I replaced all of those seals with new ones after I got the calipers back from the powdercoater, so I know the seals *should* have been good.. If that's the case, I can work with you on a solution, but you should be okay in the mean time to keep driving the car- just keep a bottle of brake fluid on hand and watch it. the caliper isn't going to suddenly fail and you have no brakes- ruptured seals will just slowly leak and not cause catastrophic failure.

 

OK, Ill check that hose on the vacuum booster. Ill have to bust out my ECM in order to know what I am looking at, and where that hose is located.

IF the calipers are leaking (at least 6oz worth of fluid) would that not leave SOME kind of fluid stain on my rims, versus just some small gunk buildup on the caliper pistons? I guess I am going to have to pull the rims and calipers tonight to check into that area.

Master cyclinders. Never had to futz with them. How hard are they to work on? Are they repairable...or do I have to do a remove and replace? Man, this is the WRONG time for the car needing money....

 

The master cylinder isn't really hard to change. The most difficult part would probably be bench bleeding it. I would not try to repair it at all. A brand new one is your best bet. Sometimes they come without the reservoir and you have to reuse your old one.

 

what he said.
they usually sell rebuild kits, but I wouldn't mess with one myself. back in the day, they had brake cylinder hones and the master cylinder pistons were large enough to be honed out and new seals put in, but they're so small now (plus they're aluminum), so they don't do well with honing. if it's leaking, just replace it. the extra money is better spent on peace of mind. you have to completely remove the MC anyway to rebuild it, so you might as well just replace and be done.

that's assuming it's gone bad. heck my car is 10 yrs old with 215k miles on it and the MC is still in good shape.

 

Yeah, but thats back in the day when they were not cutting corners everywhere trying to make a buck. I really REALLY hope its something silly, cause I aint got the bucks to replace a MC.

 

http://www.trademotion.com/partlocat...=1&catalogid=2
About $155

 

Look inside the car. Where the brake MC enters the firewall. Pull back the carpet/pad and see if there is a fluid leak down the firewall.

 

Just in case I "have" to replace the MC....who has done it to kinda give me the Cliff Notes Version of the hard spots. Someone mentioned bench bleeding, which is a new term to me.....

Thanks for the info!

Colonel

 

Bench bleeding is the process of putting brake fluid in the MC reservoir and bleeding the air out before installing it on the vehicle. If you don't have a bench vise, you can do it on the car. If you don't get all of the air out of the MC before bleeding the rest of the system, you will have trouble getting a hard pedal. Make sure you use flare nut (line) wrenches to loosen and tighten the brake lines. Be extremely careful around your paint when working with the MC and brake fluid. Cover your fender and strut tower to prevent ruining your paint from spilled or splashed fluid. The hardest part would probably be removing and replacing the reservoir if you bought just the MC. It's hard to pop out sometimes and you may feel like it's going to break.

 

I dont have a bench vise...but I have a pressure bleeder, would I be able to make that work? I am trying to visualize how it works. The pedal attached operates the vaccuum booster...how do you "bench bleed" it...whats the process in more specifics versus just removing air from it.

I have flare wrenches, used em for my caliper SS lines assembly. I also have a fender mat.

Could you explain further the r/r the resevoir? From the basic diagram, looks like its "bolted" on...is there some kind of friction fit somewhere on it as well?

Thanks for the info...

 

Why does this "MC" not look like the diagram above? Is this just a piece used to r/r in that "bulb" shaped object?

Is this the actual MC, and the bulb piece the vacuum booster? Not purchasing here...just trying to get an idea on the parts and such.

 

yeah, the reservoir sits on top and has the filler cap. It is detachable.

 

You have to carefully pry the reservoir off with a large prybar or screwdriver with a rag wrapped around it to protect the plastic. It fits inside those black rubber rings in your picture. It pops/snaps into it. You can use some brake fluid or a little liquid soap to help install it.

 

I have done the in car inspection. There is some kind of rubber mat on the actual steel. There is no fluid anywhere that I can find on the inside of the car.

In the diagram above on the vaccuum booster, there is a nipple/hose hook up on the right side. I am assuming that this is the hose I am supposed to check for fluid. Its bone dry..not a hint or trace of anything that I can see. I did not check the other end. The hose did make a large sucking noise as I removed it from the booster.

I removed the front left caliper and all looks good.

Sigh..

Brake fluid...where art thou?!?!?

 

try having someone pump the brakes while you check all the calipers/MC/other hardware for leaks...

 

I pulled all four calipers and checked for signs of leakage. I found none.

Basically how I checked was pull the calipers, and move the pads off. I then looked for ANY dampness around the piston area. I took a Q-tip and wiped around the seal (as it had accumulated some brake dust. But thats all it was...brake dust.

I am at a loss here.

 

I would still think that it's leaking out the back of the MC bore into the vacuum booster. Anywhere else would probably show signs of leaking by now. The only sure way to tell is to remove the MC and check the bore for dampness.

 

Hmm, that will have to wait until the weekend. And if I have it apart just to check the bore, I guess it would make sense to have a MC around to r/r. Just in case.

Once I pop off the MC, I am looking in that "hole" in the middle to see if any fluid has accumulated at the bottom of the bulb? Correct?

Sigh. I just dont have cash laying around right now, but I dont want to 1/2 *** it either. Grrr

Thanks for the inputs guys....

 

Yes, you are looking at the hole in the rear of the MC for any dampness. I hope you have found your leak source by now.

 

For those that are interested, I did not remove the MC yet. I check the fluid every morning and evening now, waiting for the level to go down. So far nada. I am beginning to wonder if I

• Forgot to fill it up all the way on last rebleed
• Did not fill it properly from the get go
• loosing my mind.