in short, '93 R1, minor mods...

the clutch master cylinder went out, i replaced that with OEM and rebuilt the brake master cylinder while i was at it. i've bleed the system (brake and clutch) very well.. a few times.

here is what happend and whats wrong.

after i started the car up the inital time, it idled fine, typical tiny smoke at startup and i heard a sucking noise... sure enough the rear(firewall side) portion of the fluid housing was almost dry. enough to make me rebleed the system again. after the 2nd bleed-job i ensured proper levels of fluid(and during the rebleed-job), i decided to start the car again and the thickest, white smoke came pouring out of the exhaust with minor fluid(that i could see) and the gd fluid was almost dry (both sides now) again!.

so for the 3rd time... i rebleed and start the car, the muffler sounds muffled/clogged now, i rev the motor up to 6k and the car backfired, shooting a 4' (yes, four foot) spray of fluid out of the exhaust and my muffler sounded normal/free again.

the fluid it left has to be the clutch/brake fluid, there is no other fluid i can think of that would even vanish and show up in a V pattern behind my car.

so what i'm wondering if what could i have done wrong when i replaced these parts? i replaced the clutch master cylinder, rebuilt the brake master cylinder, replaced the two brake vacume hoses(both booster side and manifold side).
i'm using DOT4 fluid.

i really am stumped, i'm looking for anything right now. i just cant figure out how the brake fluid can shoot out of the exhaust. any ideas?

 

you must have done something wrong with the master cylinder rebuild, if the vaccuum of the engine sucks the fluid right out of it

 

IIRC there is a brake boost hose check valve. Have a look there.

Dave

 

i did; replaced that hose with a new oem hose.

 

It sounds to me like:

Somehow, the diaphragm (or a seal in the diaphragm to the rod) in the brake booster vacuum chamber has failed, and/or a vent on the master-cylinder side of this chamber is blocked, and you are sucking the brake/clutch system dry (pulling fluid from the master cylinder) through the vacuum chamber.

It doesn't sound like anything is wrong with the check valve, since it is letting air be sucked into the intake manifold, and trying to create a vacuum in the brake booster, as it should.

Also, cooljerk187 could be right, it could be partially the master cylinder's fault.

 

Yeah. The only way brake fluid could enter the engine is if the master cylinder has massively failed and leaks fluid into the brake booster. The engine then sucks it out through the vacuum hose. Pull one of the brake booster vac hoses and see if it's wet inside from brake fluid. I'm sure it will be.

The rear seal on the brake master cylinder must have completely failed where the actuator connects. Something was not right with your rebuild of the brake master cylinder.

The check valve in the line from the UIM does not have anything to do with your problem. Even if it were good, bad or backwards it can't cause this.

 

Dunno if it's possible, but if you somehow hooked the fluid line for the clutch master cylinder (it draws fluid from the brake master cylinder's reservoir) to the vacuum booster line, the engine would suck the fluid straight into the intake manifold.

That's the only way I could see this happening. I've NEVER heard of such a massive failure of the brake master cylinder and brake booster.

Dale

 

UUUUUUUUMMMMMMMMMMMMMMM.....................

 

i'm with dale. double check your hose routing for the brakes cylinder, booster and clutch lines. hit us up when you figure it out. curious... if you turn it on agin does it still suck it all out?


Carlos

 

It wouldn't require failure of the booster, only failure of the rear seal in the master cylinder. Given that the problem didn't exist until he rebuilt his master cylinder it's highly likely that it is his problem. He could have made an error in the rebuild or he could have been supplied with the wrong seals.

The master cylinder is the culprit because it's the only piece of the car between the fluid reservoir and the engine and the problem began only after he monkeyed with it. I'm sure he's going to find fluid pouring out the back if he removes it again.

You've been around long enough to know that if you're fixing something and something else acts broken immediately after you're done you somehow screwed it up without knowing. I cling to this maxim completely whenever something doesn't act right after I've been working on it. 95% of the time I prove it right!

 

It's possible but very, very hard to do. The hose from the booster would not reach to the reservoir where the clutch connects. Also keep in mind the reservoir is seperated so that if the clutch has a massive hydraulic failure you wouldn't lose all your fluid and thus your brakes to. Even if the engine vac were connected to the clutch line it couldn't empty the reservoir completely. Only way that can happen is by losing it through the brake master cylinder.

 

Dale, hope I didn't **** you off - I assumed you were joking. If you weren't, sorry for the razz.

 

The hose on the brake booster has a check valve in there to prvent boost pressure from entering the brake power booster chamber. Even if you replaced it with the wrong hose (it would still allow the vacuum to pull on the brake power booster) Unless you drasticly failed at the brake master cylinder rebuild I would find it increadible that the brake power booster could draw the fluid from the masted cylinder resivoir through the booster and into the vacuum line. If that is what happened then you need to pull the mastercylinder off of the power booster and see if fluid did travel that path. is there brake fluid in the hose on the brake power booster hose ??? It should be dry. Is there fluid in the area where the push rod enters the brake master cylinder ???? It should be dry. Brake fluid tends to work on rubber and paint pretty well so if this is a real possiblillity then hose replacement and power booster replacement is down the road. Jack

 

DaveW - no sweat . Hey, it could happen .

I just realized from re-reading the post that he rebuilt the master himself. IMHO, this is a WAY bad idea. I've tried on a number of occasions to rebuild hydraulics on FC's (clutch master, clutch slave, and brake master). It NEVER worked for me. I ended up burning a LOT of time, re-bleeding the system, etc, and had a failure in a very short order.

IMHO, *NEW* hydraulics are ALWAYS the way to go. There is quite a bit of pressure in the system, and even a tiny fault or leak will cause a major problem. Considering the amount of time spent re-bleeding brake hydraulics, you're way ahead of the curve putting in a known good new part.

Get a new brake master coming and huck the old one before you continue your troubleshooting.

Dale

 

the master cylinder rebuild wasn't "hard".

i popped off the C-clip, removed the internals, noticed in what direction the parts were going... inserted the new parts in the same order. now if i didn't do something else right... that was the point of failure.

i asked mazda to overnight a new brake cylinder. i'll have it today and will report back after i install it.

Some asked if I saw fluid in the brake-vac line. Yes I did. I thought it should ALWAYS be dry. Never any fluid... But there was a small amount of brake fluid.
because there is fluid in the hose.. i'm with a few of the other guys and blaming my brake cylinder rebuild. oh well, just throw enough at the car and it'll get fixed, right?

I'll change the fluids in the car, as well as the hoses (winter stuff). Though I'm wondering... Will the brake fluid that is in the motor/intake hurt the car? If it sits for 2 days.

 

just make sure the brake fluid dosn't stay on the paint. get that cleaned off at least. i wouldnt' worry about the engine. i doubt it'll do anything... may even clean it out inside for you hahaha.


carlos

 

You probably still have a problem with the booster diaphragm (torn, perforated, etc.) - vacuum should not be able to get to the master cylinder, since the diaphragm separates the vacuum chamber from the master cylinder.

 

Hmm, it may actually be a great thing for removing varnish and carbon buildup. However, I'd still dump a bit of MMO in (by the plug holes or UIM) and crank it to be safe.

Dave

 

It was probably a combination of both (master cyl and diaphragm) being bad that allowed your problem to happen. That's why it's apparently not very common.

 

You can still start the car up and run it for awhile without the brakes working. Just plug the vacuum hose and run the car if you want you cna use one of the small vacuum line to th UIM and let it suck a small amout of MMO into the engine to lube it back up, the brake fluid will deffinately be removing some carbon and oily build up from the engine. Just be ready to add more throttle when the oil hits (make sure the car isn't in the garage) !!!! Mucho smoke.

 

okay; here is what i've done so far...

i took the brake booster off, it was full of fluid, after getting it all out (all of it) i cleaned the booster up, installed the oem-new master cylinder and bled it.

there was at least 20oz of fluid in the booster :P
which says to me "Bad master cylinder rebuild!".

i did let the car run without the brakes being hooked up and it took about 45mins for the car to stop smoking. keep in mind that i'm doing this all at 11pm with a full apexi-n1 exhaust (no cats or res), very loud at even idle ;]

i'll let ya know how this turns out.

 

Did you inspect the diaphragm while you were cleaning it? Did it have any tears or perforations?

I'm asking because I can't see how this could have happened unless it did.

Hope everything is OK after this.

 

If the diaphram in the brake booster is torn it will act as a vacuum leak. Start the engine and let it idle. Step on the brake pedal (master cylinder not installed is ok) and see if the idle stumbles. Better yet attach a small vacuum pump to the vacuum connection on the brake booster and pull a vac. See if it holds. If the booster can hold a vac you'll need to replace it as well.