URGENT question re brake/clutch fluid complete flush - clutch master cylinder rebuild

[LostinCanada]

Hey everyone, I've been happily driving my MP5 since the last major overhaul but it's time to deal with my annoying intermittent shift issues (diagnosed earlier) which I'm hoping will be resolved by rebuilding the clutch master cylinder (bought the kit from Mazda), replacing the flex hose from the reservoir-master cylinder, completely replacing the fluid and doing a post-maintenance clutch/brake fluid bleed.

I'd like to start the job today!

Questions:

1. I'd like to drain as much as possible from at least the top end of the system so that when I remove the clutch master cylinder I don't get fluid everywhere. I presume this means that at the very least the reservoir must be completely empty (due to gravity)?
3. What happens if you completely drain the brake/clutch system from the lowest points and start over with fresh fluid once the work is complete?
5. If this method is unwise, what is the best way to ensure that the entire system is replaced by new fluid? Won't the new fluid mix with the old if you empty the reservoir and top it up with new?
7. Does it matter if you bleed the brakes first or the clutch first once a major amount of fluid is removed? I have the Speed Bleeder (stainless) kit installed on all four calipers if that makes any difference.

Looking forward to tackling this new project and hopefully restoring 100% "smooth as butter" shifting....

Thanks!

Thanks for any comments!

 

[Keno1542]

clutch and brake master cylinders are one unit on our cars. So if you have a kit just to rebuild the clutch master, you have the wrong parts. I would look into that before tearing anything apart.

You want to try not to let the fluid drain from the system completely, because then it is a pita to get the whole system bled again. Most people will just cap off the lines to prevent as much fluid from leaking as possible while they work on the system.

The best way I think for a shade tree mechanic to replace the fluid completely is after you have completed changing the parts is to remove as much fluid from the reservoir as possible with a turkey baster, refill with fresh fluid, then bleed at the calipers and clutch slave till you see fresh fluid. Make sure you don't let the reservior run dry during the bleeding, or you will be having a long day bleeding all the air out of the system.

 

[Keno1542]

Also, you sure the master even needs a rebuild? I would try bleeding the system first before replacing any parts and see if that helps your situation.

 

[LostinCanada]

Keno1542 - thank you for your comments, however you are incorrect about the brake master cylinder and clutch master cylinder (perhaps because your signature indicates you're driving an MP3 which is a different car). There is a clutch master cylinder kit available from Mazda and I have elected to go this route as opposed to aftermarket new, which I have read can have issues. I certainly rue the day I bought aftermarket calipers from Mazda, instead of the rebuild kit I had originally selected. Diagnostics were accomplished during an earlier thread... just haven't had the time or reasonable weather to commence repairs.

Anyway.... Still looking for comments re my original questions? MrGiggles?

 

[Keno1542]

You are correct, they just share the reservoir. My mistake.

 

[MrGiggles]

As long as you don't hit the brakes with the reservoir empty, you shouldn't have to bleed them. '

The cleanest way to approach this would be to suck the fluid out of the reservoir with your method of choice, then disconnect the clutch supply line, empty the last bit into a container, and continue to remove the M/C. Keep in mind that brake fluid will eat paint if not cleaned off.

When you bleed the clutch slave, remember that air can leak past the bleeder threads, and the M/C can suck air on the up-stroke back through the bleeder. Because of this, I open the bleeder, then have a helper depress the clutch pedal and hold it at the bottom, tighten the bleeder, release the clutch pedal, and repeat. If it will gravity bleed, letting it sit and drip for a long time can help remove air as well. The same goes for brake systems.

Once you have the cylinder rebuilt, I would attach the supply line and cycle the clutch a couple times with your finger lightly over the clutch line hole. Let fluid out, but don't let air back in. This should prevent an air pocket from forming above the M/C, similar to bench bleeding a brake master cylinder.

If you want to improve fluid quality in any system, just bleed until clean fluid appears. Replacing the fluid in the reservoir does help, but if the fluid looks like used engine oil, you'll want to completely flush/bleed the system. My favorite tool for this is a pressure bleeder, but there are many different ways to accomplish the same goal.

 

[LostinCanada]

Thanks Mr. Giggles. My fluid is dirty but not that dirty - though still I'd like to fully flush the system if possible. I found this tool: http://www.princessauto.com/en/detail/powerfist-vacuum-pump-and-brake-bleeder-kit/A-p8050832e Is this along the lines of what you are speaking about? Can I do just as good of a job without it?

I'm wondering if I should flush the system completely first, and then do the cylinder rebuild? I bought two jugs of DOT3 on sale so don't mind "wasting" it to get a clean system.

I have the speed bleeders in the calipers so would only need an assistant for the clutch portion of the job, though I like the gravity bleed idea - provided I can keep the brake fluid away from critical surfaces. I'm well stocked with brake clean (the good stuff)!

Thanks for the pointers, and for any further comments!

 

[MrGiggles]

Thanks Mr. Giggles. My fluid is dirty but not that dirty - though still I'd like to fully flush the system if possible. I found this tool: http://www.princessauto.com/en/detail/powerfist-vacuum-pump-and-brake-bleeder-kit/A-p8050832e Is this along the lines of what you are speaking about? Can I do just as good of a job without it?

I'm wondering if I should flush the system completely first, and then do the cylinder rebuild? I bought two jugs of DOT3 on sale so don't mind "wasting" it to get a clean system.

I have the speed bleeders in the calipers so would only need an assistant for the clutch portion of the job, though I like the gravity bleed idea - provided I can keep the brake fluid away from critical surfaces. I'm well stocked with brake clean (the good stuff)!

Thanks for the pointers, and for any further comments!

It might be best to do the flush after the rebuild while the reservoir is empty.

Vacuum bleeders work pretty well. A pressure bleeder puts positive pressure in the system through the reservoir cap. Once pressurized, you just open each bleeder until clean fluid comes out. They're expensive and usually only shops own them, but I've seen them made out of garden sprayers. You can do the job without it, it'll just take longer.

 

[LostinCanada]

Thanks! When I did the calipers last year I decided to put the speed bleeders in so I didn't have to worry about having a bleeding partner, or cart around extra equipment. I think I'll make do with what I've got and do it in the order you suggest. Hopefully the rain isn't too bad tomorrow - I'm anxious to get going on this project after sitting on the parts for over a month.

I'll report back with pictures and feedback in case someone else wants to give this a go!

 

[LostinCanada]

OK I'm back! A note for anyone doing a rebuild, the 90 degree plastic elbow is not part of the kit recommendation but definitely worth replacing - it goes into the o-ring on the top of the M/C and is a b*tch to remove, separate from the o-ring and reassemble into the M/C. The o-ring can be bought alone, or as a set with the elbow - definitely go with the latter for the extra few $$. Have fun putting it back together!

Sorry - no pictures!

Took my reservoir off and flushed it completely. Then flushed all the brake lines one by one using my speedbleeders. Finally I did the clutch slave. Gravity feed didn't work for me. Got the air out of the lower line, but there wasn't enough pressure to get the fluid up and over the bend at the master.

Had lots of trouble with the bleed screw threads at the slave - had to torque the crap out of it on each session - my clutch assistant was hard to work with and the clutch bleed wasn't the best job. I wondered if anyone has ever installed a speedbleeder at the slave cylinder? Would there be any harm in doing so? Sure would make the bleeding process a snap and reduce errors if I didn't need an assistant.

I'm thinking of pulling the slave and rebuilding that next and then replacing the bleeder valve so any comments greatly appreciated. http://speedbleeder.com/

BTW I highly recommend these for the calipers! So easy and painless for bleeding. I've read that one may need to pull them occasionally to put new threadlock (after several bleeds) but I wonder if that comes from over torquing too often (I read about that being a problem too - instructions say don't over torque).

 

[MrGiggles]

OK I'm back! A note for anyone doing a rebuild, the 90 degree plastic elbow is not part of the kit recommendation but definitely worth replacing - it goes into the o-ring on the top of the M/C and is a b*tch to remove, separate from the o-ring and reassemble into the M/C. The o-ring can be bought alone, or as a set with the elbow - definitely go with the latter for the extra few $$. Have fun putting it back together!

Sorry - no pictures!

Took my reservoir off and flushed it completely. Then flushed all the brake lines one by one using my speedbleeders. Finally I did the clutch slave. Gravity feed didn't work for me. Got the air out of the lower line, but there wasn't enough pressure to get the fluid up and over the bend at the master.

Had lots of trouble with the bleed screw threads at the slave - had to torque the crap out of it on each session - my clutch assistant was hard to work with and the clutch bleed wasn't the best job. I wondered if anyone has ever installed a speedbleeder at the slave cylinder? Would there be any harm in doing so? Sure would make the bleeding process a snap and reduce errors if I didn't need an assistant.

I'm thinking of pulling the slave and rebuilding that next and then replacing the bleeder valve so any comments greatly appreciated. http://speedbleeder.com/

BTW I highly recommend these for the calipers! So easy and painless for bleeding. I've read that one may need to pull them occasionally to put new threadlock (after several bleeds) but I wonder if that comes from over torquing too often (I read about that being a problem too - instructions say don't over torque).

The only issue I see with the speed bleeders is that they don't address the issue of air being pulled back in through the bleeder threads. This can be remedied with thick grease or teflon tape though. On brakes it's not such a big issue since the master cylinder displaces a lot of fluid, but it will be more prevalent on something that moves a lot less volume, like a clutch master.

 

[LostinCanada]

OK I think I'm having this problem you mentioned MrGiggles - air past the threads.

I bought the rebuild kit for the slave, along with the speedbleeder. Everything came apart and went back together reasonably smoothly and I was very excited to try partnerless clutch bleeding. This initially went well - a mushy pedal for a long while and then pressure started to be building up smoothly with very little air. After half a jug of fluid. Then suddenly it felt like something let go and clutch was flat again. I only had the bleed screw just cracked but I tightened it and then cracked it slightly less. Finally had to get a ride to Lordco and bought two more jugs of brake fluid. Tried different combinations of bleed screw, even tried thick grease and went through another jug of fluid and a crap load of air. Now I've packed it in for the night.

No fluid leaking out anywhere else - I thought that maybe when I pushed the new piston cup/seal into the slave cylinder that maybe something happened to the seal but I don't see any fluid leaking out anywhere.

Does this mean I'm stuck with using clutch partners? I only have one jug of fluid left so I'm wondering if I should just replace the bleed screw with original and find a clutch partner that can follow instructions better than my last partner.

Thoughts? Anyone had any success with the speedbleeder option? Or was the lack of response to my earlier question because it just doesn't work?

 

[MrGiggles]

OK I think I'm having this problem you mentioned MrGiggles - air past the threads.

I bought the rebuild kit for the slave, along with the speedbleeder. Everything came apart and went back together reasonably smoothly and I was very excited to try partnerless clutch bleeding. This initially went well - a mushy pedal for a long while and then pressure started to be building up smoothly with very little air. After half a jug of fluid. Then suddenly it felt like something let go and clutch was flat again. I only had the bleed screw just cracked but I tightened it and then cracked it slightly less. Finally had to get a ride to Lordco and bought two more jugs of brake fluid. Tried different combinations of bleed screw, even tried thick grease and went through another jug of fluid and a crap load of air. Now I've packed it in for the night.

No fluid leaking out anywhere else - I thought that maybe when I pushed the new piston cup/seal into the slave cylinder that maybe something happened to the seal but I don't see any fluid leaking out anywhere.

Does this mean I'm stuck with using clutch partners? I only have one jug of fluid left so I'm wondering if I should just replace the bleed screw with original and find a clutch partner that can follow instructions better than my last partner.

Thoughts? Anyone had any success with the speedbleeder option? Or was the lack of response to my earlier question because it just doesn't work?

It probably won't leak externally. Fluid will just bypass around the piston seal and go back into the reservoir.

You might try putting the stock bleeder in, loosen it, depress the pedal and hold, tighten it, then release the pedal. Rinse and repeat.

 

[LostinCanada]

Well I cleaned up the stock screw and waiting for a bleeding partner.

I'm pretty sure if the piston seal inside the slave cylinder were to leak the fluid will fill the boot, and then eventually leak out onto the ground. I checked over the old seal - I suppose there is a slim possibility the lip of the seal could have folded over on itself upon insertion, but I put fluid on it and went slowly. So far no fluid obvious but it is difficult to pull back the boot once installed so I'm a little reluctant to do it unless I have to.

The piston looks different in the slave - the rod that pushes it floats externally inside the rubber boot between the lever in the transaxle and the piston cup with the seal. I was surprised - no corrosion inside the bore, though I cleaned out the bore with scotchbrite and all orofices with brake clean/q-tip. Somehow there was some black stuff when I was purging the clutch fluid. I'm surprised because the system was pretty much purged (brake side and clutch side) when I did the master cylinder a few weeks ago. Both flex hoses are reasonably new - the one to the reservoir is 3 months, the lower line is about 7 months old. The lower one blew on me, leaving me stranded.

Anyway. Fingers crossed bleeding will solve my issues. Wish I had some thread sealant but my friend will be here any minute.

 

[LostinCanada]

OK! Mission successful - simply had to bleed the system the old fashioned way.

Out of curiosity, my friend brought along a suction pump bleeder which I was reluctant to try because he's not the best about buying quality equipment or keeping his tools clean. However I am intrigued. Apparently you hook it to the bleed screw, crack the screw open and suction the fluid out. Anyone tried this method/type of equipment?

 

[MrGiggles]

You're correct, I thought you were referring to the master cylinder.

Vacuum bleeders definitely do the job.

 

[Ejstoy]

I've heard people pushing the clutch down propping it down all night. Would this help our cars? Fight these same intermitted clutch issues.