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Amedee, Former ASE Master Tech
Category: Car
Satisfied Customers: 26455
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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Scion tc tc: Hello, I have been working on my 2006 Scion tcs

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I have been working on my 2006 Scion tc's manual clutch. About two weeks ago I ran into the classic clutch pedal sinking to floor. . . blah...blah. . .so, I have replaced both the Master and slave clutch cylinders. Bled out the system, success, back on the road smiling and driving. But, I felt to much free play in the clutch pedal so I decide to adjust a bit. All goes well, adjusted. Well, a little too soft of a clutch, so I decide to bleed, maybe, some tiny bit of air. This work was done at the level of the slave cylinder.
Now the problem. Well wouldn't you know it. . . clutch pedal sinks to floor again! Now, after not hours, but days of vacuum bleeding, positive pressure bleeding, helper assisted bleeding. . . I can not get enough pressure to keep the clutch pedal up? When doing the push the pedal and open the slave bled screw, I get tiny, tiny air bubbles. . . but I have been getting them for days. . . not generating the pressure. The original switch went smooth as glass. Helper did a few pedal pushes, open slave bleeder, fluid shoots out, repeat a couple times and finished. helper pedal pushes now, whether it be one or 20 pedal pushes creates NO fluid rush when slave bleeder is opened. . . . ? ? ? Could it be the brand new master clutch cylinder just installed two weeks ago failed?? I just can't believe it. There aren't any leaks that I can see, hear in the lines. I just dont want to take the whole system apart again, and redo. It doesn't seem to make sense to do also. Also, how the heck do I know if the master clutch cylinder has failed. The master that I removed appears to function properly, i.e., depress push rod and the is flow, depress rod and there is suction. . . same was for the old slave cylinder. I just replaced that because it was easy and made sense to do so since I was replacing the master.
OK, after all that description;
1) What do you think is going on here?
2) How do I know if a slave or clutch master cylinder has failed (when no external leaks are present, and I've looked hard and lifted all rubber boots)
3) Is there some other mysterious problem that will not allow the hydraulics to create the pressure need to engage clutch and keep clutch pedal off the floor?
4) help
Hello and Welcome to Just Answer!

My name is XXXXX XXXXX I can assist you with your question.

Have you tried bench bleeding or gravity bleeding the clutch master cylinder?

If you crack the bleeder on the slave cylinder, does fluid dip out?
Customer: replied 4 years ago.

Hello Amedee,


Yes, if bleeder on slave is opened fluid does drip out.

But, no, when I installed the Master clutch cylinder, I did not bench bleed it. And I'm guessing that soft clutch after the install was still some remaining air in the master cylinder.

Just, didn't want to take that master out again, that was a pain. But I'm also wondering/asking that because I didn't bench bleed the master, could that remaining air created a kind of lock-up in the master cylinders workings, and all the bleeding I've been trying since just compounded that trapped air?

YES! You got it!

Chances are it is either a bad new master cylinder or just air in the system. I would start by bleeding out all of the air in the system and rechecking it again.

You can get a special tool that will allow you to suck the air out of the system as this helps out big time. It is rather expensive but a shop in your area might just have this tool and may do it for you.

I don't think it is going to be the slave cylinder. The slave cylinder is only bad when it starts to leak fluid.
Customer: replied 4 years ago.

I should mention I vacuum bled the system. . . . well I suppose I could go in my garage and continue. . . but I have literally bled nearly a quart of brake fluid. Interesting that if I vacuum bleed when the clutch pedal is up, I bleed solid fluid (found that by mistake) but when I vacuum bleed with the pedal depressed (and a few pedal pushes) I get those microscopic air bubbles, not a lot, but really about 2 solid hours of bleeding over the last few days, there are fewer and fewer but i would have thought I would have gotten the pressure I needed by now, considering the master was full of air when installed. Without returning to this endless bleeding procedure would you say: because a few pedal pushes does not create that quick surge of fluid when the slave bleeder is opened like it did on the install is a good indication that the master has failed?

And thanks, XXXXX XXXXX all I will ask. . . just wanted to see if someone had the magic answer that would mean I didnt have to take the master out again. I will give you an excellent rating. Thanks.


Thank you for the extra detail.

One thing you might want to keep in mind, is that there could be an air leak in the system somewhere sucking air into the system causing this condition.

Double check the line and connections/fittings and threads on both ends from the master cylinder to the slave cylinder. I have a feeling something might be sucking air into the system.

If not, the master cylinder will need to be warrantied.

I hope this helps!
Amedee and 6 other Car Specialists are ready to help you
Thanks very much for the positive rating.

Have a great evening.