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clutch bleeding problems, bad master cylinder?

This is a discussion on clutch bleeding problems, bad master cylinder? within the 2.4L LE5 Performance Tech forums, part of the Engine Technical Discussion category; edit: Just to be very clear car is a 2006 cobalt ss/na 2.4 5 speed So I just replaced my ...

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Old 12-29-2012, 08:42 PM   #1
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clutch bleeding problems, bad master cylinder?

edit: Just to be very clear car is a 2006 cobalt ss/na 2.4 5 speed

So I just replaced my clutch the other day, boy was is a pain in the ass doing it on my garage floor. After a couple hiccups I buttoned it up the other day and have attempting to bleed the clutch for about 3 days now. First a little background, parts I installed are:

KY stage 1 clutch
Exedy lightweight flywheel
NEW TOB from KY, not sure of company but its OE specs

Followed the how-to on here pretty closely and help from a friend on here got it done. Everything is currently hooked up except the fuse box/pcm so I have more room to work on bleeding.

At first I tried the manual method with a buddy (clutch in open/close bleeder clutch out) with ALOT pedal pumps in between. After a while of that not working at all I gave up.

Then I purchased a vacuum bleeder from harbor freight, did almost the exact same thing with the buddy and again got absolutely nowhere.

After this I followed the GM build book on using a vacuum bleeder at the reservoir cap explained in this thread:

Correct way to Bleed Clutch

Now this procedure did give slight pedal pressure and the slightest amount of pedal return when fully depressed but the pedal still would not return fully and was certainly not as firm as it should be.

Also during all of the processes the amount of fluid in the reservoir hardly ever went down, maybe an ounce if that.

I was told by a couple local mechanics that a power/pressure bleed may be needed to solve the problem. One came over with a motive pressure bleeder and I made a cap to fit for this. After pressure bleeding pedal went even softer and never returned at all anymore. Also even with 25psi on the pressure bleeder almost no fluid was coming out at the bleed screw on the transmission.


At first I was thinking it was just a pain in the ass to bleed, now I'm thinking it might be a bad master cylinder. Can anyone give insight/help? I'm about to remove the master right now to see if I can bench test it but I'm not even 100% sure how to tell if it's functioning correctly.

Thanks for any help guys
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Old 12-29-2012, 08:47 PM   #2
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If you take the line off at the trans, does fluid come out? If not then you have a blockage somewhere. Pinched line or crap in the master or such.

I have never had a problem using a homemade vac bleeder myself, on any Cobalt. I'd give it a couple more cycles and see if it pumps up. Seeing that you actually got a little pedal doing that the first time makes me think your master isn't bad.
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Old 12-29-2012, 09:46 PM   #3
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Quote:
Originally Posted by ItalianJoe1 View Post
If you take the line off at the trans, does fluid come out? If not then you have a blockage somewhere. Pinched line or crap in the master or such.

I have never had a problem using a homemade vac bleeder myself, on any Cobalt. I'd give it a couple more cycles and see if it pumps up. Seeing that you actually got a little pedal doing that the first time makes me think your master isn't bad.
Thanks for the reply, this has been very stressful.

I removed the line a couple times and only a very small amount of fluid came out.

I saw your posts in another thread about it, but yes it did give an initial pedal feel but after over 2 hours of vacuum, pedal pushing and repeat it got absolutely no where. I tried again and got some pressure, then as soon as I switched to manual bleeding hardly no fluid came out and pedal was dead soft again.
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Old 12-29-2012, 11:41 PM   #4
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When I did my clutch at the shop, I did that method you did and didnt get anywhere.
When we got it, we used the:
bleeder open, slowly work clutch down, close bleeder.
pump pedal a bit
bleeder open, slowly work clutch down, close bleeder.
pump pedal a while
bleeder open, slowly work clutch down, close bleeder.
pump pedal few times
...ect...
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Old 12-29-2012, 11:56 PM   #5
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problem with your tob, line and install, sad to say Nooj; it should all be perfect. That assumes correct clutch and tob for your car. F23 trans. double check the parts. my advice
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Old 12-30-2012, 12:08 AM   #6
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so you don't think it is the master cylinder john? I don't think the tob is leaking tho, I don't see any fluid coming from the bellhousing. But if it's all air in there I wouldn't really know.

I took the master cylinder out, is there any good way to tell if it is faulty?

I just did a little test and the line/ distribution blocks are fine, fluid flows right thru, but I can't tell if the master is functioning correctly
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Old 12-30-2012, 12:19 AM   #7
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Master or slave?

Quote:
Originally Posted by noorjariri View Post
edit: Just to be very clear car is a 2006 cobalt ss/na 2.4 5 speed

So I just replaced my clutch the other day, boy was is a pain in the ass doing it on my garage floor. After a couple hiccups I buttoned it up the other day and have attempting to bleed the clutch for about 3 days now. First a little background, parts I installed are:

KY stage 1 clutch
Exedy lightweight flywheel
NEW TOB from KY, not sure of company but its OE specs

Followed the how-to on here pretty closely and help from a friend on here got it done. Everything is currently hooked up except the fuse box/pcm so I have more room to work on bleeding.

At first I tried the manual method with a buddy (clutch in open/close bleeder clutch out) with ALOT pedal pumps in between. After a while of that not working at all I gave up.

Then I purchased a vacuum bleeder from harbor freight, did almost the exact same thing with the buddy and again got absolutely nowhere.

After this I followed the GM build book on using a vacuum bleeder at the reservoir cap explained in this thread:

Correct way to Bleed Clutch

Now this procedure did give slight pedal pressure and the slightest amount of pedal return when fully depressed but the pedal still would not return fully and was certainly not as firm as it should be.

Also during all of the processes the amount of fluid in the reservoir hardly ever went down, maybe an ounce if that.

I was told by a couple local mechanics that a power/pressure bleed may be needed to solve the problem. One came over with a motive pressure bleeder and I made a cap to fit for this. After pressure bleeding pedal went even softer and never returned at all anymore. Also even with 25psi on the pressure bleeder almost no fluid was coming out at the bleed screw on the transmission.


At first I was thinking it was just a pain in the ass to bleed, now I'm thinking it might be a bad master cylinder. Can anyone give insight/help? I'm about to remove the master right now to see if I can bench test it but I'm not even 100% sure how to tell if it's functioning correctly.

Thanks for any help guys
I've installed alot of clutch plates in cobalts and always replace the slave cylinder when the trans is out. The slave fails the majority of the time and most of time bleeding isn't required. If you press the center of the quick disconnect on the line you should get fluid coming out. If not then the master isn't building pressure and is bad. I had a 04 sunfire that had the line from the master rub a hole in the line under the brake booster which caused a lose in the pedal. There was a fair amount of fluid on the frame rail. I hope this helps, good luck.
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Old 12-30-2012, 01:32 PM   #8
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with the clutch pedal up (aka rod pulled out of the master cylinder) should fluid be able to flow through it?
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Old 12-30-2012, 02:15 PM   #9
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Just the fluid in the line. Disconnect the quick disconnection and have someone push the pedal while you push in the center on the connection on the master side of the line. Fluid should be forced out.
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Old 12-30-2012, 04:05 PM   #10
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absolutely no fluid can get through the master cylinder, neither from vacuum or pressure. Hooked up the pressure bleeder to force fluid through got 30 psi and even with pumping nothing was happening. I'm going to order a new one and hopefully get it by wednesday.
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Old 01-02-2013, 10:38 PM   #11
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Got the new master cylinder in, bleed easily with just manual bleeding.

NOW I CANT PUT IT IN GEAR WITH THE CAR ON!!!!

this is becoming so annoying. Anyone have advice/suggestions? Car starts fine in neutral then I hit the pedal and go to put it into first and it just won't go. It shifts 100% fine with the car off. I think I got all the air out of the TOB but maybe there is still some in there? I didn't do any vacuum bleeding so I could try that. Sorry to be so annoying with this I just want my car working.
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Old 01-02-2013, 10:58 PM   #12
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still air in system or mechanical issue with clutch
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Old 01-03-2013, 12:14 AM   #13
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turns out the flywheel to pressure plate bolts weren't all the way torqued down. FINALLY GOT HER RUNNING AGAIN, THANKS EVERYONE FOR ALL YOUR HELP!!!
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Old 01-03-2013, 07:38 AM   #14
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^^^what? wow. you are lucky. tty bolts.
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Old 01-03-2013, 08:41 AM   #15
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damn. that makes sense.
thats scary, lol
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Old 01-03-2013, 12:01 PM   #16
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John I know the flywheel to crank bolts are torque to yield but are you sure the flywheel to pressure plate bolts are too? The GM build book said they weren't and they were good to use again
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Old 01-03-2013, 12:13 PM   #17
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I've never replaced pressure plate to flywheel bolts...nor have I ever heard of anyone ever replacing them on any clutch job.

The TQ spec for a 10.9 grade 8mm bolt is 24ft-lbs....the GM TQ Spec for those bolts is 22ft-lbs.

That being said...totally fine to use again.
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Old 01-03-2013, 12:48 PM   #18
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I miss understood. I thought you left the flywheel bolts loose. Whatever, the gmpp comes with new bolts, they are loctited and should be replaced, I know you did not do GMPP as you have an F23, but yes 22 lbs is the torque and Noor what were you thinking? lol. Use a paint pen and run the cover bolts up bit by bit in a star pattern and final torque and mark with a paint pen...

yikes. loose. glad it was not me on a customer car I can hear the screaming already lol
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Old 01-03-2013, 05:28 PM   #19
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Haha oh no I definitely torqued the flywheel bolts to spec! IDK how they weren't tight I'm almost positive I put them down to 260 in-lb on my smaller torque wrench. Oh well glad its over, man was that a headache
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