cranemaster

Hate to bump this, but this is the exact issue im having too. Wish he could of updated this lol

breds2k

iTrader: (1)

I had this issue right after installing a KY Stage 3. Turns out puck clutches DO NOT mix well with a machine flywheel (2000 miles just smoothed it out) not only that but my neighbor is a old school OBD1 saab and Volvo tuner and said puck clutches and hydraulic TOB's don't go well together.

I did a highway run with an EVO and my clutch has no pressure it in with 2000 miles on a new clutch. Next day normal.... It was weird. Happened a few times until TOB burst on a launch, also did significant trans damage. Havent had time to pull it yet this month and figure out what the deal is.

09CobaltSS1

Little do people realize but, there's actually a check valve in the clutch system that is SUPPOSED to prevent bleed off like this. If you're losing massive amounts of clutch pedal pressure this is almost most certainly your issue. I'm not 100% sure when but at some point or another GM actually changed the design of the clutch line using a different style check valve system. Since replacing mine the pressure bleed off problem has all but gone away. I still have a very very slight bit of pressure bleed off, but it's no big deal. At least I'm able to now shift perfectly fine during hard 3rd-4th gear pulls. Long and short of it, a new TOB isn't going to solve anything.

blueLNFftw

iTrader: (16)

That check valve is supposedly in the TOB itself and the issue was addressed with the TOB commonly known as the LNF TOB.

blueLNFftw

iTrader: (16)

The only other place it could be is on the clutch line itself. After the MC there is a big housing that looks removable on the hard line. IDK what it is, but it is not needed. I pulled it out and replaced everything with braided stainless.

09CobaltSS1

The check valve is indeed located in the clutch line going from the distribution block to the MC. This was verified directly from GM engineers.

blueLNFftw

iTrader: (16)

Welp, I yanked it out and my car is fine. FML if that was the problem with my original KY clutch.

09CobaltSS1

Hey, as long as it all works fine now, screw it. That's all that matters in the end my man.

For me though, I did as much research and digging as I could to find out where and if there was a check valve in the system. All sources pointed me to the line. I ordered a new one, noticed it was a completely different design that what originally came in the car and tried it out. No more pressure bleed off for this guy.

no_ss

iTrader: (2)

So is this an easy job to do?

blueLNFftw

iTrader: (16)

What part?

no_ss

iTrader: (2)

The check valve.

blueLNFftw

iTrader: (16)

Replace it with this.

Cobalt Clutch Line Fits F23 and F35 Trans


20 minute job. You need to bleed the system though.

no_ss

iTrader: (2)

Never bled something like that. Is it the same as bleeding brakes?

blueLNFftw

iTrader: (16)

I dont recommend it.

I vacuum bleed it.

09CobaltSS1

That braided steel version doesn't have a check valve in it, so I can't really comment much on that. I will say this though. If you're replacing the line without removing the fuse box, it would greatly benefit you to have someone there with long skinny arms to reach back there for you. I've almost gotten my arm stuck in there before.. lol

As far as bleeding the clutch system, it's not difficult. By far the best thing to bleed with is some sort of power bleeder system. A hand vacuum pump works fine. The one I use in my shop is a pneumatic bleeder that uses shop air and you simply pull the trigger. It's a beautiful thing I tell ya.. haha

blueLNFftw

iTrader: (16)

We cant all be that lucky.

I use a hand vacuum pump and a radiator pressure test kit rented from Advance. Has a pressure fittings that fits the res on the cobalt perfectly.

I use the stainless line and there is no issue removing the valve to install it.

Its easier to remove the fuse box. The time you spend working around it is more than the time it takes to pull and install it in my experience.

breds2k

iTrader: (1)

Guys, I had this pressure bleed off after agressive highway runs on a Ky Stage 3 USING the Braided clutch line think i got it from dezod or TTR.

TOB then failed 2-3 months later. My car is just cursed... I talked to several people that resurfaced flywheels and even on LNF's and had no problems (none of which used the KY 6 puck which just hated a not 100% perfect flywheel)

minizr1

Do you have any pics of your set up after you replaced everything with the braided lines?

cranemaster

Well I will update this, replacing the TOB fixed the lose of clutch pressure.

Still not quite following this clutch cable check valve convo, you dont need a check valve?

blueLNFftw

iTrader: (16)

No; you do not need it.
I removed mine and, honestly, it firms the pedal feel up a little and make it more constant.

You can see mine installed here.

southal cobalt

iTrader: (3)

im not trying to say that I don't believe you, but thinking about the simplicity of the circuit, how the tob is essentially a single action cylinder with a spring return, and the pedal is essentially the pump, a conventional check valve would not work inline with the clutch line. it would not allow the pedal to return home as it would not allow for backflow of the fluid.

unless you are talking about a check valve between the reservoir and the master cylinder. that would make sense as it wouldn't allow for backflow into the reservoir if the master cylinder leaked by

cranemaster

[QUOTE=blueLNFftw;7588438]No; you do not need it.
I removed mine and, honestly, it firms the pedal feel up a little and make it more constant.

You can see mine installed here.

Thanks for the pictures... man! this must be one of those LEAST talked about mods for cobalts. Ive had mine for 6 years and this is the first ive heard lol.

With my stage 4 I hope it firms things up a bit.

alerosaint

Was having this issue....I saw this thread and change to a steel line which removed the check valve. Most the problem went away but I did some pulls back to back to back and the pressure faded again but came back quickly.

63 Nova SS

iTrader: (3)

Where did he go?^^^^