My wife’s 07 Chevy Aveo was towed home Tuesday. She tried downshifting on the freeway and suddenly she couldn’t get it in or out of gear. I was able to get it in all gears but the clutch engagement was all wrong. there didn’t seem to be any slip zone, it just jumped at 1/2 pedal. I found the clutchmaster cylinder leaking slightly under the boot so I changed it and bled the system, no change. I had backed the car out of the garage onto the upward sloped driveway which required a lot of RPM’s. Later I couldn’t get it out of gear and cannot disengage the clutch, even to allow it to roll. I also changed the slave cylinder, still no help.
I changed the clutch, throw out bearing, and had the flywheel resurfaced last April. ANY ideas???
anyone out there??
Caveat: New Clutch master cyls need to be “Bench Bled” prior to installation…you clamp it in a vise or hold it securely…and push in the piston with your finger over the output high pressure port until you feel that it is finally making pressure…then plug the output hole and install into vehicle. If you do NOT do this…almost all of your efforts to bleed the slave will be for naught. It will be near impossible to bleed the system.
If you did not bench bleed…you must do this. If you DID bench bleed it…the only other things I can think of is to check the pin at the clutch and master connection point… Is the pin seated and connected correctly? See if the throw of clutch has an adjustable rod and adjust it if need be…
You changed the Master Cylinder… How bout the Slave Cyl? It could be leaking slightly and what may have caused most of this trouble in the first place. If you have not swapped the slave…i would strongly recommend doing so…slave cyls fail at least 2x more often than the master cyl.
AND lastly…I would have to ask you how the clutch throwout bearing pivot FORK was holding up…sometimes these bend or crack and instead of throwing out the bearing and disengaging the clutch…they sorta bend and take up the throw of the slaves travel. It either partially disengages the clutch…or not at all really since it is bending so much.
Hoping you installed the clutch plate the correct way as well…there is a top and bottom to that plate.
Bout all I can think of
Blackbird
Hey thanks so much. I was actually thinking about bench bleeding this morning and you just reinforced it. I’ll keep you updated.
GM Published A 1 Page Technical Service Bulletin Outlining An Improved Method For Bleeding The Clutch Hydraulic System On That 2007 Aveo And Other GM Passenger Cars To Help Technicians With Troublesome Bleeding Of Air Introduced Into The System.
It might be worth the time to search for, download, and read TSB #01-07-31-002B, especially if your attempt fails.
CSA
Thanks CSA, where do you go to download that TSB? couldn’t find it any of the obvious sites.
All Good advice…but if you did not bench bleed that new master…The lord himself wont be able to help you bleed it. Please do that first…
Blackbird
“Thanks CSA, where do you go to download that TSB? couldn’t find it any of the obvious sites.”
Here’s one of many such downloads:
http://www.cadillacfaq.com/faq/tsb/data/01-07-31-002b
CSA
Look at the piston rod of the slave cylinder while your SO pushes the pedal.
It should come out 1" or so and stay out if SO holds the pedal down.
If you’re getting plenty of fork movement the problem could be a broken pressure plate spring.
He replaced the clutch tho…but could happen sure. Start simple and work your way up to the bigger stuff
Yes, I’ve heard the broken pressure plate scenario before but does it make sense with the clutch engagement/disengagement getting worse after the car was towed home?
I would think a broken spring would be bad and stay that way., not steadily get worse until I can no longer disengage it.
I feel I’m thinking myself into a corner…arghhh. I love this car!
Suppose the spring developed a crack that got bigger and bigger.
Observing the slave and fork is a easy no-cost test, assuming it’s on the outside of the trans.
Please dont move beyond the new master just yet…sure it can be a lot of things and the guys are nailing them for you…however you changed the master and you did not bench bleed it… Im not saying this to be a pain…Im saying this cause it needs to be done…ask me how I know? I could tell you stories of tearing my hair out as a younger grease monkey…and wouldn’t ya know it…I didn’t bench bleed it.
Until you state that you have bench bled that thing…I wouldn’t move anywhere else… Once you have done so…I would next go to the slave since they wear out at a ratio of about 2-3 to one compared to the master.
After that? We can get into fatigued pressure plate springs or throwout fork etc…but youre still on step one as far as Im concerned.
Blackbird
The clutch master uses the brake master reservoir so I bled it on the car but not bolted on.I used the reservoir and left the pressure port open and just actuated the pushrod until fluid squirted out with every stroke, then let it run out while securing the pressure line.
Is this method good enough?
And to circuitsmith,
The fork is not visible from outside the transmission. It’s actuated by a keyed rod that drops down through the top and has a plate welded to the top where the slave makes contact.
A terrible design that forced me twice to drop the transmission because the plate spot weld to the rod failed. All that work for a $20 part. Nuts! Well, that’s what they should have done, keyed the top of the rod and secured the plate with a nut.
There’s no noticeable gap between the plate and pushrod but that doesn’t rule out a broken spring. Thanks for pointing out that springs don’t always completely crack from the start. Makes sense.
I can’t speak to the Aveo, but for my Corolla with this problem securing a replacement clutch MC, bench bleeding the clutch MC per the instructions that came with the replacement, then installing it on the car, and finally bleeding the whole system from the clutch MC to the slave cylinder did the trick. If you haven’t done the following steps yet, suggest to give it a try
- Remove the clutch MC and bench bleed, being careful to only use the vice on the flange
- Reinstall
- Top off clutch MC with fluid
- Open slave bleed screw, attach a clear plastic tube from it into a jar
- Press on the clutch pedal slowly with your hand only, and only to the 3/4 down point. Hold the pedal there while you close the slave bleed screw (see Note 1).
- Slowly allow the pedal to turn to the top. Repeat until all of the original clutch MC fluid has moved into the Slave cylinder and out into the jar. Top off the MC periodically as required to prevent it from going below the 1/2 full mark.
Note 1: Either use a helper, or – I think this works better – find a stick the right length to wedge between the seat and the pedal hold the clutch pedal down while you move to the engine compartment to close the bleed screw.
I think you meet the requirement for a “Bench Bleed” of the master…OK…I feel a little better. Next suspect is the slave…they go bad often and are pretty cheap. All the advice the guys are giving is pretty spot on…just be mindful of the flow of troubleshooting this. I would start at the new master cyl…be sure she is properly “burped” then…replace the slave…with those two out of the equation then and only then move on to more serious…Transmission dropping issues…like the pressure plate and the throw out fork. But methinks you wont reach that point…I think with a new master AND slave…you will be ok… I would have started at the slave and then went to the master…but thats just me. I see slaves go on vacation much more than their masters… That didn’t sound too good did it? You know what I mean though.
Let us know after you replace that slave and bleed again…then we can move on toward more serious equipment. You really cannot proceed until this is completed…unless you know something I do not.
Everyone is pretty spot on here…but we need a new slave in the equation before proceeding…get me? It cant be much money. Honestly I replace FAR FAR more slave cyls than masters…just how it be.
As for bleeding? I enjoy reverse pressure bleeding…works nice…but equally nice is to simply let it leak with a small piece of rubber hose on the slave bleed nipple…point one end of the hose UP…this ensures a vertical column of pure fluid so all air just bubbles to the top of the hose…when you see solid fluid coming out of the hose…the system is bled…and you will have a solid pedal if there are no mechanical failures within the clutch
Blackbird
Original post states the slave has been replaced.
You are correct @insightful I missed that last sentence… But you are correct Sir…
OK…perhaps it IS time we roll up our sleeves and look for bigger fish to fry…and there are several as many of you have indicated…
I just hope everything is bled properly…would be a shame to move on toward the other culprits as none of them will be “easy” to do quickly. Be nice if the problem was where he could easily get to it. If the system was bled to perfection and we still have a not fully disengaging clutch…we know where he will be going next now dont we.
I think everyone hit all the suspects to look for after the system was properly bled…uh oh…I was hoping to keep it simple…
Blackbird