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Old 08-05-2011, 12:13 PM   #1
dennis_houston
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Question shifter bad behaviour depending on AC being on or off (SL 98)

1998 SL
133K
original clutch/tran

This is strange, and it has taken a few years for me to pinpoint (perhaps incorrectly) a problem with my shifter. Whenever the hot weather arrives -- which last for several months in Houston -- I begin using the AC. After a while, I notice that shifting becomes difficult, having to double- and triple-clutch to move the shifter around the low gears. Generally, this problem recedes as the engine gets hotter, but can still be troublesome nonetheless. Gradually (a few weeks), the shifter behaves normally again (all with the AC on). Now, if I drive the car with the AC off, the shifter is difficult again, but if I turn AC on, the shifter returns to normal function. Only after a few weeks of driving without persistent AC use does the shifter finally return to normal function. Am I crazy, or do you think there is something to these observations? Perhaps the AC drag on the engine affects the positioning of the clutch parts or something along those lines????

Thanks for any info or speculation.
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Old 08-05-2011, 12:37 PM   #2
td1238
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1999 SL2
Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Sounds to me more like you have the common 'hydraulics can't fully release a worn clutch' problem. This doesn't mean that the hydraulics are bad. Mine, and others' who have had this problem, measure proper travel, but the clutch doesn't fully release. It gets better when things are hotter. Running the AC will make things hotter around the clutch.

I am lazy and cheap, and do not want to replace the clutch, and I also saw that it has plenty of wear left, when I had the transmission off to replace the diff pin. The pressure plate fingers also looked fine (though for all I know, the diaphragm could have a crack). ...And so, when I get to it, I'd actually like to increase the throw of the master piston, so-as to increase the travel of the slave piston. ...But I haven't gotten around to it yet. Previously I had an idea to place a small piston behind the master piston, between the piston and the push rod, to take up the remaining slack between the clutch pedal arm and the dash frame, but now I'm thinking more on the lines of cutting the spare piston rod I own in half, threading it, and fitting it with an adjustable sleeve. ...Or I might try threading the plastic coupling on the end so that it may be turned to lengthen or shorten the over-all rod length. Not sure yet.

My theory is based on the fact that a diaphragm type clutch spring actually applies more pressure as the clutch driven disc wears, requiring more pressure for release. The diaphragm spring has an over-center quality, which tends to increase necessary pressure as this over-center position is further passed. My theory is that, depending on how the clutch hydraulics were designed, they might not have been designed to release a worn clutch, but only a fairly new one (after all, after the warranty, how cares?). Temperature might have something to do with slightly altering the shape of the spring or something else related to the pressure plate, allowing for easier release.

Or I could be completely wrong, and the pressure plate is in fact cracked or otherwise defective, but temperature still has something to do with its easier release when hot.

...But anyway, check hydraulic throw with a wire through the tiny hole in the bell housing next to the slave cylinder. If it's good when the clutch is not releasing fully, then your hydraulics are fine.

Start the engine. Watch for excessive sideway movement of the crank pulley. With the engine off, try to gently pry it back and forth. If excessive play does not exist, the thrust surfaces on the #3 crank bearing are fine. Otherwise they may need replacement, as excessive clearance absorbs clutch piston throw, which makes for less remaining travel for releasing the clutch.

...Otherwise your remaining options are likely either a bent throw-out fork (unlikely but possible), or the pressure plate itself.

Last edited by td1238; 08-05-2011 at 12:40 PM. Reason: word add
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Old 08-06-2011, 02:01 AM   #3
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1995 SL1
Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Though I agree with the above as possible causes, there are a number of people that have complained about sloppy or difficult shifting with the AC on. This is reverse of the OPs concern but may be related.

Do you get a "sticky" clutch pedal under certain conditions? On my car with the AC on the clutch sometimes gets inconsistent. My theory has been that the extra heat being blown over the motor affects the hydraulics in the clutch system. Between that and the AC draw making engine revs change a little quicker, it's slightly harder to pull off a smooth shift in the lower gears.
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Old 08-13-2011, 10:49 PM   #4
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Thanks Signmaster and td1238. I apologize for not replying earlier. I haphazardly thought that I'd get an email when someone responded to my post.

Anyways, for my skill level, it sounds like the type of thing I should live with since (A) it is only a nuisance, and (B) it sounds expensive to fix (or if I did it myself I might make it mess everything up!), if indeed there is anything to fix.

Thanks for the info. Yes, my clutch is sloppy in the low gears. Where my issue seems to differ from what you guys see with other owners: my problem seems to come about at the transitions, from not using AC to using AC (e.g., spring going into summer, when AC is on all the time), and vice versa. For example, right now, I must have the AC on in order for the shifter to work nicely. But when the cooler months come, I will transition ack to no AC use, and will need it to be off in order to have nice shifting.

Thanks again
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Old 08-13-2011, 10:54 PM   #5
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Signmaster,
I did not perfectly answer your question. While my shifter is what gives me problems, I do not seem to have any issues with the clutch pedal.
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Old 08-15-2011, 10:01 PM   #6
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1995 SL1
Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Sounds like a strange issue. Just out of curiosity, do you know for certain the type of transmission fluid in the tranny? Just a wild shot in the dark but it's possible that the temperature range of the fluid is affecting the shifting, and the AC use is just a coincidental by product of the ambient temp?

I really doubt it's the problem, but doing a fluid change might be worth a try regardless. It's only three quarts of fluid in cost, and a lot of people neglect to do it as maintenance.
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Old 08-21-2011, 09:29 PM   #7
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Interesting observation I had the other day. The weather was a bit cooler, and so of course it was more difficult to shift into first, especially when the car was first turned on. Well, I put it in first, and then brought it out half-way so that I could grind the gears. The gears grinded slowly, and ground faster when the clutch was let out fully. Then, if I'd put the clutch pedal back in really quickly, the gears would stop grinding all together. Then, after a brief moment, they'd start grinding slowly again, but they'd maintain the same speed, which indicated that the hydraulic system leaked back just a bit of fluid, but stopped after that, or maybe something in the system expanded or shifted.

This is a new hydraulic system, so I doubt it is faulty. It also passes the wire test at all times. My guess is that it does in fact not have enough travel for the clutch in use.

My friend's '01 SL2 clutch is far easier to release, possibly indicating a weaker diaphragm spring. It releases about half-way. It has good grab and doesn't slip, but behaves like a normal clutch. I notice, though, that it is super easy to disengage, as opposed to my clutch.

Here and there I have read things about two different clutches and hydraulic systems being used in Saturn S series cars throughout the years, so I'm wondering if I and others with my problem perhaps have a mismatched pressure plate and hydraulic system. I'm guessing that my clutch would require a hydraulic system with more travel at the slave cylinder. It seems like my slave cylinder is just barely making it, and on colder days, due to contraction, isn't making it.
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Old 08-21-2011, 09:52 PM   #8
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Fascinating. I'm not surprised, however.

I went through many of the Saturn S years on both napaonline.com and autozone.com. NAPA lists a master cylinder of about .875'' bore for all years up to '99. For '00 and higher, a .625'' bore master cylinder is listed.

Makes sense. If by chance they changed the clutch to one with a weaker diaphragm spring and/or one that has the same strength but doesn't require as much pressure for disengagement, I would understand why they'd switch to a master cylinder with smaller displacement for those higher years.

However, AutoZone does the exact OPPOSITE! They have the larger piston listed for the years after '99, and the smaller piston listed for years '99 and earlier!!!!!

As I have no idea what was done to my car prior to my owning it, it would not surprise me if the hydraulic system that was installed when I bought my car came from AutoZone. I would not be surprised if others with this same problem had an AutoZone (or other vendor with incorrect part numbers listed) hydraulic system installed. The hydraulic system I currently have installed is from AutoZone. It improved clutch release slightly, but not by much.

Well, there's only one sure way to find out. I'm going to go to NAPA and buy the CORRECT master cylinder for my '99 SL2, and put it in place of the one from AutoZone.

Also, on a side note, AutoZone lists slave cylinders up to '99 as .828'' bore, and after '99 .836'' bore. ...A slight difference, but not much. Unfortunately NAPA does not list slave cylinder specifications, at least where I looked. At this point I am just going to have to assume that my master cylinder is wrong, and that it must be swapped out.

This incorrect part listing is on par to 'OReilly selling me a TPS for my '99 that's actually supposed to be for an '00+. However, I found out by this mistake that I like the '00+ TPS performance better in my '99 than the correct TPS.
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Old 08-23-2011, 11:21 PM   #9
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

...So today I had an idea that if the master cylinder for a '00-01 is larger than that for a '99, as sold by AutoZone, I'd swap mine for an '00-01 model. They are slightly different in appearance, but work similarly. Well my hydraulic system has a lifetime warranty, and I told the store of my problem and my suspicion. They gave me the okay to try a '00-01 system in my car. Tried it. Same, if not worse. The master cylinder main portion actually looked the same diameter as my '99 master cylinder.

Well, so then I put back in the system spec'd for a '99, and guess what?! The clutch started releasing perfectly, and at the middle of the pedal travel. ...But then I parked the car for a moment, a while later, and the clutch went back to releasing at the bottom of the pedal's travel. Pumping it mulitple times brought it to the middle, and it moves around from there, though it mostly releases okay.

...So I'm guessing it really is the hydraulics that are messed up, even though the system is only a year old. When I bought it a year ago, it worked perfectly for a few weeks, and then started behaving just like the old system.

I really don't know what's going on inside, or if the pistons really are incorrect, or if they just posted the incorrect information on their web site. It seems to me, however, that the piston might have some problem, as sometimes I can put the clutch in and the gears won't grind, but a moment later they will slightly, but not more, so it seems like it is leaking just a bit, but is then stopping. ....Or maybe whoever bleeds these is sloppy, and there's air in the line, but I personally bled the system that was installed when I bought the car, and it behaved no differently after the bleed. Like the new system I have installed, it would release well in hot weather, and poorly when it was cold.
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Old 08-23-2011, 11:27 PM   #10
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1998 SC2
Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

The cheap ones will suck air and it goes and hides in the pulsation damper.
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Old 08-24-2011, 09:19 AM   #11
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Well, I think that it was priced like the rest, but comes with a lifetime warranty. Still, I bet that it sucked in air. I guess I should go with a NAPA system or something.

I did fully bleed my previous system, however, and it made no difference.
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Old 08-24-2011, 10:17 AM   #12
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Quote:
Originally Posted by td1238 View Post
Well, I think that it was priced like the rest, but comes with a lifetime warranty. Still, I bet that it sucked in air. I guess I should go with a NAPA system or something.

I did fully bleed my previous system, however, and it made no difference.
You can not bleed those. It is a urban legend, does not reliably work.
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Old 08-24-2011, 10:53 AM   #13
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Well, they are bled from the factory. What I did was mount the slave up high with the piston removed. I then pumped the master until the slave was full and without bubbles. I then inserted the slave piston. The cylinder is shaped such that the ebd is wider than the main bore, so if full, the piston seal would be fully submerged before contacting the bore.
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Old 08-24-2011, 12:17 PM   #14
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

De-bubbling the pulsation damper is near impossible. Thee have been many attempts to bleed these things including 2 TSBs and the common denominator is either immediate or delayed FAIL.

The definition of insanity is repeatedly doing the same thing that failed last time it was tried.
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Old 08-24-2011, 11:07 PM   #15
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Wow! That was harsh.

Your insults don't solve anything, and not much else you have offered has solved anything, either. When I use my own logical brain, however, I get results, and some of the best results reported thus far in this forum.

Anyway, I bled the system today. I turned the slave cylinder so that it was open-end up. I then removed the double layer retainer ring to allow the piston to come out. After removing the piston, I had a friend rapidly depress the clutch pedal, so that the fluid would move through the system violently and dislodge any bubbles present. At first I heard a few bubbles work through the line. Then all bubble noises went away. After each pedal depression I was sure to top off the master cylinder.

As a final measure, with the slave cylinder perfectly vertical, I topped it off so that it was full up to the brim. I also filled the recess in the back of the piston and covered it with my finger. As the piston was immersed in the fluid, I removed my finger. I pushed the piston into place and put the snap ring back in place. I put the push rod and dust cover in place, and pushed the push rod down into the piston. With one of the plastic push rod tensioners still present, I held the push rod in place so that the anti-slack spring couldn't push it out and possibly draw in air. For anyone whose slave cylinder lacks these retainers (once they are used up), I recommend leaving the piston full out and allowing the throwout fork to push the rod in.

Well, I reassembled the slave cylinder and gave the car a try. The clutch now perfectly releases and the gears shift well. The clutch now releases at about 1/2 to 2/3 of the way down. Hopefully it won't move any further. If it goes back to not fully releasing, I'm going to get a NAPA system. So far, however, it has been working consistently.
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Old 08-25-2011, 12:04 AM   #16
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Well, my clutch went back to not fully releasing just barely--enough to make it slightly difficult to shift, where-as before it was like cutting warm butter.

I guess I will get the NAPA system. I wish I knew what caused this. Seems most definitely to be hydraulic related.

Well, hopefully my persistence will pay off. Paid off for Thomas Edison. Even if persistence is insanity, it made him rich.
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Old 08-25-2011, 12:10 AM   #17
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

Could also be that the valve that closes off the reservoir upon clutch application isn't sealing properly, allowing some fluid to go back into the reservoir as the clutch pedal is first depressed. When the clutch is fully depressed, I noticed earlier that sometimes it will fully disengage and then start to re-engage just slightly again. Leakage past this valve would cause this problem.

It would be interesting to increase the tension of the spring on this valve. This valve (a rubber disc) is attached to a device within the master piston which keeps it away from the reservoir orfice, but when the piston is moved forward, the rubber disc closes off the orfice, and a spring behind the retainer maintains pressure against this valve to keep it closed.

Well, it's worth a try, if it will solve this problem once and for all for everyone.

Also, regarding master cylinder diameter, I measured wrong before. My master cylinder outer diameter is in fact over 7/8'', so I am guessing that the internal bore is the correct size. It is more likely that AutoZone just mixed up the numbers in their literature. When I disassemble my master cylinder, however, I will know for sure, as I will take measurements.
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Old 08-25-2011, 11:05 PM   #18
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

I changed the reservoir valve spring (in the master cylinder) to a spring with slightly more tension. It made operation somewhat more definite, but now the clutch definitely releases every time right at the floor, and not sometimes mid-way and sometimes at the floor. Still, for the most part, it releases fully. I cannot be sure how it will behave when cold, until I try it out tomorrow morning.

However, I measured the diameter of the master piston, and it is 5/8'', and not 7/8''. NAPA lists all years up to '99 as having a 7/8'' master piston (more displacement), and all years after '99 as having a 5/8'' master piston. AutoZone lists the opposite, which, according to what I have found, is true. With less displacement, the hydraulic system is surely more likely to release the clutch closer to the floor, and to possibly not release the clutch at all, depending on if cold weather builds up vacuum in the reservoir and system due to contraction, etc.

...And so tomorrow I am most definitely going to purchase a NAPA master cylinder, and attach it in place of the AutoZone master cylinder. The rest I will leave as-is.

Hopefully this will solve the problem once and for all, and hopefully this is the reason why many others have this problem--because AutoZone perhaps specs the wrong master cylinders for the wrong years. Physically, however, their product is correct, as before '00 the master cylinders have the reservoir mounted on them, and at '00 and after the reservoir is remote.

....Or maybe I'll just take back the entire AutoZone system if possible, and get my money back, and just get an entire sealed NAPA system. That will be easier, I guess.
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Old 08-25-2011, 11:18 PM   #19
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

These are reported to work properly when received. The difference between the 91-99 and 00+ is the reservoir mounting. http://www.clutchcityonline.com/saturn_sc.htm
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Old 08-26-2011, 01:03 AM   #20
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Default Re: shifter bad behaviour depending on AC being on or off (SL 98)

No specs, but priced cheaper than NAPA. Still, for now, I like the convenience of NAPA, and that I know what the master cylinder is spec'd at. If possible I will return the AutoZone system and purchase a NAPA system. If the NAPA system also performs poorly, I will purchase one of the ones sold on that site.
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