Clutch fluid a little low

[Stingray1967]

I noticed that my clutch fluid was a little low. See the attached photo. The fluid doesn't look all that bad. Can I just top it off? Or should I completely pull it out and refill? It looks like the way to get it out is to suck it out with some kind of vacuum tool, as opposed to a drain valve.

If the recommendation is to top it off, is there any issue with mixing fluid types? I see both DOT 3 and DOT 4 mentioned. I don't know what is in the car right now.

I should say too, the clutch works just fine, but every once in a while there is a little trouble getting it into 3rd.

[Neat]

Depending on the style of rubber gasket beneath your clutch fluid reservoir cap, that level may be alright. One style of rubber seal has a large cup that sits down into the reservoir; if that's what you have that fluid level looks pretty close to correct. When that type of seal is used, it protrudes into the reservoir quite a bit, displaces some fluid, and causes the fluid level to rise from about where yours is to the full mark on the reservoir. If that's the style cap seal you have, to me it looks like the fluid level is OK but the rubber cup is collapsed / retracted up into the cap.

The other style of seal is a more conventional / commonly seen rubber washer. Since none of that seal protrudes into the reservoir the fluid level doesn't rise when the cap is installed. If that's the type of cap you have, the fluid level is a little low.

The most commonly recommended fluid for the clutch system is Valvoline DOT 4. I'm not aware of any issues mixing the Valvoline DOT 4 with other fluids. That being said, just because I'm not aware of any issues doesn't mean there isn't a compatibility problem with X or Y fluid; so be sure to double check me before adding fluid.

If you can get under the car, you might want to closely examine the slave cylinder for leaks / wetness / seeping. They typically leak out of the rubber boot that is inside the bell housing. The leak will usually be noticeable as a drip out the bottom of the bell housing or a weeping between the slave and the bell housing. If there is a drip / wetness present at the bottom of the bell housing, it's commonly misdiagnosed as an oil leak; the clutch fluid picks up black clutch dust as it runs down the inside of the bell housing and looks / feels very much like dirty motor oil.

You can also look for wetness / feel for wetness on the carpet up near where the clutch mounts to the firewall.

The slave cylinders are notorious for quality control issues, and are usually the first component to start to leak. The tiny bits of slave cylinder seal that make their way into the fluid eventually take out the seals in the master cylinder. It's extremely common to replace a slave, and a few weeks later have to replace the master. I would recommend doing both at the same time.

If you do replace one / both of the cylinders, bleeding the system can be sort of aggravating. If you get stuck, ping me and I'll shoot you a couple different methods to bleed it.

[lfalzarano]

Shifting into 3rd can be awkward until you get use to it. It may not be due to the clutch fluid level, but all fluids should be topped off.


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[Neat]

For your third gear issues, this is from Bill at zfdoc.com:

Q) On my car I can power shift 2nd and 4th, but I'm having problems with 3rd. During normal driving going to 3rd does not feel as smooth as going to 4th or 5th. Sometimes I don't even feel like it went into gear. The shifter grabs third gear, but it feels like it is half way there, like it has an additional 1/8" of travel left to go, not like all the others gears where you feel the shifter securely engaging the gear. Third grabs, but you feel like the shifter did not go in all the way.

A) There may be an issue with linkage that is slowing down the actuation of the 3rd gear shift event. How is the "return to center" spring action of the shifter feel? This is how well the shifter springs back to the 3/4 neutral position when released from the 1/2 neutral position or the 5/6 neutral position. The return to center action should be quick and crisp. This return to center action is initiated by the mountain detent of the shift shaft (internal) and the ball detent (roller) and two springs located just forward of the CAGS bung. If the ball detent gets crud in it, the return to center action becomes diminished. This condition is of the easiest to correct. It requires a new Ball Roller($15), 2 Compression Springs($5) and less than 5 minutes to install once access under the vehicle is gained.

When installing a Hurst Billet/Plus gear shift handle, there is the possibility that the shifter setup may be binding somewhat at the axis points. I have found this to be the case when installing the Hurst shifters unless removing all of the powder coat from the contact areas at the pivot points prior to installation into the shifter. There should be no hang-up in movement in the x and y axis and no play in the axis joints. The condition of the shifter frame (Remote Control Arm) is also important. If you can rock the frame (Remote Control Arm) and it rolls more than just the slightest little bit, it has a delaminated rubber eyelet at the front mount point. This condition will also work against you when transitioning from gate to gate (1-2 gate, 3-4 gate, 5-6 gate).

Once you have cleared these items as possible issues and you are certain that the clutch hydraulic system is good, you can be certain that the problem lies internally at the specific problematic synchronizer.


http://www.zfdoc.com/faq.htm

[Paul Workman]

FYI:

Recommended
clutch Master (USA) = Dorman @ Rock Auto #CM39763
clutch Slave (USA) = Dorman @ Rock Auto #CS360017

Sometimes not a good idea to mix fluids (antifreeze comes to mind). Suggest you stick with DOT 3 and you'll be safe.

Note: As an annual maintenance item, I remove the fluid from the reservoir and replace it with fresh fluid. Then pump the clutch 25-30 times and replace the fluid again (and again) until the fluid remains clean.

[Jagdpanzer]

Clutch fluid can get pretty skunky after four or five years, especially in the slave cylinder where I?ve seen corrosion set in. Best to drain and flush the complete system every three or four years. Sooner if the car sees a lot of humidity.


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[Paul Workman]

Originally Posted by Jagdpanzer

Clutch fluid can get pretty skunky after four or five years, especially in the slave cylinder where I?ve seen corrosion set in. Best to drain and flush the complete system every three or four years. Sooner if the car sees a lot of humidity.


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Yes! And, just to add:

IF you have a '90, and you replace your slave for any reason, get the ones with the bleeder valve on the bottom where they're accessible to a Mitivac* vacuum pump. That way you can easily purge the clutch master and slave cylinders without having to pump the clutch pedal. And, if you purchase a fluid reservoir (clip-on) bottle (Mitivac again) you won't have to have an assistant maintaining the master reservoir as you pump fluid out at the slave bleeder. (Did I also mention getting the braided clutch line instead of the solid metal tube (90s)?)

*Summit Racing or Amazon has them