I’ve been having shifting issues in the 85 z31 i bought recently. on cold startups its impossible to get it into first and sometimes second. i took out the master cylinder and bench bled it then bled from the slave so i could know it was neither of those and it was good for a bit until this morning. first and second were gone (second was grinding) so i had to start it in first and go straight off that. nearly everytime all problems resolve after driving for around 20 minutes but it did not this time. changing gears with the engine off feels completely fine. it was EXTRA cold this morning if that means anything. any suggestions?
The clutch master cylinder may be leaking internally and not producing enough hydraulic pressure to operate the clutch.
Tester
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Yeah, old rubber cups can lose flexibility in the cold. Any rebuild kits available (if there’s no corrosion in the bore)? Or just replace it.
I just checked Rockauto, the master cylinder is cheap, lest than $20, same for slave. I’d replace them both.
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theyre both only a couple months old?
Is there a flex line that might be deteriorating on the inside? Sometimes old rubber brake line develop blockages.
You can get bad parts.
Look at it logically.
The master cylinder is what produces the hydraulic pressure.
From your description, there isn’t any.
Tester
Are you asking us? How are we to know?
Are you telling us? Then don’t end the sentence with a question mark!
I once had a new or factory rebuilt brake master cylinder that did not work. Exchanged it after much messing around. The new one was fine from the get-go. Good luck to you.
could definitely be the line. thanks for the tips i didnt know about the rubber reacting to cold
Blockquote very true i understand. ill replace em later today. does the shifting while the engines off eliminate any potential for gearbox issues? my buddy mentioned a synchromesh problem and spooked me. also would old transmission fluid mean anything?
With engine off, the transmission gears aren’t rotating.
So it’s easy to shift thru the gears.
With the engine running, and the clutch doesn’t disengage when the clutch pedal is depressed is like trying to sift thru the gears without stepping on the clutch pedal.
Tester
If you don’t know how old the transmission fluid it, replace it with the factory-recommended fluid. Do that before making other repairs, just on the (slight) chance it helps.
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Try quickly pumping the clutch pedal 2-3 times before making the otherwise difficult shift. Does that have any positive (or negative) effect? If so (positive), pretty good chance CMC needs replacing. I’ve had to replace my Corolla’s CMC about every 10 years, symptom is hard to shift into first or second gear from N w/engine idling. I’ve learned to replace the CMC very soon after first noticing this symptom, b/c it won’t be long before car is un-driveable.
forgot to update but its all fixed! i went crazy because after replacing both cylinders how on earth was the problem persisting? lucky for me the previous owner left me an ol’ repair manual for the car so i read it front to back. turns out theres a little gizmo in between the two called a clutch damper. tore it out and sure enough the problem was gone but i ran a brand flexible line just in case. blast of a car to drive (now that it stopped trying to kill me)
Interesting! . I’ve heard of a clutch damper function done by the clutch disc and pressure plate , but a special tube in-line between CMC and slave to dampen clutch operation? That’s a new one on me. I’m assuming the clutch damper is a flexible hose, which contracts/extends slightly, & prevents clutch parts from moving too quickly into place when pressing the clutch pedal. Used I guess to extend life of clutch material and reduce jolting on engine and transmission. Glad you are shifting & rolling like new again. That’s for the update!
Maybe this is common on high performance racing-types of cars?
it was a small rectangular piece that screwed in behind the brake lines, had the hardline come in from the master then out through a half meter line into the slave. apparel it can cause real issues if you replace your clutch with anything but oem so theres tons of videos online bypassing it.
Might be a good idea to treat the clutch/transmission a little on the conservative side until you get the feel of the newly configured arrangement.
In high school one of my friends had a 240 Z, used to ride with him to ski resorts sometimes, very fun car, and very reliable. He referred to it as “The DAAAAAT-son”. lol