85 4+3 clutch issues
Thread Starter
Instructor
Joined: Aug 2008
Posts: 102
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From: Methuen MA
85 4+3 clutch issues
For the third time tis season our clutch is no working right. We had the slave and master cylinders replaced two years ago and it worked fine until this year. Initially the fluid level dropped. Sent it to a good transmission shop (the owner has an 84 with a 4+3) They flushed it out, replaced the fluid and put a shield around the slave cylinder thinking it may too close to the exhaust and heating up the fluid, causing it break down (loss of pedal and pressure). couple of weeks later it was having trouble again this time the fluid was at the proper level and had broken down. Sent it back to the tranny shop and they replaced the fluid with synthetic fluid and compared to the owner's 84 to see if any shields, etc. were missing. Now, about two weeks later it is headed back to shop again as it was grinding going into reverse and the fluid had turned a grayish color again, as it has done in the past.
Has any one else run into this problem and what was the fix?
Thanks,
Tom Hargreaves
Has any one else run into this problem and what was the fix?
Thanks,
Tom Hargreaves
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
I still have the original slave cylinder and the original hose on my '87 and so far I haven't had a problem. I installed headers last year and I still don't see any indication of heat-related problems. Of course it could fail tomorrow 
For fluid, I just use a DOT3 brake fluid; specifically the Ford Motorsports HD fluid.
I think it's typical of the fluid changing color (getting darker) after some point in time. C5's also see a changing of the color of the clutch fluid and most people will simply suck out the fluid from the clutch master and re-fill it. I can put fresh fluid in my C5 clutch m/c and within two weeks it's dark again.
Have you ever replaced the hydraulic line? It could be that the hose has weakened over the years and the pressure causes an expansion which could reduce the travels of the slave piston and you get grinding. There "should" be replacement hoses available but any competent brake shop or hydraulic shop can make a new line for you. I would recommend using stainless flex line.
Grinding going into reverse can also be an indication of a worn-out disc. How old is the clutch?
For fluid, I just use a DOT3 brake fluid; specifically the Ford Motorsports HD fluid. I think it's typical of the fluid changing color (getting darker) after some point in time. C5's also see a changing of the color of the clutch fluid and most people will simply suck out the fluid from the clutch master and re-fill it. I can put fresh fluid in my C5 clutch m/c and within two weeks it's dark again.
Have you ever replaced the hydraulic line? It could be that the hose has weakened over the years and the pressure causes an expansion which could reduce the travels of the slave piston and you get grinding. There "should" be replacement hoses available but any competent brake shop or hydraulic shop can make a new line for you. I would recommend using stainless flex line.
Grinding going into reverse can also be an indication of a worn-out disc. How old is the clutch?
Safety Car
Joined: Aug 2013
Posts: 4,430
Likes: 608
From: Minneapolis Mn
Thoughts
I had to have the clutch master and slave replaced on mine right after buying it last year. Had a bear of a time bleeding the air out of it and before got all of it out of the line, one symptom was grinding going into reverse.
A test that may tell something, try pumping the clutch pedal 4 or 5 times before trying to shift into reverse. If it goes in clean, then it's likely air. If it goes in fine, here's something you can try at your own risk that a former GM mechanic suggested to me (and tried, and worked in my case). Pump the clutch pedal a half dozen times or so and then hold it down for about 5 minutes with the cap off the clutch master reservour. At the end of the 5 minutes, slide your foot off the clutch and let it pop back on it's own. If there's air in the line in that loop over the reservour, it may push it back to the reservour as it did with mine.
Good luck
A test that may tell something, try pumping the clutch pedal 4 or 5 times before trying to shift into reverse. If it goes in clean, then it's likely air. If it goes in fine, here's something you can try at your own risk that a former GM mechanic suggested to me (and tried, and worked in my case). Pump the clutch pedal a half dozen times or so and then hold it down for about 5 minutes with the cap off the clutch master reservour. At the end of the 5 minutes, slide your foot off the clutch and let it pop back on it's own. If there's air in the line in that loop over the reservour, it may push it back to the reservour as it did with mine.
Good luck
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
I had similar problems when I replaced the clutch on my 85. If you had your flywheel surfaced, you may need a longer rod between the slave and pressure plate lever. To check the bleed, remove the rod and gently press in the clutch pedal , until the slave piston bottoms out on the clip that holds it in the bore. If the pedal goes hard, your bleed is fine. I made a quarter inch longer rod out of a 8mm ball allen wrench. I cannot tell you how much bleeding/fluid replacement/parts replacement it took to figure this out. And unless you completely change out all the parts, hoses included, you will darken the fluid in short order.
Thread Starter
Instructor
Joined: Aug 2008
Posts: 102
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From: Methuen MA
c4 cruiser, hcbph and powerclutch51, thanks for the responses. I haven't responded until now as I wanted to see if the last trip to the shop fixed the issue, and it appears it did. A check of the records show we had the master and slave cylinders replaced three (3) years ago. They replaced them again and it has been good ever since. The shop thought the rings around the piston were breaking down and allowing air to get into the system. They also stated that the parts are now made in china, etc and are not as good as the OEM
I'll keep all of your suggestions on file if it starts up again.
Thanks, again.
Tom Hargreaves
I'll keep all of your suggestions on file if it starts up again.
Thanks, again.
Tom Hargreaves
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
I had to replace the master and slave cylinders on my 85 4+3 multiple times in the past 2 years of owning it with normal/occasional driving. Always had dark grey fluid. I suspect it was the cheap seals on the crappy Chinese replacement master cylinders from A-zone and O-blah-blah. Even as I poured new clear fluid in, the second I'd pump the clutch to bleed it, the fluid went dark. Before I pulled the 4+3, I had an AC Delco master cylinder and it seemed to work, but still gave me some obvious clutch chirping when engaged. I've been told these units are also now made in China so I'm not so happy about putting one in my ZF6, but it's better than going back to the other lousy brands.
