'92 F-150, 5.0L, 5-sp integral trans and bell, Hydraulic clutch, 4x4.

So this is rather sudden... My clutch, which has been fine through Saturday when I last drove it, now only disengages just before the floor when it used to be about half travel.

This is the first hydraulic clutch I've owned, my others have always been rod linkages, so I'm trying to understand where my problem may be.

It has been cold, today's high was in the 20's. I'm wondering if any moisture in the system could have frozen up to create this problem. I just found the problem at about 11:30pm ET, New Jersey.

My '79 F-250 had a similar problem where the fingers on the diaphram clutch started breaking off. But this was after 150k miles and 22 years of use. And it's problem progressively got worse over a couple of months.

This is rather sudden. I have had some shifting problems this past week or 2, but I associated it with my new pair of shoes and lacking a feel for the clutch. I also discovered that my master cylinder was low on fluid. After topping off the cylinder, all seemed fine again. This was about 5 days ago and the fluid level is still good, as of tonight, with no visible signs of leakage anywhere in the system, as of 2 days ago.

The clutch, plate, and bearing have about 60k miles on them, about 5 years, whereas the master cylinder is the original unit with 193k miles on it. Could the problem be with the cylinder piston seals? This is where I'm leaning.

Though the suddenness of the problem, given the cold temps, it seems plausible that icing could be the issue. The system calls for DOT 4 brake fluid which, to the best of my knowledge, is water absorbent. Plausible, or am I stretching here?

It seems less likely that the issue is within the bellhousing. Maybe wishful thinking as I'm not particularly interested in dropping the trans and transfer case...

Thoughts or suggestions? Thanks.

 

if some fluid was lost at one point then there is probley air in the system causing he lower pedal disengagment. if its the origanal master them i would be looking at that first. look for fluid leaking around it on the inside of the truck or it could be leaking past the seals internaly. mine did the same thing and would get better for a little bit by pumping the crap out of it.

 

I was concerned, when I added fluid, that I may end up with air in the line. At first it was a little spongy, as it was when it was low, but the feel restored. If air is in the line, could it's affects come and go?

The more I think about it, the more it seems like a leak within the master cylinder.

 

Bad master cyl gets my vote.

 

Air compresses. So pushing the clutch or brake pedal when there is air in the line, just compresses the air first, and then the fluid.

 

Exactly Happen to me last week. But the temp was 60degrees. I Had air in my system so i had to bleed it to get the air out. I spent a good hour, by bleeding, pumping clutch then filling master cyl. then bleeding then pump and keep going. THen my clutch got so much better, so it was air that was causing that problem.

 

Also, it's hydraulic so when it gets that cold, the fluid gets thick and causes the slave cylinder to act funny.

 

See if this might apply to your problem. I just posted this in another thread where a clutch wasn't disengaging properly.

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One thing you have to check is the pedal linkage, especially where the pivoting bracket on the shaft that rotates when you depress the pedal meets the eye clevis on the clutch master cylinder pushrod.

The clutch on my '93 was engaging way too close to the floor, and this connection was extremely worn out. The pin on the bracket had a big groove in it, the plastic bushing was shot, and the clevis eye was very "egged out". All that play made it impossible to fully disengage the clutch.

Here's a picture of the fix I made, which I think is far superior to the original design.



I pressed out the original pin that was in the bracket, drilled a 1/2" hole, and welded in a 1/2" bolt. Select a length that will give you a smooth 1/2" surface for the clevis eye to ride on, and not threads. Obviously, cut off the unused part of the threads. The clevis eye still had enough meat on it so that the 1/2" bolt had plenty of surface to press against, and I didn't have to do anything to it. A 1/2" bolt fits into it perfectly. Add a nylok nut, and presto. The nylok nut will allow you to get the clearance just right; no play at all, but not tight, so everything can move freely. I covered the bolt and eye with my best graphite moly lube, and it should be good for many years. A shot of penetrating grease once a year wouldn't hurt.

If this doesn't need doing on your truck, which I tend to doubt, then just check the obvious: a clutch master that's allowing fluid to get past the piston, which probably wouldn't result in an external leak, and a bad slave cylinder, which probably would cause an external leak.

Worst case would be a clutch disc that's so worn out that the clutch mechanisms can't compensate for it.

Good luck; let us know how it all works out.

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See if yours is worn there; even if it's not the main problem, removing any play at that point will makes the clutch release and engage closer to where it's supposed to.

I know you said that it came on suddenly, but maybe the plastic bushing just decided to disintegrate.

 

Good post john D. I'm gonna look at doin that also. I'm so into modification work on rigs, that your idea is ' there ' .

 

I had a similar i guess you could say issue the other day while plowing. The clutch pedal didn't come back all the way, and wasn't disengaging. I opened up the master to check fluid, and it was full and pulled the pedal back and seemed to work fine from then on.

 

Thanks. Forgot to include in that post: The bracket that needs modifying obviously has to come off. It has a splined hole that fits onto spines on the clutch pedal shaft. I think the nut that holds it on takes an 18mm socket. Just be sure to put a mark on both bracket and shaft before you take it off, since there's no locating arrangement that ensures that they go back together in their original orientation. I used some bright red nail polish that I keep on hand for such occasions, and also for when I decide to let down my hair and take a little walk on the wild side.

It takes a bit of prying with a couple of big-*** screwdrivers or small pry bars to get it off, but just when you think the damn thing will never come off, it does.

 

Interesting you should say that. While I was working on my linkage modification, I inadvertantly pushed against the clutch pedal when it wasn't attached to anything and noticed that that part of the linkage has an "over-the-center" type of geometry. If the rest of the linkage has enough free play in it (or is unattached), the pedal will go "boing", right over to the other side of the "over the center" deal. Sounds like you're right on the edge of this effect. Check the connection I described and modified; I bet it's worn out.

 

i did something similar to your john d but used a spherical rod end instead of the origanl piece. i had gotten an adjustable rod with a new master once so it works great and is adjustable.

 

John D - I've had similar problems with rod linkage systems in the past and fixed them in much the same manner as you and MAS96 have described.

This didn't occur to me. I'll take a look at this when the weather isn't lousy. I'm not confident it will be the whole problem due to the extremity and sudden change, but could definitely be a contributor. Could explain some of my missed shifts.

Thanks a ton.

 

SoCar -

"Suddenly going bad" + cold weather just gave me an eerie reminder of the horrific Space Shuttle Challenger disaster from 1986. Cold weather implicated in the failure of a solid rocket booster o-ring.

Made me think that maybe the seal on the piston in either the master or slave is leaking because it's less pliable due to the cold. Have you tried having an accomplice press down on the clutch pedal while you look at exactly what's going on at both cylinders? (Maybe bleed the system first so you can rule out air in the system). If nothing is leaking out of either one, then I'm stymied.