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91 F150 Clutch

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Old 12-02-2007, 02:41 PM
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Unhappy 91 F150 Clutch

Ever since it started to snow here in CO my clutch has been giving me problems. So far it has happened three times, yesterday being the final straw - In the mornings there is no pressure on the clutch at all, it will fall to the floor and refuse to come back up, pumping it for an hour sometimes help but normally I just have to call for a ride - and then later that day or in the evening it runs like nothing was wrong

Yesterday I was driving down to the base no problems, at the first red light it was just about impossible to get into gear, I had to make an emergency lane change and pull over (couldnt force it out of first!) and just let the truck die

Now I am totally new to trucks AND the whole clutch/stick thing (~45 days into this) so I have almost no idea whats wrong. I checked the fluid, its maybe 80% full (it was empty about a month ago, but that was an easy fix). Capped it off, started the truck, pumped the clutch like mad, absolutely no improvement. Today I went back to the truck, I could get pressure but not enough, if the clutch was down it would lose pressure at a high rate of speed - I just limped into the nearest parking lot and got a ride back to base

I followed the line from the clutch cylinder (master?) all the way to the transmission, I could hear a couple drips of fluid and am sure its leaking somewhere... problem is the slave cylinder (right?) looks like it is impossible to reach to diagnose (inside transmission housing?)- Its the holiday season and I dont make enough money for any big repairs (another day another quarter) - any chance somebody can guide me through getting this thing running? What do I need to check, what could the problems be, could it just be a crappy line and thats all that needs replacing or some gasket somewhere - anything but a $$$ repair $$$ shop taking a look would be great. Somebody please guide me through this like a two year old, im not familiar with the terms or parts of this vehicle

Thanks for your time guys
Old 12-02-2007, 03:29 PM
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Welcome to the site!

Sounds like you may have air in the lines and/or a bypassing master or slave cylinder.

My Chilton's book shows a bleed port for the slave cylinder accessible from the outside??? If so, then suggest to bleed the system, much the same procedure as for bleeding brakes.

Since the problem seems to change - suggest that one of the cylinders is bypassing. If the slave is leaking - that probably should be replaced anyway before you sling brake fluid all over your clutch lining.

However, since the reservoir was empty, it's a safe bet that air is in the system - suggest to bleed the system to see where that leaves you.

So, in essence -
Bleed lines
Replace leaking slave - or fix whatever you hear leaking.
Then, if the problem still exists - probably looking at replacing the clutch master cylinder.

Good luck, and let us know what you find.
Old 12-02-2007, 06:37 PM
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Thanks for the response, I will take a look later tonight and see if it is just air in the lines

Not to be a pain, but do you know what tools will be required to bleed the lines? I have a fresh sealed bottle of DOT3 behind the seat, will I just need a pair of pliers or should I go pick up my toolbox beforehand

As for the slave cylinder bypassing... to replace the slave on this gen Ford you have to drop the transmission right? Not exactly a DIY thing for me - oh well if it has to get done so be it

Thanks for the help wde3477
Old 12-02-2007, 07:19 PM
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Eww - no pliers, please!

Suggest you will need something on the order of a 3/8" or 10mm box-end wrench or socket - be doggone careful not to round the bleeder port or to twist it off.

Perhaps use some penetrating oil like PB-Blaster, and try tightening the bleeder port just a very SMALL smidge, before trying to loosen. Also may want to grab a section of vacuum hose or fuel line to help direct the cylinder output into a bottle or the like.

As far as where the slave is - it should be internal unless you have the Mazda 5-speed transmission - then it would be external (which has a slightly different bleeding procedure also). Either way, a quick inspection underneath should reveal for sure where it's at. And yes, if it's internal, going to be dropping the tranny to replace.

Be absolutely sure the slave is leaking - nothing like going to the effort on the scale of a tranny drop, only to find the problem isn't there. Probably will see seepage around the bellhousing mating surface.

Could always take the chance, that if the bleeding solves the immediate operation problem, to let things ride. Then if the slave is leaking bad enough to eventually cause clutch problems sometime down the road - deal with it then.

You'll trade a tranny pull now for a tranny pull later, the slave would have to be replaced either way, the downside would be that in addition to the slave, you would likely be replacing the clutch disc too if it were contaminated by any fluid slinging. Monitor your reservoir level to gauge the rate of leakage. It's a tough decision on when to pull the trigger whenever budgets are tight.
Old 12-03-2007, 12:21 AM
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Well I took a look, its leaking somewhere around the slave, Class III leak, but pretty slowly. After 20 min of pumping the clutch there was minimal change in fluid levels (and none in pressure)

I do have a 5 speed transmission, I believe the bleeder is right above where the line is that runs from master to slave so I will get that done in the morning assuming the weather isn't too terrible

End of the month a couple of big checks should finally roll in and I can afford whatever the truck requires
Old 12-03-2007, 09:39 AM
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How many miles on the truck?
Old 12-04-2007, 02:44 PM
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Miles, we about to tick over to the big 270k. I don't normally buy something that has high miles but its a truck, and its not terribly expensive to maintain and my good friend had receipts for everything that was done

As for what ended up happening, the master/slaves were replaced to repair the problem. I had them do some work on the clutch itself (down to 50%) and some transmission rebuilding was in order as we found three large pieces of metal, and when it was all flushed ended up with seven (it wasn't causing issues but better safe then sorry, especially when the transmission is already dropped).

The issue I have now is the clutch wont engage until the pedal is almost all the way up (~80%), I am used to getting maybe 30-40% of the way up and having it start to engage. Any way I can adjust that? (Not a killer but personal preference)

Also now spotted the exhaust is breaking away from the muffler - so I will just get a buddy to weld that back on

Oh the total price, I was amazed. Just under $800, pretty much 1-2k under what everyone else wanted for it

I appreciate all the help you guys were, too bad it wasnt a simple air bubble but the story ended well anyways
Old 12-04-2007, 07:04 PM
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There's no adjustment that I am aware of on the hydraulic clutches. That's one of the benefits of the hydraulic system - automatic adjustment.

I assume the correct cylinders were installed for the application, so that the clutch throws are the spec distances.

You said some work was done on the clutch itself. If new friction surface parts were installed, it may take a few miles to 'break-in'. If oil, grease, or other contamination is present, may not change. Also assuming here that any new parts were correct for the application and were installed and torqued correctly.

I would agree that 80% seems a bit much before engaging. My concern would be just how close you are to slipping the clutch under load, or whether the throw-out bearing is fully unloaded when the pedal is fully up.

May give it a few miles (~50 or so), then if things haven't cleared up - take it back to the shop for their opinion.

I'm going to have to show your last post to my truck and tell it not to even start thinking about giving up on me yet. 270K miles is great! :-)



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