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Pre-Power Stroke Diesel (7.3L IDI & 6.9L) Diesel Topics Only

zf5 problems

Old May 12, 2008 | 09:05 AM
  #1  
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Angry zf5 problems

i have an 88 ford f-350 2wd dually, zf5, 7.3 idi diesel. Recently the clutch wouldnt disengage all the way so puttin it in gear was impossible. I replaced the slave cylinder because it was leaking thinking that would fix it. It didnt, so i pulled the transmission and replaced the clutch which looked new and the pressure plate that was rather worn. (the finger like prongs didnt stick out as far as the new one.) put in a new through out and pilot bearing. Put it all back together and it worked great. Well this morning i was driving along and the slave cylinder fell off. So put it back on and clamped it down with vice grips for the tie being. Went to press the clutch and it went straight to the floor. So i bleed it and it still goes stright to the floor with 1 or 3 inches of hard pedal. And it wont return up to the level of the other pedals you have to help it with your foot.

Sorry for the long post, just need the truck back on the road.

Thanks in advance.
 
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Old May 12, 2008 | 10:16 AM
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First thing is to check the firewall by the booster for flexing and cracks....... then all the bushings and attachment points of the clutch pedal assy for excess wear......... then think ZF5.
 
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Old May 12, 2008 | 10:23 AM
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is there two types of slave cylinders. One with a bleed screw and one without? Or can i buy a new slave cylinder, resivior, and line? maybe that will work
 
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Old May 12, 2008 | 12:02 PM
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If your firewall is cracked, a new slave and master cylinder will not fix your problem.

I had to fix my 86 five years ago, your truck is only two years newer.

Simple to check, watch the clutch master cylinder while someone else pushes down on the clutch.
If there is 1/4" or more movement of the master cylinder, you have found the problem.
 
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Old May 12, 2008 | 12:49 PM
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The clutch line should self purge of air if you fully depress the pedal and quickly release several times, assuming air intrusion is really your problem (not likely by the sound of it). Is your clutch fluid low or are there any leaks?

I agree with the possibility of a cracked firewall.
 
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Old May 12, 2008 | 03:15 PM
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Clutch

Sure sounds like a cracked firewall. There is a re-inforcement bracket availalbe in case you have cracks in your firewall.

Also check the pedal support bracket for cracks around loops where the shaft turns in. You can buy a new bracket.

As for bleeding, the recommended way would be to remove the master cylinder, line and slave cylinder from the truck and bench bleed it as an assembly and then re-install as an assembly. There are no bleeder screws as the system in theory should bleed itself thru the master cylinder which has a small check valve in the valve body for air to escape. As I said this works fine in theory but guys have found it to be a lot more difficult in practice hence the recommendation to bench bleed.

Dave's method above to mash the pedal will work if you are able to get enough pedal to drive the truck. The remaining air will work itself out eventually.
 
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Old May 12, 2008 | 10:26 PM
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When did they quit putting bleeders on the slave cylinders. firewall may be cracked common problem but it won't make slave cyl fall off was it working correctly when it fell off.
 
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Old May 12, 2008 | 11:57 PM
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Some have bleed screw, some have fittings like you would find on a wheel cylinder and some have none of the above.

If you need a new slave or master cylinder, NAPA has the stock plastic units.

And from my experience, this is one place I will take plastic over metal any day.
 
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Old May 13, 2008 | 08:23 AM
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well it turned out to be the slave cylinder. It was leaking through the blleder at the top of the cylinder. Put a new one on and bled it. Now it woks like new. Thanks for all the help
 
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