Sheener Posted July 2, 2022 Author Share Posted July 2, 2022 The firewall cracks badly where the master cylinder bolts on. Have you verified that the firewall isn't broken and flexing with the clutch pedal? Firewall seems solid. Has anyone ever experienced the hydraulic line getting soft and weak when underhood temps go up? Being plastic, i wonder? Will check that next time I am under the truck. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 2, 2022 Share Posted July 2, 2022 Firewall seems solid. Has anyone ever experienced the hydraulic line getting soft and weak when underhood temps go up? Being plastic, i wonder? Will check that next time I am under the truck. Chad is right about the firewall, and it is hard to see it move. The best thing to do is to use something to measure any movement. Some have used a 2x4 on the radiator support back to the firewall to see if it moves. Others have put a tape on the radiator support back to the firewall. Then push the clutch in to see how much the firewall moves. Link to comment Share on other sites More sharing options...
Sheener Posted July 3, 2022 Author Share Posted July 3, 2022 Chad is right about the firewall, and it is hard to see it move. The best thing to do is to use something to measure any movement. Some have used a 2x4 on the radiator support back to the firewall to see if it moves. Others have put a tape on the radiator support back to the firewall. Then push the clutch in to see how much the firewall moves. I did check that yesterday, just rocking the master cylinder as I did the first time did not show much movement. Had the boss of me push the pedal while I measured. Between 1/8-3/16”. Ordered a reinforcement plate from bronco graveyard. I will add that before I change any parts. Thanks for the help. Link to comment Share on other sites More sharing options...
Littlebeefy Posted July 3, 2022 Share Posted July 3, 2022 I did check that yesterday, just rocking the master cylinder as I did the first time did not show much movement. Had the boss of me push the pedal while I measured. Between 1/8-3/16”. Ordered a reinforcement plate from bronco graveyard. I will add that before I change any parts. Thanks for the help. Good luck with the reinforcement plate. I got it in but I abandoned the part that has to be installed under the cowl (still works fine and my firewall was definitely cracked). If I recall correctly, you will need to pull the entire pedal assembly; that would give you a good opportunity to check and replace those bushings. I had a 4sp (T170) in my 84 before I swapped it out. I never had any problem with my hydraulics for it, but it's possible it had replacement parts from a PO. This is a shot in the dark, but is it possible you are using the wrong type of brake fluid for that system and it is failing at temp? Link to comment Share on other sites More sharing options...
Sheener Posted July 3, 2022 Author Share Posted July 3, 2022 Good luck with the reinforcement plate. I got it in but I abandoned the part that has to be installed under the cowl (still works fine and my firewall was definitely cracked). If I recall correctly, you will need to pull the entire pedal assembly; that would give you a good opportunity to check and replace those bushings. I had a 4sp (T170) in my 84 before I swapped it out. I never had any problem with my hydraulics for it, but it's possible it had replacement parts from a PO. This is a shot in the dark, but is it possible you are using the wrong type of brake fluid for that system and it is failing at temp? That would be worth changing and not a big job. Thanks. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 3, 2022 Share Posted July 3, 2022 That would be worth changing and not a big job. Thanks. I should have pointed you to TSB 90-16-07 in the first place. It takes you through an inspection process for the clutch linkage and then discusses installing the reinforcement plate. As for replacing the fluid, it is a pain to bleed these systems, so if I wanted to replace what is in there I'd pull it down to just enough in the bottom of the master to ensure air does not get in and refill with new. then I'd pump that through and refill as it gets low again. After a couple of rounds of that you'll have new fluid in and no air. Link to comment Share on other sites More sharing options...
Sheener Posted July 3, 2022 Author Share Posted July 3, 2022 I should have pointed you to TSB 90-16-07 in the first place. It takes you through an inspection process for the clutch linkage and then discusses installing the reinforcement plate. As for replacing the fluid, it is a pain to bleed these systems, so if I wanted to replace what is in there I'd pull it down to just enough in the bottom of the master to ensure air does not get in and refill with new. then I'd pump that through and refill as it gets low again. After a couple of rounds of that you'll have new fluid in and no air. Thank you Gary. Link to comment Share on other sites More sharing options...
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