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Bowden cable maintenance and lubrication

Bill Boyd

Bill Boyd

Well Known Member
Doing my C I, noted that the cabin heat control was frozen. It's an A-730BL0720 from Spruce. Removed the cable after lubrication was unsuccessful, found on autopsy that the jam was in the final few inches nearest to the carb heat box - it's absolutely seized up, and it appears the inner plastic jacket is deformed and the center wire is touching the spiral metal sheath. I'll be replacing this, obviously, but would like to prevent this failure from repeating itself in another 4 years.

What's the proper way to lubricate these cables that have a plastic inner liner? Is there a high-temp model I should consider instead? Another cable of similar construction running through the same area for the emergency air intake on the bottom of the FAB is the same age and operates smoothly. Not sure what made this one fail.
 
Try to route the cable with gentle bends. I also insure the cable has a decent straight length before whatever it’s actuating, so no side loading where it exits. I’ve never lubricated them, but I suppose it might extend its life a bit, but the linings, while not self lubricating technically, are made of a low resistance plastic like PTFE or such.
Fortunately, they are cheap and usually easy to replace.
 
I adhered to all the above in my install. Interestingly, the seizure of the inner wire occurred in the last few inches, which is a straight shot into the cabin heat box. I cut the end of the cable off after removal and the 4+ feet of cable between the dash control and where I cut the last bit off, where all the bends and Adel clamps were along its route, operates smooth as silk. It's a puzzlement.

Considering an Edelbrock replacement from Summit Racing for under $30. I consider the $80 that Spruce wants for another one like the original to be spendy for what it is and how quickly it failed.
 
Bill Boyd said:
I adhered to all the above in my install. Interestingly, the seizure of the inner wire occurred in the last few inches, which is a straight shot into the cabin heat box. I cut the end of the cable off after removal and the 4+ feet of cable between the dash control and where I cut the last bit off, where all the bends and Adel clamps were along its route, operates smooth as silk. It's a puzzlement.

Considering an Edelbrock replacement from Summit Racing for under $30. I consider the $80 that Spruce wants for another one like the original to be spendy for what it is and how quickly it failed.
Click to expand...
Any chance it deformed due to heat? Some plastics have a pretty low melting point. Maybe near an exhaust pipe?
 
Bill Boyd said:
I adhered to all the above in my install. Interestingly, the seizure of the inner wire occurred in the last few inches, which is a straight shot into the cabin heat box. I cut the end of the cable off after removal and the 4+ feet of cable between the dash control and where I cut the last bit off, where all the bends and Adel clamps were along its route, operates smooth as silk. It's a puzzlement.

Considering an Edelbrock replacement from Summit Racing for under $30. I consider the $80 that Spruce wants for another one like the original to be spendy for what it is and how quickly it failed.
Click to expand...
Weird. No clue. Mine have 1000 hrs and 18 years and work as new.
 
lr172 said:
Any chance it deformed due to heat? Some plastics have a pretty low melting point. Maybe near an exhaust pipe?
Click to expand...
Not sure, Larry. It exited the firewall high on the pilot's side, alongside the oil cooler air control cable (which functions normally and is the same vintage), makes a gentle 180 back against the firewall and hugs it all the way to the heater box. Heat in the lower cowl can be a strange thing, including after shutdown.

I think I may have better luck replacing it with an all metal cheap-o design and lubricating it with graphite or a dry silicone.
 
Bill Boyd said:
Not sure, Larry. It exited the firewall high on the pilot's side, alongside the oil cooler air control cable (which functions normally and is the same vintage), makes a gentle 180 back against the firewall and hugs it all the way to the heater box. Heat in the lower cowl can be a strange thing, including after shutdown.

I think I may have better luck replacing it with an all metal cheap-o design and lubricating it with graphite or a dry silicone.
Click to expand...
Yeah, doesn't get real hot there. even though you said heater, I was thinking of the carb heat cable. Could have been some king of mfg defect. don't hear about that problem much.
 
I just wrap a rag around the open end of the sheath and shoot LPS-2 in there with the "straw".
 
Carl,

Ended up ordering from Amazon. It arrives tomorrow; will advise suitability when I get it installed this week. Edelbrock 8013.
 
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