Howdy,
75 F-150 w/V8 460 with no mods. Bought it with 86,000 and now has 117,000 miles. About two weeks ago I noticed my temp gauge started registering colder than normal. Usually runs right at lower limit of "normal operating range" and now registers about halfway between that and dead cold. Drove 35 minutes from work, stopped at a gas station for just a minute, when I tried to start her she barely turned and lights dimmed as if battery had gone bad but for some reason I suspected it was hot and binding (just a feeling I guess). Waited about 30 minutes and a generous fellow offered a jump. Didn't really believe battery was problem but did it anyway. About 15 minutes later she started and I drove a mile on to the house. Turned off engine, waited a few seconds, tried her again with the same result. Engine turned very slowly and lights dimmed and would not start. Went in the house, came out about an hour later and she started up. Was convinced at that point it was overheating even though temp gauge registered cold. Thought maybe thermostat was stuck open and water was flowing too fast to remove heat but thermostat seemed OK. I was able to pull down on the "cup" part and it seemed to move fine, wasn't stuck open. Looked into radiator as engine ran and couldn't see water circulating so though maybe water pump went out. Changed water pump out this past weekend. Monday started right up, went 35 minutes to work, parked, worked all day, started right up at end of the day, drove 35 minutes home, parked, shut engine off, waited just a few seconds, tried to start her and got the same thing. Engine just barely turns and lights go dim as if starter is having a hard time turning it. (starter is only 2 months old) Waited an hour, went out and it started right up.
Now I'm really confused. My only guess left is that it may be something with the transmission which would not register the heat on the temp gauge (right?) and might be hard to turn over if it is hot.
Any and all ideas are appreciated. Thanks, Jim

 

You need to change your battery cables. The ground cable seems to be the culprit with the 460 engine for some strange reason. To test this theory, get your truck to the point where it fails (drive 35 minutes and then turn it off and try to start it). If it fails to start, connect a set of jumper cables between the negative battery post and a good ground on your engine block (WATCH THE FAN!!!) Try to start the engine. If it starts fine, then your negative battery cable is failing when it gets hot.

This stimied me until I tried to get a jump and it STILL wouldn't start. It started fine when I connected the negative cable directly to the engine block.

John Neary

 

What you are describing sounds like the timing is too high, It is trying to fire while the pistion is coming up.
The only other scenerio is that you have an air pocket in the engineant it is hotter than the gauge reads. run it with the cap off for about 1/2 hour and see if it burps any air out of the cap.
Are both heater hoses hot? if mot, then there is definately air in the system.
wahtch the water in the radiator, fill it to just over the fins for now, and when you see the thermotat open up, go see where the gauge is sitting. This is the point on the gauge the reads whatever temp thermostat that you have.
Usualy a 160 will read in between C and the left line of the norm range. 180 is right on the left normal range line, 195 usually reads around the "O" in normal from my experienced with both of my 77's.
Jimmy

Oh, you could just have a weak starter that doesn't wanna turn when it gets hot. This could also be caused by bad connections of bad ground or positive cables. I had a mustang do this once and turned out that the ground cable from the battery to the block was bad, even though it looked perfect.
Jimmy