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Just recently purchase a partially restored 71 Mustang with an aftermarket 460 crate engine And a C6 transmission. Most of the restore has been on the outside of the vehicle and its in good condition with very minimal to no rust. Some of the electrical work leaves something to be desired though.

So I noticed an issue that when I had any electronic device in the car turned on (headlights, A/C, radio) the cars temp would begin to climb and at idle the rpms would drop and you could hear the 2 electric radiator fans rpm drop as well. Figured out it was a 75amp alternator that was going bad. Replaced with a 1 wire 140 amp alt, and took it to a local shop to have them look the vehicle over.

They found exhaust leaks in the headers on both the driver and passenger side, turns out the gaskets were manifold gaskets cut to shape and installed upside down. Had a small oil leak due to a bad cap and vacuum hose. And had a coolant leak around the thermostat housing. They fixed all of those issues and installed an overflow tank for the radiator so I don't lose my fluids anymore and replaced my 192 degree thermostat with a 160 degree one.

Well after I picked it up from them I noticed that the car would start overheating after about 8-12 miles. Both the dash gauge and the radiator cap were telling me it was hot. So I was careful with it. I ran the car at temp with the radiator cap off so I could see if coolant was flowing in the radiator and it was. I took it back to them and they said they couldn't get it to overheat. I picked it up from them and drove it 24 miles without overheating. But then I filled it with gas, went home to pack for a wedding, and got on the highway. After about 12-20 miles the temp started to climb again, and then my fuel pump (or fuel filter in the gas tank or the fuel line) gave out on me and I was stranded and had to get towed home. I've heard that overheating can cause fuel pumps to fail.

I guess my questions would be what do you think the problem could be? I feel like the water pump is still working at least at low rpms. Is it possible the thermostat is bad and that it gets stuck sometimes but not all the time? Or am I just not getting rid of enough heat? I know its hard to diagnose from the internet but any ideas would be helpful.

Edit: The fans are always on btw, they come on with the acc power.

  • does the radiator have a shroud the elec fans are mounted to? or are they just mounted to the radiator? Are these high speed fans? 2,3 or 4 core radiator? – Moab Jun 5 at 15:12
  • @Moab The fans are fairly high speed. I'm not sure of the exact speed, but they can move some air. Probably around 2000+rpm and they are something like 10-12 inch fans side by side. There is no shroud, just the dual fan mounting bracket. The Radiator is probably 2 core (if you are referring to the number of tubes in the radiator), I'm not entirely sure about that is it almosts looks like a single tube wide tube, but it might be split down the middle. Currently there is about <2 inches of clearance between the A/C drive belt and the radiator fan back. Its a Griffin radiator and fan package. – Kyle Struck Jun 5 at 17:22
  • @Moab, I have been wondering if the ambient temp outside has that much effect on the engine temp. It's been about 95+ here in South GA recently. Before I got the thermostat replaced the engine would run at about 200 F (with a 192 F thermostat mind you), but now with a 160 F thermostat I'm getting 220-230 (at the radiator cap so could be hot air right there before I cut her off for fear of damage). It was also probably between 75-90 degrees out back during Easter weekend when I drove it to Auburn AL without any trouble. – Kyle Struck Jun 5 at 17:25
  • Most griffins are 4 core, sounds like you need a radiator shroud for the electric fans. – Moab Jun 5 at 20:21
  • @Moab I'm pretty sure its not a 4 core because it seems too thin to have that many unless each core is smaller on a 4 core than a 2 core. So the shop I took it to (some really nice guys who love classics) just messaged me on FB asking how the Stang was and I told them what had happened. They said that the failing fuel pump could be making the engine overheat because it was running lean. What do you think? I still think I want to get a fan shroud (I seen some that go with my setup) anyways. However the question now is, do I dump the A/C for more space and less draw on the system? – Kyle Struck Jun 5 at 23:44

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