Hey all — I’ve got a ’79 FJ40 with a Chevy 350 swap. I upgraded the radiator because the stock cooling system couldn’t handle the V8 and was running hot. Temps are good now, but I’ve been running into something weird:
Coolant gets pushed out of the system through what I think is the overflow hose, and the overflow tank ends up empty after a drive — even though the engine doesn’t overheat.
Here’s how my current setup works:
• The radiator cap has a hose running to the top of the overflow tank.
• Inside the tank, that hose connects to a T-fitting. One leg of the T goes down into the tank with a rubber “straw” that reaches the bottom.
• The other leg of the T-fitting has a hose that vents out (not sure where exactly — possibly the ground or the fenderwell).
• The tank isn’t pressurized, but it does have a cap that seals somewhat well.
From what I understand, this sounds like a basic open overflow setup — but now that I’m running a higher-output engine and bigger radiator, I’m wondering if this design is working against me. Could that side hose be letting coolant escape too easily or pulling in air when things cool down?
I’m not trying to convert anything right now — just want to understand:
• Was this kind of setup normal for older FJ40s?
• Why doesn’t coolant get pulled back into the radiator?
• Has anyone here sealed that side vent hose or modified a similar setup to make it work better with a V8?
Coolant gets pushed out of the system through what I think is the overflow hose, and the overflow tank ends up empty after a drive — even though the engine doesn’t overheat.
Here’s how my current setup works:
• The radiator cap has a hose running to the top of the overflow tank.
• Inside the tank, that hose connects to a T-fitting. One leg of the T goes down into the tank with a rubber “straw” that reaches the bottom.
• The other leg of the T-fitting has a hose that vents out (not sure where exactly — possibly the ground or the fenderwell).
• The tank isn’t pressurized, but it does have a cap that seals somewhat well.
From what I understand, this sounds like a basic open overflow setup — but now that I’m running a higher-output engine and bigger radiator, I’m wondering if this design is working against me. Could that side hose be letting coolant escape too easily or pulling in air when things cool down?
I’m not trying to convert anything right now — just want to understand:
• Was this kind of setup normal for older FJ40s?
• Why doesn’t coolant get pulled back into the radiator?
• Has anyone here sealed that side vent hose or modified a similar setup to make it work better with a V8?
