'70 FJ40 dumps coolant right after shut off

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My '70 FJ40 will dump a load of coolant right after shut off, then the temp gauge will increase all the way to hottest reading. When driving, gauge stays cool, never even in the middle. I have only a hose that goes from the radiator fill point directly to the ground; no overflow tank.
 
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I put on the new radiator cap two days ago thinking this was the issue. It definitely is not coming out of the cap. When I shut the vehicle off I opened up the hood and watched it just shoot out the tube straight to the ground. I guess I could check the thermostat because I have no idea if it's defective or not
 
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JohnnyC

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You need an overflow tank on your 70’ ... then you can compare to your 76’

Overtime the more you piss out the more air gets in ... you most likely got quite a bit of air in making each time worse and worse
 
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My '70 FJ40 will dump a load of coolant right after shut off, then the temp gauge will increase all the way to hottest reading. When driving, gauge stays cool, never even in the middle. I have only a hose that goes from the radiator fill point directly to the ground; no overflow tank.
Had similar problem a year ago. A new cap took care of it. I also have an overflow tank that keeps the coolant off the ground.
 

brian

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To me it seems quite abnormal because I'm having to fill it up with about half a gallon of water every 4 days and I don't remember having to do that with my 1976. But I guess different years do different things
hence the reason for the overflow tank that everyone is telling you to get.
it will "burp" like that almost every time you bring it up to normal operating temp and shut down.
with an over flow tank, the rad and engine filled with coolant and the over flow bottle filled to its line, will self regulate its coolant level....when the system warms up and the coolant expands the excess will burp pass the rad cap, when the system cools down and the coolant contracts, it will suck some back out of the over flow bottle into the rad.
 
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Living in the Past

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You need an overflow tank on your 70’ ... then you can compare to your 76’

Overtime the more you piss out the more air gets in ... you most likely got quite a bit of air in making each time worse and worse

Really never had this problem since unless fluid in the radiator gets low enough to suck air from the bottom air will stay there and be the first think vented out the radiator cap. Problem once the engine start to overheat like climbing a heat in the summer heat that coolant is gone verses being drawn back in from the overflow tank and the engine cools down. Not sure on the early FJ40 but the FJ25 the overflow tube is metal and runs down the side the radiator.

Since heat rises and the engine temperature sensor is at the top it's going to read higher at the gauge once the engine is shut off.

I put on the new radiator cap two days ago thinking this was the issue. It definitely is not coming out of the cap. When I shut the vehicle off I opened up the hood and watched it just shoot out the tube straight to the ground. I guess I could check the thermostat because I have no idea if it's defective or not

Do not think it was answered a radiator cap is spring loaded and when pressure builds in the system and release enough pressure and then closes again the released pressure comes out that tube by design. This tube is outside the closed system. Your radiator cap is the source of the coolant and tube is only where it drains. If for any reason you have coolant leaking right around the cap you have a real problem and need to be extremely careful. Living in Phoenix and driving old company vehicles that were second hand phone company vans learned a lot about over heating vehicles and what to do as far as safety. Also the correct way to cool down a over heating engine so it not destroyed. Happy to report I never got burn or did a engine ever cease up or block crack on me.
 

73FJ40

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@84lumberman

From the 1973 Owner's manual (73 has no overflow tank)

If you fill your radiator to the brim, and don't leave the 3/4" air space, thermal expansion of the fluid will always push fluid out the overflow tube.

If the cap doesn't hold the required pressure, the fluid may boil upon shutdown of the engine when the fluid is no longer circulating and residual engine heat increases fluid temp past the boiling point. Boiling will force fluid out the overflow.

Note that from 212 deg F, every 1 lb of pressure increases the boiling point of water about 3 degrees F.
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Any suggestions on what overflow would be a good choice? It's impossible to find a decent price FJ60 container. I don't need to spend a whole bunch because I'm not doing a restoration but I want one that works well
 

hobbes

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I grabbed a used FJ60 bottle overflow from cruiserjunktion a year or so ago. Been working great on my 1974. Prior to that I had ye old coolant bottle wedged behind the headlight with a hole drilled in the cap. Ran like that for a few years.
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