| rawlir | -- 08-25-2022 @ 7:37 PM |
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Howdy. I have a NOS 1940 Mercury FH 8 that overheating when climbing hills. Is/are there thermostats with these engines? Where might they be? Any thoughts on what might cause this overheating? Thanks.
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| carcrazy | -- 08-25-2022 @ 8:32 PM |
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There are two thermostats in the engine. One mounts in each upper radiator hose on the top of each cylinder head. There are two different kinds available, one type opens at 160 degrees F and the other type opens at 180 degrees F. The 160 degree F units are the ones to use in hot climates. How do you know your engine is overheating? What is the outside temperature when your engine overheats? Flatheads do have a tendency to run hot when climbing hills under high ambient temperatures. From my experience, the engine coolant temperature will generally be about 100 degrees F higher than the outside ambient temperature when the engine is fully warmed up. It can go higher than that when climbing hills or accelerating.
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| trjford8 | -- 08-26-2022 @ 5:24 AM |
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Along with the thermostats, there are other reasons for overheating. Incorrect timing or a radiator that has plugged up over the years. Also there is the possibility that your gauge may not be accurate. I would double check the engine heat with an infrared heat gun aimed at the heads and radiator tank to determine an accurate reading.
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| rawlir | -- 08-27-2022 @ 3:14 PM |
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Thank you, guys!! Radiator has been rebuilt, engine compartment temps moves into 180 to 210 range at heads, just idling, temp gauge moves to half way between N & H idling in shaded but warm garage, climbing hills radiator spits some overflow & steam & gauge went right up to Hot....it is a NOS rebuilt block Mercury (85hp, i think) engine, I THINK the engine is fine as well as radiator....I will work to explore both your comments......Thanks again!!!
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| 1931 Flamingo | -- 08-28-2022 @ 5:57 AM |
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Get an infrared temp gun at Harbor Freight, My FlatHead drops the temp 30+ from the top of the radiator to the bottom, 48 block in a 40 (NO thermostats). Paul in CT
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| carcrazy | -- 08-28-2022 @ 8:27 AM |
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Your engine is running way too hot. Remove both thermostats and drive the car to see if the problem goes away. In theory the thermostats are supposed to fail in the open position. I have had them fail in the closed position with disastrous results - cracked block!
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