79 Overheating Help!
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New User
Joined: Dec 2004
Posts: 20
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From: Kansas
79 Overheating Help!
I have a '79 F-150 4wd with a mildly built 400 C6 auto tranny. It overheats at highway speeds 220 230 degrees. When I drop down to 40 mph temp driops back to 180-190. Around town it will heat up but again it takes some time. I have installed a 5 row aluminum radiator with 450-500 sq inches of core. It is better but still heats up on hot days. I have two elec fans 2200 cfm of air flow. I put a transmissiopn cooler on and took the trans fluid away from the radiator completely.
What can I do next. I don't understand an engine running hot on the highway at 70 mph and cooler at 40 mph.
Any ideas????
What can I do next. I don't understand an engine running hot on the highway at 70 mph and cooler at 40 mph.
Any ideas????
Postmaster
Joined: Apr 2000
Posts: 2,838
Likes: 6
From: SD
I would guess you have one of two problems: not enough air flow or not enough water flow.
There should be rubber 'flaps' between the top of the grill surround and the radiator support - does yours have this? It's to direct the air flow through the radiator instead of over the radiator support. The factory 'flaps' don't cover it completely, some guys prefer to make larger ones to fill it in completely, making it more effective.
Water flow could be slow from faulty water pump or bad hoses. I've seen radiator hoses suck closed at high rpms but fine around town - that was a tough one to find...
Marty
There should be rubber 'flaps' between the top of the grill surround and the radiator support - does yours have this? It's to direct the air flow through the radiator instead of over the radiator support. The factory 'flaps' don't cover it completely, some guys prefer to make larger ones to fill it in completely, making it more effective.
Water flow could be slow from faulty water pump or bad hoses. I've seen radiator hoses suck closed at high rpms but fine around town - that was a tough one to find...
Marty
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New User
Joined: Dec 2004
Posts: 20
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From: Kansas
I have run this engine at 8 degrees and at 12 degrees. There is no difference. Heat begins to build up over time at highway speed. 30-50 minutes of operation puts me at 230 degrees depending on the temperature that day. Slow down to 40 mph and it runs 180-190.
