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Old 05-22-2012, 12:20 PM
ianacole ianacole is offline
Join Date: Jan 2008
Location: Lakewood
Posts: 180
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Default Back for more help - SBC cooling issues

This issue just began a couple of months ago. Drove it all last summer with no issues, and in the winter I was worried that I wasn't getting enough heat into it. No changes other than the number of miles on it, but as of a month and half ago the heat started climbing. In a 30 minute drive home or to work it starts pushing 210 degrees. Radiator is hot top and bottom. No leaks. Truck is running just as it did last year - decent power, no backfires, no lugging, no more smoke than there has been previously, it's just overheating now. Need some advice on next steps.

  • 73 FJ40
  • 75ish SBC, Carb'd
  • Stock sized radiator, 4-core, no shroud
  • 160 degree thermostat

What I've done:
  • Swapped the water pump (minor drip around impeller shaft)
  • When I swapped the water pump I checked the radiator for sediment buildup - looked clean
  • Put in a new thermostat (used same 160 degree)
  • Removed siezed fan clutch and put in new fan clutch
  • Replaced spark plugs - cylinder 1 looked ugly, a lot of gray ash buildup, the rest looked fine
  • Checked timing - looks okay
  • Turned up the fuel mix screw on the carb to run a little richer
  • Pulled the York compressor to minimize drag/parasitic loss
  • Checked hoses, don't seem to be collapsing
  • Replaced radiator cap
  • Replaced oil pump - doubled the oil pressure, but seems to have accelerated heat-up
  • Flushed and refilled with 50/50 antifreeze/water mixture
What's left to do, other than replace the motor? Could it be water channels plugging up? I could go to an aluminum radiator and/or a shroud, but this wasn't necessary last year. Am I missing something?

Anyone want to buy a truck?

Thanks all!

Ian A. Cole
Blue '73 FJ40 - My DD
Blue '06 Tacoma Quad Cab 4x4 longbed - 's DD
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