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Old 10-07-2011, 03:04 PM
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bad thermostat

my sbc doesn't get past 170 on cold mornings or in warm weather but gets to 195 on hot days in traffic..its has 195 degree thermostat. It only started been cool after car overheated from leaking water pump. when I replaced water pump the temps haven't been right since.

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Old 10-07-2011, 04:40 PM
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If you follow the gauge, and it's accurate, you should see temps reaching 190-200, the thermostat opening, and then the temps dropping back down. Are you entirely sure your gauge is accurate?
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Old 10-07-2011, 04:52 PM
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yes its accurate..I have watched the gauge when the thermostat used to open but now it reaches 190 then stops..not up to 200 or so then drops
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Old 10-07-2011, 05:54 PM
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What kind of fan are you using? It sounds like you have put together a real good cooling system! I have a 180* and that's as warm as it get's except when I'm running 65 on the hwy on a 100* day at 3,000rpm with 4:10's in the rear. Then it stay's under 200. During the winter I either have to put my custom clear plexiglass grill cover on it or change to a 195* stat or I freeze my butt off .
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Old 10-07-2011, 05:57 PM
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clutch fan
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Old 10-07-2011, 06:07 PM
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The thermostatic clutch on clutch fans are rated for different temps two ways. one is the old fluid type and the other has a therm. spring coil. You might just have one on there that's rated to low there by pulling more air through the radiator than needed. Check with Auto Zone and see what different temp rating replacement clutches they have. I run a broad blade manual fan and that's why I have a too cool system for winter driving.
Good accurate temp check is shoot the therm. housing with a laser temp gun and compare with the gauge. My gauge is actually 2* cooler the temp gun reading.
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Old 10-07-2011, 06:40 PM
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but it was getting up to correct temp before
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Old 10-07-2011, 07:18 PM
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Quote:
Originally Posted by whojohnjones
but it was getting up to correct temp before
You are assuming the temp was "right" before- but the new pump may be that much more efficient than the old, worn out one. Differences in the impeller could make a difference in the temps.
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Old 10-07-2011, 08:26 PM
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Anytime you overheat an engine you need to replace the thermostat. it is cheap insurance. It is not unusual for them to go bad after an over heat
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Old 10-07-2011, 10:08 PM
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Your thermostat is stuck open.Easy way to check it when the motor is cold,open the radiator cap and look while it's running,if the fluid on running across the radiator top, fast.
Good Luck,Paisano
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Old 10-07-2011, 11:35 PM
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yes it has constant flow from heater core when cold
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Old 10-08-2011, 05:58 AM
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If you are looking at flow in the hose coming from the heater core to a fitting on the radiator, that does not mean the thermostat is open. When SBC cooling is plumbed with that direct hose to the radiator (quite common), it always has flow from the heater core.

I think that with the thermostat opening early, your clutch fan is controlling the temp in hotter weather. The thermostat is opening early at about 165-170, so in cool weather that is the temp where it stays. In hot weather it opens, and with minimal cooling from the fan the temp continues to rise until the clutch fan kicks in and the extra air flow pulls the temp down.

I would recommend a high flow thermostat if you can find one (Robert Shaw, Mr. Gasket, etc.). However, the local places did not have the 195 degree version of the high flow and I had to get it mail order from Summit.

Bruce
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