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could someone pls advise as to the max operating temperatures for an SR 5 4x4 extended cab truck, with the 20R engine. It is a first generation EFI.

I had a new temp gauge installed and it registers 230 deg. coming up a 6000' grade in the mountains at 55-60 mph. My AAA rated mechanic states it should not exceed 210-220. So this concerns me. The truck is fully tuned- has a new thermostat- new belts- the fan has been checked and the radiator flushed and has new coolant.

Once in the canyon it starts to descend to the about 220. There is seemingly no loss of coolant.

??

thank you
 

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230 is bad news, especially for the head and head gasket. Spray a forcefull stream of water through the radiator to make sure there isn't leaves/mud/garbage blocking airflow. Replacing the radiator cap is the cheapest and easiest place to start. Next, replace the thermostat. If that doesn't fix it, time to replace the radiator (don't bother flushing it; that rarely ever works. When it does, it''s short lived).
 

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230 is bad news, especially for the head and head gasket. Spray a forcefull stream of water through the radiator to make sure there isn't leaves/mud/garbage blocking airflow. Replacing the radiator cap is the cheapest and easiest place to start. Next, replace the thermostat. If that doesn't fix it, time to replace the radiator (don't bother flushing it; that rarely ever works. When it does, it''s short lived).
thank you for taking the time to respond. Last week I did have the thermostat replaced with a 160 deg one. It did lower the in town operating temp to about 186- my 93 jeep wrangler runs at 180 so that is ok. The radiator cap is still rated at 13 pds, as they could not find a 15 pd. type. Coming up the mtn it is still about 230. So the radiator while apparently clean is next. The toyota shop manual states they can run up to 230 but I am not comfortable with that, even though it cools rapidly once I am home..ba
 

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i was towing a 2,000lb trailer all weekend through canyons, traffic and freeway. my temp never got over 200. i dont even have a fan shroud on it. it isnt a stock motor either, cam, header, exahust, intake etc.
 

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Corona is gone.
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thank you for taking the time to respond. Last week I did have the thermostat replaced with a 160 deg one. It did lower the in town operating temp to about 186- my 93 jeep wrangler runs at 180 so that is ok. The radiator cap is still rated at 13 pds, as they could not find a 15 pd. type. Coming up the mtn it is still about 230. So the radiator while apparently clean is next. The toyota shop manual states they can run up to 230 but I am not comfortable with that, even though it cools rapidly once I am home..ba
The purpose of antifreeze is to raise the boiling point of the water (212 degrees F) and eliminate freezing in winter. The purpose of the thermostat is to maintain a minimum temperature, primarily for winter but also moderate climates. It does not keep the temperature from rising above its value (e.g., 180 degrees). Raising the boiling point of your water allows the engine to run at a high cooling temperature, which is good for economy. If the water boils it will over pressure the cooling system. Your radiator cap will relieve this pressure at 15 psig, but you don't want it to do this every time you drive, so consequently antifreeze helps you in hot weather. Is your radiator fan working properly, it has a clutch you know? Checking the radiator for blockage is also good, but I'm not sure all blockage can be identified without disassembly.
 

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bilt not bot
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another thing to look at is the POS stock fan clutch.



as it gets hotter it should get stiffer. there is no gasket to keep the fluid in and over time the fluid will disapate. they tend to work fine around town but when you get on the freeway the incoming air will simply stop the fan. your speed is the only thing pushing air through the radiator.


i tend to do this to stock fans with great results, with a lil bit of extra noise and power loss near redline. but nothing you'll ever miss.
http://www.celica-gts.com/forums/index.php?showtopic=11041&hl=stock+fan



i would blame the fan WAY before i blamed anything else.


electric fans are a good way to go too.
 

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sounds to me like your temperature gauge is about 26 degrees off calibration since the temp gauge reads 186 degrees at idle with your 160 degree thermostat. You can verify this by removing the radiator cap and idling the engine for 10-15 minutes, then stick a candy thermometer into the radiator coolant and you'll probably see the thermometer reads about 160 even though your temp gauge reads 186.

If this is the case, then when your temp gauge reads 230, the actual coolant temp is 205 and 205 is normal for strenuous uphill climbs and won't hurt anything.
 

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sounds to me like your temperature gauge is about 26 degrees off calibration since the temp gauge reads 186 degrees at idle with your 160 degree thermostat. You can verify this by removing the radiator cap and idling the engine for 10-15 minutes, then stick a candy thermometer into the radiator coolant and you'll probably see the thermometer reads about 160 even though your temp gauge reads 186.

If this is the case, then when your temp gauge reads 230, the actual coolant temp is 205 and 205 is normal for strenuous uphill climbs and won't hurt anything.
Good point, do you think replacing the gauge would solve the problem?
 
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