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Dj, ASE Certified Technician
Category: Toyota
Satisfied Customers: 1910
Experience:  ASE Master Tech, 30+ years in automotive repair.
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Toyota pickup: 22r running hot at idle with A/C running I have

Customer Question

22r running hot at idle with A/C running I have changed thermostat 3 times changed radiator changed fan clutch and now change to a flex fan and it still runs hot
Submitted: 2 years ago.
Category: Toyota
Expert:  Dj replied 2 years ago.
Hello and thank you for trusting us with your question. I'm DJ.How long has this been going on? Did it start suddenly or get worse over time.Just how hot does the engine get? Have you verified that the engine temperature gauge is correct and it's actually overheating and not a faulty gauge?Is there anything else that's strange that's going on with this?Please let me know and we'll figure this out.DJ
Customer: replied 2 years ago.
Happening about two years now when it gets to half way between hot and cold I turn a/c off I believe the gauge is good because it has got in the red and boiled over
Customer: replied 2 years ago.
Can the timing play a part in the over heating at idle with a/c running or would it run hot all the time
Expert:  Dj replied 2 years ago.
If the timing is advanced too far it can cause the engine to run hotter. Does the engine ping?
Also if the head has been milled too much, or if the engine is running too lean it can cause the problem because it increases the compression ratio.
Here's the theory. The engine is producing heat the is dissipated into the air passing through the radiator.
When the AC is running, the AC system is dissipating heat into the air also. But since the evaporator is in front of the radiator, the air is heated before it gets into the radiator. This reduces the efficiency of the radiator.
Nearly all the time this is because the radiator is partially plugged, but you've already replaced it.
So let me just throw some things out that I've see cause this.
Too much gap between the shroud and the fan, or the shroud missing. It caused the air that's already gone through the radiator to circulate and pass back through the radiator again.
Old coolant which becomes acidic over time. It dissolved most of the vanes on the water pump causing the coolant to circulate slower than normal.
Stacking. This is when air could come in through the radiator, but couldn't get out. This was because the customer put a belly pan under the engine.
Any of these sound possible?
Customer: replied 2 years ago.
I'll check timing this week let you know how that turns out the truck does have a belly pan but it has been on it since I got it I have also replaced water pump
Expert:  Dj replied 2 years ago.
If it's the factory belly pan, then that's not the problem.
Check for a foam seal around the front of the radiator. It's important that only fresh air comes through the radiator, not recycled air that's already been heated.
Let me know what you find.