Toyota Sienna Radiator pressure - Toyota Sienna Forum -
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post #1 of 3 (permalink) Old 05-18-2017, 08:35 PM Thread Starter
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Question Toyota Sienna Radiator pressure

Toyota Sienna 2008 3.5L, it's seem engine compartment is too hot when open the hood, in hot weather and Ac running, also radiator upper hose has too much pressure in it, which decrease after vehicle cools down, just concerning if having too much pressure in hose is normal when vehicle is moving around on local roads slowly, under 25 mile in the hot weather with Ac on or vehicle idling with Ac on for a while? Temperature gauge is normal, I hope symptoms not leading towards the head gasket, since vehicle was overheated last year due to the radiator failure.
Original Radiator cap was replaced and antifreeze was flushed recently but notice no change, newer radiator was replaced last year with original replacement, I notice the pressure there always but since hot weather start and more Ac was in used and more concerning about now, before any issue come up, thanks
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post #2 of 3 (permalink) Old 05-18-2017, 09:28 PM
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Re: Toyota Sienna Radiator pressure

The dash gauge is a rough indicator of 'normal' - it's dampened quite a bit and doesn't indicate small changes in actual temperature. It will hold steady with an engine temperature of around 185 to 215, and then start to rise if the system temperature exceeds this. For a more accurate reading you can use the OBD port and one of the better laptop or smartphone apps to read out real time the temperature sender.

This assumes, of course, that the temperature sender is accurate, and outputting valid data. And that your thermostat is opening and allowing the hottest water to circulate. And that the coolant level is right (the system is full) so that sensor is fully submerged in the hottest water. Lots of dependencies....

As the temperature rises, so does the system pressure. If your pressure cap is working right, it should be releasing at just above one atmosphere (1.1 ATM, or around 15 lbs). Assuming the cap is working, if you don't see the overflow bottle filling fast, the system is not over the specified pressure.

Current: '15 Sienna Limited Premium (FWD), '14 Subaru Outback, '13 Honda CRV AWD.

Past: '08 Sienna LE (FWD), '02 Subaru Outback, '02 Honda Odyssey EX
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post #3 of 3 (permalink) Old 05-18-2017, 10:13 PM Thread Starter
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Re: Toyota Sienna Radiator pressure

Thank you for explanation, that helped me a lot, since overflow bottle doesn't overfill, it's mean the pressure is not above the specified, I will find the OBD port which work with smartphone app and will check the real time temperature to double check, appreciate much for useful information.

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