Need help with 1999 Toyota Sienna overheating...?

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Old 05 Apr 2014, 07:55 am   #1 (permalink)
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Default Need help with 1999 Toyota Sienna overheating...?

I have a 99 Toyota sienna mini van that started overheating out of the blue. We changed the thermostat and it stopped over heating only for the water pump to start leaking coolant. We then changed the waterpump and timing belt. During changing the waterpump the temperature coolant sender/switch was broke so we replaced it.....all parts are new not salvage....now that its all back together it is now overheating again....any suggestions as to what it can be?
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Old 05 Apr 2014, 08:09 am   #2 (permalink)
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When you changed the timing belt, did you check the timing , with a dowel meter? A few degrees off could make a big difference, also check the fuses, especially the one for the fan. Last, but not least check the eradicator fpr blockage.
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Old 05 Apr 2014, 08:24 am   #3 (permalink)
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Look here's the deal. A timing belt and water pump replacement will not cause your problem.















The water pump probably had some crud on the bottom side of it! It was already seeping. Them you changed the coolant, and if autozone had anything to do with it you bought radiator flush ... This procedure ( I never would do) can cause leaks because it will remove rust and other buildup that can slow or stop a small leak.















As a advanced level ASE master auto tech I would need to confirm an overheat conditionI would use a infrared thermometer aimed at the t-stat housing for starters. And if (as you say ) the thermostat ect sensor was messed up , remember most cars have one for the gauge and one for the ECM That being said it would be useful information to plug in to an obd compatible machine that can give you live sensor data to compare with.















But just so you understand. Sometimes ppl that claim to be mechanics will do work on a car and all is good. A grounded temp wire will read full hot
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Old 05 Apr 2014, 08:40 am   #4 (permalink)
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Nothing obvious in your description. It would help to know what the overheating is like, though. Does it ever cool down on its own or does it just get hot and stay hot? Does it heat up on the road and cool down at idle, or the other way around? Is the heater hot when the engine is overheating? Does it overheat immediately? Finally (and maybe most important) does it lose coolant now?































Getting hot and staying hot, often with worse heating when on the road or freeway, is usually a sign of a radiator blockage or of coolant loss. Overheating at idle and cooling when you get going is either air flow trouble (like a fan not running) or water flow (like a bubble... no bleed valve in the 1999, though). If the heater is not hot when the engine is hot you can count on a water flow problem.































It could be worse. In the 2007 and later Sienna replacing the water pump requires removing the engine/transmission completely!
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Old 05 Apr 2014, 08:55 am   #5 (permalink)
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Autozone did recommend the flush and it was only after that, that the water pump starting leaking and we replaced it...the heater works and will help keep the temperature down for a little while, while driving.....I've only noticed the fans coming on when I turn the ac on but they don't seem to be engaging even when the dash gauge is saying I'm starting to overheat. How do I check if a wire is grounded and how do u check if a fuse is bad?
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