QuestionI have a 99 Sienna LE w/63k miles. The issue is the temp gauge fluxuates from normal to past Hot during long trips and sometimes in town. The A/C also stops working during those time. AC works fine otherwise. The first time I took it to the dealer and flushed cooling system...it didn't fix the problem. Temp gauge still fluxuated. Second time I took it in they replaced the thermostat...still didn't fix the problem.
I noticed that the water reservior was over filled to the point of leaking out from the top. The next morning, reservior came down an inch. I opened the rad cap and didn't see any (red) anti-freeze. Poored contents from reservior into engine and added more anti freeze. A total of .75 gal of water/anti freeze mix replenished engine and reservior. When releasing rad cap, air escaped.
I've read on other forums that replacing the radiator didn't help. So far nobody I've talked to seem to give a clear answer to address this problem.
Please help...you're my last hope before selling it!
AnswerThere are a couple of areas to check, have it checked for a possible headgasket problem and have the cooling system pressure tested for an extenal leak, your dealer should be able to do these tests, the fact is that the coolant is going someplace causing the engine to overheat or the engine is overheating for another reason,possibly a radiator restriction or poor circulation, this will force the coolant out of the radiator into the overflow bottle and eventually out of the bottle, there are not many headgasket problems on this engine so I would check for an external leak or maybe a partially clogged radiator, also make sure that the cooling fans come on.
The reason the A/C stops working is because of the overheating, the system is designed to shut off the compressor if the engine overheats.
