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(1995 Toyota Previa)
in Fremont, CA on June 29, 2010
My van overheating after 20 to 30 minute of drive, overheated in hot and aircond on. But after cool down 4 hrs then drive for 30 mile it overheated water leaked.filled agian with coolant and water. Drivivg 10 to 15 mile it does not overheat.please advise what could be wrong. have new radiator thermostat one year ago.
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Popular Answer
on August 20, 2010
After experiencing some overheating, I recently self drained & flushed my 1993 Previa's radiator and reservoir tank with interesting results. I noticed something was wrong when my temperature needle moved to hot, my radiator reservoir tank was full and remained cool, and the heater did not normally come on to heat inside the van. I think the hot coolant was not flowing past the heater core because of a blockage in the cooling system. So I guessed the reservoir was the bottle neck keeping the system flowing.

First, I removed the top plastic air duct intake cover. Then I removed the radiator reservoir tank. After unscrewing the bottom radiator drain plug to drain coolant, I ran a yard water hose (with on/off hand grip for control) from the top radiator inlet hole and flushed out the old coolant.

The interesting part came when I completely cleaned and flushed the coolant reservoir tank with a the yard water hose. I noticed that one or two of the three inlet/outlet nozzles had been clogged with debris and/or coolant sealant. So I cleared the reservoir's thin nozzles with a Q-tip and thin ice pick or screwdriver. It appeared that the reservoir tank had been clogged which made the cooling system inefficient, especially during warm weather with the AC on.

To flush out the old coolant from the engine, I ran the yard water hose from top radiator hose with the engine on for about 1 minute. Eventually I saw old water/coolant flush out from the hoses that connects to the reservoir tank (which had been removed.)

After 45 minutes of draining, cleaning, flushing, I connected everything back up and refilled the radiator with fresh coolant. Be careful when removing the hoses... the nozzles, nipples, or hose connection tips can easily be broken if the rubber hoses are pulled the wrong way.

For now it seems the radiator is keeping cool. If your temperature needle is showing up hot past the middle mark, try flushing out the reservoir tank, radiator, and hoses to make the cooling system more efficient. In my case, it seems the reservoir tank was clogged because 3 of the 4 inlet/outlet holes are very thin and can easily get clogged with old coolant, debris, dirt and/or sealant
on June 29, 2010
by overheating it so many times, you may have done internal damage to the motor. take it to a shop to have a hydro carbon check to the cooling system. then pressure test to find out why it overheated.

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