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Rear Radiator Clogged, How To Unclog?

1002 Views 13 Replies 6 Participants Last post by  BillG
I have a 2007 Sienna XLE. The heat runs in the front seat but in the rear, it blows out only cold/cool air. After troubleshooting it over the phone with a mechanic friend, it seems that the rear radiator (maybe "radiator" is not the correct term but part that the radiator fluid flows into in the rear behind the passenger side back panel) is clogged. He said that the only way to unclog it was to either remove it completely or hook up the hose pipe to it and flush it out (which could make a mess). I called the Auto Parts Store and the person I spoke to said that it could be flushed from the engine. So, I am looking for advice on what options might exist to flush out the clog. (Trying to find the method that will avoid radiator fluid flowing all over the back seat). Also, I checked the servo motor in the back and that seems to be working okay. My mechanic friend thinks it is clogged because of the two pipes running into it the top one gets warm but the bottom one stays cool.
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The cooling system will only draw from the reservoir as the system cools causing a vacuum in the cooling system. The vacuum side of the pressure cap has to be in good shape. If there’s a system leak, it might draw air instead of coolant. With 200K miles on the clock, I remove the pressure cap to check coolant level weekly regardless of reservoir level. Too much to leave to chance.

I have no experience with a 2GR with bleed port but bleeding a 3MZ with a big funnel over the pressure cap fitting, excess coolant in the funnel and idling with both heater cores flowing until the thermostat opens works very well.

The coolant lines to the rear core are awkward to get hands on. Maybe easier without the spare. That should confirm whether coolant is flowing to the heater core.

‘04 LE FWD 203K miles
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