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.
Rear Radiator Clogged, How To Unclog?
1 - 14 of 14 Posts
It could be clogged or it could be "clogged" (with air). The only way it could actually be clogged is if you (or someone else) put something (i.e. stop leak) into the cooling system or you have another problem where something got into the cooling system (i.e. trans fluid or oil) and congealed in the rear heater core. The system is a closed system. What typically happens isn't a clog, but a bubble of air will get stuck in the rear heater core. The only fix for that is to get the air out by bleeding the system and hope you don't have a leak somewhere.
Toyota calls it rear heater radiator. Typically in North America it's called rear heater core.
There's a few inches of snow on the ground right now on my driveway and it's still snowing so I'm not going to go crawl under my van to look, but as I recall there are hard pipes going from the engine compartment to the rear heater core but at some point underneath before they enter the interior there are rubber lines. If I recall corrrectly, it would be easy enough to disconnect those rubber lines underneath and flush the rear heater core from underneath the van, w/o any disassembly of the interior rear HVAC assembly.
Any backstory on the cooling system? Recent work? If so, BillG may well be right about an air bubble in the rear heater core.
I put in a new radiator recently and it blew cold in the back. Getting the air pocket out of the back is why I believe. I parked on a fairly steep hill nose up for a few minutes at operating temp. And let it idle.
Hoping to get that air to move towards the engine or radiator.
It was warmed up when I did it .I opened the bleeder in the block a few times during this to let any air out. It blows warm now. I changed the coolant awhile back and had the same issue. It might work itself over time but its stubborn.
Hoping to get that air to move towards the engine or radiator.
It was warmed up when I did it .I opened the bleeder in the block a few times during this to let any air out. It blows warm now. I changed the coolant awhile back and had the same issue. It might work itself over time but its stubborn.
Thank you BillG. I haven't put anything in it and to my knowledge a mechanic hasn't done anything like that either. This is making me think that if I rinse it out it would potentially get another air bubble in there. I did notice that the coolant tank was incredibly low but filling it up didn't seem to change the situation any. The front (before and after) filling it up blew hot air and the back before and after still only blew cold air. I will have to look online to see how to bleed it. Thank you again for your advice!
Hi Roader! I will have to check underneath. I was under there some time back for a mechanic to show me about an exhaust issue but I didn't pay attention looking for anything with the heater core. There hasn't been any work done on the cooling system since I bought it in 2017. I did notice that the coolant looked really low and I put more in it but filling it up didn't seem to change the situation any. The front (before and after) filling it up blew hot air and the back before and after still only blew cold air. Thank you again for your advice!
Hi jseyfert3, I checked the motors on the dampers and they seemed to be working okay. I checked the one on the passenger side front and in the rear. I assume that the one on the driver side is working okay because it sends hot air out of the driver front side. Thank you for the suggestion!
Hi Eric, Thank you for this suggestion! How do I open the bleeder in the block? I noticed that the coolant was very low. To be honest, I don't remember adding any coolant to it since I bought it in 2017. I put more in it but filling it up didn't seem to change the situation any. The front (before and after filling it) up blew hot air and the back before and after still only blew cold air. Could this have possibly caused an air bubble or some other issue? Thank you for your advice!
If the overflow tank was low then it's likely you have a leak somewhere. Autoparts stores loan out cooling system pressure checkers for free. Easy enough to pressurize the system and look for a leak.
The cooling system is filled via the cooling system pressurized cap. Filling the overflow tank won't get the air bled out. On mine it took three or four days of topping off the coolant in the morning and driving as I normally do to get the air bled out.
The cooling system is filled via the cooling system pressurized cap. Filling the overflow tank won't get the air bled out. On mine it took three or four days of topping off the coolant in the morning and driving as I normally do to get the air bled out.
Thank you Roader! I will do some research on cooling system pressure checkers and how to use one. Thank you again for your advice and help!
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.
Sixto
‘04 LE FWD 203K miles
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.
Sixto
‘04 LE FWD 203K miles
I believe the '07 has a 1-year cooling system which a was a transition from the '06 to the '08. So, you may have the radiator with the filler back near the firewall or you may have the one with the fill neck on the radiator itself. If your coolant is low enough to starve the rear heater core, it's probably too low to find the leak with a pressure tester. To fill it, you get yourself a spill-proof funnel and fill it with the proper 50/50 mix of coolant and then run the car with all heaters on, blowers on full and let it come up to temp. Every so often, you squeeze the fat radiator hose (unless it's too hot to touch). As it draws in coolant from the funnel, you have to keep topping it off. It'll probably take 20-30 minutes of running to get most of the air out. Once the system is full, make sure the overflow tank is at the correct "full" level because, as it cools off, it should draw coolant from the overflow tank. After that, you will probably see the wetness/dripping of coolant. There are a few cases where you won't, though. It can leak in the front, between the condenser and the radiator. It can leak into the transmission (which can be fatal) and it can leak into the combustion chamber (from a definitely fatal head gasket leak). I know the '04-'06 can leak into the valley, but I don't know if that affects the '07. The heater cores can also leak, although, that's uncommon. The rear one leaking should be visible from under the van. The front one would cause the front passenger carpet to get wet. If you can't spot the leak with a visual check, you'll need to do the pressure test to verify if it happened to just be low. You can loose a drop or two every so often, and that can add up over the years to make it low. Still good to verify though.
1 - 14 of 14 Posts
