2004 Toyota Sienna overheating

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Originally Posted By: MaximaGuy

One experiment to do if you replace the coolant, when the radiator drain is opened, it should flow really fast and then a small trickle. If it drains and drains you have a partially clogged radiator - aftermarket radiators are far better than stock and bigger and better.


Not sure with Siennas, but at least with my Liberty the OEM one is far thicker and better than the aftermarket ones. Most people on the Liberty forum are lucky to get a few months or a year from an aftermarket rad. I got 3 years from one compared to 9 years from a factory one. One guy went through 12 Napa/Spectra ones in a year, went to Mopar and not an issue since.

On the XJ forums people seem to have good luck with aftermarket. Not sure which category the Sienna falls into but I think OEM is best.

I have a feeling this issue was a bad t stat, get OEM only.
 
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Originally Posted By: HoosierJeeper
Not sure with Siennas, but at least with my Liberty the OEM one is far thicker and better than the aftermarket ones. Most people on the Liberty forum are lucky to get a few months or a year from an aftermarket rad. I got 3 years from one compared to 9 years from a factory one. One guy went through 12 Napa/Spectra ones in a year, went to Mopar and not an issue since.

On the XJ forums people seem to have good luck with aftermarket. Not sure which category the Sienna falls into but I think OEM is best.

To pile on a bit, the aftermarket Denso radiator may be identical to the OEM Toyota one. When the original radiator in my old Sienna started leaking the Denso replacement I bought from Rockauto was the same.
 
Originally Posted By: MaximaGuy
Originally Posted By: wag123
michaelluscher said:
The cooling systems on 3.3L V/6 Siennas do not trap air so they don't need to be bled. The 3.3L is also not known to have head gasket problems unless it has been badly overheated.


Complete [censored]. When an engine is higher than the radiator, it needs to be bled. Period, open the radiator cap and run it through for 15 min on a ramp.

3.3L with HG problems, another piece of [censored], they are made to last, bullet proof.

Nonsense, you are wrong! When it comes to Siennas, you don't know what you are talking about.
I have a 2005 Sienna with the 3.3L V/6, just like the OP has. First off, the engine is NOT higher than the radiator. I have changed the coolant on mine several times, exactly 2 gallons come out (including draining the engine block on BOTH sides) and EXACTLY 2 gallons go back in. The cooling system does NOT need to be bled! Like another poster stated, the location of the radiator cap just in front of the firewall and under the cowl precludes the use of any kind of funnel to fill the system, I have had to use a hose mounted to a funnel to fill mine.
Regarding my advice on replacing the radiator, I have had to replace the radiator in mine, doing so resolved a problem I was having with it getting abnormally hot, so I consider my advice to be sound. Radiators don't last forever and they aren't outrageously expensive. I purchased a DENSO, it was identical to the radiator that came out and it was half the price of an OEM from the dealer.
Also, I have known MANY people that own different Toyota models with the 3.3L V/6 with MANY miles on them (mine included) and I have yet to hear of anyone having a head gasket problem that wasn't caused by a major overheating event. That's not to say that a head gasket problem is totally out of the question, quite the contrary. It just isn't a common problem.
You may know something about Maximas, but you don't know anything about Toyota Siennas so please consider letting someone who DOES know about Siennas help the OP. One last thing, insulting posters is not acceptable behavior in this forum.
 
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Originally Posted By: Rtstrider
Yep radiator fan works. The mechanic said everything looked good with the thermostat out. They also stated there seemed to be some moisture under the thermostat so I'm thinking the thermostat didn't get a good seal. Anywho they said drive it without a thermostat for a week or two, bring it back by so they can check the levels and such, and if all looks good they'll order an OEM thermostat from the dealer and put that in.


If you have moisture near the thermostat area, I am almost certain that your water inlet plate cover or the bypass hose (forgot the exact term) is leaking.
 
Well went to drive it and the transmission linkage cable bushing busted on the inside gear shifter (little rubber grommet) So thats ordered and should be here tomorrow. I'll get that replaced and continue driving.
 
I have a 3MZ in my Camry, and I just put a thermostat in it last month

Check for wetness following the lower hose up towards the engine block, there's an o-ring there that can leak with time, or tear during service

If you open up the cooling system on most engines, you will have to bleed the system

Mine didn't need the whole 2 gallons of coolant, but it spent half an hour burping air and taking down coolant until the thermostat and fan cycled

The funnel comes with angles and extensions that can be used to fit the funnel on a Sienna
 
Bushing has been replaced and so far the coolant level isn't moving. I'm thinking these are just a bear to bleed air out of. So maybe this wasn't a bad thermostat after all! Called the mechanic and said I wanted to drive for one more week to make sure the coolant level stays the same. Will keep everyone posted!
 
I am wrong on the Sienna radiator is lower than the engine, checked on my neighbors Sienna.

Having said that it is a general rule that the if the radiator is lower than engine it needs bleeding (my Lexus ES350 has a bleed valve and my brothers RX350 doesn't)
 
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