[bobengr]

Cooling fan has been cycling more often, no hot air from the heater, and the temperature guage keeps fluctuating. Guage stays in the normal range when driving, but almost reaches the red zone when vehicle is stopped (drops back down when in motion). Coolant level was topped off, but this is still happening.

Any suggestions? If it points towartds the thermostat being replaced, any instructions on how to replace it?

 

[bobengr]

It is a 2007 LE with 67,000 milkes on it.

 

[jh818]

I would try replacing the thermostat. The housing for the thermostat should be on the engine block with the hose attached to it.

 

[wegngis]

At first it sounded to me like you were low on coolant, but if it's topped off then it's probably not that. Are you losing coolant, then topping off?

Could be a sticky thermostat. Other things to consider is your cooling system having a leak and not remaining pressurized. That could be as simple as a bad cap. Also, if you have air pockets in the system that could mess with it too. Is the top hose hot to the touch when you're at normal operating temperature? (be careful, if it's hot, it will be REALLY hot)

 

[brian_bp]

I find the combination of symptoms to be strange.

Cooling well when moving but not when stationary points to the fan not running, but it is reported to be running, and the lack of heater would be completely unrelated.

The fluctuating temperature does indicate an erratically opening thermostat, but that would only affect the heater if it were sticking wide open and the engine temperature were dropping very low.

An ongoing lack of heat from the heater suggests a lot of air trapped in the heater core, unless the core of one of the heater hoses is badly blocked; however, the air usually works its way out through the cap as the system bleeds itself with temperature cycles.

I really wonder about the condition of the coolant circulating around this system.

 

[wegngis]

I really wonder about the condition of the coolant circulating around this system.

You mean from a chemical and/or mixture standpoint, correct?

I'm also thinking it might be worth getting the system and/or cap pressure tested.

 

[brian_bp]

I really wonder about the condition of the coolant circulating around this system.

You mean from a chemical and/or mixture standpoint, correct?

I'm also thinking it might be worth getting the system and/or cap pressure tested.

I'm thinking from the standpoint of how much crud (corrosion products? just dirt?) is circulating around, making the thermostat stick and possibly blocking the heater core. Water and glycol do have different heat transfer properties, but even straight water should cool fine (it just boils too easily and freezes solid in our winters) and the stuff inherently mixes so well that variations in composition as it circulates around should not be a concern. Some race cars use plain water, since they don't care about freezing and water is both easier to deal with and a more effective coolant.

I agree that checking for pressure retention is a good idea.

 

[bobengr]

Is the thermostat in an easy to get to location?

Is changing the thermostate a DYI job?

 

[wiswind]

I changed the thermostat on my 2003 with the 1MZFE motor.
I recommend you get the thermostat from TOYOTA.

I don't know how similar the process is for your 2006.

This is roughly how things go together for the 1MZFE motor Thermostat


On the 1MZFE motor, you remove the zip tie that holds the oxygen sensor wires to the radiator hose.....then remove the radiator hose from the "inlet pipe".
Then you remove the 12mm bolt that holds the inlet pipe to the motor.


Then you pull (wiggle it) the inlet pipe out of the thermostat housing.
After that....unplug any electrical connection(s) on the thermostat housing or that are in the way of access to it.
Remove the 3 10mm nuts that hold the thermostat housing onto the studs
and remove the thermostat housing and thermostat.

The NEW thermostat gets the gasket mounted ONTO the thermostat as shown in this picture.....and the "giggle" valve will be aligned with the thermostat mounting stud that is at the 11 o'clock position, + or - 15 degrees.


TOYOTA calls for a new "O" ring gasket for the inlet pipe AND for the thermostat.
These are the NEW OEM parts needed for the 1MZFE motor.

 

[94dlx]

Definitely use Toyota OEM parts for the thermostat AND the radiator cap. Either one of these, alone or together, could be causing the problem.

You mentioned the fan is running, albeit more often than normal. My 2004 has two (2) cooling fans so make sure both of them are operating properly (assuming you also have two fans).

The summary of your issue immediately brings to mind a fan clutch failure in older engine cooling systems. The moving vehicle cools by default with airflow from the forward movement flowing over the engine. But when standing still, the clutch doesn't engage the fan to create additional airflow. This makes me think it could be an issue with the cooling fan(s) on your vehicle.

Let us know what you find out.

 

[bobengr]

New development - Driving home from work, after the van sat for at least 8 hours, the temperature gauge increased to normal operating range rapidly, and then stabilized. No heat/minimal heat when the van was stationary (stopped at a light), but extreme heat when the van was moving. Temp. gauge stayed in same position.

 

[jh818]

Maybe your temperature sensor is messed up?

 

[wiswind]

To check your radiator cap......after driving the vehicle and with the motor OFF......with a glove on or with a rag to protect your hand from the heat.....raise the hood and give one of the radiator hoses a squeeze.......it should be firm.
If not....your radiator cap is not holding pressure.
It could be a simple as dirt on the sealing location.......or a defective radiator cap.

No heat under certain conditions sure sounds like there is air in the system.
Really seems early in life of the vehicle to be having a defective water pump......those seem to be pretty reliable.

One other thing.......a small leak can not only let coolant out......it can let air into the system.

 

[robo5]

Where are you checking the coolant level? This has ALL the signs of low coolant level. Are you checking the fluid level at rad cap on the engine not just the overflow on the radiator. Check it with the engine cold. When filling it up you may have to squeeze the upper and lower rad hoses to burb some air bubbles out of it. Fill it up with the engine not running. Once it is full and no more air bubbles are present start it up and top it off.

 

[bobengr]

Looks like it is the water pump now. Leaking pretty good in that area once system is up to temperature. Hard to see exactly where the water is coming out at (had the tire off and splash guard off), but it is coming from above the crankshaft pulley.

 

[wiswind]

I am sorry to hear that.......that can be expensive.....and I like cheap and easy solutions.
No alternative to replacement of water pump......if close to timing belt (if your year has one), then I would have that done as well....as the only addition is the cost of the new belt.......they have to take the belt off and put it on to do the water pump.

 

[bobengr]

Water pump was replaced by the dealer. Van was 7,000 miles out of warranty, but they only charged me for labor and not parts becuase they want future business servicing the vehicle. Had them replace the serpentine belt and do an alignment while it was in. Job was completed in 1-1/2 days. Cost was 60% less than what a local shop quoted.

 

[bmwpower]

Wow. Now water pumps are failing ahead of schedule.

 

[88irocarmy]

Having the same issue right now,
Will try the thermostat first...we will see

 

[brian_bp]

Wow. Now water pumps are failing ahead of schedule.

... but how many of them? One in a thousand? One in ten thousand? If it's one in a hundred I might be a bit concerned, but I don't know that it's that high.