2001 Camry LE w/2.2 liter overheating

Hi! This is my first time on the forum. I have done most of my own car work for many years, but have recently been trying to improve my diagnostics skills--then this (seemingly simple) issue came along and I am stumped:

I have several Camrys--this one is a 2001 LE with about 180K miles on the 2.2 liter. It began overheating while my daughter was at an internship in Florida. She took it to a shop where they put a thermostat and a radiator into it...still overheating. She drove it home (about 350 miles) with the heater turned on the whole way to keep it from overheating...

The engine was running ok, but seemed kind of loud, so I thought the worst--head gasket. But as I listened, I realized the water pump was making most if not all of noise. The timing belt was a little loose too, because of the play in the pump shaft, so I thought I had found my problem. While I had everything apart, I replaced cam, crank, and oil pump seals, oil pump gasket(there were some leaks!), timing belt, water pump, and the water pump housing. Put everything back together...and it's still overheating!

Here's what happens: It comes up to normal operating temperature, then floats up until the temperature reads about 213F, then the fans come on and cool it back down--then the whole cycle starts all over again. This is when it is just sitting idling. When driving, it never quite recovers; it stays hot, fans come on to cool it some--but not much--it creeps back up, then the fans come back on, etc.

Other than the overheat issue, it seems to run fine. My daughter said it lost power on hills while she was driving home, but while driving it as I have been testing it, I haven't detected a serious power issue...So, I made sure I had no air pockets in the cooling system, pressure tested the cooling system (20 lbs--held fine), checked for CO2 in the coolant--none, checked compression--all 4 cylinders between 210-225, checked for white smoke out the exhaust--none, spark plugs were not perfect, but looked ok--no ugly deposits, and no obvious coolant in the oil.

FYI: I was really careful installing the timing belt--I always am--but I checked it afterwards with a timing light just to be sure--5 degrees BTDC at idle, right within spec.

My daughter did say she thought she lost coolant during her trip, but I"m not sure that's accurate--and I don't see any evidence of coolant in the oil or exhaust anyway (and the coolant pressure test did not indicate a leak).

Oh, and I checked for exhaust back-pressure--just in case it might be a catalytic converter issue. I checked this by using both a vacuum gauge and by installing a pressure gauge in place of the B1S1 AF ratio sensor--negative. I also did a leakdown pressure test, which proved inconclusive--I don't believe my equipment is working correctly. I will be trying that again. But even with my faulty results, I definitely did not see any air getting into the cooling system.

What am I missing? I don't pretend to be an expert--or even close. But this seemed like an easy diagnosis and (though time consuming) fix. I have now run out of ideas! I don't want to take the head off if I don't have to; none of my tests has absolutely condemned it or the head gasket.

I don't have a sophisticated scanner or a lab scope, so I feel like I looked at everything I have the capability of checking, given the equipment I have. Could it be something I'm not even looking at or thinking about? Any thoughts would be greatly appreciated...

My 2005 Camry I4 water temp switch 2 closes at 194 and water temp switch 1 at 203.
BBBind.com probably has wiring schematic for your Camry.

Studying your post what I see as the essential points (1) The car is running hot when it reaches running temperature (2) It isn't boiling or using excessive coolant. (3) Temperature stays higher than expected even with air flow through the radiator.

The minimum running temperature is controlled by the thermostat ---- with this in mind I looked up the thermostat for your engine. According to the "First Line" catalogue listing for the european model it is an 82c stat --- 180f which is cool running stat by modern standards. As the stat is a fairly standard design I wonder if the wrong thermostat has been fiited.

I would also consider replacing the coolant temperature sensor as they tend to drift off calibration with age.

What is the temperature of the coolant entering the radiator, and what is the temperature of the water leaving the radiator? There should be approximately 10 degrees difference.

If the temperature of the coolant exiting the radiator is say 30 degrees cooler than what is entering the radiator, then that indicates a flow problem. The coolant is staying in the radiator too long, thus giving off more heat. But at the same time the coolant is staying in the engine too long and thus is not able to cool the engine. The cause of this could be a possible not fully opening thermostat or a faulty water pump impeller.

If the coolant exiting the radiator is close to the same temp as the coolant entering the radiator, then the radiator is not able to shed the heat of the coolant. This is usually caused by poor airflow or clogged passages in the radiator. If this is the issue, check the AC Condenser for cleanliness. If it is clogged with debris, it will result in poor airflow through the radiator. Also check for the plastic shrouds to be in place. They channel and force as much air as possible directly through the radiator. Also check the impeller on the plastic fan blades.

If the coolant entering the radiator is 190, and is leaving the radiator at 180 for example, then you probably dont have an over heating issue at all but is most likely a sensor issue.

This should give you a direction of what is actually happening.

I have seen many issues with overheating after radiator / waterpump replacement and they were pretty much all caused by air in the coolant system. A couple ways to verify no air in the system is to check the heater tubs and make sure they are both hot. If one is hot and the other isnt, there is air there. The air has to be bled out. I have raised the front of the vehicle over three feet in the air with the rear tires on the ground. This helps to make the radiator opening the highest point in the system and the air pockets will move more readily to the radiator. Another method for this is to use a vacuum fill tool.

I keep coming back to the thermostat. Its the only thing I cant see that I didnt replace myself (the Florida shop did). But the car is running the same as it did before the replacement--so it would have to be a defective new one...something I feel is unlikely. If I come up with no other ideas, i might stick another one in there, but I really hate being a parts changer!

The temps I'm reading are using my scanner and using an infrared thermometer. Things are definitely getting hot when the gauge floats up (which happens fairly quickly)--so i believe the gauge and sensor. The thermostat i did not replace myself but is new and seemingly reacting the same way as the old one. I do, however keep thinking about it--constantly!...

Thanks for all the ideas. I will start checking some temps and see what I come up with.

I do believe the radiator air flow is fine, though--when the fans run, things cool very quickly...

I feel like I got all air out of the system, but who knows. All i know is this problem started before any messing with the cooling system, so IMO something else changed

Also, I installed a new water pump (and housing) and nothing has changed. I did not change the thermostat. But that was (supposedly) installed new in Florida...

No one wants to be a parts changer, but I wouldn't blame you one bit if you wanted to change it again. :lol: OE only.

I've been down this path before, where the thermostat only opens far enough to keep the coolant from boiling. More common if it's a double sided thermostat. I'd also suggest checking ECT rationality after leaving the car overnight.

"I do believe the radiator air flow is fine, though--when the fans run, things cool very quickly."

Something you could try is when the temp gets around 200 is to initiate the high fan speed to see if it will hold temp down.
If so then the water temp switch #1 should initiate the same response.
Disconnecting this switch should cause both fans to run at high speed.
i'm just looking at the wiring diagram, don't know location of switch.

I don't want to be Mr. Negative here, but I am thinking Head Gasket. I know you have, already, ruled this out but, in my experience, otherwise UN-explainable overheating and loss of coolant

My daughter did say she thought she lost coolant during her trip

has, almost, always turned out to be a head-gasket issue.

checked for CO2 in the coolant--none

How did you do this. With a gas analyzer? Or, the Color-changing fluid? I use the color-changing fluid and, although many don't like this method, for me, It proves to be a reliable method. I, recently, had a car with similar problems that I, ALMOST, ruled-out the head-gasket because my initial block leak test did not change color. I ended up revisiting the Block/Combustion Leak. After 20 minutes of high idle, and occasional snap-throttles, the fluid did not change. Then I put it in gear and, while power-braking, many consecutive snaps of the throttle, the fluid began to change. It took much longer to change than I have ever seen, but it DID change. A head-gasket fixed the problem.

I am not suggesting you throw a head-gasket at it. But, if the thermostat turns out to be the proper one, I would recommend revisiting the coolant test.

Temps are definitely high--especially the water pump housing at the thermostat (and at the coolant temperature sensor). I compared them with one of my other Camrys.

The water pump housing gets up around 230 degrees before the cooling fans come on (compared with around 205 on my other car). Also, temp at the coolant temperature sensor gets to nearly 200 degrees whereas my other car is at around 180. All temps were taken with an ir thermometer.

Flow issue (therm or wp)? Or coolant temperature sensor? Or something else?

Im looking at all suggestions. I'm nervous that new therm or wp could be faulty--but obviously not good enough at this to decide what direction to go next.

New radiator (air flow is fine)
Thermostat is new (I didnt install)
Water pump is new
Temps are definitely higher than normal
Fans are working
No (apparent) combustibles getting into cooling system (I will be rechecking for a third time)
No (apparent) coolant in the oil

All testing/measurements thus far have been on idling engine.

Is there a definitive way (besides rad. temps) to prove good coolant flow?

The temp at the ECT sensor of 186-200 seems normal.
Is the temp on the scan tool tracking the same numbers?
Also does instrument temp gauge indicate normal range?

Gauge floats up to indicate quite hot. The water pump housing temp reading is REALLY high compared with my other car. Scanner readings are in the same neighborhood--reads about 216 before fans come on ( versus 205 in the other camry). I just tested the coolant temperature sensor according to the manual (should have no contiuity up until 183F) and it failed--but I dont see how that would produce the effect I am seeing...

Can you verify the different types of "coolant temp sensors" on the vehicle?
The no continuity up until 186 sounds like a one wire temp fan switch spec.
The 2 wire sensor should show continuity and open up at maybe 200.
In addition there may be a a third sensor used to send info to instrument gauge.
As i have a 05 Camry I4 not sure of the comparison.

What year/engine in the Camry you are comparing with?

My other Camry is a 2000. Manual (Haynes) calls the sensor in the bottom of the radiator ECT 1 and the one adjacent to the head, ECT 2. ECT 1 should have continuity below 190, no continuity above 208. ECT 2 should have no continuity below 181, continuity above 190. Thats what it says!

amstrum wrote: My other Camry is a 2000. Manual (Haynes) calls the sensor in the bottom of the radiator ECT 1 and the one adjacent to the head, ECT 2. ECT 1 should have continuity below 190, no continuity above 208. ECT 2 should have no continuity below 181, continuity above 190. Thats what it says!

Ok, so the ECT2 seems to be the low speed fan circuit sensor. With a/c off, the low speed fans will turn on when ECT2 temp exceeds 181-190.

ECT1 is the high speed fan circuit sensor and will turn on the circuit when temp exceeds 190-208( the scan tool reading of 2013 is close to specs.)

Can you verify fans operate within the ECT sensor specs.

As you have noted these readings are at idle so engine running under load may be a different story.

Cylinder head gasket failures ("HGF") are rarely and easy call to make unless you have the proverbial smoking gun in the form of a gas test or bubbles in the coolant or coolant in the oil or a misfire. In this case I am still suspecting the thermostat is either the wrong temperature spec or the wrong design ie. not a double ended type.


The cooling system on these engines is pretty old school 1970s style.
The OEM thermostat is a double ended type at the cylinder head outlet, the water pump is on the cold side of the circuit it pumps from the radiator bottom hose and/or bypass hose back into the bottom of the engine, the coolant then flows up through the engine and out of the cylinder head through the thermostat

From a cold start before the thermostat opens all the coolant flow is diverted through the smaller bore by-pass heater hoses from the cylinder head back to the water pump inlet. This continuous flow of warmed coolant ensures the cylinder block and cylinder head warm up at the same rate it also ensure coolant is circulating around the wax bulb of the thermostat which allows the thermostat to open or close in response to changes in coolant temperature.

As the coolant flow through the bypass warms the thermostat starts to open to allow coolant through the radiator, as the thermostat is a double ended type it also throttles back the bypass flow. As a result the thermostat controls the minimum temperature of the engine by blending the colder coolant from the radiator with the hotter coolant flow from the bypass hoses.

Thanks for all the suggestions everyone! I am taking a bike trip and leaving this project behind for a coue days. Ill be back on monday to continue tracking this thing down...

I think next im going to at least check the thermostat and probably swap for a new one--then check for exhaust gases (again!) and look at the sensors.

Stay tuned!....

Andy, would the bypass not being closed account for the higher temp seen a t the water pump.

cj1 wrote: Andy, would the bypass not being closed account for the higher temp seen a t the water pump.

Truth is I don't know on older designs engines I have seen it done without major issues but I live in a cold climate and the cooling systems on all engines aren't the same.
Car manufacturers are running engines a lot hotter than they were in the 1970's for example on my own daily driver the thermostat starts to open at 88c/190f and is fully open at 91c/196f the fan cuts in on slow speed at 105c/221f and high speed at 115c/225f --- those temperatures are about 10c/18f higher than they would have been on the 1970's engines.

The stat I have listed for this Toyota is 82c the temperature should marked on the stat and an 82c stat is easy enough to test in almost boiling water. Hotter temperature stats aren't so easy to test because the fully open temperature is so much closer to boil point.