95 Camry overheating at stoplights but not on freeway

[AC398]

Ok well I have a 95 camry Ive had for like 2 weeks. My problem is after driving the car around for about 20 minutes or so (normal operating temp and coolant both hot) when i stop the car and am idling the temp needle starts to creep towards the red and almost gets to the point of overheating. It would overheat but I can cool the motor down by revving the car in neutral at a stoplight, 2500 rpm will cool it down some but revvin to 3-3500 rpm works better and the car will cool itself all the way down to normal temp or even just below normal. Im thinking its doing this because the fuel and combustion are cooling down the cylinders. It happens on hot or cold days except much quicker on hot days since it gets to normal operating temp much quicker. If Im driving on the freeway the temp needle doesnt move from halfway which is normal with cruising rpm being at about 2k. The only time the temp needle will start moving up to hot on the freeway is if I turn on the ac then it will start trying to overheat. Anybody have any experience with an issue like this, to start I'm going to change the thermostat tomorrow but Im not sure if its a thermostat because any other thermostat Ive had go bad the car temp slowly keeps getting hotter till eventually the thermostat doesnt open and it overheats(american cars). I know this car has a bypass valve so it doesnt get stuck closed, not exactly sure how a bypass valve works on a thermostat but I was maybe thinking the thermostat is busted and the bypass valve is only opening part way and its restricting flow and I have just enough coolant flow to keep the car operating at speed and then when I idle it needs more coolant flow since theres no combustion to keep it cool. Also another thing I've noticed is the heater doesnt seem to get very hot except when the temp needle starts creeping up and I rev it to 3k, then it comes out really hot for 10 secs. and then goes back to kinda warm. Also i recently replaced all my coolant w/ a 50/50 mix and made sure to fill it up twice with once being after the car was at operating temp so the thermostat would be open. Problem was happening before I changed the coolant. If anybody has any suggestions or experience with something like this please let me know. The car is not losing coolant but the coolant overflow doesn't have a cap if it matters. I can easily do basic mech. work on my car but I'm def not a mechanic just know something about cars. Thanks

[TMetalMan]

Hi, welcome!

Mine will do this when the coolant in the radiator is low (after it has expelled all coolant including the reservoir), as there is a leak at one of the front freeze plugs. When my thermostat was bad the temp. needle would drop considerably on the freeway (maybe 1/8" above the cold mark) and go up to about half when in city driving.

Revving the engine will speed up the water pump, which will make the coolant cool off faster. To me this really sounds like a low coolant issue, but I'd like to hear what the result is after replacing the thermostat.

[Frodo65]

Look at the obvious:

1. Coolant level - make sure it's up to the top, no bubbles. With engine cool, remove rad cap, make sure there's enough. Low coolant, including a system that hasn't been 'burped' (air in the system) will cause problems like you describe. Properly bleeding the system and making sure it's full is a #1 priority.
2. Are the fans coming on? At idle, when temps start going up, the fan(s) should kick in. If not, figure out why - relay or temp sensors are usual suspects. With A/C on, the fans should come on.
3. How old is the water pump? OEM or aftermarket? Hoses in good shape (like lowers collapsing from water pump suction)?
4. Thermostat is a possibility, but least likely for your symptoms; one that doesn't open would cause more problem at higher RPM than lower.
5. Radiator age, condition? A rad that's corroded or plugged will cause problems, but again, more likely at higher cooling loads than at idle.

[ballinshots]

had the same exact problem. its because your fan isn't spinning fast enough, i went to a junkyard and found a decent sized rv fan and installed it into my car(ill try to take some pics) every time i turned the a/c i would have to shut it off within a few minutes of turning it on or risk the car overheating. i added a temp sensor with the fan so it would shut off after the coolant reached a certain temp so it stays for about 15 seconds after the car shuts off it also happened with the a/c off but it just took a lot longer

[AC398]

ok well i just checked the coolant level and added maybe 1-2 oz to the radiator, really almost nothing and the reservoir is at the full line. I'm pretty sure i purged the system of air properly. With the radiator cap off I let the car run till it was at normal temp., had the heater running and revved the motor a little till there were no more air bubbles. Now both of my fans come on right away and theyre spinning pretty fast when I start the car and its dead cold, they might start spinning alittle faster when it gets to normal temp. hard to tell because they were spinning fast right away. Im not sure about the water pump I just got the car and it had 118k miles on it, the timing belt was replaced at 80k miles, theres a little metal tag on the motor saying it was done at 80k, I have no service records from the prev. owner so I dont know if the pump was done at the same time. The radiator seems really clean on the outside grill, inside the coolant I added from 2 weeks ago is really green doesnt look dirty or rusty, but theres a little bit of red stain on the inside of the radiator under the filler neck, not much. Anyways after filing the coolant and burping it I drove it around again and same thing kept hapening it just wants to overheat at idle.

[AC398]

alright i was thinking I would pull out the thermostat temporarily to see if that would help and maybe i could diagnose it as a thermostat problem. Well the person who sold it to me had already pulled the thermostat off so the car was def already experiencing cooling issues. Im pretty sure its the water pump now, not too sure what else it could be and I hear a loud rumblingg noise coming from what seems to be just below the alternator whenever I rev the motor esp. when cold. I think its goin to the mechanic because I dont haver time to do an indepth job right now as Im starting a new 6 day a week job. what do you guys think

[JohnGD]

Well one possibility is that the pump may be going out because some people would skip a pump replacement until the next timing belt. The idler pulleys may be old ones too, so maybe those are the ones making noises.

It's not a thermostat, because you said it doesn't have one. And if the fans are working and the radiator is properly filled then it may also be a restricted radiator. Your mechanic should be able to check the temperatures before and after the radiator and see if there is sufficient cooling.

If the radiator is plugged you may need to get a new one given the possible cost and time to flush it and still might not work. Also, your heater core may not be far behind.

[JohnGD]

One more thing. You should get a dealer thermostat and don't go with an aftermarket. Thermostat is one thing I've never found a good aftermarket for (domestic or import).

These import thermostats also plug up a passage when warm. So I wonder if this had something to do with the weird circulation problem, at least contribute to it.

While there are some people reported no problems using other coolants, I would still suggest Toyota Red with distilled water only.