Thermostat and temp

[2unknown]

98 I4 Cam...

Lately since the weather has been getting hotter...
After my car has been warmed up to normal temp
The temp would stay constant if the car is moving
but if it idles for a bit like at a busy intersection, train crossing...
the temp would go up between the red and half...
This happens more often during the afternoon hours...
The temp rises quickly, but decreases sometimes fast or slow...

I know the fans are working...
I thought about changing the thermostat, but i wanted to
get more info on here first..

I guess the question is:
Is it the thermostat...?

Im thinking of changing it, and if the problem is still present,
I can work from there....

Thanks...

I know there are threads similar to this, but most of them are dead
or left without an answer...

[slpr1mz]

hmm, idk i would check your radiator and then coolant to make sure that enough is there...
any possible oil leaks too... engine and transmission
with most, if not all, if a thermostats isn't working then there should be a CEL
good luck an hopefully you don't blow anything up...

[hill8570]

Real unlikely to be the thermostat if she maintains temp at road speed -- once the thermo opens up (roughly 80 Celcius coolant temp), it's out of the picture (well, unless a defective one closes up again, but if that's going to happen, it's most likely not going to depend on the speed of the car).

I know you say you know your fans are working, but they may not be working enough. If the fans aren't running at idle, while the temp gauge continues to rise, I'd suspect that little temperature switch in the radiator that triggers the fan on and off. Until proven otherwise, that's my prime suspect.

However, if she's overheating even when the radiator fans are running, like, if you're sitting in the driveway, the fans are rockin and rollin, and the temp gauge is still going up, it gets more complex. If so, I'd check:

(1) first suspect low coolant / air in the system. Is the overflow tank empty? If you pop the radiator cap, is the coolant level up to the top of the neck?

(2) second suspect, radiator cap's gone bad. Does the overflow tank bubble even during normal operation? If so, the pressure cap isn't working anymore, and so your coolant is boiling before it should...coolant doesn't circulate very well when it's full of bubbles.

(3) third suspect, running mostly (or all) water with no antifreeze. Same problem as #2 -- the coolant boils too soon.

(4) fourth suspect, radiator fins are really, really, really dirty. Actually, this is like my last suspect, but it's easy to check -- just look through the grill to the radiator (actually, you'll probably be looking at the A/C condensor, which is in front of the radiator proper). If she's filthy, spray a hose from the engine side out to dislodge some of the crud.

(5) fifth suspect, the tubes in the radiator are mostly clogged. I've seen this on occasion with rads that are topped off with tap water or where the antifreeze has been seriously neglected. If it's really bad, you can probably see the corrosion looking in the top of the rad...otherwise you'd have to get the rad testing. I probably wouldn't do this until I've ruled out just about everything else.

(6) six suspect, water pump on it's last legs. Real unlikely...usually a water pump is noisy as hell long before it isn't pumping well.

[2unknown]

Thanks for the reply guys...

hill8570: That statement about the thermostat seems right...its pretty much normal temp the whole time while driving..

Other than that, the coolant level is full,
The radiator seems to be corrosion free so far...coolant is clean..
Coolant is 60/40 mix...
0o also the fins are clear...

About that temperature switch, does it trigger the fans after the temperature rises or before...?

I'll have to check that pressure cap and look to see if it bubbles...

So far today, the car ran fine...

[hill8570]

Y'know, you'd think that something like cooling fans would be simple stuff, but the controls for those suckers are actually pretty complex. Rather than try to parrot the Toyota manuals, I refer you to the wiring diagram at http://www.camrystuff.com/manuals/Ge...ry94wiring.pdf . Page 242 is the wiring diagram, while page 243 is the theory of operation for the fans.

Depending on coolant temps, A/C on or off, and A/C refrigerant pressures, you can have no fans on, a single (the radiator fan) fan on low speed, both fans on low speed, or both fans on high speed. I suspect that if we can narrow down the circumstances causing the overheating, we can narrow down the troublesome component without having to test every relay and switch in the circuit.

[2unknown]

Thanks...
That wiring diagram and theory or operation was informative...
I glanced through the diagram and theory,
But i'll have to go over it in details after work tomorrow..

0o, i forgot to mention earlier, the car's temp was fine with the ac on today...
hope it goes fine tomorrow

[JCamry94]

So many problems lately bro!

[2unknown]

Originally Posted by JCamry94

So many problems lately bro!

I know...why cant it come one by one...? haha
Somehow it all comes at once...

Hopefully I can fully inspect the car this weekend...
Been to busy lately...

[2unknown]

Hey guys..
Haha...bringing this thread back from being dead..

I figured why the temp was rising..
Most of the water in the coolant evaporated...just leaving
the pure coolant...
Even though coolant wasnt low...it just needed water..
Added more water in and the engine cooled normally now...

[hill8570]

Originally Posted by 2unknown

Hey guys..
Haha...bringing this thread back from being dead..

I figured why the temp was rising..
Most of the water in the coolant evaporated...just leaving
the pure coolant...
Even though coolant wasnt low...it just needed water..
Added more water in and the engine cooled normally now...

Glad you got it working. Sure like to know how in the <bleep> water evaporated from a closed system. Wouldn't surprise me if someone added straight undiluted antifreeze to the rig, 'tho (the old "a little is good, more's gotta be better" thing). I've seen that before.