matt7184

Ive been trying to figure out my cooling problem and I cant figure it out. Changed out the thermostat and that didnt do it. I was thinking bad radiator fan but I am unfamiliar with the system. Can anyone explain it please?

Also about my overheating: It will never overheat when I am moving at about 20+mph. Usually it starts moving up from normal operating temp after about a minute or two at idle. Once I start moving, after about 30-50 seconds, the temp drops back to normal (or close to it). Any gueses? I was thinking my fan since the new thermostat didnt work, is there a way to check the stock fan?

joelchicago

Sounds like the fan isn't coming on. I'm not sure how the system works, but I'd assume it's either the fan motor (unlikely) or the switch/relay to turn it on. Sensors sound like they are working OK. Apply 12V directly from your battery to the fan wires (connectors) and see if the fan runs. That will tell you where the problem lies.

Also, if you haven't had your radiator flushed in a while, sounds like you may be due, maybe even for a core cleaning.

Be careful not to run too hot or idle too long. Aluminum engines and excessive heat are a bad combination!! If you can't find the problem right away but must drive the car, in the past I've connected a relay to the ignition so that the fan runs constantly everytime the car is on. Hopefully you have the time to do it right though.

matt7184

I just had the radiator flushed 1k miles ago, but may flush it again just to be safe.

Are you talking about the sc400 fan electrical relays? I dont see any electrical wires near the fan. All I see are fluid lines going from the engine fan fluid container to somewhere down near the block and some more lines from the block to the fan and then the fan to somewhere under the left side of the headlight.

Id just take all of it out and put some SIMPLE electric fans in there, but I want to know I wont be hurting my car.

933005spd

If I remember correctly my fan on the 92 400 was fluid driven. Have you checked your levels yet? On my 300 the upgrade from the clutch fan to dual e fans made all the difference in the world as far as power was concerned.

matt7184

Unfortunately I dont think we'll see the gains of an electric fan unless we can bypass the pump or whatever is controlling the fan. The benefit of the electric fan is it will be a LOT simpler!

My car was doing something really similar last month and I was low on fan fluid. Now the fluid is at the lvl where it says cold (when the car is cold) on the fan fluid container, maybe i'll try to put even more ATF in.

ToyLexmods

Matt,

Simple test....will the car start to overheat if your parked and idling for extended periods? If so...then pop the hood and have a look at the fan while the car is starting to creep up the temp gauge. You have fluid driven system with a solenoid that controls the fluid pressure. What trips the solenoid is a simple temp sender...known to fail. So, do the above first....see if the fan is actually coming on...if not. Then you must start the diagnosis procedure and check that temp sender.

Joel,

See above...we cant trip the elec fans like the Supra. ;(

matt7184

After initial warmup, if I stop for about 2 minutes at idle, the car will overheat, until I get driving again.

The fan turns on when the car starts up, is it supposed to spin noticibly faster when the temp creeps up?

matt7184

Just my luck, I went to remove the radiator cap to triple check that the tank was full and I hear a soft hissing sound (car has been off for at least 12 hours). Then the cap will not come off. It turns about a 1/4 way and it will not come off. Any recommendations? (I really want to bash my car with a hammer since I am getting frustrated with it
)

I checked my fan fluid level and it is full to the top.

ToyLexmods

Matt,

If the temp is goin up...and your sitting at a stop. ....that fan should be going much faster. Check your temp sender...or have it checked. As for the rad cap...cant you see in the clear res...if there is a/f in there?

matt7184

I cant see that good in my garage and with a flashlight through the plastic.

How much is the temp sender and how do I check if it works or not?

Erfan

How many K do you have on the clock? You might have a blown head gasket or probalby the fans are not spinning and turning on. Might have a bad relay or temp sensor for the activation of the fans, why dont you take your car into the service shop and let them do a full diagnostic.

matt7184

I have about 71k now. There is no smoke from the engine or exhaust, so I dont think it is a head gasket, plus my coolant level appears to be normal.

I rather just do things myself, dont really like mechanics working on my car if I dont know them.

Does anyone know how to check the fan solenoid relays, etc? (Thanks for the help so far guys!)

black sc

Your radiator may have to be rodded and cleaned or there may be a air bubble in the coolant system. Do some research on previous posts.

Erfan

I feel bad about this, i dont like any mechanical problems at all, I get them fixed ASAP at my local Toyota dealership. Please keep us up to date on your status.

ToyLexmods

Matt,

Sorry, I cant type out all the diagnostics. If your fan is not running on high speed when the car is overheating....you must check the fan circuit. Not blown headgaskets....lets keep it simple here folks. It does sound like the temp sender for the fans...its in the lower rad tank.

My suggestion is to buy the service manuals for the car if you dont trust any local shops.