leeslove4

My a/c causes my engine to overheat!! My hubby replaced both the compressor and the evaporator thinking that this may have been the problem, but nothing helped. The problem is that the fan maintains the same speed even with the a/c blowing. It is not speeding up when the a/c is on to cool off the engine.

One website said that it is the cooling fan modulator, but when we ask around, no one's ever heard of it! The dealerships don't even know what it is! Anyone know what controls the speed of the hydraulic fan?

GEORGE_JET

The controller is located behind the glove compartment. First check the soleniod valve, located on the power steering pump. Make sure the electrical connector is secure. The soleniod valve controls the power steering fluid flow to the fan.

leeslove4

What exactly is the "controller" called? No one seems to know what we are talking about!! We do plan to check the solenoid valve and clean it out with break part cleaner (my husband's favorite). If that doesn't work, we want to replace the "controller" behind the glove box, but NO ONE KNOWS WHAT TO CALL IT!!

HELP ME PLEASE, IT'S SOOOO HOT OUTSIDE!!!

byf43

Look at your other post/thread.

There's a couple of ideas that I gave.

xoloski

I have a similar situation except, my 1992 ES300 overheats only when I go from highway speed to a stop. It'll heat up fast, then cools slowly once I drive fast again. I've replaced the radiator (that was partially plugged by hard water deposits), and the thermostat (just in case).
Now I need to test the solenoid [ is this a simple continuity test, or should I energize the solenoid with +12vdc and test operationally]
and the controller under the glove box.
How is this tested?
Thanks,

xoloski

I have a similar situation except, my 1992 ES300 overheats only when I go from highway speed to a stop. It'll heat up fast, then cools slowly once I drive fast again. I've replaced the radiator (that was partially plugged by hard water deposits), and the thermostat (just in case).
Now I need to test the solenoid [ is this a simple continuity test, or should I energize the solenoid with +12vdc and test operationally]
and the controller under the glove box.
How is this tested?
Thanks,

xoloski

I have a similar situation except, my 1992 ES300 overheats only when I go from highway speed to a stop. It'll heat up fast, then cools slowly once I drive fast again. I've replaced the radiator (that was partially plugged by hard water deposits), and the thermostat (just in case).
Now I need to test the solenoid [ is this a simple continuity test, or should I energize the solenoid with +12vdc and test operationally]
and the controller under the glove box.
How is this tested?
Thanks,

byf43

I had this same issue with overheating.

My dilema was head gaskets.


Is your radiator cap releasing pressure and 'burping' coolant back through the reservoir???

xoloski

I am loosing coolant through the pressure caps.

The part that confuses me is; if my head gasket is passing combustion gases into the coolant system, why doesn't this show up when I do a combustion gas presence check using the blue chemical?

The ASC certified mechanics where I work say the combustion gas presence check very accurate, has always worked for them if gasses were present, works very fast, and detects even the smallest leak. I even left the detector on for about 20 minutes when the instruction inspection period was listed at only 5 minutes.

How did you finally determine the head gaskets were at fault?
Did you change your own head gaskets and how difficult was the job?
What did it end up costing?

I'll try to inspect the hydraulic side coolant fan solenoid this evening.

xoloski

I just came from my machinist.
I asked him about the reliability of the coolant system combustion gas test product. He said he uses this all the time and it works right now and the color change is very distinct.
He also said the product is highly reliable.

I am now confident the tiny bubbles in my coolant are not exhaust gases.

leeslove4

Well, my husband did the tests you guys recommended and he determined that it is in fact the hydraulic cooling fan solenoid on the power steering pump.

He tested the fan with and without the a/c on, and the speed never changed. Since the cooling fan solenoid controls the temperature of the hydraulic fans, and the fact that it is rusted, we now know that this is the problem! After calling a couple of dealerships, we found out that Lexus does not sell the solenoid by itself--you gotta buy the whole pump--and the dealers prices ranged from $396 to $800

But...we all know the power of the internet So, I found one for $197 with a $40 core at www.autohausaz.com and it's on the way.

Stay tuned....

xoloski

I did test the cooling fan hydraulic circuit and found it to be in working order.
I then changed the recently installed thermostat & gaskets.
The problem went away.
The recently new thermostat came from Checker Auto.
The new thermostat came from Auto Zone.
I probably could have gotten by without a new radaitor but, mine was an original 1992 and did have hard water deposits, so I'm ok with replacing it.
I also used new antifreeze and distilled water at 50/50.
Thank you all for your help and guidance.
Steve

siscolad

it amazes me how so called experts in here never seem to mention anything about the sensor that controls the hydraulic fan ,but instead talk a lot of rubbish and never actually explain what to do to fix the problem everyone talks about replacing the thermostat or the fan or the water pump and never actually explain how the fan is controlled by the sensor that works with the ecu for the fan to open the solenoid