Hydraulic Cooling Fan And Overheating Problems

[CUMan]

I just went through about ten days of searching for a solution to overheating problems in my 94 ES. The answer was not easy to find given the complexity of the hydraulically-operated cooling fan, so I thought I would pass on my lessons learned to everyone else.

We have had extreme heat for about two weeks now. Every day, the temperature is approaching 100. The early part of last week, my wife called and said that her ES was blowing steam under the hood. She had been sitting in the drive-thru at a fast food place.

I drove to where she was and looked under the hood. Coolant was everywhere. I also noted that the top of the coolant reservoir was off. It appeared to me that the top of the reservoir had been blown off, and the belt underneath threw the coolant all over the engine compartment. I could not find any leaks in any of the hoses. She was located less than a mile from a garage that I use, and we took the car there for them to check it out.

They worked on it for a day or so and ended up replacing the thermostat. I picked the car up and drove home while watching the temperature gauge very carefully. The needle stayed right on the second mark up from "C" the entire time I was on the freeway. After I got off the freeway and stopped at a traffic light, it started to creep up. When I started moving again, it moved back down.

When I got home, I left the car idling for about five minutes. I opened the hood and looked at the fan. It seemed to me that the fan was not moving as fast as it should. Also, the temperature gauge headed toward the last mark before the red zone. (The outside temperature was close to 100.) I shut the car off and called the folks at the garage and told them they had not fixed the problem.

The next day, I took it back to the garage. They felt and I agreed that the problem apparently involved the cooling fan not increasing its rotational speed as the car engine heated up. They checked sensors and relays and finally decided that the problem involved the solenoid that is located on the power steering pump. They indicated to me that they did not want to replace this without being certain it was the problem. They suggested that I take the car to the Lexus dealer.

Well, I wouldn't take a worn-out lawnmower to my local Lexus dealer due to numerous past bad experiences. Instead, I took the car to a local service operation that specializes in Lexus and Volvo repairs. This was yesterday.

This morning, they called and said they had the car fixed. My repair cost was $86.10. The problem was the connection which runs between the cooling system ECU (under the glove box) and the solenoid on the power steering pump. I had the valve cover gaskets replaced on the car in May, and I would suspect that something was damaged while that work was being done. The fan has probably been operating at a slow speed since that time, but the weather was never hot enough for this to cause a problem.

The lessons learned are several. First, if the car overheats while idling, look at the speed of the cooling fan. If it doesn't appear to be turning very rapidly, check out this solenoid. The purpose of the solenoid is to increase the flow of fluid through the power steering system when the car heats up. This increased flow increases the speed of the fan.

The solenoid itself is part number 90925-05086. It retails for $57.16 at Lexus. It is also used on Toyota cars, and the Toyota retail is $44.84.

Second, the best way to check the condition of this solenoid is to unplug the connector at the cooling system ECU and check the resistance between ports 2 and 3. The values should be between 7.6 - 8.0 ohms at 77 degrees F. If you check the resistance at the solenoid itself, you might get the correct values; however, in my case, the problem was not the solenoid, but the connection. By checking at the ECU end, you would also check the condition of the connection.

This type fan is apparently used on all 92-96 ES models. In 97, Lexus went to an electrically-operated fan.

The MSN auto section reports that this solenoid is a major problem area on 96 ES models. I have no idea why they would report it as being a problem on just this model year. I would suspect that the same solenoid is on all the 92-96 models.

[Toysrme]

92-94 only.

Yes, if you bridge OP1 & E1 in the diagnostics port, the solenoid trips, causing the fan to rotate faster.

Generally, it get's unplugged (For no reason) during a belt change & left unplugged.

You, mechanically, have a 100% toyota camry. minus a tea tiny number of changes.

Toyota dealers

Independant mechanics

Lexus dealers :(

[mehullica]

I really doubt the problem was from the ecu to the solenoid. Since you had valve cover gaskets replaced, the engine wire harness has to be moved to get the rear valve cover off. During the repair you have to unplug the connector for the fan motor from the p/s pump. The shop never plugged the connector back in the p/s pump after the wire harness was put back on the rear valve cover.

[lexidudee]

I had bridged OP1 and E1 in the diagnostic port and don't get an increase in the fan, what is the problem?

I have checked the resistance between ports 2 and 3, getting a reading between 2 to 3 ohms.

Like all other overheating problems, I get coolant loss at the overflow reservoir when the car is not at high speed. Cooling fan is operating at one speed, SLOW...

Any and all help is requested, thanks.......

[CUMan]

It sounds like the solenoid is bad.

[Toysrme]

or the solenoid is unplugged / bad wiring / bad harness.

[lexidudee]

Solenoid sound bad because of the reading between points 2 and 3, but with OP1 and E1 jumpered, should this bypass the solenoid and get an immediate fan response?

[SKperformance]

Great post , it may not apply to may for reasons of previous damage but is good insight into the system.

[CUMan]

Solenoid sound bad because of the reading between points 2 and 3, but with OP1 and E1 jumpered, should this bypass the solenoid and get an immediate fan response?

I would doubt that the signal generated when you jumper the two points bypasses the solenoid. It probably is routed through the same wiring which runs from the cooling system ECU to the solenoid. If the solenoid is bad, the signal is not going to accomplish what is is supposed to.

[lexidudee]

I just got off the phone with the Lexus part guy, and the 90925-05086 part number is not the solenoid from the power steering. It is labeled as bimetal vacuum switch and part of the EGR system.

They say the the part that controls the speed of the fan off the power steering is in the motor assembly of the ps pump, a 16920 number, which cost $300 plus.

I am really confused what I need now after jumping OP2 and E1 and not getting any response. Two conflicting responses.

Someone please clarify, thanks.

[CUMan]

I got that part number and price from Jose in the parts department at Park Place Lexus (www.newlexusparts.com) in Plano, Texas.

The part does not come up on their system by entering that number.

Their phone number is (800) 275-5398. I would suggest you call him.

[mehullica]

Is the 2 wire connector plugged into the p/s pump? That is what controls the solenoid. When you jump OP1 and E1, you fully opening the solenoid, causing the fan to run full speed.

[CUMan]

I just checked with www.irontoad.com about the part number and price of the cooling fan solenoid.

They indicate that the part number is 16929-62020 with a price of $108.92. Their name for the part is: "Hydraulic Motor Control Valve."

I did some further checking after I got the part number.

This part number comes up on the www.newlexusparts.com website. Their price is $101.72.

It also comes up on the website at www.toyotaworld.com with a price of $91.91. They identify the part as "Cooling fan - solenoid valve." They also indicate that it is used on the 92-95 Camry models.

This particular dealership also sells Lexus parts. When you enter the same part number under the Lexus name, the price becomes $104.17.