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Lexdesert
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Hi, Vehicle is an LS400, it has a hydraulic operated cooling fan, however time comes when my fan speeds extra ordinary, I have changed the fan oil/hydraulic fluids, it never helped, time comes when it speeds out of hand, even when the car engine is in idle.

How do I fix this? where I am, i can not access a lexus dealership. The car doesn't have heating problems, just a speeding fan, I have had this vehicle for 3 years, it started doing that last week, someone had mentioned that a part called solenoid valve could be the problem, however I failed to locate this part, he said its the one that controls the speed/pressure of hydraulic flow; causing a stable speed towards the fan, so how do I fix this problem, somebody please help, pleeeeeese!!! Here am on my own!

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The fan you refer to is a "viscous drive" fan, not really hydraulic. I was unaware that one could drain the oil in them. If you have done so, a special silicone oil has to be used, not hydraulic or petroleum oil. If that's what you used, it's over for the clutch. There is no solenoid valve that I'm aware of that controls them - the point of them is that with increasing air temperature passing through the radiator the silicone oil causes them to progressively lock up and begin cooling air movement, otherwise the fan "idles" at a relatively slow rpm and doesn't make noise or cause engine drag. Large trucks use air operated fan clutches, but I've never seen one on a car.

So you need a new viscous fan hub. That's it. No repair possible as far as I know.

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The fan you refer to is a "viscous drive" fan, not really hydraulic. I was unaware that one could drain the oil in them. If you have done so, a special silicone oil has to be used, not hydraulic or petroleum oil. If that's what you used, it's over for the clutch. There is no solenoid valve that I'm aware of that controls them - the point of them is that with increasing air temperature passing through the radiator the silicone oil causes them to progressively lock up and begin cooling air movement, otherwise the fan "idles" at a relatively slow rpm and doesn't make noise or cause engine drag. Large trucks use air operated fan clutches, but I've never seen one on a car.

So you need a new viscous fan hub. That's it. No repair possible as far as I know.

Thank you very much for your reply, my fan is run by oil from the steering pump, I have attached a diagram which is just like my system, however am told that something that controls the flow speed/oil flow speed is called a Solenoid valve, which is visible in the diagram, and I was told if the solenoid valve has a problem, fluids flow faster, causing the fan to overspeed, however I don't know how this solenoid looks like, and where to locate it in my vehicle, otherwise my problem is a high speeding fan sounding like a jet engine.

This solenoid valve, do you know where I can locate it in my car?

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Well I stand corrected. You must have some sort of option used in very high temperature environments. Slick system.

So the solenoid valve is on the high pressure delivery pipe from the pump. You'll need to follow from the pump along to the fan motor. In that line will be the solenoid, and it will have a two wire connector I suppose. If you disconnect that connector and the fan stops, then I would think the temperature sensor is faulty. You mentioned that the fan runs all the time. If you disconnect the connector and the fan continues to turn, then the solenoid valve is locked up in the open position.

So find the pipes that lead from the pump - one to the steering, and the other elsewhere. It's the one that doesn't go to the steering that you follow along, and you'll find the solenoid valve on it. I'm guessing, but it may be on the body of the car and not located close to the pump.

Good luck!

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Hi, I posted an example picture/diagram of what is similar to my fan mechanism, however I have followed the hydraulic pipe line from the steering pump heading towards the fan, it is to compact and squeezed by various parts and pipes, does anyone have a picture of how a solenoid valve looks like or where exactly it is located in LS400, I thought it could be close to the steering pump, but just cant see it.

Chris

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I have checked the diagrams, they don't show a complete cooling system for the LS400 UCF21 engine, in the diagrams I don't see the hydraulic oil fan pump, also still I don't see the location of the solenoid valve because it is missing in the diagram, however because of user curiousB, by use of the website he recommended to me, I managed to fix my navigation system, it too had a loose connection, thank you very much, however I haven't yet resolved the speeding fan issue because I can't find the part that controls fan oil flowing speed/pressure!

Still need help, however thank you very much guys for the support provided for now, Where I am; am on my own, no Lexus dealership, am only depending on you guys to help me fix this problem.

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I'm not sure this is any help, but the full mechanical manualss and wiring diagrams and owners manuals are available for purchase at the Lexus Material Distribution Center, 800-622-2033. This is for any model.

Paul

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I have checked the diagrams, they don't show a complete cooling system for the LS400 UCF21 engine, in the diagrams I don't see the hydraulic oil fan pump, also still I don't see the location of the solenoid valve because it is missing in the diagram, however because of user curiousB, by use of the website he recommended to me, I managed to fix my navigation system, it too had a loose connection, thank you very much, however I haven't yet resolved the speeding fan issue because I can't find the part that controls fan oil flowing speed/pressure!

Still need help, however thank you very much guys for the support provided for now, Where I am; am on my own, no Lexus dealership, am only depending on you guys to help me fix this problem.

Join this website for 2 days @$15 and you can download exact service manual for your model..

https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti;TISESSIONID=dTm2J68DCLGk1vq4CGhm2Hb3c6Q1GylCxdg1gT0QNfnwL21QwnYS!-2021909055?_nfpb=true&_pageLabel=ti_home_page

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Try this

http://www.toyotalexusforum.com/toyota-camry-club/7500-92-camry-v6-hydraulic-cooling-fan-problem.html

It seems there is an ECU to control the solenoid. What I don't know is if the solenoid has no power is it fully open or fully closed? You could pull the plug to see. It might be that no power is open fully as a fail safe mechanism.

So its either:

1) the temp sensor giving the wrong signal to the ECU and the ECU controlling fan for max rpm.

2) The ecu faulty and unable to control the solenoid

3) The solenoid coil is damaged electrically (either open or short circuit of coil)

4) The solenoid is jammed or seized mechanically and doesn't operate

Good luck

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Are you sure you don't have an ES300? It has the hydraulic cooling fan. Here are its diagrams:

http://www.toyodiy.com/parts/p_U_1996_LEXUS_ES300_MCV10L-BTPGKA_4502.html

http://www.toyodiy.com/parts/p_U_1996_LEXUS_ES300_MCV10L-BTPGKA_1603.2.html

The solenoid valve here is Lexus PN 16929-62020 $124.28 at www.parts.com

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Thank you very much for the help, thank you very much indeed, you're all starting to give me some hope.

How and where is the ECU that controls the fan located?

Can old gearbox oil cause the fan to overspeed, or does the gear box too have a temp sensor in the LS400?

You asked if the solenoid is fully open or closed, it does it randomely, it speeds, then after a short while, it returns back to normal speed, when A/C is off.

Guys, once again I would like to thank you all for the help offered, am only depending on you all to help me resolve this issue.

Chris

Try this

http://www.toyotalexusforum.com/toyota-camry-club/7500-92-camry-v6-hydraulic-cooling-fan-problem.html

It seems there is an ECU to control the solenoid. What I don't know is if the solenoid has no power is it fully open or fully closed? You could pull the plug to see. It might be that no power is open fully as a fail safe mechanism.

So its either:

1) the temp sensor giving the wrong signal to the ECU and the ECU controlling fan for max rpm.

2) The ecu faulty and unable to control the solenoid

3) The solenoid coil is damaged electrically (either open or short circuit of coil)

4) The solenoid is jammed or seized mechanically and doesn't operate

Good luck

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I guess we've come full circle then. At the root of it there is no certainty that anything is wrong other than your observation "its too fast".

The solenoid probably is merely a on off switch that causes the hydraulic fluid to flow at one of two speeds correlating to a slow and fast fan. It’s very logical that the ECU would set the fan at a higher speed once you switch on A/C to allow more air draw through the radiator and A/C condenser.

Since the fan toggles between two speeds it tells me the solenoid is electrically and mechanically operating.

There is a possibility the solenoid can be varied to partial open positions and the ECU would vary the speed proportionately. This is more complicated and I am not sure if they would bother with the complexity.

Anyway I am not sure you are even chasing a problem here. The old adage, if it ain’t broke don’t fix it seems to apply.

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