WK Grand Cherokee Hydraulic Fan Solenoid - JeepForum.com
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post #1 of 18 Old 04-11-2017, 07:29 PM Thread Starter
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WK Grand Cherokee Hydraulic Fan Solenoid

Hi:

I am troubleshooting a 2007 WK Diesel with a non spinning Hydraulic fan. I can not get the fan to kick in turn on, or move at all actually. I am guessing solenoid is blocked or dead. Anybody have any experience with this on a WK Hemi or CRD? I have read a lot on the WJ threads, but it is a little different than the WK hydraulic cooling fan.

I have done a few checks of three wire connector going to solenoid, and I get voltage on all three. About 14.4 volts on ground and hot, and then less than a volt range fluctuating on the other wire and ground, which I guess is the Pulse Width Modulation.

Not sure what acceptable range is here, and of course it varies based on input form transmission, AC and engine temp.

One thing I did succeed in today was to "build a special wrench" to remove the solenoid with.

I converted a large unused wrench to the needed 23 mm by 5 mm thick in order to fit in between the hydraulic pump assembly, and the solenoid body. Worked like a charm as there is a lot of space between fan and engine. I put an oil drain pan underneath to catch the drip, which was not too much. maybe a few ounces.

I know there are similar cooling system elated threads, but I have been searching for some time and not seen anything related to how to test, fix, or deal with this issue, let alone pictures of this solenoid. If you know of any pease point me in that direction.

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Last edited by omsok; 04-11-2017 at 08:00 PM. Reason: Added info.
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post #2 of 18 Old 04-11-2017, 09:16 PM Thread Starter
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So, I think I need to take a step back, and see if one of my hoses has collapsed. I pulled the pin from the solenoid, and left all the other internals in correct order. No difference in fan speed. Unless I am misunderstanding how solenoid works, which I have done before with ELSD actuating solenoid, I may have to examine if it is getting any pressure feed.
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post #3 of 18 Old 04-12-2017, 02:49 AM
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Short out the centre solenoid wire, the fan should ramp up to full speed if its good.

http://plus.google.com/u/0/+DownunderJeep/posts/p/pub
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post #4 of 18 Old 04-12-2017, 08:10 AM Thread Starter
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Shorting Solenoid to activate fan

Hi, thanks.

Just to clarify, the center wire, RD/VT (Red/Violet?) grounded out should trigger a fully open solenoid?

Looking at the Chrysler/Jeep TSB. (albeit 2006-2006) the color coding is BR/VT (Brown Violet) for the center wire, is different. http://www.wkjeeps.com/TSB/tsb_wk_0700205.pdf

Just trying to nail down some facts for mother people dealing with this issue in the future.

As I wrote in the last post, I pulled the pin, which in my mind should have allowed for the fan to spin at full speed, but it did not change anything, which makes me think it is an issue with fluid flow. I may try to pull all the internals from the solenoid, and see what happens then.

Quote:
Originally Posted by Clarkyau View Post
Short out the centre solenoid wire, the fan should ramp up to full speed if its good.
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post #5 of 18 Old 04-12-2017, 12:43 PM Thread Starter
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So I bench tested the solenoid, and it seems good. Power steering works, but zero turns on the fan. Looking at the fluid flow diagram in the Jeep TSB link: http://www.wkjeeps.com/TSB/tsb_wk_0700205.pdf seems straightforward to me. High pressure fluid goes from pump to fan assembly, and onto Steering rack. Some of that pressure os bled off to turn fan as needed, and low pressure fluid from that line goes back to the reservoir.

Any ideas what this could be? Fan spins easily by hand, so it is not seized. Maybe hydraulic end is fried?

For reference I made a video bench testing the solenoid. Be forewarned there are 4 pieces, plus O-rings that can fall out of solenoid once you remove it from the fan assembly.

Video of Hydraulic solenoid:

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post #6 of 18 Old 04-12-2017, 02:03 PM Thread Starter
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Found this thread for solenoid replacement today.

http://www.jeepforum.com/forum/f67/w...enoid-3869561/
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post #7 of 18 Old 04-14-2017, 02:04 AM
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Here is a pic taken from underneath the Jeep.
Definitely Brown & Violet. There is always voltage to the solenoid via the red/gray wire. The Black wire is always earthed. The speed of the fan is varied by changing the resistance of the brown/violet wire to ground (this is done by the front control module). No resistance (shorting to ground) is 100% fan speed.



Check the power steering cooler in front of the radiator, it may have a blockage & is restricting flow.
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post #8 of 18 Old 04-14-2017, 07:16 AM Thread Starter
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Solenoid seems to work, but fan does not spin.

I guess next step is to drain the system and check it out.
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post #9 of 18 Old 04-15-2017, 08:30 AM
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following this with interest.
thanks for posting

2009 WK Overland 5.7 hemi. OME 2" lift
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post #10 of 18 Old 04-21-2017, 08:03 PM Thread Starter
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So, plan was to check signal to solenoid form (ECU, ECM?) with Lab scope, but my donor scope was busy today. Not to be deterred I built an oscilloscope wire to use a smart phone app to see if I coudl get any idea. For more on the oscilloscope build PM me. Took two resistors, ohms law, some wires, soldering, heat shrink, 3.5 mm mic jack, etc to accomplish, but seems to work. I uploaded two videos, one showing PWM signal when Jeep was cold and just started, and OBD scanner showed PWM signal at 0%.


After that I disconnected the thermostat wire, and the OBD scanner immediately jumps to PWM 84% (maybe 86%, I forget)


The Second video shows this bigger peak in the signal. Although this is a very basic oscilloscope, it seems to show that the computer is not the issue, which I wanted to make sure before starting to buy parts. Seems it will be a solenoid, or fan assembly, or both. As per Clarkyau idea, I have not yet checked the PS cooler for obstruction, but that should likely be on the list. If anybody had an extra solenoid, I would love to try it. Wonder if my neighbour would mind if I borrowed his for a few hours.
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post #11 of 18 Old 04-24-2017, 09:06 PM Thread Starter
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Checked signal with a lab scope today, with thermostat wire connected and then disconnected. Basically showed the same as my free app, and home made two resistor wire.

After a lengthy discussion and looking at the system, we have narrowed it down to something in the hydraulics, thus eliminating electrical for the time being.

Next step will be to disconnect the hoses, and possibly pull the fan assembly and check for a blockage that is stopping the fan form taking fluid pressure to spin the assembly. Other option is the impellers are toast on the back of the fan.

As per Clarkyau suggestion will also check the ps cooler, but since the fluid enters the ps cooler after the steering rack, and the steering rack is operating without issues, it stands to reason this is not where the impass could be.
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post #12 of 18 Old 05-03-2017, 07:09 PM Thread Starter
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Cooling Fan Solved

So in the end I went to a scrap dealer, purchased an entire fan assembly including power steering fluid tank already attached with hose, and dropped the whole thing in. Problem solved.

The day before that I pulled my own and inspected it. On the back are two balance solenoids (not sure if that is what they are called) You can remove the plug caps with an allen key, and pull out these plungers. There are light springs behind both. They are two different lengths, and look to have a flow path inside, and an internal spring. On mine the external body was scored on both.

(You can see both plungers and caps removed in the photo circled in red. Springs still in bore.)

Since the previous had owner used ATF+4 ( I don't now if it was him, dealer or who the culprit was) I am assuming it caused these pistons to become scored and impede movement. The longer of the two was difficult to remove, and required coaxing. I used needle nose pliers, which I do not recommend. I took some emery cloth to both, in a haphazard attempt to clean them up. When I put them back in, I was able to push the longer plunger much further in. Installed the whole assembly again and la voila. The fan started working and spinning at low RPM. When I pulled the thermostat wire it did not speed up though. I bled it by lifting the front wheels and turning the steering wheel side to side, and letting it run. Funny thing was as long as the fan was working I no longer had power steering, which reminds me of a post by somebody else with a similar fan, pump problem.

I went to get a scrappers fan assembly, and somewhere doing the drive, the fan stopped working and the PS started again.

I am guessing somebody could clean up the scored parts, hone out the motor body etc, but that is not me. Too important a component to mess with without really understanding.

Anyway seems to be done now. My old solenoid was good. If any body need sone let me know.

Before I put the new assembly in I removed the solenoid, cleaned it up, as well as cleaning up the overall assembly in general.

As part of the process I decided to pull the power steering cooler as well. I can not remember exactly why, I think it was to drain it fully as part of the flush procedure.

Very IMPORTANT If you are going to remove your power steering cooler, please make sure you use two wrenches to remove the fluid input pipe (passenger side). One to hold the fitting on the cooler, and one to turn out the pipe fitting. I would also suggest removing the cooler from the front end assembly so you can judge if stress is being put into the cooler via the thread fitting.

This thing is about as durable as a honeycomb and a moderate amount of force immediately separated the top cooling row and broke the pipe.

You can see red square highlighting the break. This happened when I was removing the assembly the night before so it gave me lots of time to fix it properly. JB Weld Marine. Cleaned the area with Varsol, wire brushed the paint off, and let it have a good solid coating. Marine JB Weld take a long time to cure, I hung the cooler, and then switched ends every hour or so to make sure the wed did not sag. I was not sure if it would hold, but did not leak at all, and that was a week ago.

I also pulled my intercooler, hung it, drained it, and flushed it with hot water and Dawn. Not that difficult a job.
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Last edited by omsok; 05-03-2017 at 07:47 PM. Reason: Additional Info added
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post #13 of 18 Old 05-06-2017, 06:35 AM
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Hi omsok thanks for this posting, very informative.

2009 WK Overland 5.7 hemi. OME 2" lift
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post #14 of 18 Old 05-07-2017, 06:02 AM
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Hi Clarkyau, thanks for your info. So if I connect the centre wire from the solenoid with a variable rheostat to ground, the fan speed can be controlled manually?
What resistance range should the rheostat be, if you can take a guess? And just to be 100% sure, that centre wire goes to ground not positive on battery?

Thanks

2009 WK Overland 5.7 hemi. OME 2" lift
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post #15 of 18 Old 05-07-2017, 08:48 PM
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Quote:
Originally Posted by Clarkyau View Post
Short out the centre solenoid wire, the fan should ramp up to full speed if its good.
Thanks for Posting that !!

Think I'll keep it handy incase mine breaks down in the Mojave.

Life is hard-John Wayne
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2007 , crd , grand cherokee , hydraulic fan , solenoid

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