4.7 Hydraulic cooling fan manual switch - JeepForum.com
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post #1 of 32 Old 05-08-2019, 01:25 PM Thread Starter
Moose Magnet
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4.7 Hydraulic cooling fan manual switch

I want a switch to force the hydraulic cooling fan to spin. Has anyone done this?
I believe the fan comes on too late, when the temp it too hot. It should come on sooner.
New: water pump, radiator, hoses, thermostat, coolant and flush.
The fan has come on only once when the water pump gasket failed the engine overheated. Seems it came on late. Should come on BEFORE it overheats.
Anyone devise a manual switch for the hydraulic fan?

I really want to do this.
Thank you in advance.

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post #2 of 32 Old 05-08-2019, 01:55 PM
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What temp is the fan coming on now? Would need a scanner.
IIRC @220deg someone will know offhand and will add.

The PCM controls fan speed, it is PWM to desirable speed % . So a switch would get you 100% and I am not sure about that speed being desirable long term.. ALSO codes may likely set as fan circuits being modified may be an issue. I am not sure the logic here as codes affect systems - ie lack of cooling and AC restricted.

I would go thru current system performance be sure its 100% operating.
MAYBE MAYBE you could program a temp change for fan operation, I am no fan of rrewriting programs. Unintended consequence 's

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 32 Old 05-08-2019, 01:58 PM
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If you had no coolant then the sensor has no coolant to sense and the scenario you describe is a possibility, fan did not come on. Just a thought.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 32 Old 05-08-2019, 02:15 PM Thread Starter
Moose Magnet
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Dealer says the hydra fan can not be programmed (only elec fans).
I don't know what temp the fan comes on. It never comes on - only the one time.
Came on only once when the needle was PEGGED and it was already spewing coolant.
I believe 220 is too hot. The fan should come on sooner.
It might cause a code, I don't know.
I don't plan on running it 100% all the time. Only briefly to bring the temp back down.
When driving slow, the temp goes up. Maybe not 220. But I believe too hot anyway.
I don't want it to get that hot. I believe the overheat issues of these jeeps is because the fan doesn't come on until it's too late.
I had a 1995 Dakota, and could force the fan briefly by turning on the A/C. No such option with this jeep.
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post #5 of 32 Old 05-08-2019, 02:45 PM
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Fan never comes on? you have no idea if there are codes stored , I would need to check if AC activates fan not sure at the moment.


you should troubleshoot your system, get the tools needed to check system BEFORE modifying.

Time permitting I will get manual and check for fan on temp, and the AC question.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 32 Old 05-08-2019, 03:08 PM
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The other day after a total flush of my "sticking" hyd fan circuit ( about 3qts) i had my code reader on it and i watched the temp when the fan ramped up from idle. At about 205* it sped up a little and at 207* a little more. So somewhere around 205* it seems to "kick in" from idle. Mine works fine now.
instead of opening up a can of worms, flush the hell out of it first........ if all else fails u could get a good quality ele fan with a adjustable temp controller and place it in front of the radiator.

I dont believe turning on the ac ramps up the fan.


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post #7 of 32 Old 05-08-2019, 03:12 PM Thread Starter
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No codes. Two mechanics have said "all is as it should be."

When the fan did come on - the one time only - it was LOUD. Blew a LOT of air.
Has never come on again. I'm guessing it needs to get HOT before it comes on.

Another shop I spoke to on the phone said "They'll run 210-215 all day."
I don't want it to run above 210 very long at all.
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post #8 of 32 Old 05-08-2019, 03:33 PM
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The hydraulic fan on that's found the later 4.7's always runs. At idle, even when the engine is first started, the fan has an idle speed of its own, usually a couple hundred RPMs.

If your fan is dead and doesn't spin at all at, then there's something wrong.

You can unplug the ECT (engine coolant temp) sensor with the engine running and the fan should rapidly ramp up to full speed, regardless of coolant temp. If not, then it's likely that solenoid is the culprit.

Of course, first things first, check to make sure your PS fluid is full and is the correct type (ie; not PSF+4, which is a red ATF based PS fluid that Mopar specs in most vehicles now).


EDIT:

The hydraulic cooling fan is not like an electric fan in the sense that it operates in an on/off fashion or at high/low speeds. It essentially has an infinite number of speeds since the ECM can command increased fan speed via the fan control solenoid. Even with the engine at normal operating temps it's very quiet, typically the only time you'll hear the fan run is when the engine is under extreme load or at high ambient temps with low vehicle speed (such as crawling along a trail in Moab with triple digit outside temps).

You mentioned that the fan only kicked to high after the water pump gasket had failed (and presumably after a fair amount of coolant leaked out), which I would find is a normal function of the fan as the engine was starting to over heat due to lack of coolant. No fan speed is going to overcome a cooling system that's low on coolant.

One other thing to consider, if the vehicle is still running hot, you may want to verify that the thermostat is installed correctly. It's entirely possible to install it backwards in the thermostat housing (with the spring pointing towards the radiator), which will cause the engine to overheat.

EDIT EDIT:

Ok, last one, I promise. Is the vehicle currently over heating or running hotter than normal? Have you verified the coolant temp via a scan tool?

If you have a Limited with the automatic climate control you can pull the engine coolant temp through the HVAC head unit with the engine running and in park:

Press both the AC and Recirc buttons at the same time and hold.
Using your other hand, turn the left temp control knob to the left one 'click' and release the two buttons.

This will enter the diagnostic mode within the HVAC head unit. Usually you'll have 00 displayed where the temp is usually found. Turn the the left temp knob until the number 66 is displayed and then press the AC button...this will display the current coolant temp. Press both the AC and recirc buttons to exit this menu.

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This is easily the worst post, and thread, I have ever seen in 7 years of being on JF.
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post #9 of 32 Old 05-08-2019, 08:55 PM
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@Jeeples , does the temp "trick" on the ac also work on the overland?


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post #10 of 32 Old 05-08-2019, 09:09 PM
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Keeping in mind the info already mentioned about making sure the rest of your system is running right, I remembered that 'Martinbuilt' on YouTube recently uploaded a video about modifying the control solenoid for slightly increased speed. Perhaps this will be of interest after working out any bugs present.


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post #11 of 32 Old 05-09-2019, 06:53 AM
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The fan should always be spinning. If it is not there is a problem.

Check to see if it is spinning when the stream is cold and at temperature.

Consider putting a filter on the power steering fluid. Helped me a lot

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post #12 of 32 Old 05-09-2019, 07:53 AM
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Quote:
Originally Posted by 97Mule View Post
@Jeeples , does the temp "trick" on the ac also work on the overland?

Yes, sorry I should have clarified that it will work on any Auto Climate Control equipped WJ.
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post #13 of 32 Old 05-09-2019, 08:01 AM
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Quote:
Originally Posted by Jeeples View Post
Yes, sorry I should have clarified that it will work on any Auto Climate Control equipped WJ.
After posting the question i realized how dumb it was. I was just to lazy to delete it!
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post #14 of 32 Old 05-09-2019, 08:56 AM
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I've often wondered if it was possible to file just a bit off the end of the solenoid to fool it into spinning faster. I never had it apart, so I didn't know it was adjustable. I'll be doing this soon. Texas summers are hell on earth!

However, don't just twist the shaft. Watch closely as he does it and you'll see a sliver of the thin outer shell break off, where it was crimped in to lock the adjustment. Metal bits and hydraulic systems are mutually exclusive. I plan to tap the crimped part of the shell out of the groove, adjust, then lock it down again.

Mine does speed up when the a/c is turned on. Not a huge increase, but I can hear it change and feel the increased airflow.
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post #15 of 32 Old 05-09-2019, 03:12 PM Thread Starter
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Ha! I was just going to post that video!


HarryH3 I didn't see a piece break. You mean around 8:50 of the video?



This could be a very cool (pun) deal if it works. I'm going to do it.
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