4.0L engine temps rising - Need Help / Feedback - - JeepForum.com
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post #1 of 16 Old 07-26-2021, 10:06 AM Thread Starter
TrueGrit
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4.0L engine temps rising - Need Help / Feedback -

Hey everyone,

I own a 04 WJ w/ the 4.0L , and the other day I am having some higher temperature issues. The temp it is going to is over 210 degrees. I did find out that one of my 3 wires on my radiator fan was broken, but I did solder it back and now the fan is working. So I got that out of the way.

Even after getting the fan to work, my WJ is still getting up and over 210 degrees. When parked, I did increase the rpms to about 3K, then the motor kinda jerked, CEL came on and the motor stalled.

Pulled the code, it stated increase temperature and misfire on cylinder #1 and #6.

The WJ did start back up.

So I started to do some basic tests. I pulled off the thermostat which is set to 195 degrees and I did pull it off and dropped it in boiling water and it did open up. As being concerned , I did end up buying a new thermostat from my auto part store and got a new one that is also 195 degrees. I also did get a new radiator cap just to make sure I am not loosing any pressure on the radiator.

Installed everything back up, slowly burping the system and the motor temp started to increase over 200+ degrees.

Now I am not sure what else to look at.

The water pump was replaced less than a year ago. The radiator was replaced about 1.5 years ago.

There are no leaks on the heater core or my floor board.

Now the only thing I can pin-point is when I was using the radiator burp funnel it was not bubbling as much as I think it should since I did lose a good bit of radiator fluid when removing the thermostat housing when replacing the t-stat.

Anyone here know what else it could be?

Thanks for any tips / pointers.

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post #2 of 16 Old 07-26-2021, 10:40 AM
Waterluvr
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I see as many fan relay failures on the 04 model where they moved both high and low into the pdc box under the hood as I did on the earlier models when it was behind the bumper cover, I know you mentioned the fan was working but this time of year it will need low and high speed operation without the ac on and high all the time with ac on.

These issues are easy to find with a decent scan tool that allows you to command the pcm to power both those relays, if you don't have access to one get in there with a meter and you'll find the problem.
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post #3 of 16 Old 07-26-2021, 10:54 AM
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Might be concerning but Your system temps are around normal it is not until @220 degrees where the fans are commanded on.

I would be sure there are NO codes.
MAYBE unplug the ECT sensor - did the fans come on? NOTE this will set a code, you can erase or it will 'go' away after several trips/starts with it plugged back.

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 16 Old 07-26-2021, 11:07 AM Thread Starter
TrueGrit
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Quote:
Originally Posted by Waterluvr View Post
I see as many fan relay failures on the 04 model where they moved both high and low into the pdc box under the hood as I did on the earlier models when it was behind the bumper cover, I know you mentioned the fan was working but this time of year it will need low and high speed operation without the ac on and high all the time with ac on.

These issues are easy to find with a decent scan tool that allows you to command the pcm to power both those relays, if you don't have access to one get in there with a meter and you'll find the problem.
Hi Waterluvr - Awesome name BTW!!! So you think I should replace the fan relay? This is the one under the front passenger headlight?

As for the fan, I can tell you it does kick on normal. Since I was burping the coolant system, I did not run the AC as I was running the heater on high as I was letting the coolant burp from air bubbles.

I did notice once it hit higher level temps (210 degrees) the fan on the radiator did kick on to the higher rpm speed.

I don't mind replacing it. You think since my CEL is on, you think I should just reset it and see if it comes back on or leave it alone and hopefully it'll turn off on its own?

Thanks
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post #5 of 16 Old 07-26-2021, 11:09 AM Thread Starter
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Originally Posted by jtec View Post
Might be concerning but Your system temps are around normal it is not until @220 degrees where the fans are commanded on.

I would be sure there are NO codes.
MAYBE unplug the ECT sensor - did the fans come on? NOTE this will set a code, you can erase or it will 'go' away after several trips/starts with it plugged back.
So this ECT sensor, that located the the thermostat housing?
I am willing to disconnect it, but my CEL is currently on.

This part seems to be available at my local auto part store.
The ECT sensor looks old. lol.
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post #6 of 16 Old 07-26-2021, 11:19 AM Thread Starter
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@jtec -

I haven't pulled the ECT sensor yet, but here are the current codes it pulls up:

P0300 - Cylinder misfire

P0304 Cylinder 4 misfire

P0306 Cylinder 6 misfire

So if I was to unplug the ECT Sensor and it pulls a code, does that mean its good? and if no code, replace it?

Thanks
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post #7 of 16 Old 07-26-2021, 12:07 PM
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unplugging the sensor will cause fan to come on - this will show if the PCM has control over the fans without waiting for 220deg.

Codes are basic misfire codes- start by checking plugs, appearance tells alot.

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 #8 of 16 Old 07-26-2021, 07:38 PM Thread Starter
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@jtec - So I decided to purchase a new ECT sensor and fan relay switch.

Here's the weird thing, I pulled the front headlight on the passenger side and low and behold, looks like maybe the previous owner cut the plastic out of the bottom where the fan relay switch would be, however.... there is nothing there. Like not even the connector.
I looked all over the place for the fan relay switch on that side and no results.

I am wondering if it was bypassed?

As for the ECT, that was installed.

I ended up driving the jeep around and the temp never exceed over 210 degrees on the temp gauge. I know today it was a little over 100 degrees outside.

I also disconnected the battery for about 30 min and the CEL light was off. The WJ drove fine for about 20 miles and didn't seem to come back on or perform with misfires ect. WJ drove normal.

The thermostat I put in was for 195 degrees.

Here some pics where the fan relay switch is suppose to be at. This was the only connector that was exposed, but it over by radiator area below the battery plate. I have no idea what it is.
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20210726_141736.jpg   20210726_144202.jpg   20210726_141731.jpg  
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post #9 of 16 Old 07-26-2021, 08:20 PM
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Quote:
Originally Posted by TrueGrit View Post
Hi Waterluvr - Awesome name BTW!!! So you think I should replace the fan relay? This is the one under the front passenger headlight?

As for the fan, I can tell you it does kick on normal. Since I was burping the coolant system, I did not run the AC as I was running the heater on high as I was letting the coolant burp from air bubbles.

I did notice once it hit higher level temps (210 degrees) the fan on the radiator did kick on to the higher rpm speed.

I don't mind replacing it. You think since my CEL is on, you think I should just reset it and see if it comes back on or leave it alone and hopefully it'll turn off on its own?

Thanks

This is normal operation. You're good to go. Your fan relays are in the fuse box under the hood.
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post #10 of 16 Old 07-26-2021, 08:55 PM Thread Starter
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Originally Posted by snowbuggy View Post
This is normal operation. You're good to go. Your fan relays are in the fuse box under the hood.
The part we're talking about is the fan relay switch (this is the new one I purchased).

This is what is supposed to be where the cut out is when I removed my passenger headlight.
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post #11 of 16 Old 07-26-2021, 09:25 PM
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You have a 2004...the 04 does not have that under the headlight. The 04 has high and low relays in the pdc under the hood, passenger fender...99-03 have it under the light

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post #12 of 16 Old 07-26-2021, 10:01 PM Thread Starter
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Originally Posted by HAZCAT View Post
You have a 2004...the 04 does not have that under the headlight. The 04 has high and low relays in the pdc under the hood, passenger fender...99-03 have it under the light
Oh man... thats so funny . Do you have any links to know exactly where I need to look / location?

This really helps. Too funny whom ever owned it did the same thing. Its crazy cause theres two screw holes under the headlight as if there is suppose to be one there. lol.

So the part I have that O'reillys sold me not accurate? This is interesting.....



Thanks for your help.
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post #13 of 16 Old 07-26-2021, 10:24 PM Thread Starter
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Originally Posted by TrueGrit View Post
Oh man... thats so funny . Do you have any links to know exactly where I need to look / location?

This really helps. Too funny whom ever owned it did the same thing. Its crazy cause theres two screw holes under the headlight as if there is suppose to be one there. lol.

So the part I have that O'reillys sold me not accurate? This is interesting.....



Thanks for your help.

Ok... I just read the info on this link: https://www.jeepforum.com/forum/f310...78/index3.html

I don't think I need to worry about fan relays as I know the fan did kick on low and also faster when the temps increased and shut off at regular temps. However 210 is not regular since my Tstat is 195, not 210 ect.
I'm not gonna worry about it, but i'll keep an eye on my temp gauge. Have a big trip to the Rockies next month. I'm depending on my WJ to be reliable (189K miles) .

Next task is Upper and lower control arms. that'll be fun!! lol

Thanks everyone
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post #14 of 16 Old 07-26-2021, 11:44 PM
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4L 04s have a set of two relays at PDC (fuse box) indeed. 99-03s use pulse-width modulation. O'Reilly clearly sold you the wrong part; they have no idea what they're selling, that's pretty typical.

A working fan can be deceiving. Doesn't mean you have sufficient flow. Temp rising when stopped then dropping while in motion is a telltale sign your fan is not working as it should. If not the case and problem persists, you might want to consider a new rad.

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post #15 of 16 Old 07-27-2021, 09:00 AM
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PDC legend
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File Type: pdf 04WJ PDC fan relays.pdf (132.6 KB, 3 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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