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Discussion Starter · #1 ·
Hi all. Cooling systems are simple, right? I'm not so sure anymore.. Hoping for some help..

2005 TJ Rubi 4.0 Stock engine except electric fan with shroud due to massive winch/compressor on front. Manual xmission. Note that I did NOT have an overheating problem when I first bought the rig. 4" lift.. 38's (i think).. Note there is only 45k miles on it.

Overheating, pretty much no matter what I do, but under load (highway, AC, 100' out), it's worse (will get to 230 easily). What I've done..

1) changed thermostat (put in a 180). Used aftermarket that doesn't have the air bleed hole. More on this later.

2) Checked the lower hose while reving.. it's fine.. has a spring in it, and doesn't collapse

3) Water pump feels solid.. no play.. no leaks out weep hole. Also, with no thermostat and when rev'ing.. VERY obvious flow

4) Flushed system.. back flushed everything (radiator, heater, engine), and everything was clear. No grunge. Refilled with yellow AF and distilled water.

5) Took out thermostat.. no help.. I've purchased a t-stat from dealer once I've figured out the problem.

6) I checked the temperature of the AC condenser and with full AC, it was running 145'. However, the AC only causes about a 10' jump in the engine coolant temp when running in overheating condition. Without AC on, it's still overheating

7) Checked the fins, and though there's a few grains of sand and twigs in there, nothing major. The fan is pulling major air thru the radiator/condenser

8) I have not burped the system, but i AM getting good flow. I plan to burp next once it cools down from my last test. I'm gonna park it on a steep hill, nose up.. and fill.

9) the only codes I've seen so far are missing. I need to do another read.

10) O2 sensors are all over the place, but always less than 1

Any thoughts? help?
 

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First, installing the incorrect 180 degree thermostat did nothing to lower the engine temperature because it can't when the ambient air temps are warm or hot. A lower temperature thermostat will ONLY (!) lower the engine's temperature in extremely cold weather. A lower temp thermostat will not and cannot lower engine temps in warm or hot weather.

And having installed a Warn Powerplant winch/compressor was no need to replace the OE fan and shroud with an electric fan. That was a cooling system downgrade. The TJ doesn't overheat with the Warn Powerplant with the OE cooling system. I play 75% of the time in the desert and the experienced TJ owners run the OE cooling system... it will keep the engine cool in the hottest of conditions. I have both a big Warn winch in front of my TJ in addition to having a power steering cooler mounted in front of the radiator further blocking airflow. Nope, my engine doesn't overheat.

Is the radiator clogged internally with hard water deposits? Lower the coolant level and look inside through the radiator cap opening with a flashlight. See if you see any white crud built up which means hard water deposits are blocking coolant flow.

Could the external fins of your radiator be clogged with mud? That will cause it to overheat too.

Personally, I'd restore the OE cooling system, install the correct 195 degree thermostat (NOT a "failsafe" model), and look at the radiator to see if it could be the cause. Many (most!) aftermarket radiators will not cool as well as the OE Mopar radiator. Really. It has an exceptional design. So good that us desert wheelers usually run the OE radiator and cooling system.

You can see that above my Warn winch that I also have a power steering cooler mounted in front of the radiator. I have zero cooling problems. The last time my engine overheated was maybe 5 years ago when the OE thermostat stuck shut while wheeling. Replacing it fixed it. No overheating before then, none since. With the factory cooling system. :)

P.S. What temperature does it normally run at on a hot day and what is its peak temperature.
 

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Discussion Starter · #3 ·
Hi Jerry.. Thanx for the reply and inputs.. Some answers..

the 180' t-stat was what I was told I needed. I agree with your thoughts on that one which is why I have a 195' ready to go (OEM from dealer). The t-stat though is not the cause of my overheating. I only mentioned it so it was clear that I had checked that out. (I also checked it in hot water to note when it opened.. and it was right on 180')

As for the winch, mine is like 3-4 times larger than what you show in your pic. Note that this as well as the fan was there when I purchased it. I feel really good about the fan as it throws an ungodly amount of air and for the winch I have, I really think I need it. I tried to attach a pic so you can see what I have.

No hard water deposits. It's really clean when looking inside the cap and down the rods.

No mud on the fins. This goes for both the condenser and also the radiator. (I checked the latter using a flashlight peering thru the gap between the two). As I said originally, the only thing in the condenser fins is a few tiny pebbles and some twigs.

Note also that I didn't have any cooling problems for the first few years I owned it, and all the same equipment. Also, this is original OEM radiator. Remember this only has 45k miles.

Thanx
 

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Have you confirmed an actual overheat? I see no mention of boiling or spewing antifreeze in the overflow, you only mention that the temp gauge goes high. Check the hoses and radiator top tank with an IR temp gun. Could be your gauge or temp sensor is bad. Yes, get that 195* t-stat in there, you're not doing your motor any favors by not running it.
 
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Is your fan running?
That ^^ made me think of this.....If you have an Adjustable Thermostat Controller for the fan could it be the setting got unintentionally changed?
 

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Discussion Starter · #7 ·
I confirmed the overheat with a thermal gun, and also use Torque Pro. Everything matches.

As for the fan, it runs when I turn on the ignition switch. It's quite obvious and I've altered this a few times. Most recently, it would only turn on when it's sensor (inserted in to the radiator) surpassed a given (adjustable) temperature. I decided to re-route to make it turn on whenever ignition is on, so yes, the fan is running.
 

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did your higher temps start when you changed to an electric fan?
many have fixed their high running temp/overheating issue by going back to OEM after thinking they needed something else.

as for blocking it with things in front, I run a warn 9.5ti winch and a PSC trans/steering cooler in front of the AC condenser. engine still runs between 204 and 214 no matter the outside temp
 

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I confirmed the overheat with a thermal gun, and also use Torque Pro. Everything matches.
Let's for now forget all the IR thermal guns and phone apps... exactly what does the temperature gauge in the instrument cluster indicate when you consider the engine to be overheating. And what temperature does it normally run at on the highway.

And trust me, IR guns can provide very misleading indications at times.
 

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Discussion Starter · #10 ·
hi guys.. again, i appreciate all the feedback and suggestions..

So, i bought the jeep in November 2011 and it had the winch and electric fan at that time. It was not a mod that I did. I drove it with no overheating issues until last summer. At that time, I changed out the thermostat but that didn't really fix it. It was close to winter so I let it ride and was OK during the winter. Now that it's hot here again, I'm having the issues.

There's no doubt it's actually overheating. the gauge reads over 230, matches the Torque reading and matches the thermal IR scan. Also, it runs rough and if I let it go, it then starts to throw codes for missing. If I stop the motor at this time, wait, then restart, it red-lines. There's absolutely no doubt it's overheating.

Here's my winch.. it completely blocks the grill. I'm guessing that's why they put the electric fan in. Not saying I think it was a good idea.. I'm just saying that this may be why they did it.

I'm also wondering now if the OEM fan might help.. BUT.. like I said, I did NOT have the issue for 5 years with this identical setup, so something else has shifted. I'm wondering if when I had the first overheating issues (and they were VERY severe), if I possibly warped or screwed something that causes the engine to run hotter than it did before.

There's ALSO a chance that the electric fan motor is just not as strong as it used to be. There's no way for me to know that or not.
 

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Here are some possibilities:
1. Belt is slipping on the water pump pulley. Is your belt hard and glazed?
2. The water pump impeller is slipping on the shaft and you are not getting full flow. The pump is easy to pull and check that the impeller isn't damaged or slipping.
3. Blown head gasket is leaking hot exhaust gases into the cooling system.
 

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I recently had an issue w bad overheating in my 04... turned out that the PLASTIC impeller on the pump had shattered...

My thought is this.... at the age of the rig, I would install a new water pump even if it wasn't having issues.... I'd venture a guess that you have about a 60% chance that this is your issue.
 

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Would a bad O2 Sensor cause overheating if it were running rich? Might also explain the rough idle. Don't know just throwing that out there
 

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did the symptom change at all after the original overheat? 4.0l heads can warp at high temp due to length inherit to straight six design

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Rich no.. lean maybe but probably would throw codes first
 

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Hey new to the site. I just purchased a 2005 unlimited and the first week I had it (80's and 90's temps) it went past 210 all the time. Checked everything, did a pressure test checked fine. Spent $5.47 on a new 18 pound radiator cap and the system stays at or below 210 (4 weeks of temps in the mid to upper 80's and low 90's). Might not be your issue, but it's not expensive and then hey, new radiator cap!
 

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Discussion Starter · #17 ·
HI guys.. so.. yes, i forgot to mention that i did in fact replace the cap (18 lb), so don't think that's my problem. As for if the problem has changed since my first overheat.. The way this went is.. I was suspecting an overheat issue before I went in to the back country so picked up a t-stat (the 180' one.. what they said was right. didn't have internet).. Sure enough. the next hill I hit, i pegged the temp. PUlled over and after it cooled enough, did a roadside t-stat change but wasn't perfect and leaked a bit. This didn't solve me problem on the trip.. I was already 2-feet in so continued to higher elevation. More pegging, water from streams, etc.. I was more careful coming home but it still wanted to overheat on me. Each time it overheats, i'd get the missing, adn of course if bad enough and I stop the motor, it won't even turn over (yeah.. got that bad). I also was worried about a warped head but I guess I don't see how that would cause overheating. Even on compression, if exhaust gases pushed in to the cooling system, i don't think the thermal mass coupled with the volume of gas would put any kind of dent in the coolant/block temp. I could be wrong of course. I've not done a compression test yet. I'll probably do that this weekend. So anyway, long story short, the problem really didn't change from the initial overheat to now. It DOES run a bit rougher though when I first start it.. so that MIGHT point to a head gasket problem..
 

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you need to have a block test done to check for combustion gases in the cooling system. many times have I seen a warped head or bad head gasket cause overheat issues. also, like I said before if your engine got that hot being a straight six, there is a good chance that the head warped.

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Did you replace the stock mechanical fan with the electric, or was it there when you bought the Jeep?

I'm not expert but I take cooling seriously given my locale, and have done a significant amount of reading. I don't recall coming across any arguments for aftermarket electric being better than stock. To the contrary, it seems the consensus is to use the stock fan, shroud, and clutch for top cooling.

Perhaps a look at going back to mechanical with a fan clutch is in top shape is worth doing.
 

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Did you replace the stock mechanical fan with the electric, or was it there when you bought the Jeep?

I'm not expert but I take cooling seriously given my locale, and have done a significant amount of reading. I don't recall coming across any arguments for aftermarket electric being better than stock. To the contrary, it seems the consensus is to use the stock fan, shroud, and clutch for top cooling.

Perhaps a look at going back to mechanical with a fan clutch is in top shape is worth doing.
already stated that there was no issue with the electric fan for the last 5 years. it may be possible that the fan is not working as well though. you could verify that the fan is using the full voltage with a voltage drop test if wiring is in question. other wise check the amperage being used by the fan and compare to manufacture specs to see if the fan is pulling excessive load indicating an issue with the fan motor windings

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