Look like a rad with the integrated trans cooler connected in the first pic and the trans cooler capped in the second.

 

does one have a tow package with an outboard trans cooler

 

Isn’t that rubber plug protecting the threads on the fitting?

 

No tow package on either vehicle.

Why would it be capped on the 2004 but not on the 2003? Why does the 2003 have a line going to it, but the 2004 doesn’t? I’m totally stumped here.

 

The pressure is the same throughout your cooling system. There is no blow off valve on one side of the radiator and not on the other. The cap is the pressure release regardless of being a closed loop with a pressurized reservoir or open loop system with an over flow bottle. Assuming that it is your Coolant temp sensor is bad diagnostics. Was it low on coolant prior to overheating? Does it have a leak somewhere? The fan relays and fan itself are more likely to fail than the CTS. Are the radiator fins clogged with fuzzies? Tis the season. There are many things that can cause an overheat.

It sounds like you overheated it pretty bad. That can have long term effects.

 

The pressure is the same throughout your cooling system. There is no blow off valve on one side of the radiator and not on the other. The cap is the pressure release regardless of being a closed loop with a pressurized reservoir or open loop system with an over flow bottle. Assuming that it is your Coolant temp sensor is bad diagnostics. Was it low on coolant prior to overheating? Does it have a leak somewhere? The fan relays and fan itself are more likely to fail than the CTS. Are the radiator fins clogged with fuzzies? Tis the season. There are many things that can cause an overheat.

It sounds like you overheated it pretty bad. That can have long term effects.

Never said that I thought the system had different pressure in different areas. By blowoff valve on one side of the radiator, I was assuming and referring to the cap.

Regarding my “bad diagnostics”, a mechanic friend said that he’s had more than a few vehicles come in overheating because the temp sensor is bad, the vehicle doesn’t know it’s overheating and thus does not turn the fans on. Said he had a WJ doing exactly that a year or two ago. Literally the same type of vehicle.

Buddy said there were no leaks or overheating issues, but they recently bought it and were trying to figure out why it occasionally stalls out and has starting issues. Were running down the list thinking plugs, injectors, etc when the temp sensor came up again from the mechanic mutual friend who said those also sometimes can cause issues like that because, and this is a direct quote from their text:

“Temp sensors have direct input on how much fuel to inject; like starting in winter vs summer will require different amount of fuel. Sometimes they short out and it doesn't know what to do for the amount of fuel or sometimes mass air flow sensors get ****ed up. Most of the times these will send a code. To eliminate coolant temp and mass airflow, you could unplug each one at a time and try starting in. It will run with default settings.”

So that’s two issues where the temp sensor is near the top for possible cause, indicating a high probability that’s what it is.

There is no debris clogging the fins.

And I did not overheat the vehicle, it’s a friend’s WJ. They said they ran it for 10 mins while popping laundry in on a cool morning last week and came out the door to see coolant raining down.

 

you may want to consider getting a separate transmission fluid cooler and not use the trans cooler part of the radiator. The integral rad + trans cooler have been know to leak, doing real damage to trans and engine. What a stupid design IMHO. Sure, the percentage of failures is low but why take the risk?

 

The 2004 radiator is different and the trans cooler goes to the AC condenser. When buying a replacement for a 2004 the trans cooler fittings remain capped.

 

Yeah
I found this out at the Pull and Save

I removed the lines to the ac side (It still was charged)
Then The other side had transmission fluid .
I thought What the Heck.

Then I was searching on this forum and found the answer.

 

Your radiators aren't different. They both have a transmission cooling port. The port just isn't connected to anything on his. For most applications, the aftermarket only makes one of each radiator size, and includes a transmission cooler in all of them. It saves them money in the long run, as they only have to make and stock one part instead of two. So even if you have a vehicle with a manual transmission, the replacement radiator is likely to have an auto trans cooler in it. It just won't be used.

You'll need a live data scanner and some troubleshooting to determine the exact cause of overheating. Watch what the computer thinks the engine temp is and see if it tells the fans to turn on. The most often reported failure on WJ's is the fan relay. It gets the signal to turn on the fans but doesn't do it's job.

 

BooJo and 3 Jeeps are right. One WJ has the trans cooler, one does not.
There is no pressure relief device other then the cap.
Juat get the radiator specified for that WJ and if it comes with the integrated cooler fitting, no problem, don't do anything with it. It was a bad design anyway.
Harry is also right about the relay on the 4.0L. It is a known fail point.

The radiators in the WJ are only good for about 7 years of normal use. If the radiator in your friend's WJ was older or the original, they were on borrowed time anyway and you should think about swappping yours. Those plastic end caps should convince anyone of that lifespan being serious.

 

So I guess where we are at is… my WJ has the transmission line going to the radiator for cooling, while theirs has a different cooling method for their transmission? Is that a “Trail Rated” thing?

 

This scenario is very common across all vehicle brands. The radiator gets old, gets a pin hole, loses a little coolant, owner doesn't notice until it over heats. Then he thinks there is something wrong with the vehicle and checks a lot of unnecessary things. I would just put a new radiator in it and fill it with coolant and run it in the driveway or a quick 1 mile ride. It will either start to overheat or the fan will come on as normal.

 

And solid heads up on the relays and the radiators failing after X amount of time. I have had a million relays go, just not for the fans yet. As far as the radiator, mine is 20 years old. But yeah, probably should replace as a preventative.

 

Another addition: I just checked my second WJ, another nothing special Laredo, in fact even less special because this one is a 2WD (I know I know..), and it also has a line connected at that spot. So, out of 3 WJ’s, the only one with that rubber plug there is the Trail Rated.

 

Where does the line in the first photo go? Whats the other end connected to?

 

Probably a tow package thing

 

My 99 Limited has a tow package, uses the internal radiator trans cooler AND has an external cooler AND a external power steering cooler.

I've seen AC condensers that had a trans cooler built into them at the wrecking yard before on WJ's.

Lots of small differences between options.

Same radiator tho.

 

Ok so I just got more information from my friend. They said their temperature gauge on the dash was acting up, not reading any temps at times even though they had been driving for awhile and it was definitely hot. Is the gauge being messed up an indicator of the temp sensor?

I had a similar gauge issue like this with the oil pressure sensor.

 

Ok so I just got more information from my friend. They said their temperature gauge on the dash was acting up, not reading any temps at times even though they had been driving for awhile and it was definitely hot. Is the gauge being messed up an indicator of the temp sensor.

Ok. Here is where you are at now...

Regarding my “bad diagnostics”, a mechanic friend said that he’s had more than a few vehicles come in overheating because the temp sensor is bad, the vehicle doesn’t know it’s overheating and thus does not turn the fans on. Said he had a WJ doing exactly that a year or two ago. Literally the same type of vehicle.

Buddy said there were no leaks or overheating issues, but they recently bought it and were trying to figure out why it occasionally stalls out and has starting issues. Were running down the list thinking plugs, injectors, etc when the temp sensor came up again from the mechanic mutual friend who said those also sometimes can cause issues like that because, and this is a direct quote from their text:

“Temp sensors have direct input on how much fuel to inject; like starting in winter vs summer will require different amount of fuel. Sometimes they short out and it doesn't know what to do for the amount of fuel or sometimes mass air flow sensors get ****ed up. Most of the times these will send a code. To eliminate coolant temp and mass airflow, you could unplug each one at a time and try starting in. It will run with default settings.”

So that’s two issues where the temp sensor is near the top for possible cause, indicating a high probability that’s what it is.

There is no debris clogging the fins.

And I did not overheat the vehicle, it’s a friend’s WJ. They said they ran it for 10 mins while popping laundry in on a cool morning last week and came out the door to see coolant raining down.

Here is where you where a while ago when you were "teaching" me how things work.

I am just going to put out there. I have been a ASE and State of Michigan certified Master Auto Tech for 42 years. I have compiled GOD knows how many hours of factory training over those years. I am factory certified in CDJR, GM, Honda, Acura, Hyundai, and Kia.

Thanks for the spanking.

Out here.

 

I think there's a CEL code if the temp sensor is outside of what the ECU expects, maybe the gauge is just messed up?

 

I have never had a temp sensor go bad in any vehicle I have owned in the last 30 years including my 4 WJ's. I don't think it is very common and they are usually just low tech resistance measurers. However, if the gauge wasn't working then you may legitimately have a bad temp sensor or bad connection and it is probably easier to change it out. good luck.

 

Temp sensor will not read if there's no more water in the system.

I've not seen a WJ, of any year without the trans cooler connected to the radiator.
I imagine it was an available configuration at some point but maybe I've also not seen many ...and then I'll also fess up that my experience is with the 4.7 only so maybe it is a 4.0 thing not to use that configuration.
In any case, ditch it and use an external cooler if one is used at all. It's a bad design.

 

2004 4.0L only swapped Trans cooler from Radiator to AC condenser. Plain and Simple. You can use a 99-04 Radiator in any of them just takes effort. But It is an Extremely common practice to leave the Trans-cooler in the radiator disconnected and use an External Trans cooler.

Temp sensors can cause havoc as they are used for Fuel trimming etc on start ups etc. WJ's also have a Problem with the PWM fan controller under the Passenger side headlight. IF you didn't have tow package you wouldn't have a Mechanical clutch as a primary cooling and EFAN second.

You can test this by pushing the AC button as the fan should spin into High gear Regardless of temp as the Clutch command sends the request for full.

 

Odd, as the FSM(for the 2004 model) I have states that no aux trans cooler is available or needed.

 

If I trusted the WJ engineers to tell me no external cooler is needed, that would be a different story. When new, they probably considered it as "efficient" and would never leak, making your trans a stawberry milkshake holder.
We all know differently now. It can happen and has.
Put on the external cooler. You've been told.

 

If I trusted the WJ engineers to tell me no external cooler is needed, that would be a different story. When new, they probably considered it as "efficient" and would never leak, making your trans a stawberry milkshake holder.
We all know differently now. It can happen and has.
Put on the external cooler. You've been told.

My point being that the manual should have mentioned a specific model that didn't use the integrated cooler. I'd suspect this was a later mod to use an external cooler, either by a dealer via TSB, recall, or even a used dealer having seen too many of the pink chocolate milk, doing a mod on their own.

Never said that I thought the system had different pressure in different areas. By blowoff valve on one side of the radiator, I was assuming and referring to the cap.

Regarding my “bad diagnostics”, a mechanic friend said that he’s had more than a few vehicles come in overheating because the temp sensor is bad, the vehicle doesn’t know it’s overheating and thus does not turn the fans on. Said he had a WJ doing exactly that a year or two ago. Literally the same type of vehicle.

Buddy said there were no leaks or overheating issues, but they recently bought it and were trying to figure out why it occasionally stalls out and has starting issues. Were running down the list thinking plugs, injectors, etc when the temp sensor came up again from the mechanic mutual friend who said those also sometimes can cause issues like that because, and this is a direct quote from their text:

“Temp sensors have direct input on how much fuel to inject; like starting in winter vs summer will require different amount of fuel. Sometimes they short out and it doesn't know what to do for the amount of fuel or sometimes mass air flow sensors get ****ed up. Most of the times these will send a code. To eliminate coolant temp and mass airflow, you could unplug each one at a time and try starting in. It will run with default settings.”

So that’s two issues where the temp sensor is near the top for possible cause, indicating a high probability that’s what it is.

There is no debris clogging the fins.

And I did not overheat the vehicle, it’s a friend’s WJ. They said they ran it for 10 mins while popping laundry in on a cool morning last week and came out the door to see coolant raining down.

As someone who's overheated their WJ to the point of stalling while idling(left it running while I jumped in a skidsteer to plow out my parking spot, radiator tank blew), and it got hot enough to cook the water pump gasket; and having also blown engines due to low coolant in the block(temp sensor is supposed to submerged in coolant.... If coolant level is below the sensor, you wouldn't even know the engines running hot before it drops valve seats(Chrysler 2.5l in a 1991 Caravan) Did that on it's own once(never figured out why), then my ignorance at that time of cooling systems meant I filled the tank and thought it was good); I'd heavily agree with your mechanic friends assessment. Nearly blew up the engine in the skidsteer I run at work last winter for the same reason. Mechanics sent it back after a coolant hose burst without checking the radiator coolant level(non-existent), and also without tightening the drive belt. Took 2 return trips to the shop overheating, first time they figured out the loose belt, second trip they checked the coolant level...

 

Well, thanks for (mostly) all of the responses. The radiator and temp sensor is coming in the mail tomorrow. I’ve got some work to finish up on two of my own WJ’s…

… and then I’ll begin their project. I’ll post my progress on here and see how it goes.

Regarding the separate trans cooler, I’m assuming theirs already has one if that connection on the radiator isn’t used, right? Regardless, the WJ I’m rebuilding right now doesn’t have one and I’m interested in doing so. Where do I get one, the usual suspects? Where does it get mounted?

Also, regarding the pink/brown milkshake… I believe they said something to me about tiny bubbles on their trans dipstick. Possibly related? Buddy said bad filter but was taking a super late night guess.

 

Tiny bubbles are not an issue.
The external trans cooler to get is the Derale unit. Here is the one I got: Bypassing transmission cooler

I'm curious about that one not having it (not interested enough to debate why the service manual created in 1999 or earlier did not include the possibility of a production change to save a few dollars)
...but is clearly not and then if not, what lines are going to be used to re-route the trans fluid and where will it come from. The external cooler is just added to the existing circuit ...but it appears you do not have the exiting circuit. I'm thiking aftter a look through that service manual to find where they go into the trans that there is a visit to the boneyard in your future.

Oh and that water pump gasket that failed...it is most likely the cause of the overheat as opposed to the result. On th 4.7, they will give out and blow out all of your coolant. Had this happen to me as well.