Why are our radiators different??

Boojo35 said:

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.

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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.

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.