Peytoven

So today I was on the trail and my upper radiator hose just blew off and coolant went everywhere. I'm not sure if it was an anomaly or not because of a series of heat related events that lead up to this so I am going to try to be as thorough as possible.

A couple of days ago I was driving home on a mountain pass after a long day on the trail and I noticed the temperature needle on my 2008 JKU started fluctuating, I have never seen this before and it started to approach the red zone so I pulled over. I plugged my code reader in and got code P0128 "Transmission High-Temperature Operation Activated." After that I let my car cool down a bit and made it home nice and slow making sure I did not overheat. After doing some research it seemed the best way to solve this problem was to order an extra trans cooler.

Fast forward to two days later (No extra trans cooler installed yet), I am on a dirt road and the whole radiator hose just blows off. Fluid everywhere. The hose appears fine, no cracks or anything. I get the hose back on, let it all cool, and start the engine while carefully watching the temperature. The overflow reservoir has a big load of coolant but none of it would cycle into the radiator and the hose that blew off remained empty. Because of my earlier heating issues, I believe there is something more to this like maybe a bad thermostat or even water pump issue(which was replaced recently). My fan also appears to be working.

So now my jeep is sitting in my driveway with no coolant in the system. Did the hose just fail and needs to be replaced? Or did something else cause this to fail like a bad thermostat?

cb4017

Hard to say. It could be the thermostat acting up. I would check the hose and clamp and replace as needed. I would also go ahead and replace the thermostat. Fill with the correct coolant through the radiator cap then drive.

ronjenx

Radiator cap may need replacing, too. It relieves the pressure into the overflow bottle.
Lack of pressure relief can cause a hose to blow off.

hornetman

Not to hijack your thread but i to am getting the P0128 code as well. My hoses appear to be fine, I replaced my water pump (after market) for the 2nd time in February (currently 75K), after water pump change (5K miles) my radiator started a leak on the upper seam on the drivers side. I replaced the radiator early May with OEM and thermostat with an after market from Advance Auto. Now with in the past week I started getting the CEL with P0128 code. I'm assuming that this may be from the thermostat IDK, I have been just resetting the code and stays gone for a day or two but comes back, has not shown any indication of overheating and actually on the temp gauge indicates running cooler than normal (has always been right on the 1/2 way point on gauge). I'm wondering if running like this would have any adverse effect on the engine and has anyone else had problem with after market thermostats? Probably swap out another thermostat but wondering if I should get OEM.

Peytoven

I have my transmission cooler on the way and I am hoping that will fix my P0128 code. From what I understand running after market thermostats can cause it to open up at cooler temperatures which can affect the temperature the engine runs at. I guess this affects things like gas mileage.

For now, I am not going to rack my brain too much. I will replace my thermostat with OEM, new hoses, radiator cap, and add a transmission cooler. Hopefully, this will solve my cooling/over pressure problem. If it does not I will investigate radiator and water pump.

hornetman

I went ahead and got an OEM Thermostat kit P/N 68273161AA, $26.24 from dealership. I'm pretty sure this is twice the cost of the aftermarket that I had recently replaced. I will know in a couple days if this fixes my problem. After installing I saw the instructions to use sharp hoppy knife to trim the locating tab of the perimeter gasket flush with the outer surface of the gasket. Well my bad for not reading but installed easy and for now it's not leaking.

I hope your transmission cooler fixes your problem at least your transmission will be happy, to me sounds like a stuck Thermostat.

hornetman

Wasn't the thermostat, got the P1028 code again today. Guess I'll try a new ECT sensor.

Peytoven

I just picked up my thermostat today. Hopefully, this works and I do not have to get the sensor as well.

Peytoven

So I went ahead and just decided to replace the temperature sensor. I am pretty positive this is the ETC. The one I pulled is made of plastic and the new one is made of metal. Did I pull the wrong sensor?

hornetman

On the 3.8 it is right behind the thermostat. They wanted $53.00 for it at Jeep, hopefully not making a mistake but going to go with an after market. P/N at dealership was 5149077AB