2004 Jeep Grand Cherokee radiator temp problem

Tiny
CANTFIGUREITOUT90
  • MEMBER
  • 2004 JEEP GRAND CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 116,000 MILES
I had recently changed my thermostat because my a/c would over heat my vehicle. After changing my thermostat my gauge would say it was it was between 100 and 210 while driving. But when stopped the gauge would go up to 195. Now a week later and my gauge went up to 195. Turned my jeep off turned to pick up kiddo. Turned it on it was at 210. Stopped at the gas station turned off my jeep started it and it went up past 210. I also had check engine light come on code was p1281 when jeep was running between 100 and 210. Any idea what is going on? It was trying to "over heat" today with nothing running like the a/c in fact I had to drive with the heat on.
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Monday, June 22nd, 2015 AT 5:39 PM

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Tiny
CARADIODOC
  • EXPERT
P1281 - Engine Is Cold Too Long

First of all, dash gauges are notoriously inaccurate. They are only good for you to notice when something is not "normal". As apparently you have.

Do you really mean "between 100 and 210", or did you mean "200 and 210"? 210 degrees is not excessive. In fact, that's the temperature at which a lot of electric radiator fans first turn on.

First, check the cooling fins on the radiator. If you live in a state where they throw a pound of salt on an ounce of snow, those fins are likely corroded away or they will crumble easily. That makes it hard for the radiator to give up its heat to the surrounding air. Next, have your mechanic connect a scanner so you can see at exactly what temperature the engine is running. The coolant temperature senors for Engine Computers are much more accurate than those for dash gauges.

The fault code 1281 sets on almost all Chrysler products in cold climates, in winter. It sets when the coolant doesn't get up to normal temperature within six minutes of starting the engine. This code will not turn on the Check Engine light.
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Monday, June 22nd, 2015 AT 9:56 PM
Tiny
CANTFIGUREITOUT90
  • MEMBER
Yes the fan is fine. Ive watched it turn on. Amd yes I mean its sitting between 100 and 210. I believe the temp is 160. I recently bought the vehical from a private owner a couple months ago and didnt have problems until it ot hot out my jeep always ran 210 before I changed the thermostat. And when I had the a/c on it would slowly go past 210 and went to 260 a couple of times I was able to turn it off right away though because I was parked watching it. But even while driving it tried to over heat.

And yes it was 80 out in the evening when my check engine light came on and the code was p1281. Its the only code that comes up. So I believe your information there sir is incorrect. I was driving on the interstate for about 15 minutes when my check engine light came one and my temp was at 160 ( or what ever number the line is that is between 100 and 210) the whole time. Its been in the lower 90's all weekend. Yesterday was a tad bit warmer and it tried to over heat meaning it was going past 210.

I have a fail safe thermostat and I didnt want it to over heat because I would have to change it again. And I just did it last monday. So any information as to what is causing this?
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Tuesday, June 23rd, 2015 AT 4:58 AM
Tiny
CARADIODOC
  • EXPERT
210 is not overheating. Obviously 260 degrees is, but there are a lot of vehicles, GMs in particular, that don't even turn on the fans until 220 degrees.

I don't make up the codes. Is it possible that code has been in the computer since winter? Remember, that code doesn't turn on the Check Engine light, so you'll never even know it was set. If your gauge is as accurate as you think it is, that code will set if the engine stays at 160.

The next thing to consider is getting an inexpensive scanner so you can view live data and see exactly at what temperature the engine is running. There are units out there that take a few seconds to update the readings, so they aren't good for some tests, but for something like this they will work just fine. I have one to borrow out that cost less than fifty bucks.

As for running hot, there are some things to look at when it's a vehicle you're unfamiliar with, meaning unfamiliar with its history. Specifically, look for the rubber seal under the front edge of the hood, and check for plugs and flaps missing on the core support. Either of those will allow air to bypass the radiator. Some people mistakenly think the engine will cool better if they take the shroud off the radiator to get more air flow, but in reality, that lets the air go through the radiator, then back around and go through it again. The same air keeps getting reheated so it gets hotter and hotter and doesn't cool the radiator.

Sometimes people add oil and transmission coolers and those present too much obstruction to air flow. If your radiator fan is powered by power steering fluid, be sure that unit is working. You said your fan is working, but stupid as this sounds, check that it's spinning the right way. Some replacement fan motors are somewhat generic and can be used in more applications if it doesn't come with the connector body. You're supposed to plug the terminals into your old connector body. Even when you understand that those terminals can't be switched, you can't be sure the person who assembled the motor soldered the correct wires together. Just tonight I helped a friend figure out that someone poked the only two wires for an ABS wheel speed sensor in the wrong holes in the connector. This is the first time I've ever seen a wheel speed sensor with a polarity, so it was not something we thought we needed to check for.

For a quick check too, when the gauge says the engine is over 220 or 230 degrees, feel the upper radiator hose. Normally they get too hot to hold onto for very long, but you can stand it for a few seconds. If the coolant really is at 220 degrees, the hose will burn your hand if you try to keep on holding it.

Feel across the radiator for cold spots. If you find any, those tubes are plugged. Have the coolant checked for freeze point. The testers that use floating balls or pointers are only accurate down to about minus 50 degrees. From there, if you add a higher concentration of antifreeze, the tester will show a colder freeze point, but the actual freeze point will go up closer to 0 degrees. The lowest freeze point you can get is with 70 percent antifreeze, not 100 percent. The reason those testers incorrectly indicate a colder temperature is they simply compare the weight of the coolant to the weight of straight water. To get the most accurate reading, you need a "refractometer". Those are relatively expensive, and for most shop use they are not needed, so very few mechanics have them.

The reason for testing the freeze point is if someone added too much antifreeze and not enough water, the freeze point might falsely appear to be really good, but antifreeze can't hold as many BTUs of heat as water does. That means that almost any engine could overheat if it has just antifreeze in it. The coolant can't absorb the heat fast enough as it flows through the engine, and it can't flow fast enough to get that heat to the radiator. The cooling system is most efficient at doing its job when it has only water, but we still need antifreeze for its corrosion inhibitor and water pump lubricant additives.

The last thing to consider is having a chemical test performed at the radiator for a leaking cylinder head gasket. That involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow. Combustion gases that sneak into the cooling system can pool under the thermostat and cause it to not open. Thermostats have to be hit with hot liquid to open; hot air won't do it.

What do you mean by a "fail safe" thermostat?
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Wednesday, June 24th, 2015 AT 9:24 PM

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