Hi everyone, I'm obviously new to the forum. I recently bought a 2003 tj se from a friend who let it sit for the last 3 years because it wouldn't start. It shows 150k on the clock. Got it home, put a good battery in it and it fired right up. Drove it in town, changed the oil after checking all other fluids (to all be changed later). Anyway the first colder day her in central il I drove it and got a cel for engine temp too low for too long. So I replaced the t-stat with a 195 non fail safe murray. That didn't help the temp come up so I flushed the system with prestone coolant system cleaner. Drove with that in for a couple hours and filled it back up with 50/50 mix coolant. I replaced the temp sensor at this time also. The weird part is the heat seems ok from the vents. If you let it sit and idle for 20 min or so the temp will come up but as soon as you start driving it goes back down to 170-180. I use the torque pro app to see live data and the gauge and sending unit are reading correctly also verified with ir thermometer. Not real sure what to think at this point. Water pump not flowing properly is the only thing I can think of. Also put on a new 18lb radiator cap. For some reason at speed 40mph or above the heat will switch to defrost vent on it's own too. As soon as you slow down it will turn back to whatever setting you have it on. Any help with this would be greatly appreciated. Thanks!!
Thermostat / engine temp problems
- Thread starter Thegen58
- Start date
What it sounds like to me is your thermostat is either sticking or you have air in the system. I'd replace that thermostat with either a factory Mopar thermostat or a Stant thermostat. You'll also want to drill a bigger hole in the thermostat so that the self-bleeding actually works. See this thread for more info: Jeep Wrangler TJ Cooling System Overhaul FAQ
That thread has info on drilling the hole, as well as which thermostat you should be running (as well as a link).
If you're smart, you'll replace the water pump while you're in there as well. It makes no sense not to do it at the same time. Not only to eliminate it from being a potential culprit, but also because if it has 150k miles, it needs to be replaced as part of a preventative maintenance schedule.
That thread has info on drilling the hole, as well as which thermostat you should be running (as well as a link).
If you're smart, you'll replace the water pump while you're in there as well. It makes no sense not to do it at the same time. Not only to eliminate it from being a potential culprit, but also because if it has 150k miles, it needs to be replaced as part of a preventative maintenance schedule.
Ok, so I just got done an hour or so ago finishing up a new water pump, timing belt and thermostat. I used a stant brand. I realize the importance of engine timing and the timing is computer controlled on this vehicle and the old belt was loose for sure. However, I'm not sure if it's in my head or if it does seem to run smoother than before. Either way, I am still having issues with it warming up while driving. It definitely seems like air still in the system. At idle with the heat on if I rev to 1500 rpm or so the heat will start to rise and the heat inside definitely gets hotter. But as soon as I let off the throttle or start driving, it cools back off. Thank you so much again for your replies!!!
Air pockets in the engine a lot of times can be the culprit. They can also be somewhat tricky at times to overcome. At this point it looks to me like you've covered all bases within parts that would cause your problem. Unfortunately The symptoms that you are describing almost sounds to me like a blown head gasket (very small) . There are many different scenarios in a blown head gasket. The symptoms that you are describing would be more between the water jackets and combustion chamber. Small enough to where you're not losing any coolant yet with the engine at operating temperature and at higher RPMs allowing small amounts of combustion to Xscape into the cooling system. This type of scenario can be very difficult to diagnose. Most times it will not show up in a pressure test on the cooling system. Most cooling systems operate with only 16 to 18 lb of pressure. The combustion chamber should be operating at 120 lb at its weakest.
I would suggest a block test. A block test will detect any carbon monoxide in the cooling system. Any carbon monoxide detected in the cooling system would confirm a problem with either the head gasket or in some cases the cylinder head itself.
If within your test carbon monoxide was detected in the cooling system I would also look into the casting number on your cylinder head. I can't remember off the top of my head but I do recall some of the casting numbers had certain weaknesses.
I would suggest a block test. A block test will detect any carbon monoxide in the cooling system. Any carbon monoxide detected in the cooling system would confirm a problem with either the head gasket or in some cases the cylinder head itself.
If within your test carbon monoxide was detected in the cooling system I would also look into the casting number on your cylinder head. I can't remember off the top of my head but I do recall some of the casting numbers had certain weaknesses.
Did you use a funnel kit for filling and bleeding? I can't recommend these things enough, they work much much better than just leaving the cap off. It's a lot less messy too. You can just leave the funnel on there with coolant in it, rev the engine to get it circulating and observe any air working its way out of the system.
https://www.amazon.com/dp/B01I40ZQWE/?tag=wranglerorg-20
You can also pick one up at your local Harbor Freight for around $24 if you don't want to wait for it to come in the mail. They do work quite well for any cooling system
Agreed. I too hope it's not a blown head gasket. Because it's a new vehicle to you ,you really don't know the history. A block test would be a inexpensive and effective way to rule out any internal engine issues. It can also confirm The Dreadful idea of having to pull the head for further investigation. You can purchase a block test at any of your local parts stores. Be sure to read the directions carefully. Any mistakes will give you a false reading. Just keep in mind the blue fluid that comes with the kit will turn green if carbon monoxide is detected in your cooling system. If you accidentally allow coolant / antifreeze to enter your test it will also make the blue fluid turn green giving you a false reading. Before the test be sure to draw enough coolant out of your cooling system to ensure the coolant will not contaminate your test. You should not have to withdrawal no more than two cups of coolant
Stick with the possibility of air pockets causing your problem first. Air pockets have been known to cause multiple different symptoms depending on manufacturers and what engine you're dealing with including your own.
Once you think you have exhausted all possibilities of having an air pocket and you still have the same symptoms then invest in the block test. I hope that helps
Once you think you have exhausted all possibilities of having an air pocket and you still have the same symptoms then invest in the block test. I hope that helps
Is there any possibility or way I could have put the thermostat in wrong? The hasket can be flipped either way and rotated around the thermostat itself. So long as the notch goes in. Also the plunger is off center so I'm not sure if the placement matters on that or not.
Did you follow the guide that Chris posted, and drilled a hole in thermostat?
Out of 4 times that i changed coolant, only once i was successful to do it right the first time. Other times it was a tedious process of getting air out.
What helped me is to fill it up while its running hot, you can look inside radiator and see when its low, add fluid accordingly. Squeeze upper hose few times, let it overflow a little bit, and add as fluid starts to get sucked to the bottom again. Just make sure to wash serpentine belt after, i was told that coolant is not good for it.
Another thing i do is get it to operating temps, and then twist radiator cap half way off. That lets lots of steam out, so make sure to protect yourself. Squeeze the hose and keep it squeezed while closing the cap.
Some people suggest filling it up while front is raised/facing up hill. That one time when i did it right from the 1st go, jeep was facing up the hill, so maybe that helped.
Out of 4 times that i changed coolant, only once i was successful to do it right the first time. Other times it was a tedious process of getting air out.
What helped me is to fill it up while its running hot, you can look inside radiator and see when its low, add fluid accordingly. Squeeze upper hose few times, let it overflow a little bit, and add as fluid starts to get sucked to the bottom again. Just make sure to wash serpentine belt after, i was told that coolant is not good for it.
Another thing i do is get it to operating temps, and then twist radiator cap half way off. That lets lots of steam out, so make sure to protect yourself. Squeeze the hose and keep it squeezed while closing the cap.
Some people suggest filling it up while front is raised/facing up hill. That one time when i did it right from the 1st go, jeep was facing up the hill, so maybe that helped.
Went back and got more air out of it. It seems as though I cant get all the air out though no matter how long I pump the upper hose. It gets hot enough i cant hold the hose for more than a couple seconds. I did follow the guide, it just simply wont reach operating temp. This is frustrating to say the least. While taking some temp readings with my ir thermometer, I noticed the neck on top of the thermostat is around the correct temp or a little higher. But if I go down an inch or so where the temp sensor is so 20-30 degrees lower. If I can get one tomorrow I will pick up a block test kit just to see if it's the cause or not.
Air pockets normally cause overheating. A bad water pump will flow less water. Normally causing overheating. A bad thermostat doesn't open or not enough. Normally causing overheating. A thermostat can get stuck open. This can cause under heating and cooler engine temp. But then it would be stuck open. Regardless of rpm. Are you sure you have the correct radiator? Oversized can cause excessive cooling. How about the fan? Electric or the correct belt driven one? If the clutch in the fan is seized then it can overcool with rpm. If an electric fan it can come on or stay on for too long. What does the temp gauge read during all of this? Does it show normal temp and then drop with rpms?
It seems like you are trying to fix an overheating condition while experiencing the opposite.
The fan clutch would be my first place to go.
It seems like you are trying to fix an overheating condition while experiencing the opposite.
The fan clutch would be my first place to go.
The radiator is stock, it's an electric fan. I have only seen it run if I unplug the temp sensor. The temp gauge itself stays around the "1/4" mark or just above. While it is warming up (as far as it will go) the upper hose gets warm long before the stat should be opening. Almost telling me its bypassing the stat somehow. I just picked up a block test tool from o'Reilly so I'm going to try it as soon as I can get back home. During all this the gas valve on my hanging furnace in the garage went and started leaking
. So I just left menards with a new furnace since this one is from the 70s and not worth puting on a new valve. Apparently I hate cold weather and it hates me back lol.
. So I just left menards with a new furnace since this one is from the 70s and not worth puting on a new valve. Apparently I hate cold weather and it hates me back lol.Block test came back good. No hydrocarbons in the coolant at all. Going to drive 45 miles to a dealership in the am for a mopar thermostat. If that doesnt work then idk what to do st that point.
rouxbicon
TJ Enthusiast
I think you’re on the right track with a new quality thermostat. The new one you already installed may be defective from the get go. There is really only one thing that will make an engine run too cool, and that is a defective thermostat stuck open, or opening at lower than it’s rated temperature.
So after the newest thermostat and all this testing it is still going to 170 and stopping. Watching live data and the coolant and feeling the upper rad hose, it opened at exactly 163. I'm at a loss. The only thing I haven't done is a pressure test. Could this possibly be a radiator problem somehow?
Welp had a revelation just now. If you shoot an ir gun at a shiny surface the reading will come back incorrect. I found this out while checking the temp on my flu pipe on my new garage heater install. So this temp sening unit definitely isn't reading correctly.