Overheats after driving a just a couple miles. Just replaced the radiator and thermostat. Still over heats. Goes from the notch right after 210 once it’s there it shoots straight to 260 and I have to pull over.

Im not too mechanically inclined so any suggestions bare with my knowledge haha thanks!

 

What year and engine?

 

You probably have some air in the cooling system from the recent work. This could explain in part the erratic temperature gauge reading. The thermostat probably has a small air bleed hole that should be oriented "up" to help bleed air. A few warm up and cool down cycles should self-bleed much of the air as air gets pushed out into the overflow container on heat up and then coolant is sucked in on cooldown. Do not drive and overheat until this is resolved. Get all the air out and then see what you have.

 

2001 Cherokee sport

 

How do I do this

 

Google it and you will find lots of info. And as I said a few heat up and cool down cycles should get the air out of the 4.0 cooling system if the thermostat is installed correctly (no RTV used, right?). Squeezing the top radiator hose while cool may help get some air out. Judging from the crud on the radiator cap you might get a new cap and verify that the line to the coolant expansion tank is not plugged with stop leak sludge. Pull if off the radiator end and blow into it. You should get bubbles in the expansion tank. You will likely need to clean the expansion tank out also. Remove and hose it out.
Note: you should not allow coolant to run into the ground or storm sewer and keep it away from animals.

 

So just start it up til 210 and cool it start up again etc? And what is rtv?
no crud brand new radiator

 

Bleed XJ radiator..(or any other SOB cooling system)

If you park the vehicle with nose steeply up, radiator cap off overnight, that should nearly do it

for extra, start the engine cold like that in the morning...keep adding coolant using a cutoff plastic drink bottle to raise level, squeeze radiator pipes, do this till thermostat opens

once all thats done, keep a claose eye on overflow bottle level

a dud radiator cap can also cause overheat

 

What temperature thermostat did you put in?

Do you have an IR temperature gun?

I agree it's probably air. But with a $20 temp gun it's easy to verify thermostat is opening at the correct temp and that your dash gauge is accurate.

 

Yes, just let it heat up to 210 or mid range on temperature gauge and then let it cool down.
RTV is a silicone type of sealant (RTV = Room Temperature Vulcanizing) sometimes used in place of or in addition to a gasket. Similar to silicone bathtub caulk. Those unfamiliar with it often use RTV in wrong locations or way too much of it. It typically should not be used in fuel systems, oxygen sensors, head gaskets, manifold gaskets. Careful with use in cooling systems as too much can ooze into the system and can block passages such as thermostat, radiator and heater. Again, if you are at all computer savvy Google is your friend in finding out about this type of thing.

 

An accurate no cost and relatively easy way to check a thermostat is to put it in a pan of water and heat the water until it begins to boil. Water boils at approximately 212 degrees at sea level so you should see the typical 190 to 195 degree thermostat move open when in boiling water. The temperature of the thermostat should be stamped on it.
Most all cooling systems are pressurized and use a coolant/water mix, increasing the temperature at which the coolant boils. Normally you will not have boiling in a properly operating system. If you continue to see bubbles in a cooling system this is an indication that there may be head or head gasket issues allowing combustion gas to enter the system.

 

Ok.

If it's installed....I would use a temp gun to verify its operating correctly. No need to disassemble. This also validates your dash gauge is working correctly.

 

No ir temp gun. Also it overheated prior to the new radiator and new thermostat

 

So with a rapid heat up within the first few minutes of starting the vehicle, that can usually be a sign of a bad thermostat, one that is closed.

Is the top radiator hose (coming from the thermostat housing) to the radiator, hot when the gauge is reading 210? It should be hot to the touch (like you should not be able to hold it for more than a second) and if you wrap your hand around it and squeeze it should be hard to squeeze. If the hose is cooler when it is showing that temperature on the gauge, you may want to look at replacing the thermostat, really easy to do. If you do ending up getting a new one, try and get a Mopar or factory part from the dealership. Maybe a little pricier but the thermostats at the auto parts stores are not reliable (in my opinion).

Air in the system could be a culprit, but typically within a few warming and cooling cycles, the air should naturally work it's way out. The cooling system is designed to release pressure (or air) out the highest part of the cooling system (the radiator cap). Others have already said this but to make sure there is no air in the cooling system, turn your heater control in the vehicle to Hot (like you are turning on the heater). Take the radiator cap off of the radiator and fill with coolant to near the top. Start the vehicle. When you do this you want to get the vehicle up to operating temperature or when the thermostat begins to open (close to when your gauge hits 210), or when you feel the top radiator hose get hot. Once this happens, turn the vehicle off, replace the radiator cap, make sure that coolant in the reservoir (the plastic container) is the appropriate mark. That would get any air out of the system. Here is the thing though, if you are doing this and you are not feeling the top radiator hose getting hot at all, the thermostat would be the first thing to replace.

 

This.