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Overheating questions

2K views 14 replies 7 participants last post by  CoyRoberson 
#1 ·
So I've done a lot of searching and reading to start out. I had an overheating issue where my needle would spike up to the red and then a minute or so later would drop back to normal operating temp with the heater on which was a little confusing. It would happen more frequently going down the highway usually in fifth gear. So I went ahead and replaced the thermostat and radiator cap in hopes it was an easy fix. It wasn't so I went to my radiator. It was pretty dirty from mudding on the backside so this morning I took my shroud off and cleaned it up pretty good. Still some dirt between the fins but water could flow through pretty well. Anyways I let it heat up and plugged in my banks programmer to watch the engine temp more closely. It did fine at idle and would come up to about 220 then drop to around 210. I went for a drive down the highway and it sat comfortably around 215-220 spiking up to 224 at lights when I would be stopped. Come home and let it idle and it got up to around 230. All of which was with the heater off. Having the heat on full blast would get me to 210 and below. My question is are these pretty normal operating temperatures or is it still running a bit hot. My gauge reads right about the 210 mark and never moved above that. Maybe the radiator needs to come out for a deep cleaning to get all the shit out from the fins? The coolant looked good in the radiator and overflow and was at an appropriate level. Any advice is appreciated.

Oh it's a 2003 X 4.0 5 speed.
 
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#2 ·
You're running hot if you're spiking to 230°
Sounds like a flow problem (since you already replaces the thermostat and cap)

You could flush the radiator, but if its the original, I would replace it and the hoses.
You can get an OEM for about $200 at: RADIATOR for 2003 Jeep Wrangler|55037652AA | WeRMopar

edit: …since you're spiking at a stop, could be the fan clutch.

With the engine cool and off:

TESTING
If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), replace the fan drive. This spin test must be performed when the engine is cool.
 
#4 ·
Also, did you put a 50/50 mix of coolant in or just straight coolant? (1) Straight coolant can case this issue (experience talking)along with (2) air pockets that prevent the coolant from circulating, (3) lack of air flow (bad clutch fan or as was my case electric fan not pulling enough air through) or (4) broken impeller on the water pump (which can be caused by #1 above).
 
#6 ·
What to add depends on what you have done. The final ratio should be 50-50. If you have flushed the system with fresh water and run all of the existing coolant out, if you drain the radiator a lot of water will remain in the block. Adding premixed 50-50 will result in a weak mix. Generally adding straight coolant with what remains in the block will be pretty close to 50-50. You can buy an inexpensive float tester to check the ratio
 
#5 ·
Well the fan doesn't spin easily. I have to try to get it to spin at all. I didn't burp the system. I don't really know how to go about that. I know my thermostat had that hole in it that's supposed to help bleed air bubbles out. I used distiller water to replace the lost coolant. My coolant is orange and I wasn't sure if it was dexcool or not and I was nervous after reading all the stories of mixing coolants. Is there a way to check the impeller short of pulling the pump?
 
#10 ·
I didn't burp the system. I don't really know how to go about that. I know my thermostat had that hole in it that's supposed to help bleed air bubbles out.
To burp the coolant system, you will need coolant, catch pan, running water hose, and face shield or goggles.


1) while the engine is cold, remove radiator cap. add whatever coolant is needed to fill juuuust below the fill neck. squeeze the upper radiator hose to help draw coolant toward the thermostat housing.

2) turn your a/c on, with the climate control knob from blue to red, all the way to the right. left, if you're in Australia.

3) start the engine and let it run. keep a catch pan and a running water hose at the ready.

4) after about 3-5 minutes you may notice the coolant level in the radiator go down. at this time, add more coolant, but juuuuuust below the fill neck. squeeze the upper radiator hose as you fill to help draw coolant toward the thermostat housing. **BE ADVISED, OVERFLOW WILL OCCUR. WATCH YOUR EYES AND MOUTH AS THE FAN BLADES WILL SPRAY THE COOLANT EVERYWHERE!!**

5) Pay attention to the temp gauge and the level of the coolant within the radiator. **BE ADVISED, OVERFLOW WILL OCCUR. WATCH YOUR EYES AND MOUTH AS THE FAN BLADES WILL SPRAY THE COOLANT EVERYWHERE!!**

6) when free of bubbles or air pockets, the coolant will stay within the radiator fill neck even while the engine is running. top off coolant and replace the cap.

7) be sure to rinse off any antifreeze residue from the overflow on the grill and radiator. wash your hands before you put them back in your mouth, or whatever you do with them.

-Joe
 
#8 ·
The fan has viscous fluid inside of it, and the warmer that fluid gets the more resistance it has (it gets thicker). So if youir engine was warmed up so that the fan was pulling air through the hot radiator the fan should hardly spin freely at all... it should be real stiff. Don't confuse spinnging the fan with spinning the water pump. With the belt on, the fan should spin fairly well with a cold engine, pretty stiff (hard to spin or won't spin at all) with a warm engine right after shutting it down.

FYI the small hole in the Tstat is actually to allow a small trickle of coolant to flow through even when the enginen is cold, not for bleeding bubbles out. The water pump depends on coolant for lubrication, so you always want just a trickle to be going through your system to lubricate the pump.

Air bubbles usually work theimselse out, but occasionally if there is a large one the coolant won't flow past it, but this only affects one passage and not the entire system. Coolant is like a teenager... it flows through the path of least resistance. If it has to fight to get past an air pocket, it will take another route.
 
#12 ·
So I burped the system and let it idle for about 30 minutes to check for a temp spike. Idling in the sun I got up to 215 at the 30 minute mark. It would drop 10 degrees or so with some revving. I went for a drive for about 15 minutes and never got above 210 during my drive. So it looks like that did the trick. I'll be driving from Raleigh to Norfolk in a couple days so that will be the test I suppose. I'll be monitoring with my tuner since that opened my eyes to how big of a difference there can be between the gauge and actual temps haha. All the help is much appreciated and fingers crossed everything goes well.
 
#13 ·
well you had a good idea with the heater on to bring the temperature back down, as stated in your first post. so if you ever see another temp spike, you'll know what to do.

but what did the coolant and the inside of your radiator look like when you drained it for the t-stat swap?

i carry a Plano Marine box stocked with basic tools, tow strap, portable air pump, a few extra bolts and nuts, sheet metal screws, electrical tape, 550 paracord, gloves, and multi-tool, along with extra coolant jugs and water for those long hauls. it never failed me yet. i live on the Big Island of HI and the drives are not too bad, but you get outside cell coverage and city limits real quick. fortunately the CB radio community is tight here =)
 
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