• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Strange overheating

S

SeansBlueXJ

NAXJA Forum User
Location
Plainfield Township, PA
Ok so here is what's going on, and what I have done so far. 2000 XJ overheats, sometimes to the point of redline. Heats up faster on the highway then side roads. So far I have changed all the typical cooling issue things and nothing has helped. I have done a fill/drain flush, new t-stat, new water pump. I first suspected an 0331 head crack as my mother's 00 did the same thing when the head went, but so far no crack, and no antifreeze in oil or vicea versa. The raditor fins are clear and clean and the fans both spin. It's getting to the point where I cant go anywhere. Is it a clogged raditor that didnt clear with my drain/fill? Any other ideas?
 
I would check compression to rule out crack or even head gasket. Mine was acting similar though and it ended up being a crusty radiator. Not too expensive and relatively easy to replace.
 
I am praying it's the radiator, I picked up a new cap to be sure of that. I also got one of those flush kits where you splice in to the heater hose and hook up the garden hose. going to run that tomorrow and see what comes out.
 
by any chance do you have the stock bumper or aftermarket ? i had the same problem only started after i changed the bumper and have been trying to figure it out ever since .. ran so hot on the hiway the kids shoes melted to the floor .. anyway changed everything but the rad complete rebuild of the 300,00 km motor stilll running hot.. i installed hood vents ok noticed a change right away but only in town so what gives.. then the lights went on .. i reinstalled the rubber slash gard under the motor and that helped a bit.. finally i made a deflector out of tin anfd jammed it under the bumper and zip tied the bottom end to the sway bar.. WOO HOO !! it worked temps are perfect again.. next week i will be fabing up a ''skid plate/air deflector'' from some diamond plate i see so many threads on here about overheating xj's and everybody is talkin bout vents and stuff .. upgrading the rads , 2 core/3core aluminium . if the stock rad is good check the air flow under your jeep
 
Other people have had the same problem. I think it's an airflow issue. Air gets pushed into the grill at highway speed, but then it has to exit somewhere-- underneath the engine compartment. The issue I think is that high pressure builds up under there thanks to the big ol solid axle we have, especially with a lift. Swampman's experience with the rubber splash guard confirms that. A skid plate should do the same thing-- deflect air down underneath and create a vacuum.
An air dam would help too
 
well it has the stock bumper, stock air damn, the rubber splash guard is still there, and there is only 2.5" of lift which have been on it for like 2 yrs now. New cap helped some but still getting hotter then I like, going to use the back flush kit tomorrow after another round of prestone chem flush stuff, see if that churns out any more crap.
 
When it overheats, are the hoses collapsing?

Last summer on the way home from the Rubicon, I had an issue where my Jeep would get really hot. I had to pull over about 10 times to let it cool off. The last time, I looked at the hoses immediately, and they were both collapsed. Then in a few seconds, they would return to normal.

Turns out that the hose from the radiator to the overflow bottle was clogged and that was causing the hoses to collapse at highway speed. I tried blowing through the hose, but couldn't. So I used compressed air to blow out some crud that was stuck in the hose.

Never had the overheating problem again. It's an easy thing to check. And you might get lucky.
 
Ill check that, I don't think so, but I haven't looked specifically either.
 
alright i have alittle update on this went down to seans house last weekend to lend some help with this. we replaced the radiator with a performance unit and added a trans cooler to take more of a load off of the cooling system. so the list is new water pump, radiator, radiator cap, trans cooler and we drove around and the temps stayed perfect and we thought we got the problem. FAIL i get a call from Sean today and tells me his truck made the 70 mile drive from his house to jersey pulling a trailer no problem takes the trailer off and starts driving back to PA on 287 and it over heats. the head isn't cracked no oil in coolent no coolent in oil we checked everything ,everything is working as it should we are going insane
 
check for a head gasket lead/craked head with a block tester. even though you dont have coolant in the oil, you may still have a cracked head. it will detect exhaust gases in the cooling system and the tester is only a few bucks at NAPA.

you may also have air in the cooling system causing the intermitent hot times.
 
stewie said:
check for a head gasket lead/craked head with a block tester. even though you dont have coolant in the oil, you may still have a cracked head. it will detect exhaust gases in the cooling system and the tester is only a few bucks at NAPA.

you may also have air in the cooling system causing the intermitent hot times.
Click to expand...


good call this was next on my list off things to test
 
Could the new thermostat be faulty? I hear they can be unpredicable. Was there anything different about the 2 parts of the round trip? It sounds backwards, one would expect it to overheat during the tow, but did he drive differently, diffent ambient temps, day versus night, AC on or off, etc.

Is the electric fan always coming on when it should? Is the fan clutch toast?

It is starting to sound like it might be running lean intermitently. Intermitently clogging fuel injectors, exhaust, sticking valves, exhaust blowing (leak) on the block...etc., but it would need to something that come and go. Maybe an O2 sensor that is reading rich (and lying to the PCM), and pushing the engine too lean.
 
i was worried about the t-stat so that was checked in a boiling pot, fine. Nothing too different about the round trip, same part of the day (went out one day stayed over night) only a few degrees difference in ambient temp (less then 10). Both fans are functioning as they should. I might be leaning toward your running lean idea. I mean since the new rad it doesn't even run close to 210 except the one major bs overheat on the return trip.

And may not be related but just to see if it told anything i pulled the plugs yesterday (bosh platinum plus single lead jobs) and the ceramic insulator had gone red on all the plugs no clue what that means, besides that normal wear. Since installing the plugs 1.5 yrs ago I learned (from here of course) the 4.0 probably likes copper core plugs better so i installed AutoLite copper properly gapped. Oh and I took the truck for a 5 mile highway jog last night and I couldn't get it anywhere over 200-205 again much less 210... WTF?
 
Are you sure it's really running hot, of could it possibly just be the gage? Does it actually boil over? Do you have an infrared thermometer or some other way to confirm the gage? A really hot motor crackles when you turn it off. You also wouldn't be able to hold the dipstick. Of course, especially with the 0331 head, you don't want to play around with overheating!
 
oh it boils over if i shut it down before letting it come back down (it will eventually cool at idle) it's not the gauge for sure.
 
Sure sounds like something is tricking it into running lean once in a while.

I can't see the cooling system working great one minute, and not the next, not with all the new hardware you have now.

I have said in the past we need to rig up dash gauges and wiring under the hood where we can drive and monitor one or more engine FI sensors live, like O2, CTS, MAT MAP, TPS to catch the invisable gremlins in the act!:eyes:
 
Ok so here's and update mabye it will make someone think of something. So I did another NJ round trip today same as my last overheat DITA talked about... On the way out all is fine and cool, on the way back, didn't overheat but got a little warmer then the 210 I would like to see it at. So I thought ok, whats happening on the return trip. Then it clicked, both trips out I did not stop, the truck was on from point A to B. On both return trips I had to make a 10 min or so stop on the way back, it was only after the truck sat off, at temp for a few min did it decide to keep getting warm. So what is getting pissed off by being left to heat soak for a few min? Could the fuel injector issue i had where it would run rough after a heat soak cause this? Im thinking if it messes with the injector then maybe it's messing with the spray pattern = lean running? does that make sense, or maybe the symptom points to something else for one of you.
 
It sure doesn't seem like the heat soak issue could make it run lean for long enough to make it overheat. The fix for that issue however is to wire up a switch to keep the efan running (possibly a timer in line). This is well documented if you search for it. If you really want to find out, turn the motor off when you overheat and coast to the side. Pull the spark plugs and see if they are white.
 
You must log in or register to reply here.

Similar threads

C
Cowl leak seems to be unreachable. solution.. Seal the hood cowl?
Replies
5
Views
2K
clean96XJ
C
O
0331 Strikes Again...?
Replies
11
Views
301
Ol Blue
O
X
Replacing my entire cooling system
2
Replies
23
Views
4K
RCP Phx
R
Root Moose
Cooling System Reset (2000 XJ)
Replies
1
Views
1K
Rob Mayercik
R
G
Coolant System No Pressure
Replies
9
Views
2K
Woodswanderer
W
Back
Top