XJ Overheating Q

Air dam and cooling?

  • Pulled air dam, had issues, no coolant loss, nothing fixed it but louvers

    Votes: 2 50.0%

  • Pulled air dam, had issues, replaced everything and rad and fixed it.

    Votes: 0 0.0%

  • Pulled air dam and had no issues.

    Votes: 2 50.0%
  • Total voters
    4
a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
I got a radiator yesterday (not put in yet), but on my drive home I got to thinking.. I pulled the air dam off the front.. It warms up over like 45mph and cools off between 20-45mph.. Think thats got something to do with it?

I figure the air is cutting off the flow under the engine bay from coming out and cooling the radiator..

I've replaced water pump, thermostat, fan clutch, shroud is in place.

But what I was wondering is how many other people that ha[s,d] overheating issues pulled the air dam off before it happened.
 
There's an air dam on an XJ??? Do you mean that plastic flap that hangs from the bumper? If so, mine has been gone for quite a while and had overheating issues during trail rides. Never had issues on the street. Replaced the rad with all metal 2-row and the t-stat. No issues on road or trail since.
 
replaced my whole cooling system and upgraded to an electric fan. havent had a prob yet and my air dam is missing. I run just under 210 rolling and a lil over 210 sitting in traffic.
 
cant seem to get mine fixed.... @ the radiator shop now...
 
well, i got the one almost new in box (knew it had been run since there was trans fluid in it) i guess i'll drop that in and see whatsup before I cut holes in my hood.. although i think if i slot + twist the metal to make a louver itd be just as good as buying one... mines got new tstat, pump, and clutch.. rad is next before pulling head and putting in a gasket.. motor has 216k on it.. no svc records. bet its never been done before on it likely.. pulled a plug and its the same plugs as was in it as when i got it and the one i pulled was at .070! looks like new plugs too.
 
well.. put the rad in, had to bypass the trans cooler since my old rad didnt have a screw in bottom fitting for the trans.. some trip to the hardware store will solve that.. but anyhow, filled + ran til it warmed up, hit 210 then kept going.. looks like im going to have to tear down the motor and put in a head gasket.. last thing i can think is that the block/head water passages are plugged and/or leaking. seems to have vapor out of the tailpipe and it does have a hole in the muffler. enough to condense on a cold can.. so i've replaced all but hoses and heater core, and i have heat, all hoses heat up, but the thing that gets me is the sensor for the computer/fan is on the water outlet and the temp sensor is on the back of the block.. now everyone says HO XJ's the fan kicks on like around 213-217.. mine does not kick on until it hits like 230++ or turn on AC. thats why i'm thinking the head gasket is fubar'd. i could try a new computer sensor but still yet it shouldnt get that hot running down the road, period, stock rad/pump/tstat or not..
 
Well mine is a '88 cooling system so its closed system, but that doesn't make any difference whatsoever. (as long as the water is there, doesn't escape, and can expand, it'll work for a coolant system) I'm'a'feared at what I may find pulling the head.. its got 216k miles.. I bet it has a small leak from a combustion chamber to the cooling jacket, or the cooling jacket is plugged. or my gauge is wayyyyyyyyy messed up, but I doubt that seriously. It all started after I put the 93 motor in the 88 body + swapped the harness. Ran FINE with no overheating before I put it in, neither did the 88 motor when it was in.. I'm STILL trying to figure out what happened..

Oh and to answer my own question.. It was overheating in the pictures in my profile.. if you look at it you'll see the air dam was on then, so my poll is out the window. I'll just have to tear it down.. and see whats wrong. it's gotta be plugged in there, cause the fan isnt kicking on when it should, and the temp gauge is wayyy past where the fan should kick on. I need a non contact thermometer..

Dylan: http://www.cherokeeforum.com/f2/replaced-everything-xj-still-overheats-47643/
 
Both of these paragraphs have me hoping this is my case. They are both copy/pasted from the link that a-kelley sent..Thanks!

Someone else on this forum had a post about overheating and found out after replacing everything that the line from the radiator to the overflow bottle was plugged up. I popped mine off today and sure enough it was plugged from one end to the other. I should have just bought a new line but being used to doing combat fixes I grab some weedeater line I had laying around and worked it through the hose(you have better luck if you have a mallet, I layed my hose on the ground and tapped it a couple of times). After I got the line worked thru the hose I tied a knot in the weedeater line and pulled it all the way thru the hose, you would not believe the crap that came out of other end. Anyway I took it for a test drive and it stayed steady at 195 which is the thermostat temp I'm running. At idle with the AC on it will stay just under 210 degrees, so thanks to whoever posted that on one of the overheating threads

another guy wrote

I've had the same prob after a head job I did, so I did a full cooling system swap, then my little bro showed up & bled some valve, or maybe it was a sencer & fixed it. If you can't find it all call him to locate it but we just bled it tell coolant flowed out and it returned to running at normal temp. good luck (I knew it wasn't the head gasket, it was brand new)


anyone know here this burping valve is?
 
just got mine back from the radiator shop and he couldnt get it to overheat, seems it only does it to me while driving..... my next stop is to just pull the tstat and run it, then hgasket im guessn
 
jweezyferg said:
just got mine back from the radiator shop and he couldnt get it to overheat, seems it only does it to me while driving..... my next stop is to just pull the tstat and run it, then hgasket im guessn
Click to expand...


always heard that simply pulling the t stat would allow plenty of water to flow..problem is,,this water has not been in the radiator long enough to cool properly.



Ok for a trail fix to get out of the woods, but maybe not a great long term fix...idk
 
this came from the rad shop... he said no issues will arise from this other than no heat
 
my radiator guy said just the opposite, but I race mine..so maybe thats different. I guess it really all depends on who ya talk with. huh?
 
Don't forget, if you have the closed system you'll need to "burp" the system. If you have a air pocket then your water won't flow properly and you'll have overheating issues.
 
The temp reading on the gauge is not what's turning on your fans. that's why the engine has two sensors, or more correctly, one sending unit, and one temp switch. The one at the thermostat is the temp switch that is responsible for turning on fans. The one at the back of the head, is only for your dash gauge. And has nothing to do with the fans or ECU.

Also, as said above, with a closed cooling system, you could have one of the purge lines that go to the expansion tank plugged, or air trapped in the system. the small internal diameter of those lines are bad about getting plugged, as well as where it connects on the tank itself.


If the engine wasn't overheating in the truck you took it out of, it shouldn't do it in your xj either.
 
i understand there are 2 separate sensors. air may be trapped, but all lines get cooking to the touch when it says its like 230.. i mean just absolutely you can touch em longer than 2 seconds.. the one i pulled the motor from had 4 rows of fins missing out of the radiator, and i remember now it was cool out, like 50 degrees.. so it may well could be the gasket, i'll pump 175psi in each cylinder and see where it goes, if anywhere.. if it does bubble the antifreeze, well...
 
jweezyferg said:
just got mine back from the radiator shop and he couldnt get it to overheat, seems it only does it to me while driving..... my next stop is to just pull the tstat and run it, then hgasket im guessn
Click to expand...

I talked to a guy once before who had that problem, and it was the lower radiator hose sucking shut or partially collapsing and restricting water flow. That is why they have a spring inside them. It is something to check if you haven't replaced that hose.
 
drkelly said:
I talked to a guy once before who had that problem, and it was the lower radiator hose sucking shut or partially collapsing and restricting water flow. That is why they have a spring inside them. It is something to check if you haven't replaced that hose.
Click to expand...

ive replaced rad x2(used) water pump, thermostat + housing, temp sensor, and all hoses and lines(with the exception of trans)
 
well after many days and nights of stressing over it and throwing new parts at it, it came down to taking it to the local rad shop and the prognosis.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................$4.00 for a 16lb cap
 

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well, $30, head gasket, valve cover, intake exhaust gasket later, still the same.. grr.. no visible head cracks.. lots of crusty oil crud though.. gobs and gobs.. cylinders are in good shape though. think its the head cracked internal?
 
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