I know this forum is already over saturated with overheating issue threads, however, here is another one. I'm manly looking for you experts out there to confirm my findings.


98 4.0 5spd


temp at idle and city driving is just slightly high, 215-220, just high enough to kick on the aux fan. At highway speeds it runs as high as 230. I've recently drained and flushed the system and have bled it 3 times since, thermostat was replaced in 2012. There is no coolant in the oil and the old coolant was cleanish when I drained it, no signs of cracked head or blown head gasket. I suspect since its running hotter at higher speeds its most likely the water pump starting to show its age or the recent flush loosened up something and clogged the radiator. Anyone agree or have a different opinion.


The only reason I'm somewhat concerned about it is because I'm about to make a 1500m trip and don't want to get stranded due to break down

 

You are right! Your are running hot, you should be around 210. You are also right that it may be the radiator. You can pick up a new rad from Auto Zone for around $100. I would also replace your t-stat set at 195 along with a new rad cap set a 16lbs.

 

i would guess more likely your radiator is partially clogged.



RTorrez beat me.
I'm a slow typer!

 

As I suspected... Would it be easier to pull and clean out the old one or spend the scratch on a new one?

 

Also need to make sure that your fan clutch is good and the the fins on the a/c condenser and radiator aren't clogged up (like with leaves or bugs on the outside). I had this happen once.

 

New radiators are so cheap, hardly any radiator shop works on passenger car stuff anymore.

 

As Mr. Firestorm said, It is well worth the $100 for a new one.

 

Yep, just got back from picking up a new radiator, thermostat, cap, and fluid. Changing it all out tomorrow.


And Im not worried about the fan clutch. 1) the fan blows like a tornado and 2) if it was the fan clutch I would be having idle low speed issues, to which I currently am not having

 

Replace the water pump at the same time. They aren't that expensive and as long as you have things torn apart, do the pump. Absolutely.

 

Well, looks to me you actually do. Your idle/low speed driving temp is high and kicks on the aux fan, you say.

I would take out all the guessing with this and move on and replace the viscous fan as well. In fact, why don't you include the wp and hoses and be done with the whole cooling system overhaul for under $250?

 

I was just about to suggest this same thing. With an XJ, do not piece together your cooling system replacement and diagnosis. Replace every single component for under 300 dollars and be done with it (I say 300 since I did the overflow bottle, sending units, thermostat housing, ect...).

Your sending unit or gauge may not be completely accurate either.

I am very ANTI part swapping, but with the cooling systems on XJ's being common failure points, just get this one over with.

 

Thanks for the input everyone. I'm going to run out this morning and get new hoses and a new water pump as well and just do the whole thing like you guys are saying

 

Good on ye, mate. Investing in XJ cooling system maintenance is money well spent.

With winter coming up for you guys, might be ahead of the " no heat" thread and flush your heater core while you have drained the coolant.