Interestingly in the 94-96 parts manual (my model) it lists only 2 thermostats, an unrated unit and a 180* (severe use) unit. Another interesting thing is my '95 model had a radiator in it specified for a '94 model and I thought it was alloy/plastic when in fact when I removed it recently I found that it was actually copper/plastic and had been there at least 8yrs as that is how long I have owned it and only once did I have an issue of overheating!!!!!

I drove my xj into the workshop at lunch & hooked her up to the jeep Techconnec just to run her numbers & check for any ecm pcm updates & low & behold what popped up HIGH AMBIENT OR HOT SOAK TEMPERATURES 2000 - 2001 XJ its a software update that lowers the temp threshold used to determine when the engine fans are turned on , Cooling fans will cycle more often .

Service Bulletin 18-031-03 18-039-03

Ran the PCM update & my thermos used to come on at 104 c to 105 c now they come on at about 98c or by the temp gage a needle width before 100c & thats where it stays , im pretty happy with that , but i have also just fully replaced all the cooling system & removed the AC gear so i have greater air flow through the front so it may vary a little from Jeep TO Jeep ;)

PCM update & re-program is for 4.0 ltr Auto's only


Top work there Rodger , cant wait to read the followups & sorry for the little Hijack but i thinkk it may also help the update xjer's ;)

excellent comments and rebuttals guys! exactly why i encouraged it (dont worry Carves, your opinions are safe - everyone has one so always share). I just thought it would be nice to have this discussion which has been beat to death countless times in one place: RIGHT HERE! i wont hold my breathe but maybe it will slow down the repeat questions we all get. sometimes i wish i had a stamp when answering them lol. :cool:

http://www.freesmileys.org/smileys/smiley-happy057.gif ... Best I tie an icecube to my typing finger and get started then ... :mrgreen:

Nahhhhh ... I'll be fairly shush on this thread http://www.freesmileys.org/smileys/smiley-scared003.gif .... as you covered most of my gripes & concerns at the start.


Can you use the techconnec thingy to find out whether that computer flash can be done on any OBDII 4.0l XJ here.

I mentioned it as only being suitable for the 2000/2001 in the other, general cooling thread last year, coz my local dealer reckoned it was year model specific .... but the dealers say a lot of things .... ;)


Best you check for belly dancers & camels under the backseat jj - as that was the stock radiator for the hot climate, saudi/middle east market ... was also available as a heavyduty cooling option elsewhere .... If the dealer knew about it :roll:

Should be in your parts book too.

It was listed in the parts book, that is how I know it is from a '94 model, maybe this is part of the reason that I had so little cooling issues.....
Buggered if I know what thermostat is in it though as I have never checked..... oops!!!

Rodge, why the recommend minimum 44% mix? A lot a fellas are recommending and running 33% ratio for our hotter climate. A lot of engines, consisting of the same materials and marketed to Australia are running 33% and don't have any shorter life span because of it.

im not pissed off, was just a friendly reminder that we are discussing the xj 4.0L cooling system here - not other irrelevant stuff. adding those comments just makes it harder for folks to wade through the posts to get the info they really need. even my post here adds to it so i will state this one time only: lets stay on topic please. its all good so dont anyone stress over my comment! :cool:

as for the 44% figure - that is straight out of the FSM but as others have pointed out it may not be suitable for warmer climates. my choice has always been to run a 50/50 mix but that is just me. i suppose too it should be clarified what is 30% and what is 70% - the water or the coolant? lets make that distinction for those people who may not know (remember, this is an info page). also remember, my original post is PURELY my own opinion based on my own experiences and guided loosely by the FSM - i WANT you guys to share YOUR opinions and why you think they are plausible. That way a consensus might be formed based on shared experiences. if 30/70 works tell us why - i hear that number a lot too and may change my thinking if i hear a good reason for it. i guess also i am from a cold region so that number from the FSM rings true for my past experiences but like everyone, i learn something new everyday! suppose i should know better without being told but sometimes ya just go with what ya know! keep it coming guys! :cool: