I'm thinking of running a high flow water pump, 190 degree thermostat and hf therm housing to try to drop my temp down..she's not running hot..runs at 210 but what if i got her to run at lets say 195-200 degrees constant wouldn't that make for a cooler running i.e. better performing engine..

 

210 is normal operating temp. Nothing to worry about. Factory temp gauges are not 100% accurate anyway, so that 210 could be +/- a couple degrees. Last time i used the code reader on my 97, the temp read 197. The gauge read 210. If it aint broke, dont fix it.

 

No. Over time it will produce negative side effects. Rich fuel mixture, built up carbon, less then desirable oil lubricity, etc... Hot engines are clean engines. 195 - 200 may not be a danger area I'm not a pro so I don't know, but I cant imagine you'd see any measurable performance gain with a 10 degree drop in engine temperature. It very well may be worse. I'd just stick with the 210 and only address it above 215 - 220.

 

Today's 4.0 is tweaked as much as possible to reduce emissions and is designed to run at or near 210*F for proper mixture control. The biggest problem with XJs is getting enough airflow past the engine and accessories to keep it cool. The engine compartment was designed around the 2.5L 4-banger and a tiny V6, not for the huge long block of the 4.0L. Because of this, the electric fan is more essential than you realize. Airflow from that is much less restricted.

I think it was right around the time your jeep was built that they reduced the compression ratio from 9.2:1 to 8.8:1 in order to control emissions. This also may have had something to do with cooling.

 

No reason an oem cooling system operating at peak efficiency won't keep the temp under control unless something else is the problem.

 

Oh I agree. The problem is most often they are not optimal. My 2000 XJ had a brand new radiator, waterpump, fan clutch, and hoses when I bought it and I've not had any problems with it at all, but it makes me wonder why the PO changed those parts because the jeep only had 125K miles on it!

 

Dave,
Sorry. My post above wasn't aimed at you. It was for the OP. We get a lot of owners who consider upgrading their cooling system when there may be no need.

Hard to say why the PO of yours replaced those parts. Just a guess but maybe the radiator had to be replaced for some reason so the other parts were replaced because of ease of access. What ever the reason you made out on it.

 

All things considered, the Mopar all metal HD rad is sexy as hell. If I were going to do any "upgrades" to the coolant system, that would be it. I've had bad luck with plastic tanks in winter.

 

How long did the original radiator last? What brand did you replace it with?

 

I was having the radiators fail in my 98. The original had already been replaced when I got it. One that lasted longest was from AutoZone, after that went I put in another from Napa. I think I was averaging 2 years on the plastic tanks. Always failing in winter it seems.

Haven't had any issues with the 99 XJ yet but I've only had it 5 months. The rad is another plastic tank. When it goes, I'm getting the Mopar HD.

 

I'm just guessing that the one from AutoZone was a Spectra. Most recommended replacement one here. My original one lasted until ~160K miles. Got almost three years on the Spectra. Were the tanks cracking?

 

I'm not sure what brand it was but it did have the longest operational life. The tanks were cracking vertically. Sometimes several cracks at once.

 

Mine split vertically to. Took me about a month to locate where it was seeping coolant from. Evidently it started out as a short crack and ended up being only about 2" long. But I've never read or heard of it being a chronic problem.

 

"The biggest problem with XJs is getting enough airflow past the engine and accessories to keep it cool. The engine compartment was designed around the 2.5L 4-banger and a tiny V6, not for the huge long block of the 4.0L." ..... Exactly Right............ dave1123
Years ago I had a (Australian Ford) 1994 ED 250ci/4 Litre straight 6 .. Auto A thirsty but Bulletproof Engine Point being there was so much room under the Hood No such thing as HOT unless something Broke!
My Cherokee a 96 Limited was a overheating nightmare from the day I got it ......... It ended up being a Bad Head not enough to show up in the oil or coolant it was leaking into num 4 and burning it off But it was injecting air bubbles into the cooling system
All sorted these days ..... steel radiator .. high volume water pump .. 195 deg thermostat (important) .. good hoses .. functioning clutch fan .. fan shrouds in good condition .. I use a light bar instead of spot lights to minimise air flow disruption ... I even installed louvered vents in the hood BIG ONES! You can see the heat rising out of them !!!
A XJ Needs a Perfect Cooling System ......
The louvered vents are helpful until it rains heave and you have to run out and throw a tarp over the hood "LOL"

 

I went through my cooling system and replaced all components (radiator, water pump, thermostat, hoses. fan clutch) with OEM parts and my temps run in the 200°F area. Definitely below the 210°F mark, even pushing 90°F ambient temps without running AC. I flushed/back-flushed the heater core and block as best as I could while changing everything also.