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coolant temp?


NAXJA Forum User
Peabody, MA
what should the temperature of the coolant be after warm up. i drove my 90 for about 2hrs and the gauge never makes it to half way. so when i got back i put my digital probe in the coolant bottle. and its 175°F so is this normal anr cold. i do have a 3 row radiator in it. it was about 65° out.
What temp is your thermostat? Sounds like you've got a lower temp one in there. Mine runs that cool with a 180 degree t-stat and a high flow water pump.
some XJ's just run cold. My 89 does. When it gets colder outside stick some cardboard infront of the radiator to take it out of an open loop.
i think im going to go with the cardboard solution. as i have never drove my jeep in the summer i cant say what id does on the temperature of it.
Halfway on the gauge is 210. The gauge measures in the water jacket at rear of the head. I would expect the temp at the bottle to be less.

I have a 2 core CSF with a 195 Stant, still running with the closed system. On a hot day idling, it just barely reaches 210. Once I get moving, it drops.
well on the other hand how can i tell if its going closed loop. i know how vague the computer is on this but is there some kind of home made thing i can hook up to the computer port to maybe light up or something. i read some where that certain pins show some pulses but that was an old cj7 i think.
Thermostat's are cheap, and malfunction often. I replace mine with new Anti-Freeze every 2 years.

If a thermostat goes bad, it usually doesn't show until the change of the seasons, when the cooling load for the motor changes. Your Thermostat might NOT be closing far enough, probably unnoticeable during the summer, but now that its fall it does make a difference.

Most XJ's measure temp with a separate sensor in the head, where the temp changes the most, even when cooling properly. Most vehicles measure temperature at the thermostat, where the temp doesn't change at all, provided the cooling system is working properly. (I'm referring to after warm-up). Thats why you see the temp gauge go up and down some on an XJ, with engine load, while you never see it move on other vehicles, unless your cooling system is malfunctioning.

Runner the motor cooler than designed NOT only hurts gas mileage, it ALSO affects wear and deposits on the motor. Carbon collects on cooler parts (valves) and does NOT get burned off, the motor is designed with clearances that change the temp of the engine. There are lots of dyno test that show many motors make more power running a little hotter than designed temp.

I know lots of people claim that running the motor cooler, "TRICKS" the EFI into making more power, but they're explanation of how this works never holds up and I have yet to see any of them to provide the slightest evidence that it does work.

Sure, there may be some pros that run their Super Hopped Up motor cooler than stock, probably because running it under heavy load, racing or hauling, pushes it to overheating, and runner cooler thermostats gives them a little more margin and cools the motor off during low load and idle. That not the case for most of us.
a standard thermostate on cars sold in (northern) europe will open at 197f.

(Volkswagen has some that opens gradually from 185-200, with a rubber lip on the "valve disk?" to ensure tight seal!)