I would imagine the minimum number is just that, the minimum. Anything below would be a sign of either a bad blower or clogged heater core.

 

......as discussed in the FSM above the chart.

 

I didn't read it, I just looked at the chart.

 

FWIW, just took the RAV4 (kiddo has the XJ) for a spin with a "probe type" thermometer stuck in the center dash vents. Coolant temp floating 184F-189F (ScanGauge) and the dash vent thermo peaked at 148.

 

i wish i would never have mentioned the heater temp. i feel like we are trying to fix the lesser problem now. but i will mention that different heaters will probably have different temp spreads between vent and coolant temp. there are all sorts of things that can influence it. like a partially stopped up core, debris/cobwebs etc over core fins, more/less restriction in the vent system. my xj has hood vents in front of the cowl, so i could be drawing heated air from the engine compartment in through the cowl vent. also i took my reading from a dash vent, might make a difference. i doubt that the manual's 50 degree spread is an absolute. ok got that out of the way.

lets assume i didn't mention any actual numbers as far as coolant temp and oil pressure. my gauge could be off and i might not be aiming the IR at the right spot. i am not even sure if the quarter mark is actually the halfway temp between bottom (100) and straight up (210) so i maybe reading it wrong.

lets put it like this: in the summer my temp gauge points straight up when left idling. drive it down the road and the needle drops to slightly above the quarter mark. park and idle again and it returns to straight up. while this is happening the oil pressure acts inversely. about 20 psi difference at the two different idling temps.

in the cooler fall weather we have now (60 to 75 degree highs) i can let it idle forever and it won't break the quarter mark on the coolant gauge. take off down the road and within one mile or less has dropped to 1/8 gauge. in this weather the oil pressure stays at 75 psi to pegged while driving at 1500 rpm or more. it never drops below 60 while idling. in this weather i have high idle all the time, 1000+. didn't notice if i had a drop in summer or not. didn't drive it much then.

and my mileage is 12 mpg highway and substantially lower driving in town. i drive like an old man. i might hit 70-75 on the interstate but never accelerate hard. easy-does-it.

i have read several forum posts that say thermostats only regulate "minimum temp" and removing them can't make an engine run cooler. i have read many posts scolding people for removing their tstat to reduce excessive coolant temp. they say they are wasting their time and the only thing it will do is possibly lengthen the time it takes the engine to reach operating temp. they say if you have an overheating problem you can't solve it by removing the tstat. so....i have an under-heating problem. if i believe the gurus on the other forums i would have to say it can't be the tstat. if it is stuck closed i would have melted the thing down by now. if it is stuck open i should still reach normal operating temp in the summer with a load on the engine right? and definitely break 150-160 during a hundred mile interstate trip in 65 degree weather right?

i checked the map sensor connections today. mine is located on the throttle body according to chilton. the line looks fine. are there any other sensors that could prevent the fuel system from leaning out after start-up?

 

Line? If it's on the TB there is no line. Do you mean the wire? lol On the Renix 4.0s the MAP is on firewall with an actual vacuum hose running to it.

Take the MAP off and gently clean inside with some throttle body cleaner

 

Let us know what the dealer says about this. The dealer may ask how the heater works.....devils in the details for diagnosing "engine runs too cool", no?

Mathematically, the factory gauge breaks down like this.

 

I had your same problems change to a different brand thermostat i switched from stant to a dealership one and it fixed the running to cool problem

 

thats what i'll do. if they ask if my heater works well i'll say "you tell me". my standard might be different from theirs.

i will post again after the next tstat swap

 

Put a factory stat in it.

 

According to the book, your reading and their standard is within 1*.

 

lol You love to push that. I wouldn't call a bare minimum a "standard". That's like saying standard oil pressure for a 4.0 is 13 PSI...

 

I had the same problem with my temp rising when stopped and dropping when on the move. Ended up being the clutch fan.
It's perfect now.

 

Would u call it a reliable reference point maybe???? What else, besides the book, does one have to go by for reliable/valuable information........the opinions of others? Really? Opinions is what starts myths/misinformation.

Is anybody gonna take their XJ to the shop because the difference between heater vent temp and coolant temp is 50 degrees or less???? Is anybody gonna take their XJ to the shop because their oil pressure is 14 psi or more????......really, are they?

This whole thread is starting to smell like tuna fish.....u can't have a heater that works well......a properly functioning t-stat.....AND a dash gauge accurately/correctly displaying 130-150 degree coolant temp.....u just can't have all 3 at the same time. At least one of those 3 has got to be wacked.

Likewise, u can't say a cold motor is the cause of extremely high oil pressure.....what motor isn't cold after a period of not running? Is it characteristic for cold motors to blow gaskets, not. U can't blame oil filter gaskets blowing on a cold motor. Whenever there is a oil pressure question, the question should be answered with a oil pressure test using a mechanical test gauge. Shops do it every day....it's quick, cheap and easy. Git 'er done.

 

This^^ makes perfect sense to me.