loligator

Hi guys,

My temp gauge has never read properly as long as I've owned my new XJ (bought it about 3 or 4 months ago). I had to move the sensor to the thermostat housing because the PO replaced the head and there's no hole in the rear near the firewall for the sensor (it's a 96 4.0 with a 0630 head; the only year of the 0630 that used two temp sensors. The replacement head has to be 97-99 when only one sensor was used). He had it taped to back of the engine when I went to look at the jeep so it showed some kind of reading and I didn't pick up on his trickery More can be read on that here if you're really interested: https://www.cherokeeforum.com/f2/tem...6/#post2647187

I've done some googling and it seems moving the temp gauge sensor to the t-stat housing should give me an accurate reading. I replaced the gauge sensor with a BWD branded one (I know, I know use Mopar sensors only). It has good reviews on Advance's site.

I don't think it's given me an accurate reading since hooking the gauge back up. Originally, I had an 185 cheapo Stant t-stat in there. The highest reading the gauge ever gave me was about 170. I'd imagine a 185 t-stat would let the engine at least get up to 185. My heat blew luke warm so I changed the t-stat out for a Mopar 195 at cruiser's recommendation. The heat now works great but the gauge is constantly moving between 205-220 while driving and goes as high as 235-240 if I let it run while sitting before the aux fan turns on. While driving, it slowly moves up to 220 then slowly back to 205 and back to 220 again without the aux fan ever coming on. Back and forth, back and forth. That just doesn't seem right for it to move so much.

The aux fan should come on around 220 (I think the actual temp is 217) from my understanding and it isn't coming on until the gauge reads at least 235. This has me thinking it's the gauge temp sensor reading inaccurately or the gauge itself being funny. I'm worried though that it could be giving me an accurate reading and that something's wrong with the cooling system.

I changed the coolant, t-stat, and rad cap when I bought her although I didn't forcibly flush the system. I drained the radiator then filled it with distilled water, ran it until she was hot, let her cool, drain, and repeat until the drainage was clear. The jeep sat for a year unused so I was a little concerned with truly flushing the system as I didn't want to put a hole in the heater core. The PO said the radiator was done about 3 years ago and he believes the water pump was too but he's not certain about the pump. The coolant was brownish with a slight green tint when I changed it and was a little chunky on the first and second drain but was normal after that. It took about 7 or 8 fill and drains to get the drainage to come out clear.

Hopefully this isn't too much info but I wanted to be thorough. This is my DD and I have a bit of a commute so I need to make sure she's in top notch condition.

I borrowed my friend's thermal gun so I'll take some readings this afternoon and post the readings.

Any opinions? I don't want to replace anything else if I don't have to. I've had to put more than I anticipated out on fixing her up.

Thanks

loligator

One thing I left out is that I burped it after doing the coolant change and t-stat and again recently just to rule out air in the system. I let it get to temp with the rad cap off, waited for the coolant at the top of the radiator to start bubbling, and added more antifreeze as it drained into the radiator. I did this until the bubbles died down and the coolant started flowing slightly out of the radiator.

Scotty16

I would recommend getting an inferred thermometer (any auto parts store has em for a fairly descent price). or get access to one. My gauge reads 220ish-240 range but im actually at the normal range of 195-210 when checking with the thermometer....216 is the hottest ive gotten, but that's going uphill slowly for a long time.

Also, ive read that the temp sender unit can often be defective out of the box.