Skip to main content

I know this subject has been beaten to death, but I need to ask anyway. I took the Pantera out tonight for a quick roadtest after installing a half shaft. The temp gauge climb nearly to the red as I arrived back home after a 20 minute run. When I got back in the garage, I checked to see if the fans were running, they both were. I carefully put my hand on the top of the raditor, and it was not really that hot at all! Is the stock temp gauge really THAT inaccurate? No fluid overboiled, the engine itself seemed normal. I guess I need to get a mechanical gauge and go by that instead.
Original Post

Replies sorted oldest to newest


My temp gage is reasonably accurate. I had a problem with the needle pulsing to zero or just staying at zero unless I pushed on the gage bezel. The problem was a loose connection behind the gage (the 10 ohm resistor), once that connection was repaired it has read bitchen ever since.

Assuming your evaluation of your cooling system is accurate, I would suspect a wiring problem. If its reading high, that would indicate a short circuit somewhere (temperature indication increases as the resistance in the measuring circuit decreases). The resistor spliced into the circuit behind the gage may be shorting somehow. I would check the wiring behind the gage first. And the connection at the "sensor" second.

your "wired" friend on the PIBB, George
Before you suspect your temp gauge, check these out:

1) is the system bled correctly? As simple as this seems, air entering your system (from a leaky coolant cap, for example) can cause an overheat indication.

2) bad T-stat. George gave me(us) the 101 or should I say an advanced course on this recently.

3) a bad water pump. If it's leaking or you hear bearing noises, then replace it.

4) radiator plugged. How old is your rad?

TurboTim........... If you do go a replacment route, I'd highly recommend a mechanical also. I like knowing what the temp is even after the car is off before I crank her up again. (plus I check against my scanner and its dead-on).

I just recently did a cooling system "overhaul" with new rad and waterpump and have been extremely pleased with the results.

But to answer your question on accuracy, see if you can find someone local with an themo scanner to compare readings. (its especially good to have if you have just done a refill of the system where you can shoot it at the thermo housing or heads to see what the engine temp is, because you have no good temp running against the water sender yet)
As suggested, you can verify the accuracy of the gauge with an IR Temp gun (best method) or with a meat thermometer (poor man's method - it's what I used!)

On a related note, where is your sending gauge? The stock location is in one of the coolant tanks, where the temperature isn't necessary a perfect reflection of the temp in the block. Or put another way, I don't care what the temp of the tank is, I really want to know what the temp of the block is. If you have a coolant leak, for example, you may eventually read air temperature and think everything is fine, when in fact your engine is slowly melting down.
Well today I took my daughter Mary for a ride. The temp gauge stayed around 192 the whole time!? When the car was cold this morning, I opened the coolent pressure tank to check the fluid level. As soon as I cracked the pressure cap loose, fluid wanted to gush out! I thought this was odd with a cold engine? Anyway, the car seemed fine today. I plan on pulling the radiator, changing the thermostat, hoses, ect. to make sure the cooling system is fresh and ready for a trip up to Santa Cruz. I think I will install a new sending unit too. Thanks for the info guys. (By the way, I went over Goddes Pass this morning, a winding, up hill, down hill road close by here. My daughter loved the way the Pantera took the turns! I have to admit, my old 70 XKE would not have had a chance!)
Over the past several days I have been after this high temp reading on the coolent gauge.(Knowing the engine was NOT getting hot) The first thing I did was to clean the main ground connector behind the drivers side dash. I also checked the main ground at the ZF. Then I pulled the center gauge console and check the wiring behind it. While I was back there, I added an extra ground wire to the temp and oil pressure gauge to see if that would help. No change. Temp gauge was in the red after only a short driving distance. Then I remembered what George Pence said about the 10 ohm resister. Maybe mine was shorting out and sending too much current to the temp gauge. A quick trip to Radio Shack, install the resistor...guess what?....rock solid steady reading of the gauge at 189 degrees! I will let the engine cool and see what kind of measurement it shows cold. I bet its ok from now on......Thanks George....another gremlin bites the dust..
Link copied to your clipboard.