View Full Version : TR6 TR6 Temperature Gauge

Webb Sledge
10-09-2004, 06:34 PM
My TR6 always seems to run a little cool, which I find a bit unbelievable due to the terrible shape of the engine, and I suspect my temp gauge of being messed up or rigged by the PO's PO, who was a LBC salesman and did some cheap stuff to make my car look good to the PO, when it really wasn't. Is there a way to take the engine temp at regular running temperature, without using the gauge, and without getting really complicated? What's a good reading for 6 which is up to temp?

Geo Hahn
10-09-2004, 07:22 PM
This is what I use...


10-10-2004, 03:24 PM
Hello Webb,
the simple test for the temperature gauge and the fuel gauge is to disconnect the wire from the sender and connect it to earth. The gauge should then read full scale, i.e. Hot or Full. There is not much really that can be done to 'doctor' these as you suggest.


90 XJ-S
10-10-2004, 04:36 PM
Webb, Alec,

All it takes is resistance in series with the temp sensor (which would include a corroded terminal anywhere in the circuit) and your temp gauge will read low.


10-10-2004, 05:26 PM

Just buy a candy thermometer and open up your radiator and stick it in and compare the temperature to that on your gauge (as you warm the car up).

90 XJ-S
10-10-2004, 05:36 PM

...candy thermometer ...open up your radiator and stick it in ...compare the temperature to that on your gauge (as you warm the car up).

[/ QUOTE ]

After the thermostat opens!


Webb Sledge
10-10-2004, 08:15 PM
What's a good temperature for the 6 to run at once it's up to temperature? All my gauge shows is H and C for hot and cold. And won't opening up the radiator cap spray radiator fluid everywhere?

Also, how do I know when the thermostat opens?

10-10-2004, 08:50 PM

Your thermostat should open between 165 and 185 degrees (depends on what you have in there). Your radiator won't boil/spew over until it reaches boiling temperature (212 degrees with no pressure). Just leave it open from the get go. If you watch the coolant in the radiator, it's fairly obvious when the thermostat opens up. You'll see a lot of turbulance, and your temperature gauge should equalize at about the same time.

Webb Sledge
10-10-2004, 11:10 PM
Once the car is up to normal running temperature (as indicated by the interior dash gauge), should the thermometer read a steady 165-185 degrees Farenheit?

10-11-2004, 09:52 AM
Webb, the "normal" temps for these engines varies, as you've already seen. Any normal operating temp up to and including about 200F or so would be acceptable. If you have a 50-50 mix of antifreeze and water and a 7lb radiator cap, the coolant won't boil over until a temp of around 250F is reached.

My GT6 ran at about 190F most of the time, sometimes a little more on hot days in traffic. You may find that your engine will cool down a little in cooler weather.

Have you double-checked your fuel mixture?

Also, I invested in a dual water temp/oil pressure gauge (Smiths) with a fahrenheit temp scale, very useful. You'll find them on EBay, a great addition to the dash.

Let us know how it goes, keep investigating -- you'll find and fix it!

Webb Sledge
10-11-2004, 02:52 PM
Ok, I bought a candy thermometer and took the radiator fluid temperature. When the car was off, there would be enough fluid in the top of the radiator to take the temperature, but as soon as I started it, it drained down. So I let it get up to running temperature, cut it off, and then quickly took the temperature, which read 140 degrees F. That kind of confuses me, becaue if the thermostat is supposed to open between 165-185, it's never reaching that temperature. When I took the temp, the gauge read slight left of middle toward C, which is what it reads all the time once it's warmed up, no matter the whether or how hard I'm driving. Also, my overflow canister is half full all the time, whether the car is running or not. Is this right?

10-11-2004, 07:37 PM
Webb, looks like you will have to replace the thermostat, it's either stuck open or broken. Drain some collent out first and it will save some of the mess. Wayne

Webb Sledge
10-11-2004, 08:19 PM
Sounds like it's stuck open, since it never really gets up to temperature. How do I drain the coolant?

10-11-2004, 09:14 PM
Webb, I think you should have a drain plug at the bottom of your radiator, it will be tight, so some pliers will come in handy, if it doesn't go the first time be very careful as it will brake off, I think it's brass, won't stand a lot of muscle. Get a big container under the drain as it will shoot out about 2 feet. If it doesn't get too much trash in it, use two paint filters and a funnel to put it back in. What part of Virginia do you live. Oh, you really need to invest in a work shop manual, lots of Ebay and Moss catalogs are a real good visual aid. Call them or look on line, I'm sure it will help. Wayne

Webb Sledge
10-11-2004, 09:50 PM
I've got a Bentley manual, but I didn't bother to check it before I posted. Should have though.

10-12-2004, 11:30 AM
pull the bottom hose, drain the coolant....put in a new thermostat. Takes about a half hour. Make sure you put in the right seasonal thermostat...should be at least a standard this time of year. Make sure to replace it with a summer T-stat when spring gets here, or you'll be running real hot.

Webb Sledge
10-12-2004, 05:15 PM
I'm just going to leave the thermo. as it is now, since we'll be pulling the engine for a rebuild in late December or January, and it's not hurting anything now. Thanks for the information though, since I know how to do it now.

Webb Sledge
10-12-2004, 07:51 PM
Can someone explain to me what exactly the thermostat does and why?

Geo Hahn
10-12-2004, 08:07 PM
When the tstat is closed coolant circulates 'round within the engine (and thru the heater core if heat is on). This continues until a particular coolant temperature is reached (the temp stamped on the tstat). At this point the tstat begins to open and permit coolant to flow thru the radiator.

Flowing thru the rad cools the coolant before returning it to the engine. Once the coolant flowing thru the tstat cools below the temp rating the tstat begins to close and the cycle begins again.

The tstat determines the *minimum* operating temperature... i.e. if a car is overheating a 'cooler' tsat isn't going to solve the problem. It may buy you some cushion as it will send coolant to the radiator sooner, but if the engine has been overheating it will still overheat.

Some people like a higher temp tstat in the car in the winter to get more heat sooner out of the heater. Also, a cooler tstat in summer (as noted above) will buy you some time at a long stop light or in stop & go traffic.

There's more but that's a 'nickel tour'.

Webb Sledge
10-12-2004, 08:26 PM
Ah see, thankya kindly sir. My tstat sounds like it's stuck open then.