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Triumph TR6 - temp gauge

Hello everyone,
This is my third summer with a '74 TR6. My first summer the temp gauge would read 3/4
(gas gauge works fine). I replaced the sending unit, no change. Last summer rebuilt engine, new radiator and even the gauge itself and still no change. Yesterday I changed the voltage regulator and to my surprise still no change! I will say that with the wifes meat thermometer in the rad and when the temp hits 160 the gauge is straight up and down(half way). Now, all the threads I have read say half way is 180 (normal op temp)yet my 180 is at 3/4 hash. Is there anything else I can do?
JM Johnson

I meant to say voltage stabilizer

After three days I was hoping on somekind of reply but to hear nothing is disturbing.
JM Johnson

I can't answer for everyone else but my guage (72 TR-6)reads normal at 3/4. I checked mine using a temperature probe on my digital volt, ohm meter. I stuck the probe under the rubber hose at the thermostat and ran the engine until the temperature ran up a little above 180. When the thermostat opened the temperature dropped, then rose back up to 180. This test shows the actual temperature and the operation of the thernostat.
Joe Justice
Joe Justice


My TR6 (72) reads normal just about 4/10. I went trough the same test and concluded is just works fine: right temp.

I tested because i thought it stayed too cool.
Only thing you can do is test the gauge; ground it out by the transmitter; if o.k. it slowly reads out al the way.

Eric de Lange

When I first got my TR6 eons ago the temp gauge read straight up for normal. When the sending unit failed I replaced it and it has read 3/4 ever since. I suspect there may have been some significant differences in the sending units, perhaps even different part numbers, over the years.

A. J. Koschinsky

The actual engine temp vs gauge reading is a common issue on most LBCs. Most recently I was an MGB owner (sold it recently, found a TR250) and the gauge on that car would read the same: At 185 deg it was to the right of N.
Here an excellent link to the "Electrical Help" section of the MGB Technical BBS:
Based on the info there I tested my sender with an ohmmeter and a meat thermometer in the radiator and found similar results. My N was about 170 deg.
Andy Blackley

You never said whether or not you got around to changing the thermostat. On my '73 180F corresponds to N, straight up and down.

There are a couple of tricks that you can do to improve cooling:
1) Put a small valve in the line to the inlet manifold heater. Close it in the summer, open in the winter.
2) Two of the 3 water pump mounting studs protrude into the pump volute. This disturbs and restricts flow. The thing to do there is to remove the part of the stud that causes the interference.
3) There is a by-pass hole about 3/8" diameter in the water pump just under the thermostat. Remove the thermostat and look straight down in there. I cut some threads in it with a tap and epoxied in an allen screw to plug it. Sorry, I didn't write down the specifics on the size. Then I drilled a 1/8" hole in the thermostat body (180 F) so the flow would not dead-head.

Those changes took the car from always on the verge of overheating to always on N except on the hottest days in traffic.

Brent B

There is a web article I saw discribing the fix for the thermostat as Brent mentioned. I can't remember where I saw it but could try to Google for it.

Alright! That's more like it. I was feeling like the elephant man, it's good to hear that I'm not alone on the 3/4 gig. Brent, how can I tell which of the bolts is restricting flow? volute?? And can you be alittle more discriptive with "a valve inline to the manafold heater? And lastly, I did change the thermostat the first summer. I believe I stuck a 160 in and if I remember right it had a small hole in it. I gotta say that after watching for 2 1/2 years that when it was my turn to post someone was listening. thankyou, Mark
JM Johnson

Hey Mark.

If you remove the water pump (get a new gasket first) you will see that the pump impeller spins in a contoured cavity. Water is flung away from the impeller and gathers at higher pressure in this volute before flowing to the discharge. Stick your fingers in there and see if you feel the stud protruding into the cavity - Remove, cut down, replace with some sealer on the threads.

I took a 1/4" threaded ball valve, 1/4" NPT, fitted each end with hose barbs, and put in the line from the thermostat housing to the carbs. You have to squint, but it's the red handled piece here:

That line by-passes the radiator. You need that heat in the Winter, but not the Summer. Alternatively the line can be clamped closed.

Brent B

Forgive me, but I don't really understand the problem with the guage reading a bit over center normally. But adding resistance to the circuit should lower the reading, correct? Might be a bit experimental, but any electronics geek would be proud to help if a reward of beer or maybe a drive when you succeed, eh?

This thread was discussed between 02/04/2005 and 07/04/2005

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