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Triumph TR6 - Overheating but with all new parts?

Car: 1973 TR-6. I have just finished re-coring my radiator. Replaced the thermostat with a new summer one (tested it and it opened at 165 (+/-). Replaced hoses. I have also replaced the sender unit. Drained all cooling system, flushed and new cooling liquid. When i raned the car it showed over heating to past the 3/4 mark. I then took readings on the water at the radiator when car was running and read within range (180) I have also replaced the voltage stabilizer in case there was wrong voltage going to the gauge. I have replaced the actual gauge with a new one from V.B. However, when i run the car, the gauge reads at 3/4 not at half like it used to before all this work. Any suggestions?
AA Abner

2 suggestions:
1. did you clean and refit the connection at the temp transmitter driver side of car at the water pump area(under the theory that electrical gauge needs clean contacts)
2. how is your water pump functioning any consistent leakage on the passenger side just behind the water pump.
After looking at the above thread I apologize it seems as though you have done all the right things in the electrical area. As with some things in our cars maybe the guage will now read 3/4 instead of 1/2 or maybe the gauge is not correct for your year car did you try with your old gauge if you are able to it may answer the question and give you some peace of mind.
Regards, Keith '72
K.B.Dixon

Hi

Gauges and sending units are calibrated to work together in a range. Some units have a small hole in the back to allow for calibration. If you know your temps are OK and your gas gauge works you might just have to live with the Gauge.

Bill
Bill Brayford

Thanks Keith,
However, I replaced the old gauge as part of the solution, yes both gauges are reading high, I have changed the gauges several times just to check. As for the leak..... there is none. Water pump is OK. I was thinking of installing an aftermarket gauge (even though i dont like the idea of having an extra gauge inside...) It is mind bogging....
Abner

Hey, Abner.

Ahh - you replaced the sending unit. I talked with a mechanic about 10 years ago that insisted temp sending units had high variability, and that if you put a new one in and suddenly had very high temp readings, it should be replaced. But where does one stop or get a 'reference' sending unit?

If you still have the old sending unit around, put it back in. If the running temp is back where you were used to it, leave it - they seldom go bad.
Brent B

Abner
All good advice. Have you taken an actual temp. reading of the antifreeze/water mixture? I run with "water wetter"...it helps to reduce the temp of the mixture and promotes better overall engine cooling.
Rick C
Rick Crawford

Thanks guys!
Rick.... yes I took the temp at the radiator when I get home today I will look for the records (at work now) as far as I remeber the temp was 180 when the gauge was at 1/2 mark. But I will confirm this afternoon.
Brent..... i tried both sending units and they both had the same readings.
Abner

All,
Bill and Brent have commented above on the variability of the senders and that they and the guages were matched before fitting. Recent experience leads me to agree, and my experiment may be worth repeating for a larger sample:

I had three senders, any of which I could have fitted to a rebuilt engine. I tested them with a multimeter while I heated them in a water bath, starting with cold water and noting the resistance as the temperature rose. One 'meter lead went on the sender connector, the other on a loop of copper wire tightened around the threads.
Results: One was U/S - no continuity. The other two had a very different response, the change in resistance, as the temp rose from 50 to 100 degrees C, being 0.2-0.05 ohms and 1.0-0.1 ohms.

I agree that 100C is below engine working temp, but I'm not getting into heated oil baths and this shouldn't invalidate the experiment. Another criticism is that a multimeter does not reproduce the working conditions when there would be a gauge in the circuit and a regulated approx 12V across them. I'm not competent to answer that one.

Anyone out there with a few spare senders and a multimeter, please repeat my experiment. Advice on how to include a guage in the circuit, and "Match" sender nd gauge would be most appreciated.
John
JohnD

This thread was discussed between 31/03/2003 and 02/04/2003

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