Electronic engine Temperatur gauge vs original

[RichT]

Hi all

In the absence of any major problems except for fixing a collapsing brake servo vaccum pipe that only showed as a fault when the car was warm I Have been playing with some electronic thermometers

This was because of a paronoia I have about overheating partly fuel by the lack of a gauge in my morris minor

I have fitted a kenlowe to the mk 2 jag due to an overheating episode which I think can be blamed on binding brakes from the above and this is set to kick in nicely if I come to a standstill after a fast run keeping the smith gauge at just over 70

I fitted the probe from the electronic gauge to one of the head studs and were very interested to see how quickly it registered a rise in temperature. Vs the std smiths gauge the smiths gauge, the smiths gauge wouldn't move off 67 until the head was at c82 degrees and even then only slightly moved when the electronic gauge hit 90 also using a laser on the thermostat housing showed c 90 at this point. I wasn't brave enough to stop the fan kicking in!

I understand the two temperatures will be different but I was shocked by how slow the original gauge was to act and this got both of us thinking of the value of an electronic gauge to preempt boiling over especially as the sensor doesn't rely on water contact. next time I am out I will stick a second sensor in the rad and compare the two

This arrangement certainly gives me more confidence in heavy traffic as I can see the kenlowe bleeding off heat

It seems the queues to get into classic shows are ever longer so I am glad I have this

I was wondering if the potential problem of overheating struck as much fear into the hearts of others and what you might have done about it

Regards and happy motoring

Richard

[Martec]

Hi Richard can I ask what exactly you mean by 'electronic' thermometer?

And like any engineer the information a guage shows you is suspect (show me a guage and I'll show you an inaccurate one).

Brian

[oldtimer]

Yep,
And the other side of the same coin is people don't want to believe what they see.

Richard,
Back in the sixties when these were our every day cars I really cannot remember ever having an overheat problem - and there were plenty of heavy traffic tail backs, no Motorways, imagine that ! Remember, these cars were sold in hot regions of the world so had to cope with that.
Plus 27 degrees C was a cold day in Singapore and Nairobi is at five and half thousand feet above sea level so I can't see the climatic conditions at South End on Sea being too much of a problem.

By now, you may well have received this months JEC Mag. Quite by chance there is a first class article on just this subject which explains so very well- silted up water ways in the block and of course this type of contamination will be found in the radiator as well.

There , just my thoughts

Oldtimer

[RichT]

Hi both

Thanks for the replies and sorry for my tardy reply busy weekend!

I have been using a digital cooking thermometer, a cheap Lcd gauge and probe from ebay and a laser point type thermometer. My conclusion is that rate of change of block/head temperature changes correlate well to water temperature changes (measured with a probe at the radiator or from laser on thermostat housing) and that the engine is probably about 10-20 degrees hotter than the water but it all needs a little more work. I guess there must be a reason car manafacturers went for immersed probes in the first place. I would guess the block/head can get very hot as long as the cooling system keeps the water cool enough to carry away the heat by maintaining a Temperature gradient and prevent boiling.

The point about these cars being ok with regards to overheating when they were new is a good one and having just read david manners article it is easy to see why they often are not now. ( this was covered at the engine seminar I believe at which I had intended to seek you both out and thank you personally for all your help when I have posted here in the past)

I did a mini de sludge when I knocked a core plug out a couple of years ago, managed to get a coat hanger and a pressure washer drain cleaning probe in there and flush all manner of stuff out as well as de scaling and backflushing the radiator and heater matrix.

I would guess that when these cars were designed as is now the designers had no inkling they would still be around over fifty years later and like their owners they show more than a bit of wear and a potentional for occasional parts malfunctions!

Anyhow back to the original topic it certainly seems to give me some reassurance to see the temperature cycling in real time rather than relying solely on the heavily damped gauge

Cheers for now

Richard

[Martec]

Hi Richard,

I've not been well for a few months which seems to make me think slower (as if thats possible). You have just jogged my memory and in a way I am using electronics for Temperature sensing on two old cars.

I had an issue with my Marina whilst towing a trailer, it suddenly went full scale. Even thought I pulled over and left the engine idling so the radiator was in service, it showed no signs of reducing (as indicated by the gauge), but also I had gained petrol Nahhh! At home I used a remote lazer guide thermometer which showed everything was fine!!! So knowing these 'instuments' are very sensitive to voltage I put a multimeter between the sensor input wire and earth, it showed a steady alternator voltage of about 14 volts, it should be regulated for 10 volts as are two of the MkII instuments (temperature and fuel level).

The reason old instruments are heavily damped is because the 'mechanical' automatic voltage regulator (AVR) switches between dynamo voltage and off using a bimetal strip, so damping in the instrument gives an average ..ish. You will see this if you use a multimeter with a working mechanical AVR. Modern gauges (Assuming they are electric each have their own AVR .......I believe or work off the alternator current and its AVR....more likely, eitherway they instantly register.

With this in mind I looked online and found someone making Electronic instrument AVR's at about a £10 a piece so talked to my electronics guru (not long out of university) who made up my two 'Engine Control units (ECU's)' and he supplied a drawing and the chips plus diodes to make 4 for less than a £10.

The upshot of all this claptrap is the both the Marina and the MkII feed their instruments 9.98 steady volts according to 2 multimeters. But the senders and gauges are old fashioned heat and expansion units.

Now the Marina with full fuel injection and ignition plus others is all ECU controlled and the old ford (mondeo) sender feeds the ECU to allow for temperature required fuel enrichment.

How far do you want to go!!??

Best wishes

Brian

PS It takes 5 minutes to change on a MkII and about 2 hours and some nasty scratches on the Marina.