QuestionQUESTION: Hi Howard,
I have a new question. My Spitfire mk3 built in 1967 (1FD11819L) has a radiator cap of 13 lb. I think that these first mk3 had a radiator cap of 7 lb (then changed to 13lb). Never I saw flow water trough overflow tube altough that the water temperature is very hot. Is it possible that besides endanger the safety of the seals and the radiator this cap, with a higher pressure, can produce an increase in water temperature?
ANSWER: Hi Alfred,
The higher pressure will put extra pressure on the hoses, gaskets and water pump seal. The increase pressure on a fluid does raise the temperature but not enough to be noted. The reason they raise the pressure is to raise the boiling point of the coolant and also to cut down on steam pockets in the cooling system around the combustion chambers.
This does shorten the life of hoses etc and rather than do that I chose to just install a push electric fan in front of the radiator. I found it to be much more effective at controlling temperature on my cars in Florida. Especially in down town slow stop and start traffic.
Howard
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QUESTION: Hi Howard,
Thank you for your quick answer. I have installed an electric fan (Spal) in front of the radiator. The radiator has been cleaned, a new water pump was mounted and the cylinder head was rebuilt but the temperature goes a little bit beyond 3/4 of gauge (I do not know if it is normal) . I am going to put one 7 lb radiator cap (perhaps it will be worse because the water going to boil before), a manual switch for the electric fan and change the temperatura transmitter (maybe it has a wrong signal) . as I said before, never throws water through owerflow tube. Do you think that I can do something else?
Regards,
Alfred
ANSWER: Hi Alfred,
The high temp reading but not overflowing is not reason to be concerned unless you see overflow.
If it were mine I would check the thermostat to see what temp thermostat is installed. Then take a meat thermometer and after you get the high reading, carefully remove the radiator cap and check what temperature it really is. This way you will know if the temp gauge is faulty or not.
Did you run the CO test with the dye in the coolant? The dye is available in auto parts stores. This test is for CO in the coolant which is a leaking head gasket or crack in the head. A minor leak can cause high temp readings but not cause overflow.
If you have no CO in the coolant, the temp gauge is what the meat thermometer says it is and you have a 165 deg or 175 deg thermostat and it is not over flowing I would just leave it that way and as carbon builds in the combustion chamber the temp will come down. Also stay a little on the rich side on the carb adjustment and a hair on the advanced side of timing.
I have built a lot of engines in my life and I found a connection between high temp on the gauge and a clean combustion chamber and lower temps on a lightly carboned combustion chamber. On a rebuild, most shops clean all of the carbon from the top of the pistons and the combustion chamber but I found that if the carbon is a thin even coat, it is better to leave it that way as carbon does not conduct heat as much as aluminum does so more heat stays in the combustion chamber (where you want it) and less is LOST into the engine and coolant (and temp gauge). As many as 8 or 9 out of 10 will have uneven carbon and chunky carbon which must be removed so most shops just clean all of them.
Howard
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QUESTION: Hi Howard,
As you advised me I bought a meat thermometer. When the gauge shows 1/2 the thermometer says abou 75º C, at 3/4 says about 85º and near red zone says more than 90º. Maybe the thermometer is alarmist but I think that is not the problem.
I have put one light at the dashboard connected to a electric fan to know when is operating.
Circulating by the streets the fan start when the gauge is at 1/2 and the water temperature is controled (reaches at most 3 / 4), but when I am running by highway (at 100 kilometers/hour in 4 gear with overdrive at aprox. 3000 rpm) with slight but constant slope, the fan never starts and the gauge goes fast to the red zone.
My car has a 16" radiator and the electric fan is in front it. The electric fan temperature transmitter is placed externally in one hole at the side of radiator.
I think that one electric fan that not works is a problem for cool the water in the radiator. It covers a lot. Probably the problem is that running fast the temperature transmitter is receiving a flow of fresh air that keeps you from knowing the water temperature.
What do you think?
Regards,
Alfred
AnswerAlfred, you didn't answer any of my questions.
What number thermostat are you using in the car????
What was the result of the dye in the radiator????
As for the temp transmitter, the bulb on the end sticking in the coolant reads coolant temp no matter how much air blows on it.
The meat thermometer says it's hot and the temp gauge says it's hot, my guess is that it is hot.
Answer my questions.
Howard
