Questioni have a 75 mgb that reg on the white area of my temp gauge after running foe a short time. so far i have done the following new sending unit,oil cooler, ran with & without thermostat, tried bypassing heater coil, engine rebuilt 2 yrs ago, new rad,leaned the carbs ( su), brakes ok,added electic fan,added lead addative to gas,new air filters , timeing ok,no kinks in any hoses . I am at a lose here can you suggest, or any readers, what else I can do to get the temp down to normal.Thank you Rick.
AnswerHi Rick,
You did a lot but none of what you were suppose to do when checking for over heating.
This is what we had to do if a customer came to us with this problem.
First, confirm that it is really over heating. A meat thermometer into the coolant when it shows hot will confirm (don't skip this)
Second, test the coolant for CO with the dye you can get at any auto parts store to be sure you don't have a head gasket leak.
Third, Test the thermostat in a pan of water on a hot plate with your meat thermometer or replace it with a new one. (your test of removing the thermostat is not a good test because the engine runs hotter with no thermostat due to the coolant moving to fast to absorb any heat from the engine)
Forth, take the car out side and remove the thermostat housing and start the engine and watch the coolant come out of the head. It should come out very fast. This is a rough test of the impeller of the water pump to see if it is loose on the shaft.
Fifth, take the radiator to a radiator shop to have it tested for flow and to see if it needs rodding.
Also, confirm the ignition timing is correct and you went the wrong way on mixture. Lean = hotter, Rich = cooler.
let me know what you find.
Howard
