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Hi folks,
During the last weekend I changed the thermostat in my m38a1. I have a quenstion: how can check the water temperature?, because the instrument in the dashboard is not working fine. Sorry for the stupid quenstion: can i check with an external thermometer into the radiator i mean without radiator cup? while the motor is running? When the thermostat opened.
Previus install it. I had checked the thermostat in hot water and working fine. But I want to check into the engine. Obiously i have to fix the thermometer in next days.

Thanks in advance
Pacho

The thermometer in the radiator will work. You will be close enough without the pressure cap installed to determine basic operating temp. You could also use one of those infra-red heat sensors. I prefer mechanical gauges over the military electric gauges for both water temp and oil pressure. Much more reliable.

thanks Wesk for your reply.
Just another doubt: If the radiator does not have cup, what hapen with the hot water? Will flow throuhg the cup? when the thermostat open

Thanks and Reards

If the coolant system (radiator & block) are over serviced there will be a slight overflow. No harm done. But you should start the procedure from the beginning with a cool engine leaving the cap off. You do not want the radiator to build pressure. You will know when the thermostat opens by an in crease in flow thru the radiator. Keep in mind that thermostat bypass hose (between the water pump & the head) will always allow a slight flow with the thermostat closed.

Thank you very much.
I will do it next weekend and share the result.

Regards