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Proper thermostat temperature to purchase? Failed sender?

1K views 1 reply 2 participants last post by  tryingbe 
#1 ·
Hi everyone! I'm a Texan living in Sweden and driving my 1970 144 daily.

I've had an overheating problem showing ever since I fixed the dash 10V voltage supply a few months ago. It must have been the same before I bought the car and also when I owned it but hadn't fixed the voltage supply, so I drive it hot and don't notice any problems. I've cleaned the radiator and verified the pump, but the needle always creeps up into red 5 minutes after starting. I'm about to install a sandwich adapter oil cooler as I did on my Amazon back in Texas, but my father suggested a test of the thermostat first, which I hadn't thought of. I put the thermostat in boiling water and it opened in the low- to mid-nineties (Celsius) or roughly 200 F. My Haynes manual commands 82C/180F, so I figured mine failed and bought a new thermostat rated for 82C. I tested it and it ALSO opens at the low- to mid-nineties C or roughly 200 F! The seller insists the new thermostat is good and that the old one must have been fine as well. It does have "82 " stamped on it. Maybe I'm bad at testing them.

Adding to the confusion, all the local stores sell thermostats for B20 Volvos rated 88, 89 and 92 C. Swedish parts stores are generally much better for old Volvo parts than back in Texas, but apparently they get thermostats wrong. I'm looking around online and I find thermostats sold for B20s that range all the way from 77 to 95 C!

1. What's the proper temperature for a B20 thermostat?
2. Am I testing these things wrong if my thermometer measures 90-odd degrees in a pot of hot water when the 82 C thermostat opens?
3. If this car has been driving regularly for at least a couple of years with the needle in the red and showing no ill-effects, do I just have a bad temperature sender? If possible, please let me know if/how I can troubleshoot that.

I'd appreciate any help on any of these questions. Thanks!
 
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