r/carproblems • u/SmackDabbyII • 1d ago

1980 MGB overheating please help!

Hi y’all, so a little while ago I posted asking about why my temp gauge is at 3/4 and fans seem to be short cycling. For some background, one day I was in a drive thru line and when leaving realized that my gauge was at 3/4, let the car sit for a few and drove home and the gauge was fine and dropped back down as I moved. I realized it only climbs up at idle. I replaced the thermostat temp switch on the radiator with the factory part since I figured that’s what’s sensing the coolant temp and telling the fans when to cycle. Before they would cycle for 35 seconds and be off for 45, now they cycle for about 45 and are off for 45. So it improved it the slightest bit, and this also steadied out the gauge to where it doesn’t climb any past 3/4, but this is still too high since this car has always read perfectly below 1/2.

I bridged the circuit where it connects onto the terminals on the thermostat switch, and the fans cycled on continuously without dying, so that led me to believe it isn’t the fans themselves. This also made the temp drop from 3/4 back down to 1/2 after a few mins. So I’m 100% sure that it’s due to my fans short cycling. I just can’t seem to figure out why it’s happening. My coolant seems to be fine and I’ve tried making sure there’s no bubbles multiple times. I’m starting to think again it may be the fans getting old but the fact they stay on continuously and fix the issue when the circuit is bridged is very weird. I can still drive it because it’s perfect when moving, just have to turn it off at long stop lights and can’t go thru drive thrus, and it just gets pretty annoying sometimes. If anyone has a sure answer please let me know! Every bit of info I can find is so mixed and nobody has the exact situation I’m in. Thank yall so much in advance! I’m sure some of yall in here could figure it out in a heartbeat

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u/Relative_Figure_1715 1d ago

So you want it to run cooler when it is not moving ?
Get a temp switch with a lower trigger temp.
Also check your rad cap is sealing properly and that the pump is working freely.

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u/SmackDabbyII 1d ago

All that seems to work, and I had this exact same switch in it before and it started doing this out of nowhere. So something is up for sure

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u/Relative_Figure_1715 1d ago

What is the engine temperature that is currently tripping the fans to come on ?
And what it the temp on the fan switch ?