1970 olds/overheating issue
May 16th, 2017, 06:29 PM
#1
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1970 olds/overheating issue
Man, I hope there's some old dogs out there that can help me with this. I have a 1970 Oldsmobile 350 rocket. The idiot light indicating it was overheating came on. I installed gauges on it so that I can actually see what the engine temperature was. The temperature gage will run fine at 80 miles an hour with the air conditioner on at around 195 to 200° . But then suddenly out of the blue, the gauge will shoot from 200° to 260° in less than one second, and then go back down again within3 or 4 seconds. I cannot figure out what's causing this. I've gone through two temperature sending unit and two gauges. I thought maybe the lower radiator hose was collapsing so I put one of those accordion type on so I know that's not the problem. Any suggestions or ideas
?
?
May 16th, 2017, 06:56 PM
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You have an air pocket where the sensor is. It will clear itself or you can open the cap with the engine cool, start it and let the thermostat open, stick a water hose in the radiator on a slow flow for a minute to force it out.
May 16th, 2017, 07:59 PM
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May 16th, 2017, 08:02 PM
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Thanks!!
I will try that first thing tomorrow. I hate to sound stupid, but I have to ask this.; The sensors just right on top, can I unscrew the sensor and dislodge the bubble of water by pouring some water directly into it ?
May 16th, 2017, 09:01 PM
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The sensor is below the water level in the radiator, if you remove it then you'll have hot water coming out. With the hose, you just place the end inside the water neck and let it flow in for a minute or so until there is no gauge fluctuation. Its very simple.
May 17th, 2017, 07:07 AM
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May 17th, 2017, 10:20 AM
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Make sure you are not overfilling the radiator. 1970 radiators should only be filled to about 3 inches from the top. Look on the tank under the radiator cap, a factory radiator will show where to fill to. If you over fill, when the car gets to operating temp it will just push the extra fluid out of the radiator, as if it was overheating.
May 17th, 2017, 12:11 PM
#10
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Man, I hope there's some old dogs out there that can help me with this. I have a 1970 Oldsmobile 350 rocket. The idiot light indicating it was overheating came on. I installed gauges on it so that I can actually see what the engine temperature was. The temperature gage will run fine at 80 miles an hour with the air conditioner on at around 195 to 200° . But then suddenly out of the blue, the gauge will shoot from 200° to 260° in less than one second, and then go back down again within3 or 4 seconds. I cannot figure out what's causing this. I've gone through two temperature sending unit and two gauges. I thought maybe the lower radiator hose was collapsing so I put one of those accordion type on so I know that's not the problem. Any suggestions or ideas?
?I had a 409 Chevy that did the same thing, after new rad , hoses, cap, without thermostat with thermostat and SEVERAL TIMES overheating I found the impeller on the WATER PUMP did not ALWAYS turn, Ran hot so many times the piston rings had to be replaced.
Just for what it's worth has the water pump been replaced lately??
Johnny
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