Hi there, my father in laws Bonneville blew the plastic portion of his oil sending unit clear off the 1 1\16" thread nut and we replaced it. After that I discovered the car he's ownered for 2 years had not seen an oil change in 8 years total so we did that. Then we got a low oil pressure read on the dash and saw smoke coming from the the engine right valve cover. When we killed the motor and opened the oil fill cap on that valve cover, we heard a relief of back pressure come from thru out the whole motor. I replaced the PCV valve today and checked the oil again and it was close to the max oil level. I started the vehicle and after idling down the normal operating RPMs the car, on its own started to increase rpm from 1,100-1,600rpm and a whining internal noise became gradually louder as the RPMs rose. I killed the motor and checked the oil and it was now at the minimum film line, about 1 1\2qrts down. I don't know if the rings finally gave or what but there are no leaks or dripping.
My car has 213000 miles.
My car has an automatic transmission.
You might not have burned that much oil in 30 seconds of running the motor but the oil is not draining back from the upper parts of the motor. The sludge that has built up in the motor has clogged the return drains in the heads and oil gets trapped up in the valve covers. You should look in one of the valve covers to see if the engine is sludge blocking drains in the heads. If it is then you may have to clean out both valve covers and heads of sludge and then run cleaner through engine several times to remove some of the sludge build up. If this does not help then rebuilding of the motor is only option.
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