Previously did not drive for around 3 years because of bad water pump which I fixed last year with your help.

Fast forward to last month was driving it the temperature was hot in the 90s. I sat in traffic a good amount of time. The radiator was full with a perfect 50/50 mix. Drove great, but after driving and returning around the 7 mile trip, the oil pressure light started to flicker so I proceed straight home. When slowing down going into the drivway, a good amount of coolant came out of the radiator overflow hose.

So I understand the overflow of coolant as the operating level of the radiator is not 100% full. But what perplexed me a bit is the oil pressure flickered when the level is full and clean. After looking up dates the oil is probably over 5 years old with less than 100 miles on it. So I realize now that I need to change the oil asap. Do you think old oil can cause an oil pressure light to come on even when full or do you think that is another problem? When the engine cooled down and started the car, the oil pressure was out. I know in the old days the manual said to replace the oil every 6 months regardless. Just trying to imagine what could happen with oil to make such as drastic change in pressure by just sitting.

 

The oil light indicates oil pressure, which is not affected by oil level (unless your level has fallen drastically).

In our older cars, bearing wear can open up the internal clearances that the oil pump keeps supplied. With more clearance, when the oil pump is turning slowly (idle speed) and when the oil is hot (thinner oil slips through the clearances more easily) the pressure is at its lowest.

I believe that your engine--and the oil--may have been warmer than usual due to traffic and outside temperature, leading to the oil light flickering on.

 

What I would do is go out and buy an inexpensive mechanical oil pressure gauge and see what your oil pressure actually is. The issue you are having could be as simple as a bad oil pressure sender since this happened with the engine rpm's up.

 

The coolant and the oil are two separate issues.

Let's start off with this: probably not a great idea to be driving around on such old oil regardless of miles, so change the oil and filter now. Fill the engine with fresh 10W-30 of the same type (and brand, if possible) as used before. Drive it for a couple of hundred miles, monitoring the oil pressure, (you may want to install a gauge) and then change again. Save and inspect the filters after each change. Report back.

With regard to the coolant: do you not have an overflow tank? If not, install one. Until then, just keep the level topped up.

 

You might be able to rent an oil pressure gauge from the local auto parts store.

 

The above and check the idle speed. It could contribute to both overheating and low oil pressure. Also smell the oil for gasoline contamination.

 

Trying a new oil pressure switch would be cheaper than buying a gauge. but a gauge will obviously tell you much more.

The warning light is designed to come on at around 7psi. If the gauge shows oil pressure that low, more than likely the engine needs some serious work.

How many miles are on the engine? Has the timing chain ever been replaced? If it has a lot of miles with the original chain, the oil pump is probably full of nylon.

If the pressure is lower than it should be, you could “band aid” the warning light flickering by changing the oil and refilling it with 10w-40. I saw it’s a “band aid” fix because it’s not really solving the problem, just the symptom.