i’m not getting any other symptoms of a bad head gasket. Oil looks clean (no white contamination under oil cap and no white smoke coming from tail pipes)
A pressure test on the cooling system could not hurt., or just checking the hoses when warmed up and engine off, squeeze maybe the upper radiator hose when cool, it should be much firmer when the engine is warm. Maybe since the cap fixed it for a bit bad radiator cap or debris? The worn fins on the water pump as suggested previously sounds possible
That’s exactly what I am suggesting.
If the brakes are dragging a little, the engine is working harder to keep the car at 70 than it would at 35 mph. That would push the coolant temp up, as you are experiencing but not necessarily to the point where it overheats.
That is exactly to the point I was trying to make. Not a cooling problem, but another problem causing the temps to be too high. Like a transmission problem.
Transmission fluid is fine though so i’m almost certain it’s not the cause of the problem
Check the lower radiator hose for soft condition; the higher speed has a tendency to collapse the lower radiator hose if the the spring is missing or corroded so much it gets collapsed. When the engine gets hotter it gets more pressure in radiator and inflates the soft hose enough to get circulation and prevents an actual overheat condition.
Infrared temp guns are cheap at Harbor Freight, get one and drive you gar until the temp goes up.scan the gun across the radiator and up and down.
Cool sorts are where the tubes are clogged.
So should I just try replacing the entire lower radiator hose then?
I check the hose after driving for an hour and the hose is softer than it should be considering length i was just driving for. Hose should be firm after driving for an hour
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I would say yes if the hose is softer than normal replace it because of the fact that it may be collapsing at high rpm and starving the water pump reducing circulation. I would if it were mine. I had the same trouble once when the spring inside the lower hose was bad. some lower hoses had a spring molded into the hose for that purpose.
Look underneath the front of the car on the lower radiator support and note if there is a missing plastic air deflector. These are designed to force air through the radiator and if missing will cause overheating on the highway but will not have any effect in city driving.
It’s quite common for them to get knocked off by potholes, road debris, or some varmint who sacrificed their life to remove it. It looks like this…cheap and easy to install if needed.
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i think i figured out the issue…the guy that did the coolant drain and fill last time forgot to bleed the system after…so there was air in the system which would explain the erratic fluctuations in temperature and them getting progressively worse. Today the car actually overheated and i had to pull over
Because when i first got the car the coolant was practically brown but it never even ran warm and then it wasn’t until after i had someone do the drain and fill did it start acting up…so that’s what made me realize the guy didn’t bleed the system after doing the drain and fill. At the time i thought nothing of it but now that makes sense
when i bled it the radiator bubbled a lot so there was definitely a lot of air in the radiator
I’m just hoping i didn’t cause any major damage…i drove with the needle about 85% to the max H mark for 3-4 minutes before i could safely pull over and shut the car off
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Checking the coolant level should be the first step in diagnosing a cooling system issue.
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