Iron@Dirt
Senior Member
anyone have seen the lower end of the engine get 20 degrees hotter than the top and lose oil pressure
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3930 ford low oil pressure
- Thread starter Iron@Dirt
- Start date
Iron@Dirt
Senior Member
external head temp around 190, lower block around crank runs about 220. the last 10-20 degrees ,oil pressure drops to 5-10 lbs at idle 800 rpm. engine has no engine oil cooler and no factory option for one. have a new 180 thermostat on order.
El Hombre
Senior Member
Sounds like somebody got an infrared thermometer!
I doubt you'll get many replies for the simple reason nobody measures the block and head external temps. They'll shoot the exhaust manifold to see if they have a cylinder low/no power; no heat, no power. Or the radiator looking for cooler areas that are blocked with rust.
But you're not going to find much use of just the external temps. They used to sell oil temp sensing dipsticks for motorcycles. They would run 250 and more, and that was just easy riding around town. Not pulling a trailer uphill in Arizona...then it got over 300, and that was bad. Oil cooler needed for that.
Oil pressure sounds close to normal, idle speed the oil pump isn't pumping much so the pressure is low. If you rev the engine and the pressure stays low, then you might have issues.
I doubt you'll get many replies for the simple reason nobody measures the block and head external temps. They'll shoot the exhaust manifold to see if they have a cylinder low/no power; no heat, no power. Or the radiator looking for cooler areas that are blocked with rust.
But you're not going to find much use of just the external temps. They used to sell oil temp sensing dipsticks for motorcycles. They would run 250 and more, and that was just easy riding around town. Not pulling a trailer uphill in Arizona...then it got over 300, and that was bad. Oil cooler needed for that.
Oil pressure sounds close to normal, idle speed the oil pump isn't pumping much so the pressure is low. If you rev the engine and the pressure stays low, then you might have issues.
Iron@Dirt
Senior Member
thanks El. when you rev up just a little psi jumps up. gage reads in the middle of green, but the last 10-20 degrees of upper temp the oil pressure really drops off a cliff.
How many hours on the engine, and how many on the oil? If it's multigrade oil (10w something) then the friction modifiers wear out causing thinner oil when hot. Your gauge could be off a tad at the low end also.
220 is nothing for oil. It will get hotter without an oil cooler.
220 is nothing for oil. It will get hotter without an oil cooler.
Iron@Dirt
Senior Member
it has about 3k hours and about 20 hours on the oil. 10w30 rotella. the gage is manual i installed about 2 years ago. its a 1997 model bought 2.5 years ago, and brought it to the camp. use it for long weekends about once a month. when the bottom end temp hits the last 10-20 degrees pressure drops from 25-30 to 5-10. been in tractor repair for years but can always use another viewpoint , undecided if i will go deeper if new thermostat and maybe 30w oil doesnt help. cooler temps around the corner so it might delay the symtoms.
I agree that seems odd. You have more experience than I do, so I don't know what to say.
Do you know if there's a spec for minimum low idle oil pressure hot? If it's low then it has to be the gauge is off, the bearings are worn, or there's a leak somewhere else in the oil system???
I've seen oil senders that will leak through the diaphragm and look like the oil pressure drops to nothing when the engine "warms up". I know you said it's a manual gauge, but I'd still swap out another gauge when it's hot to double check, even before swapping the thermostat. 190 might be stock, 180 isn't the standard like it used to be.
Do you know if there's a spec for minimum low idle oil pressure hot? If it's low then it has to be the gauge is off, the bearings are worn, or there's a leak somewhere else in the oil system???
I've seen oil senders that will leak through the diaphragm and look like the oil pressure drops to nothing when the engine "warms up". I know you said it's a manual gauge, but I'd still swap out another gauge when it's hot to double check, even before swapping the thermostat. 190 might be stock, 180 isn't the standard like it used to be.