I've got a 2003 3.0 Ranger and it seems to have a problem with the oil pressure gauge. I'm thinking it's the sensor since it's fine after the initial start up and during driving but after it's reached temp. the oil pressure gauge will jump and act erratically if the RPM falls below 1000-800 range. I also get a slight cough/snarl/ sound when I turn off/on after having driven for 20+ and then if I don't let the engine cool all the way, when I start it.

 

Yes, replace oil pressure switch on the engine first
Behind passenger side head on the block by bell housing, on the 3.0l Vulcan engines

You will get valve train noise if oil pressure does drop and you don't mention that

Noise after shut down usually means you have air in the heads, air in cooling system, and it is in pockets in the head and is flashing to steam once circulation is shut off

 

 

Yes... that is another way to describe the same location.

 

 

One thing to check over the next few days
Before starting the COLD engine, open the hood and take off rad cap
Coolant should be at the very very top, NO AIR at all in the radiator.
Check this a few times, you can top up radiator the first few times, and should, but if it continues then there is a problem.

Best case
A small leak
Blocked overflow hose or tank

Worst case
Cracked head or head gasket leak


You have a self purging system
As engine/coolant warms up, the coolant expands in volume like any fluid does, this is where the Pressure in the system comes from
As pressure increases with temperature the radiator cap will be pushed open and allow hot coolant to flow over to Overflow tank
If there was any Air in the radiator it will flow out FIRST, when it gets to overflow tank it will bubble up to the top, and be gone
When engine is shut off and cools down the pressure in the system will go down as coolant "shrinks" back to cold volume levels, until it is -1psi, then the Smaller valve in rad cap(yes there are TWO VALVES) will open and pull IN coolant from the overflow tank
So when engine is cold there should be NO AIR at all in radiator, self purging system

 

Thanks! I will check that out, I haven't noticed any coolant leaks after having parked for an extended amount of time. Could sudden efficiency in one part cause others that may have gotten "accustomed" to lesser performance be pushed to fail? It looks like everything that is failing is OEM and the truck is 15 years old with 246K on it.

 

Small leaks won't show until engine heats up and pressure builds, and if the leak is on/in a hotter area then it evaporates instantly with no visible signs
Just keep checking radiator level, and also overflow tank level, there is a COLD line you can use on the tank, or put a piece of tape on it, if rad stays "topped up" but overflow tank level is going down then there is a small leak, but its not sucking air back in as engine cools.

There are UV Dyes that can be added to coolant, or any other fluids, that will leave a stain at the leak point, its only visible using UV Flashlight or light bulb

Yes at 10+ years old you know you have a "used" car, lol
And yes any abuse over that time will show up as failing parts, and some parts like brakes, tires, and clutches(automatics have clutches too!) just wear out from general use
Overheating is one of the more common issues that can cascade into many other issues
Coolant hoses and vacuum hoses(rubber parts) deteriorate over time, and it really depends on where you live, hot dry areas tend to cause these parts to fail earlier, but the engine bay is a hot dry area when engine is running so they will deteriorate in any case, just takes a little longer, lol.

 

I'll definitely keep an eye on the radiator and overflow tank.

There's been no heating up, that's been registered by the thermometer in the dash, during any of my drives. I've been keeping a wary eye on the temp ever since I cracked my radiator, bout a month ago now.

on a side note, the oil pressure gauge is now holding steady when driving or idling.