i have a 94 ranger 5 speed xlt v6 4.0l 288k miles original engine. in the last month the oil pressure has gradually gone way up. a manual gauge shows 65psi at cold start ( in the 90* out side) after a minute of idle it dropped to 60psi, at 2k rpms the psi was 85+. also the water temp has gotten hotter to the point of almost being unsafe. it appears that in the hotter part of the day the psi goes higher. the oil and filter was changed 1200 miles ago. the cooling system has been update in the last year with a new radiator new thermostat. no cross contamination in the fluids, engine runs good other than gauges on dash showing water and oil getting close to unsafe range and manual gauge showing high pressure.
is there an oil bypass that is bad as the engine has had goos maintenance.

 

OK, lets think about this some more. It sounds like maybe you changed the oil & filter recently before the problem, if you only have 1200 miles on this OCI. So did the oil pressure problem begin right after the most recent oil & filter change???? What viscosity oil & what part number oil filter are you using???? The 4.0L is speced to use 5W-30 & the Motorcraft FL-1A filter.

Our dash oil pressure gauge isn't reading actual oil pressure, it's pressure sender has been rigged by Ford to be nothing more than an idiot gauge/on-off switch for the meter & is rigged to cause the oil pressure gauge to read mid scale if we have about 7psi or more oil pressure.

So if the OEM dash oil pressure gauge reading is moving around, you may have a sensor resistance or ground contact problem, or maybe an alternator voltage regulation problem, that's affecting the dash gauges reading.

Is the dash volt meter reading steady, or does it go up when the oil pressure & coolant temp gauge readings climb???? Are you having problems with lamps burning out????

If the dash volt meter is showing an increase in voltage, check the alternators under load voltage output with your multimeter, or run this puppy by your favorite autoparts store for a no cost under load electrical system check up, via their portable electrical system tester. I'm thinking maybe the alternator voltage regulator has problems.

While there, have them also check that the cooling system is holding pressure (I'm thinking faulty radiator cap) & have them check the coolant temp, to verify its within range.

If all that's ok, on the coolant temp, has the water pump ever been replaced???? If not, its vanes could be worn & not circulating enough volume of water to keep the engine happy, or the thermostat may be sticking, or maybe you have a coolant hose collapsing & restricting coolant flow out of the radiator, so check the bottom/suction side radiator hose, to make sure its ok, not being sucked flat.

SO, right now without some more clues, it seems to me you might have oil pressure problems, might have coolant temp problems, OR, you might just have an alternator over voltage regulator problem that's affecting the gauges reading.

A bunch of thoughts for pondering, let us know how your trouble shoot goes.

 

new alternator in the last year meter shows it working good.
the water pump was changed around 200k miles with new hoses, new cap.
the gauge on the dash was changing up then down so he put a new on one in the last year. the problem started up around 1000 miles after oil change. i cant remember what oil but we try to us what the book said. the filter is one for auto zone we have used many before with no problem. all other gauges are steady, the coolant is mixed right,

 

Oil pressure is a measure of resistance to flow, so since the problem began shortly after the last oil & filter change, I'd install a new Motorcraft FL-1A oil filter along with a qt of 5W-30 make up oil & see how it goes. The aftermarket filter may have developed internal problems. It'll cost about $4 for the FL-1A filter & about $4 for another qt of make up oil to find out.

On the coolant temp, have you verified that its actually running hot, with another temp sensor, or IR sensor???? If coolant temp checks out ok, look to an engine coolant temp sensor (ECT) problem, so check its resistance profile verses temp, to see if its in spec. If that checks out ok, check your radiator hoses as previously suggested, or look to an acting out thermostat.

 

How about the 'chopper' voltage regulator on the backside of the instrument cluster. It chops the incoming battery B+ from the varying 12-14ish range to closer to average of 7volts. If it starts to act up, it may just be delivering higher voltage, and thus the higher readings on the analog gauges.
My bogo meter says it is unlikely for oil pressure to increase with age, and at the same time have varying temperature readings. It says look at the gauge system before the actual mechanicals.
tom

Oops. Missed the point about the mechanical oil pressure gauge. I would look at the thermostat and try using a non-contact thermometer to measure actual coolant temp.
tom

 

put new oil filter and 62psi now. dose not climb.
we have not driven it much so have not checked the temp but the mechanical gauge shows it at 62psi.

 

OK, good feedback on the oil pressure, will be interesting to hear how the coolant temp checks out. Any unusual engine noises when the oil pressure & temp was high with the other filter???? I'm thinking the other filter developed problems & was limiting oil volume flow to the engine & thus not enough oil to help carry heat away from the top end, nor do a proper lube job on things!!!????

If you still have the old filter, maybe carefully cut it open & have a look at its filter media, you may find a surprise!!!!

 

he drove it today and the temp stayed in normal range. oil psi was 62 then in 30 miles it was up to 80psi. the engine has started to leak oil for all over, im not sure what to check.
as the oil is getting warm the psi goes up.
i can not understand how are why it would do this.

i just remembered in the winter the motor will tap for a second like a lifter is not getting good oil, but in the summer it only dose it if the truck sites for several days like the oil has drained of the lifter.

 

You may have more than one problem.
On the all over oil leak/s, check the PCV valve to see if its sticking, or is clogged up, or its hose is collapsing or plugged up. If the PCV valve isn't working the engine can build excessive crankcase pressure from blow-by & that'll force oil out the weakest seal or gasket.

The high oil pressure suggests something is clogging up after the engine warms up, maybe debris from the old filter if its filter media collapsed or was other wise damaged, or maybe the oil pump pressure regulator is acting out??? Have you cut the old filter open yet????.

Is the top end of the engine sludged, or heavily varnished up???? Any signs of gum, varnish, sludge, ect on the engine oil dipstick??? When you changed the oil filter, were there any signs of debris in the base of the oil filter mount???

What viscosity oil is in the crankcase????

 

I'd think if the engine is tight, and the pump working very well, a sticking pressure relief valve could lead to higher operating pressure.
If one of the galleys were plugged, the rocker arms would squeek, or the lifters rattle, or the cam and crank would start to seize. Most times engine oil pressure will drop as the engine warms up due to viscosity changes. At temperature, the oil is like water. If you listen to a hot engine immediately after shutting it off, you can hear the oil drain back into the pan, and it sounds like water.
tom

 

i have not cut the filter open. will try to get to it this week.
the oil looks good when we changed it no sludge or trash.
i will check the pcv to see it is working.
how can i check the pressure valve for the oil pump?
i will have to check the jug to see what weight oil, but im 99% sure it is what the book shows.

im thinking he most have a plug in the block some where. but whey dose the psi go up when hot is confusing me.

 

the oil is 10w30 that is what the book said was good.
it is so hot here i dont think we needed the 5w30.

 

OK, good feedback on the oil viscosity. Yup 10W-30 is ok where you are, but 30wt is 30wt at 212F operating temp, so the 5W-30 is the same viscosity at operating temp as the 10W-30, but is less vicious when cold, so it flows easier/faster to the engine top end, to get a good fast lube job going on year round cold starts. Anyway we can move oil viscosity off the suspect list.

Seems to me we're sorta left looking at the old oil filter, oil pump popoff valve, or some deposits, or debris, that have decided to go where they shouldn't. Will be interesting to hear what the old filter media, & center tube support looks like.

When you removed the op sensor to install the mechanical oil pressure gauge, did you notice any debris coming out of the block fitting/threads, or on the op sensor????

 

no debris or deposits only oil.
is there a way to check the oil pump popoff valve?
i may be able to check the old filter and get some pics.

 

Ok no debris in the op sensor block port. I was thinking if you find the oil filter media damaged & you believe some may have gone down stream, maybe you could remove the oil pressure sensor, disable the fuel pump & ignition so the engine won't start, then crank the engine to have the oil pump flush things out the open oil pressure sensor port in the block. maybe pump out a qt or so & look to see if anything was removed & floating around in it.

If you come to suspect the oil pump pop-off valve, I'm not sure it can be reliably tested in place. I believe you'd have to lift the engine up, or remove it, to drop the oil pan to get at the oil pump & pop-off valve. Maybe another member with better info will chime in.