What causes high oil pressure?

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Working on an E150 '89, and the gauge is reading high oil pressure. It's in the very upper 'normal' range. I've read that blockage somewhere in the oil tubes can cause this. Could it be the gauge itself? Should I give it an engine flush? Thanks...
 
Thanks Chris, would a flush or cleaner like MMO clean the relief spring or should I just go ahead and change the sender and gauge?
 
Originally Posted By: dino33
I put my hand over the oil cap opening and cannot feel any noticeable pressure, obviously not very scientific...
blow by and oil pressure are completely different
 
Oil Pressure is really just a measure of restriction in the oiling system. Since you can't push a fire-hose-like volume of oil past a main bearing, some pressure is normal and can't be avoided.

A sudden increase in pressure points to a new restriction in the system. It can also be due to a faulty pressure measure. Determine which is the case and rectify.

Check the pressure measuring accuracy. It could be faulty.

Would not hurt to change the oil filter (and oil) and possibly move to an oil with higher detergent action. How many miles on the oil? Is it possible the viscosity has degraded due to age and loss of Viscosity Improver function?

As long as it's in the "normal" range there is no need to panic, but closer monitoring might be in order. If there was a serious blockage pressure would rise more than that, or rise abruptly.
 
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Thanks, I've given it a fresh oil and filter change. The normal range on the gauge is quite extreme and the needle is at the very edge of normal, I'd imagine it could only go another 1/4 of an inch or so...
 
Originally Posted By: dino33
Thanks, I've given it a fresh oil and filter change. The normal range on the gauge is quite extreme and the needle is at the very edge of normal, I'd imagine it could only go another 1/4 of an inch or so...


What oil grade is in it presently. My 5.0 mustang had similar pressure cold using a 40 grade.
Does the gauge show actual pounds or is it an idiot gauge. If it's just the idiot type they aren't much in the way of accurate

Before doing any kind of flush inspect for deposits. If the valve springs are covered in mud I suggest not using any type of flush and use good oil known for cleaning,in that engine a diesel hdeo would be my first pick in a 10w-30 flavour and change every couple thousand miles n
If deposits aren't too severe mmo/Seafoam/kreen/etc should get er done.
 
Thanks Clevy! It's got 10w30 right now. It has an 'idiot' light. I'll try a little MMO and keep the hdeo in mind. It's been using synthetic oil and mostly highway driven according to previous owners. I'll put some fuel injector cleaner through it as well.

I forgot to mention after the car has been running for fiteen or twenty minutes the gauge drops down about twenty five percent to a more tolerable level....
 
Originally Posted By: dino33
Thanks Clevy! It's got 10w30 right now. It has an 'idiot' light. I'll try a little MMO and keep the hdeo in mind. It's been using synthetic oil and mostly highway driven according to previous owners. I'll put some fuel injector cleaner through it as well.

I forgot to mention after the car has been running for fiteen or twenty minutes the gauge drops down about twenty five percent to a more tolerable level....



If well maintained I doubt deposits are an issue and to me it sounds normal however it can't hurt to keep an eye on it for any fluctuations.
It sounds to me like the gauge works fine since it's saying high pressure when cold and lowers as the engine achieves operating temp
Iirc my mustang ran 50psi cold and 20psi or so at hot idle.
 
Put an actual gauge on it and see what it is. Likely the sender is causing it, the way it is calibrated.Those Fords used an idiot gauge.Back then, Ford had a TSB which added a resitor off the sender. The sender was just a switch not a variable resistor. Don't go off the deep end on this, blaming the relief spring in the oil pump. I doubt you even have a problem.
 
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Originally Posted By: Lubener
Put an actual gauge on it and see what it is. Likely the sender is causing it, the way it is calibrated.Those Fords used an idiot gauge.Back then, Ford had a TSB which added a resitor off the sender. The sender was just a switch not a variable resistor. Don't go off the deep end on this, blaming the relief spring in the oil pump. I doubt you even have a problem.


Best advice so far. OP: don't go overboard on trying to fix this "problem". If the gauge is factory, it will read the same no matter what weight you have in the oil pan. Hook up a temporary mechanical gauge if it makes you sleep better. The electrical system on this van is 25+ years old and the readings may have changed in that time.
 
Its probably the gauge. The lack of ticking doesn't eliminate the possibility of a clogged passage but its not likely.
If the actual pressure tested with a mechanical gauge is high it probably has a sticking pressure relief valve.

Running a solvent like Berrymans Chemtool for 20 min at idle on a cold engine can sometimes free them, it will also help clean the passages if there is any slight blockage.
I didn't read the whole thread so these answers probably have all been covered by someone.
 
A few questions:

1. What engine is in this? The 300 i6, the 302 or the 351W?
2. Is this a new condition?
3. How long have you owned the vehicle?

To determine if you have a real sender or an idiot gauge is quite easy. On the 302 or 351 (don't recall exactly where it is on the 300 I6), on the drivers side of the engine, just above and to the front of the oil filter should be a hex shaped "stick" coming out of the engine with a sensor on the end. If this sensor is large and shaped a bit like a bell with one wire coming off the top, it is a real oil pressure sender. If it is quite small, it is a pressure switch.

If you have a pressure switch it is telling you NOTHING other than you have oil pressure. Which means that any fluctuation you see in the gauge is electronic and not related to the engine in any way, shape or form.

On the other hand, if you have the pressure sender, you do NOT have the idiot gauge and the behaviour you are seeing is NORMAL. A Windsor has a pump with a 65psi relief in it stock, if you are driving it cold, it will generate oil pressure north of 50psi and you may even hit the relief (unlikely). Once warmed up, you are probably down around 25psi hot at idle or in that neighbourhood.

Also, when the pressure senders go bad, erratic behaviour is the result. The one on my Mustang would be really high, then NOTHING, then low, then high then "normal" for a while. Replaced the sender and its behaviour went back to "normal".
 
Originally Posted By: dino33
Working on an E150 '89, and the gauge is reading high oil pressure. It's in the very upper 'normal' range. I've read that blockage somewhere in the oil tubes can cause this. Could it be the gauge itself? Should I give it an engine flush? Thanks...


Did it always indicate the same reading ? If so I'd say you have nothing wrong. After all, it's still in the normal range, right ?

Z
 
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