Strange Oil Pressure problem???

[J.Picard]

Hi all! I am having a strange oil pressure problem...but maybe it's not so strange. Thought I'd post and prey for someone's opinion other than relying on my inexperienced misgivings.
I bought the truck (1987 Ranger 2.9L) last month. 120KMiles, pretty good shape, cept never had any hoses replaced. Coolant system had to be flushed, oil was filthy, and temp gauge had to be replaced. I do still have to replace the valve gaskets...Not a ton of work, but I am having a strange experience with the oil pressure gauge.
When I first start the car, the pressure gauge reads is really high. After it warms up (about a mile later) the gauge drops down to mid level. Is this normal??
Before I changed the oil the pressure would run about mid level, and a little closer to high when on the freeway. Luckily it has never dropped below normal, but am concerned about the high pressure? Can this do any damage? or is it normal. I was talked into buying 10W30 instead of 15W30 at auto store (by a sells guy), would the wrong weight make this happen?
As a new owner, I haven't yet reached a level of security/trust with my new relationship/vehicle.
Any help or opinions are greatly appreciated!!

 

[Maniak]

Just for comparision..

On our '92 X (4.0 ohv motor)..

When using 10w-30 mobile 1 synthetic and starting the car for the 1st time of the day when its 70-80F out the oil pressure is 60psi or so...

Once the motor warms up idle pressure drops to 30-40psi...

When hot (say driving around town with its 105F out) it will read in the low 20's at idle..

Most of our vehicles do this (the ones that don't, don't have real pressure gauges so I can't tell)..

I noticed it was more pronounced (higher cold idle pressure) when I was running straigh 30w oil..

~Mark

 

[Scott B.]

The 4.0 OHVs have a bad habit of low oil pressure. My oil pressure gauge (converted to be a real one) on a warm day will show pressure at the low end of the scale - when I'm doing 70 down the road! I am surprised my engine is still holding together.

Best guess is as the engine bearings wear, they allow pressurized oil to seep out, instead of staying in the passages going to the top of the engine.

It is scary to watch the gauge, but the engine does not sound like it does not have enough oil.

I am running Valvoline Durablend, 10W-40. I used to run Castrol GTX 20W-50 (10W-40 in the winter.) Probably 100,000 miles on 20W-50.

 

[Willard]

Wait- Do the older rangers have a real pressure gauge?

Seeing as how explorers don't...

 

[Scott B.]

No - well, not really.

The gauge has a shunt (a 20K resistor) across it. If you remove the shunt, replace it with a wire, and change the oil pressure sender to a real one, your dash mounted oil pressure gauge will be a real one, not a 3-state one.

There is a thread on this site with instructions. I will try to look for it tomorrow for you.

93s and 94s have the same gauge cluster.

 

[Maniak]

Our modified stock preggure gauge reads between the N and O in normal at 20psi (which is about where it sits at idle when hot). I hooked up air line to it to figure out whre 20, 40 and 60psi were.

~Mark

 

[Willard]

I know you can modify the gauge to work, but I'm thinking if he has a regular gauge then he is seeing fluctuations in it that mean nothing. Mine moves around quite a bit even though it "should" stay in the middle.

 

[Scott B.]

When I changed my gauge (8 years and many miles ago) it read what I would consider "normal". Pressure increased with RPMs. As the miles wore on, the behavior changed - I am confident with the gauge.

 

[HahnsB2]

Ford gauges are garbage, put in a mechanical to see if you really have a problem. Spec is 40-60 PSI warm oil pressure at 2000RPMs.

 

[bt93]

The important thing is that it doesn't fluctuate greatly while driving.

 

[J.Picard]

Thanks all

I actually read that the 2.9L engines (in the 88 and newer models) had their (stock)oil pressure gauges changed to "mock" gauges (to hide the low oil pressure problem Ford was having with the 2.9L engines)??? Sounds scandalous.
Mine is an 87...so it is suppose to have a functional gauge. I took it out today after the original post, and The same thing happened. Ran high until it warmed up. Then read a moderate oil pressure...high on the highway but when idling on the lower side?? I'll keep plugging along to find answers. Just hope she keeps plugging along with me. I've only had her a month - and I'm pretty attached.

 

[Willard]

I actually read that the 2.9L engines (in the 88 and newer models) had their (stock)oil pressure gauges changed to "mock" gauges (to hide the low oil pressure problem Ford was having with the 2.9L engines)??? Sounds scandalous.
Mine is an 87...so it is suppose to have a functional gauge. I took it out today after the original post, and The same thing happened. Ran high until it warmed up. Then read a moderate oil pressure...high on the highway but when idling on the lower side?? I'll keep plugging along to find answers. Just hope she keeps plugging along with me. I've only had her a month - and I'm pretty attached.

You know this kind of sounds normal to me. In my dad's GMC his oil pressure is generally noticeable more when it's cold as compared to when it's hot. During really hot days, it can get down there though.

 

[rwenzing]

Oil pressure varies widely with RPM, temperature and rated viscosity. After reading some of the comments in this thread, it's easy to see why Ford gave us a "feel good" solution on later models - an idiot light disguised as an oil pressure gauge.

 

[Scott B.]

Oil pressure varies widely with RPM, temperature and rated viscosity. After reading some of the comments in this thread, it's easy to see why Ford gave us a "feel good" solution on later models - an idiot light disguised as an oil pressure gauge.

I always figured it was to keep the average (idiot/ignorant) customer from calling the service department asking why the gauge moved so much!

 

[rwenzing]

I always figured it was to keep the average (idiot/ignorant) customer from calling the service department asking why the gauge moved so much!

That's the way I heard it. Ford included the full gauge package to satisfy customer preference but converted to the on/off OP sender to cut down on warranty costs for non-problems.

 

[Ca2rie59]

Whew!!

This makes me feel so much better. A single gal alone in this world with a gem of an older tuck sometimes needs some good advice and experience. That moving oil gage made me worry just a little bit today as it got colder and the truck got warmer. But as long as there is oil in it and the engine is running fine then I'm not going to worry... (heck..I drove a darned old nova till it died..) Thanks darlin's..

C~~:exp: