Oil Pressure Question


Founding Member
Jun 20, 2002
South East Louisiana
Hi all--

Driving home today, I noticed that my oil pressure was considerably lower than usual. (No exact readings--I have the stock 66 GT gauge.) My pressure is usually in the top quarter of the gauge and today it was in the bottom 1/4, but still in the "normal" range. All of the other readings, including temp, were normal.

Should I be concerned? I am as the ol' Mustang is the only functional car we have now--Bad AC units on the VW AND the Toyota (what's the chance of that?)

Anyway, I'm letting it cool down before I poke around on it.

I figure I'll change the oil as I'm about due. While I'm under there, I'm planning on cleaning the contact on the oil pressure sending unit. Anything else to check before I replace the sending unit?

I hope it isn't the pump. Do the pumps usually just quit or do they slowly loose pressure?

Thanks for any and all help. I'm worried.:(

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What oil are you running?
I ask because you say that it is about time for the change.
Alot of folks run lighter oil in cooler months and heavier in summer. Maybe a combo of heat and age on a 'springtime' oil wieght has got you down a little. Just a thought.
Oil pumps can go suddenly, but it is rare. Usually your pump dies of old age along with the rest of the engine.
Have you had a valve cover off recently?
If the engine has some age, been sitting long term in the past, or makes lots of short trips, you could have 'sludge' build up.
This can get into your pump pick-up and clog things up.
For example: You get a car that is older and been sitting rarely used for a long time... now you get it, spit shine it, change the fluids and drive it more regular. The old sludge, over time, will be partially dissolved by the more regular oil changes and use... this is one scenario that will send chunks into the oiling system and cause a gradual oil starvation and premature failure.
Some food for thought, it's hard to diagnose this sort of thing without being in your shoes.
I'd probably just replace the sending unit right away. I worried about mine, for some silly reason without doing anything about it. Then I finally had a shop throw a gage on it and it was fine.

..so I replaced the sender and it was fine.

I'm kinda slow, but then again I'm kinda slow. :p
Dave--I realized after I posted that this is about as easy as diagnosing a "squeak in the front end" via the web. Here are answers and new developments.

ratio411 said:
What oil are you running?

Havoline 10/40

ratio411 said:
Have you had a valve cover off recently?

Yes. Had the head gasket replaced about two months ago.

Let the car cool off and checked the oil. It was 2.5 quarts low! I was amazed--the car has never used a drop of oil before. The only thing that I can can think of that is different is that I drove 2 hours at about 80 MPH to a show and back, and almost overheated on the way back due to having to stop on the interstate for a wreck in 90+ heat.

The car isn't leaking in any new spots--not enough of a oil seep to hit the ground. I'm stunned.

I've got a note pad and I'm going to check it every day and see if this is just a fluke.

No water in oil, or oil in water. Crazy . . . .

Today's lesson: Check the oil level in your car every week.

Yes, I'm a doofus.

--Paul :(
2 1/2 quarts low? Yep, that would do it... I doubt you're engine was damaged, but I'd be all over it looking for the leak. You would have definitely seen that much oil coming through the exhaust.... I seriously doubt it was a fluke... something is amiss.

If you say you're a doofus. I guess you must be. I don't know you well enough to make that call! :D

Good Luck!
i had an old ford pickup one time if i checked the oil after it had sit a long time it would be overful but if i checked it within a few minuts of running it would be fine. could never figure it out. till one day i pulled a valve cover off and oil poured out--what the hell. looked around and noticed that most of the valves didnt have seals (umbrellas) on the valve stem. looked some more and i found them, they plugged the oil return holes.the oil had to drain back through the push rod holes. so that was why it took 7.5 quarts to do an oil change on it :)
Yet another update:

I just crawled out from under it and most of the pan bolts were a tad bit loose. (1/4 to 1/2 a turn on all but a few.) The underside is covered in gunk--oil, dirt and various crap. I'm hoping--cross your fingers--that the combo of hot temps and higher than usual driving speed forced oil out around the pan. I can't see anything else. Does this sound feasable or am I blowing sunshine up my shorts? :rolleyes:

However, I am going to clean the bottom of the engine when the weather breaks here--rain, rain, rain--and keep an eye on it.

I guess I need to remind myself that the car is almost 40 years old and shouldn't be pushed like I pushed it.

Anyway, there you have it.

Doofus over and out. :D

Time to grade papers. :notnice:

--P :banana:

PS GaFord--Yes, I am a doofus in only the way an English teacher can be a doofus. Trust me. :nice:
Hey Paul, we are having the same rain as you guys from the same storm system over here in Texas so don't feel like you are alone. The loose pan can be your problem but tightening everything up and testing is going to be the only way to know so good luck.

BTW......if you ever "grade" my posts................. :D
Ronstang said:
Hey Paul, we are having the same rain as you guys from the same storm system over here in Texas so don't feel like you are alone. The loose pan can be your problem but tightening everything up and testing is going to be the only way to know so good luck.

BTW......if you ever "grade" my posts................. :D

Ron--You guys flood everytime I watch the news! We're supposed to get 4 inches today. Ah, getting us ready for hurricane season . . .

Don't worry--I only grade on the clock! (You know, the quickest way to kill a conversation at a party is to tell someone you teach English. Remember that, y'all. Want to get away from someone at a party? Tell them you teach English and they'll run from you like they are on fire!)

I'm going to clean the pan and such today in the garage. Got a gallon of simple green, a brush, a bucket and a catch pan. Gonna be a messy job, but I just put up speakers in the garage and the iPod is loaded with "work on your car" songs. . . . :nice:

Another thing to keep in mind is that on cars that are running rich, quite often the crankcase will get gas in it and when you go on a long highway blast, the oil/gas will burn off. Usually happens on cars that do mostly in town driving, then have a road trip.
Cleaned the oil pan and the front half of the tranny with simple green. Man, what a load of goop came off of that! Gummed up about 10 shop rags. (So much, in fact, that two cap fulls of detergent wouldn't get any bubbles in the washer!) I found painted items that I didn't even know where painted! :rolleyes:

You guys that detail your undercarriages have my respect. That is the pits! I have trouble enough keeping the top clean, let alone the bottom.

Changed the oil and am keeping a good eye on it. I appreciate all of the help!

--Paul :nice: