Oil Pressure Drop

[Big Tee]

I have a 94 with only 91,000 miles on her. The person I bought it from was a one owner and took good car of it. I have changed the oil religiously and just recently and my oil gauge shows it on the low side. It has always been in the middle or a tad above until now. Is this common? I hope I just have a bad sensor and pray it ain't the pump or bearings. The engine sounds quite.

Thanks in advance!

 

[D.R.Ball]

To check that you do have low oil pressure put a external oil pressure gauge and sender where the stock on is and then test run the engine....Most of the factory gauges fail over time or the sending unit fails....What weight and type of oil can also cause a false low pressure reading...

 

[timtimtimajim]

You should know (if you don't already) that the oil pressure gauge is just a dummy light. So if the oil pressure is higher than 5 psi the gauge will read in the NORMAL range, if it's lower it will read in the red. It doesn't show the actual oil pressure.

A little fluctuation in the gauge is probably normal (mine fluctuates ever so slightly) but if it is fluctuating a lot then I would say you probably need a new sending unit.

 

[Number4]

Have you run any oil treatments in the oil?

 

[natenkiki2004]

It's common, don't worry about it. If you want to make sure your engine isn't damaged, buy a real mechanical oil pressure gauge. Mine tests within spec and even after a new factory oil pressure sender, the gauge wanders around. I'm betting it's either the oil-soaked wiring or something in the dash cluster.

View the dash oil pressure gauge as an on/off. If it ever drops into the red or goes all the way left, turn the engine off and get a mechanical gauge hooked up so you can verify you're not damaging the engine. But as long as the needle moves, it's registering some pressure and you should be fine.

 

[Wolfie_85]

Mine had that issue. The oil pressure was fine, it just needed a new oil pressure switch. It's a cheap part you can get at just about any auto parts store. It can easily be accessed from under the truck. It's located by the power steering pump. Get a drip pan, as a small amount of oil will come out. It's an easy and quick job. If you still don't feel right about it, get a mechanical oil pressure guage like mentioned above, or have a shop check it.

 

[Big Tee]

Thanks for all the replies! For some of you asking I'm running 10W40, and no oil additives, and it has been doing great til now. I think it's a bad pressure switch because the engine sounds too good. I may just put an under the dash gauge then I'll know for sure. I hate idiot lights....or low- high display!

Thanks

 

[natenkiki2004]

Why are you running 10W-40? The top end of the engine already has a weak oiling system, thicker than necessary oil will cause more starvation issues.

 

[2stroke]

Why are you running 10W-40? The top end of the engine already has a weak oiling system, thicker than necessary oil will cause more starvation issues.

Because its summer, and some of us don't want our engines lubricated by the watery substance known as 5w30. I'm just messing with you, 10w40 is just fine in the summer, 5w30 works year round too.

 

[Big Tee]

Natan IDK it had weak oiling system problems. I'm in the hot south so not too worried about it.

 

[2stroke]

It doesn't, he is just referring to the nature of all OHV engines and how it takes a bit more time to get oil moving to the heads. His thinking is that you absolutely need thin oil to get that oil there faster. In winter he is dead on. In summer, it makes next to no difference. I only run 10w40 in the summer because after a long hard run of towing the oil temps rise, and the engine starts to make some clatter. No big deal, but the slightly thicker oil makes me happier and the engine quieter.

 

[Big Tee]

It doesn't, he is just referring to the nature of all OHV engines and how it takes a bit more time to get oil moving to the heads. His thinking is that you absolutely need thin oil to get that oil there faster. In winter he is dead on. In summer, it makes next to no difference. I only run 10w40 in the summer because after a long hard run of towing the oil temps rise, and the engine starts to make some clatter. No big deal, but the slightly thicker oil makes me happier and the engine quieter.

Thanks 2stroke. I plan to go back to 5W30 or 0W30 this winter. With the mileage you have logged you must be doing it right! With just 91,000 I have hope! Lol

 

[funfool]

Just my two cents, I never saw anyone suggest a T and keep the original dash gage and with the T add the mechanical gage.
Is there a correct way to do this and be accurate with the mechanical gage?
:scratch:

 

[2stroke]

You wouldn't have much room to just put in a T. I converted my stock oil gauge to an actual oil pressure gauge. I added a 90 degree fitting to give the sender some more room. If you can, I would turn the stock fitting around so the threaded hole is facing down, then run a Y shaped fitting. That should give you enough room for a switch and an oil line for a mechanical gauge.

 

[natenkiki2004]

It doesn't, he is just referring to the nature of all OHV engines and how it takes a bit more time to get oil moving to the heads. His thinking is that you absolutely need thin oil to get that oil there faster. In winter he is dead on. In summer, it makes next to no difference. I only run 10w40 in the summer because after a long hard run of towing the oil temps rise, and the engine starts to make some clatter. No big deal, but the slightly thicker oil makes me happier and the engine quieter.

These Cologne series engines do have a top end lubrication problem. Not only does it take a long time for oil to get up there but it isn't much oil to begin with. Not all OHV engines are like this, many have hollow pushrods that flow oil through the lifters, up through the pushrod and into the rocker. My understanding is that oil pressure ends at the lifters and has another passage to go up to the rockers. That is why you get problems with clogged lifters, the oil doesn't go through them enough to clean them.

Back to xw-40 weight oil, the engine was designed for 10w-30. It's not a matter of winter vs summer, it's a matter of clearances and tolerances and pump volume/design. The engine was made to run 30 weight.

My point about 40 weight is that it's only making the already well-known top end lubrication problem worse by taking longer for oil to reach the top and flowing slower due to the thicker viscosity.

The only times I'd consider running 40 weight is in extreme high temperatures & dusty conditions (I'd eyeball Rotella 10w-30 or 15w-40) or if the engine's bearings are so worn out you're trying to quiet them down and build pressure to the top end. In either case, it's not something to run all the time and it won't fix any issues.

You wouldn't have much room to just put in a T. I converted my stock oil gauge to an actual oil pressure gauge. I added a 90 degree fitting to give the sender some more room. If you can, I would turn the stock fitting around so the threaded hole is facing down, then run a Y shaped fitting. That should give you enough room for a switch and an oil line for a mechanical gauge.

I did the T thing. I'd like to do it again. My problem the first time is that I didn't get everything tight and it leaked. It's a real turd but you can make it work.