Oil Pressure problem... It's wierd!

[Spiritboy]

I'm new here and even though this is my first post and I would rather start it off with something that doesn't make me look like a complete novice, I am in need of some advice. I tried to find it with search but search wasn't working. I browsed the last 30 pages of the forum but found no answers so I gotta' start a new thread.

What's happening is after driving for a little while, the oil pressure light will come on in . The thing is tohugh, it only does this once you start to stop. If your are driving at normal speed, pressure is fine.

Now also, when the light does come on, if you switch the car into park or neutral, pressure comes back. It doesn't come back in reverse. If it comes on, as soon as you accelerate, pressure comes back.

So what I've been doing, is just driving normally, and if I'm stopped and it come sone which is rare, I just shift to neutral until I move again.

I am not sure what it is although I have a few theories.

Naturally, considering the car is old, sending unit came to mind. There is a pattern though so I don't know if it could be that. I've never heard any odd noises, or seen any smoke when this happens though. The car does burn oil, but there is no way to stop that that is economically feasable.

I also figured it might be the oil pump, and when the car is running at a certain pace, it keeps the pump turning but you stop, the pump stops. That's a theory.

Another theory is a clogged oil screen. i figure when everything is turning, enough oil could be making it through the clog but when you stop it might not.

I would prefer not to have to take it to a garage because of finances but I was hoping you guys could maybe give me some info anyway. Some theories, or if you've seen this before etc... THANKS

[sierrap615]

i'm leaning to weak oil pump, the pump's output is lowest at idle, and if you watch your tach, when you shift into gear your idle drops about another 100 RPM due to the load of the transmission.

what type of car is this? mileage?
how long has this been going on?
had a oil change lately?
are you looking to fix this yourself? if so, what is your mechinical skill level and do you have tools at your disposial?

[Spiritboy]

Yeah, I was thinking that too. I'm going to be doing about an hour's highway driving tommorow, followed by about another hour on Monday morning. That's why this became somewhat of a more pressing concern to me.

It's a 92 Dodge Spirit, got about 240,000 clicks on it so it's a veteran but it runs quite well. I just changed the head gasket not too long ago so we got to have nice deep look inside the engine and things look good.

As for the problem... It's strange. The first time it ever happened was quite some time ago but it has really been a rare occurrance lately.

The last oil change was a fairly long time ago so I'm actually going to do that tommorow and maybe that might make the difference. A fresh filter could maybe help the problem.

Other than that, I will most likely just bring it to a garage since my main mechanic friend has left town for about 6 motnhs. Bad timing unfortunately.

Hope that helps make tihngs clearer for anyone who wants to expand on what's already been said. Thanks.

[Austin8214]

Originally Posted by Spiritboy

The last oil change was a fairly long time ago so I'm actually going to do that tommorow and maybe that might make the difference. A fresh filter could maybe help the problem.

You need to change your oil every 3,000 miles not a mile more. with the amount of miles you say you have on that car I would say you have a sloppy rod or crank bearing. This is the main cause of low oil pressure in an older engine. I do not think it is your pump because it works fine at high rpm. Oil pumps useuly fail at high rpm first detonating the engine.

[curtis73]

Yep. Tolerances either in the pump or the bearings have gone out of spec and your pump isn't making enough pressure.

The oil pressure light comes on when it drops below a certain pressure. Since your engine needs approximately 10 psi per 1000 rpm, it might be starving for oil everywhere, but the light only comes on at idle.

Lets say when it was new it made between 20-60 psi and the light comes on at 10. Now, the pump may only be making 9-15 psi, but since it only comes on at idle, its giving you a false sense of security. Fix it fast or you might be making a boat anchor

[Spiritboy]

OK, I will fix it tommorow...

Question though... Could you ballpark a bearing replacement in terms of price?

THanks.

[curtis73]

Very big ball park. Its one of those things that could be very simple or very involved. Its one of those things that depends on how much you love your car. Bearings should be $50 to purchase, same for a new oil pump. The engine will probably need to be pulled for the work or at least lifted off the mounts. Very labor intensive.

Its also one of those things where its not always just as simple as replacing parts. The bearing journals (especially after that many miles) wear in an oblong shape and just putting new bearings in might do more harm than good.

Here's what I suggest, and you can decide for yourself after you get some estimates. Switch to 15w40 or 20w50 oil for the summer and see if that "cures" the problem. Its not ideal, but in a conservative engine like yours, you might be surprised at how much longer it will last.

You need a certain amount of pressure so the oil film is substantial enough to prevent metal to metal contact between the bearings and journals. If you can achieve that with just thicker oil, do it.

[Spiritboy]

Alright, I will give that a shot.

I'm bringing it in to Goodyear tommorow though to get an estimate anyway.

I was curious though...

In the Dodge Spirit, the crankshaft assembly sits on top of the cylinder assembly. To expose the shaft, you only have to remove a tin lid type of contraptionand it's all there. Do you have to drop the engine on this car?

I could be way off base, but that's what I gather from when me and my friend, who is unfortunately no longer living here, replaced the head gasket and my reading the Haynes manual...

Like I say though, I'm getting an estimate and we'll see... The problem arises during the cold Canadian winters when a thick oil means no oil ...

[curtis73]

You might be thinking of the camshaft. The crankshaft is in the bottom.

[Spiritboy]

Yup, that's probably what I'm thinking then...

Well, I'm getting an estimate tommorow so we'll see how that goes.

Thanks for the help though, you've been extremely helpful!

[curtis73]

Best of luck! Let us know how it goes.