Oil Pressure Dropping Off

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Apr 26, 2005 | 09:14 PM

jxer00

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Oil Pressure Dropping Off

Truck is an 89 F250...I start the truck, then after a few minutes the idle wants to drop down and the oil pressure drops to zero with engine light. I installed a mechanical oil guage and the pressure is dropping to zero. Im thinking that this is due to a clogged screen or bad oil pump. Do you think this is true? Just did an oil change and oil was dark but nothing special.

My second question is, can i drop the oil pan and remove the pump etc without jacking the engine? Don't know much about this and don't have alot of free time is why I ask....

Thanks

Apr 26, 2005 | 10:38 PM

MustangGT221

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From: Topsfield, MA

Do this specific task...

Change the oil (unless you've done it recently), and when the engine is cold, start it up and observe the oil presure. Is it between 40-60? Let the truck warm up as it idles and watch the oil pressure. Is this when the oil pressure drops on you? On a new motor, it doesn't drop below 40. But on a used motor it can drop to like 30 and 20 and then it'll really start to drop and before you know it you're at nearly 0 psi at idle when the oil is warm. That means it's gettin' to be rebuild time.

What happens is when the oil is cold, it's thicker, and the oil system is able to develop more pressure because of that. When the oil warms up, it thins out, and becomes more liquid-like. When that thins out, you loose pressure, and it's mainly because of worn bearings in the motor. The oil pressure will usually stay up when the rpms are above idle, but eventually the pressures at idle will get really low. My dad's truck did all of this.

Apr 27, 2005 | 12:21 PM

ronclark

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From: Fleming Ga

Quote:

Originally Posted by jxer00

My second question is, can i drop the oil pan and remove the pump etc without jacking the engine? Don't know much about this and don't have alot of free time is why I ask....

Thanks

You need to jack up the front of the engine for clearance but you can change the pump without pulling the engine. You can also change the rod and main bearings from underneath without pulling the engine but if the pressure is going all the way to 0 then the crank is probably worn and like MustangGT221 says it's gettin' to be rebuild time.

Apr 27, 2005 | 02:33 PM

jxer00

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Oil Pressure Dropping

Thanks for the replies all. Yeah its a used truck/motor (89') just got it a couple weeks ago. Just did oil change...sure enough, when I start it up oil pressure is at 40 once it warms up it starts moving down to eventually hit zero and trip engine light. Sounds like I've got some project time ahead of me. Another question for you all though.....

I really don't want to completely pull the engine...If I just do the pump, bearings etc...do you think I can get by?

I don't have a garage/lift etc....I am guessing this kind of thing would be big bucks at the shop......

Thanks again for your help everyone.

Apr 28, 2005 | 02:20 AM

jxer00

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I read some other posts where people mentioned putting heavier weight oil in to boost oil pressure....is this something I can do with mine and what weight is suggested?

Apr 28, 2005 | 08:02 AM

ronclark

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From: Fleming Ga

Quote:

Originally Posted by jxer00

I really don't want to completely pull the engine...If I just do the pump, bearings etc...do you think I can get by?

I don't have a garage/lift etc....I am guessing this kind of thing would be big bucks at the shop......

Thanks again for your help everyone.

I have pulled the pan and changed oil pump and bearings numerous times on both my vehicles and others. Most of the time it will improve the oil pressure somewhat to get you time to do a rebuild (depends on whether the crank or cam bearings are worn too much or not) but rarely does it completely fix the problem unless the problem was the oil pump. Usually if the main and rod bearings are worn enough to go to 0 pressure then the cam bearings and crank are also worn so you still won't get ideal pressure. But hey, it costs less than $100 to do and it is probably worth a try. While you are changing the pump look at the pickup screen and make sure it isn't clogged.

I assume when you changed the oil you changed the filter also.

May 6, 2005 | 02:50 PM

MustangGT221

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From: Topsfield, MA

Quote:

Originally Posted by jxer00

I read some other posts where people mentioned putting heavier weight oil in to boost oil pressure....is this something I can do with mine and what weight is suggested?

You can try different grades of oil, the thicker the better. It may help get some extra miles out of it. The only concern when trying to run the motor, is that you don't want it to be run into the ground to where the block isn't rebuildable. For example, you don't want a big failure. Listen closely for bad noises and if it starts knocking or anything, time to put it to rest. My dad's 88 F-250 ran for a year and 1/2 (atleast 10k miles) between 8-9psi down to 2-3 psi....so you may get atleast a few thousand more.