Hey guys. I have a mechanical oil pressure gauge. It reads low...really low. after some driving and a few hard accellerations, it can drop down and read Opsi. Some times it sits around 10psi at a stop light and then when i take off it drops to 0 and then climbs a bit. I dont think its ever been over 30.This cant be right. Its not an expensive gauge but a gauge is a gauge. What should it be reading at idle, cruising, acceleration. i dont want to be doing any damage.maybe a bad pump, or something. 87 f259 6.9L N/A

 

Cold mine sits at about 45-50 psi. When it is warm it idles at 25 and at any thing over idle warm it runs about 50. Yours does sound low real low.

 

Rule of thumb for any engine is 10 psi per 1,000 rpm minimum. At idle you should have atleast 9psi since the low pressure oil light would come on at 7psi. At 3300rpm should have around 40-70psi.
On cold starts you should have your best pressure, what's yours?

 

yep, ive got a problem! With a full pan of oil, cold start. maybe 40 psi. but then when i drive and it warms up, its maybe 15 to 20. the more i drive it, the lower it goes. i dont now whats going on. Do the oil pumps go bad? would anything else cause this. i do go though oil somewhat quick.

 

I'd first try a known quality gauge as a reference first to verify there is a problem or not.

 

ok. i can try a different gauge. Where is the oil pump? hard that change?

 

You have to raise the engine and drop the pan.

 

well i do have to to my motor mounts anyways. what about the oil pressure regulator valve? can that cause low pressure?

 

Of course if a piece of something has it jammed open bleeding off pressure. Actually someone awhile back had this happen to them. If you haven't done your cooler o-rings yet it would be a good time to do that too.

 

ill add o rings to the list. should i look into a new oil cooler too?

 

NEW is really expensive. You shouldn't need new but you won't know for sure what you need until it's apart. Most cases the 4 o-rings and the 2 gaskets and you can rebuild yours. Clean everything real well and use petroleum jelly when assembling the o-rings.

The pressure regulator is in the rear header of the cooler in the surface that mates the block. I would inspect it the best you can to see if there is anything holding it open. If you could possibly locate another rear header and install it instead of your original. The spring and valve is staked in the aluminum housing so it's not meant to be serviced.(though people have taken them apart)

 

ok. i ran the truck to the store today. heres what i noticed with the oil pressure gauge. cold start-20psi; 65mph,2000rpm-15psi; 35mph,1500rpm-15psi. idleing was around 10psi and dropping to 0 when i took it out of gear. i really dont want to break anything. i did notice alot of fluctuation. especially at idle (0-15psi)

 

I was worried about oil pressure on ours because of an incident I posted about recently.

I was just inspecting things over because I haven't really bothered back there until I went to replace the cdr this week.

We have a cheap harbour freight gage with a nylon line. It is pinched and there is oil puddling from where it connects to the fitting and down! So I thought we followed the directions and all that but obviously we are careless.

So now I wonder how realistic our readings are. We see around 40 with the engine warmed up and pulling down the freeway. When going around town it is less and when braking at a ligtht it dips down to less than 10.

But I need to revisit our gage this week as I try and track down other issues.

Are you getting any oil in your coolant? Ours is littered after being clean for 2,000+ miles since we rebuilt the oil cooler. I would assume a leaky oil cooler if that is our problem has an effect on readings.

 

My donor truck did not come with an oil cooler.... did the PO get rid of it? or did some not have em-- 89 F-250. I may have to get one at the JY just to have it and put in.

Your pump may be bad, pressure spring weak, bleedoff valve not closing, or the engine could just be very worn, loose bearing clearances drop oil pressure pretty fast. Im thinking it should have at least 40psi cruising our CAT 1160 has like 3 at idle, but soon as you get over 900 rpms its peggin 80. You can buy a quart of lucas oil stabilizer and dump in there, will bump the pressure up a bit. Had to run it in my 400 to keep the pressure up cuz the mains were toast.

 

My truck is what I consider low on oil press.It carries 15psi at a hot idle but it jumps right up when you touch the throttle and carries between 35&40psi going down the road.These engines don't turn a lot of rpm's so I'm not too worried.