Any one have any ideas what could be causing low oil pressure once the engine has warmed up? I'm thinking it's an oil pump, but I wanted to see if anyone else could come up with any other possible causes before I sprung for a new oil pump. The guy I bought the van (86 E350 351W) from on sunday said that he thinks it's 10W30 in the engine. The van hasn't been run on a routine basis since it had been parked at least 6 or 7 years ago.

I also have a over heating issue a well, but I wanted to address the oil issue first. I hope to get a 670 Street Avenger for it in the next few days to take care of the carburetor issue as well as a new distributor.

TIA

 

I'm no mechanic but i would look at the oil itself to start. Have you checked level and how it looks? Viscosity thin or thick?).

Check the oil pick up in the pan would be next. Plugged? tube attached correctly?

High mileage worn out engine?

Not much help I know. But......

 

Already checked it, it was actually about a quart over. Needs a change but I wanted to get the pump before I changed it so I wasnt wasting a complete oil change.

 

Forgot to mention that the oil pressure is normal when the engine is cold, just drops when the engine comes up to normal temp

 

I have had similar issues with a BB Chevy in the past. What I did was buy a HV oil pump and when I dropped the pan to install it I checked the rod bearings for wear. The mains look good but the rod bearings showed some wear. I bought a new set for the rods and installed. When I started the engine up with the new rod bearings and HV oil pump I was getting 70-80 psi cold and 50-60 at highway speeds. It never dropped below 30 psi.


I did the same thing with a 5.0 that was run with low oil level. I replaced the rod bearings and the oil pressure was back to normal.

 

Rod or crank bearings was the two things I was hoping that no one wouldn't mention, I've no reason to suspect them other than by the loss of pressure but it's the only place I can think of in the oil circuits where it could lose that much pressure. Did you use standard OE size bearings on the rods? Or were the journals worn so bad that they needed oversize bearings?

 

Man we're all over the map on this one.............

First off I'm thinking that engine would be better suited to a 10W-40 oil. I've never run oil with a lower viscosity than that in a mid-80's motor.

Next up is the rod and main bearings; if the 10W-40 doesn't produce better and more consistent oil pressure readings there's almost nothing else that will cause a drop. Not really sure how common an oil pump failure might be but if time isn't an issue and you have plenty to spend maybe change the pump and see how it works, what results it gives.

Replacing those bearings without measuring the affected journals would be another nearly senseless activity. Guessing if over-sized will work or not completely escapes me how one would even go about that.

The overheating issue could be a failing head gasket----I hope this van was bought on the cheap.

 

Throwing a set of new rod bearings in an engine when you drop the oil pan to change the oil pump is not a senseless act. On an engine like the 5.8L a set of rod bearings can cost a less then $20. Most bearings I have removed from engines have part numbers of some kind on the back. That will tell you what size to buy to replace them with. New bearings, of the correct size, won't hurt matters and could be the thing that actually fixes the low oil pressure. It has on every one that I've done.


The way I look at it is it costs almost nothing to swap the rod bearings if your going through the trouble of dropping the oil pan to change the oil pump.

 

I understand what you're saying, I just don't completely agree with you. The difference in viscocity between 10w30 and 10w40 isn't enough to cause the oil pressure to drop considerably once the engine has warmed up.

There is another option to look at, that being the sensor is going bad...IF it is an electrical pressure sensor and not mechanical. I haven't taken a look at the sensor on the engine or opened up the dash to see if it is mechanical vs electrical yet, but if it is electrical then it is possible that the sensor is having issues once it gets hot. I'm not saying that IS the problem, just saying that it is another possible cause if I've not found anything else. Besides that, being that the speedo is mechanical (guessing only) in mine I'm not exactly sure when Ford changed the sensors from mechanical to electrical, both the speedo and oil pressure.

I don't know for sure when it drops, I just remember seeing some oil pressure on it when I first started it and then when it was hot seeing none on the dash guage. I'm not sure if it gradually dropped, or if it was a sudden drop. Gradual drop in pressure would lead me to suspect something in the oil curcuits somewhere, whereas a sudden drop would lead me to suspect the sensor itself.

As far as the bearing...they are an intentional wear item in the engine. They are intended to fail fail before damage to other items is caused. I'm not saying that they ARE the cause, but for $20 or so I don't mind putting new bearings on the rods since I can access those without too much trouble. If it is the main bearings that are the problem then I'll have to pull the motor to be able to fix those. Then at that point I may as well rebuild the engine since I'll already have it out. Admittedly, if the rod bearings are worn that much I should be hearing some sort of knocking or tapping, but I haven't yet that I feel I can confidently blame on the bearings.

I'll agree with the possiblity of a failing head gasket, however I'll look at some of the externals before I start digging that far into the engine. I'll start with flushing the fluid that is in it and seeing if I can see any major flow. Minimal to no flow and I'll look at the water pump more pointedly, as well as the thermostat, I'll probably replace the thermostat anyways just for GP since there is no way to know the last time it was replaced or checked. Yes, I could boil it in a pot of water to see if it's working properly however with my current living situation I don't have that option.

I'm hoping that once I get the 670 Holley Street Avenger and new distributor on it I can start cleaning up the noise out of the engine and properly diagnosing any other issues it has.

I only bought this van for $600, so yeah, I consider it on the cheap. With a 351W I couldn't really pass it up. I may not be real knowledgable with Fords but I at least know that is good engine to have, even if I do have to rebuild it.

Thanks

 

I tend to agree, it'll only cost me a little more time and possible frustration dealing with the crossmember, but putting new bearings in for a possible fix certainly beats having to pull the whole motor out for a rebuild later because I didn't take the time to at least try the bearings while I had the chance. Of course, like JWA implied, it may not fix the problem but it certainly worth a shot if I'm already going to have the pan down.

 

use 50 wt.

 

For me the best part of our disagreeing is its your time and money so either of those that end up wasted chasing something has absolutely no effect on me at all.

I tend to prefer doing any job one time, stop gap or half way repairs aren't for me. Between time and money I have far more of the second than the first but still prefer to not waste either. One and done.......

Best of luck!

 

LOL it's not that I don't agree with you at all, because I do, it's just that under the circumstances I don't have a lot of either time or money. I'm just trying to fix the problem "temporarily" so that the van can get me back home where I'll hopefully have more of both. Besides, until I really decide what I want to do with this engine I don't want to throw a bunch of money at it that won't be going towards the end goals for it, know what I mean? For example, a high flow oil pump would be useful if I decide to go with something I read just recently about stroking the 351 out to a 408(?). No matter what I do with this engine I want it to be able to produce really strong torque and still fit under the "hood" so I'll probably get the Edelbrock Performer intake for it, but for other stuff that doesn't have an immediate gain or fix I'll probably just wait on tackling.

 

quick fix is 50wt oil

 

sorry to interrupt your conversation, but i got 2 questions to the oil theme:

1.where does the sensor work? is it placed in the oilcircle before the oil filter so its condition will change the pressure?

2. when i start the enginge, the pressure is always the same. (97' 330cui) nothing changes, nearly never. dont care for 6°c or 16°c outside.hot or cold engine.
so i thought it stucks in its position. BUT
I changed the oil (dont know what was in before) to 10w40 standard inclusive oil filter and: first no pressure (logical) and after seconds it rises to the same level (photo)
so i guess it works.

But why is my pressure that high? - maybe just because of the littel thicker oil?
is your indicator in the middle of the range?

greetings from germany