Hi all,

I kind of feel stupid asking everyone about this latest problem, but so far I have not come up with a resolution.

I have a 49 F1 with a 226 engine. Vehicle had sat for probably 15 years. About nine months ago, I started replacing items to get it to run. I have ran the engine for several hours and had driven the vehicle a few miles.

When I got it running again, it would start right up and show 80 lbs. oil pressure at idle on full choke. Once it was warmed up, it would show about 50 lbs at higher rpm, and would show about 15 lbs. with the idle set at 500 rpm.

Just recently, when starting the vehicle, I now show 30 to 40 lbs when cold, dropping to under 30 when warm at higher rpm. Idle now is at between 2 and maybe 10 lbs.

The only thing that has changed since this latest low oil pressure reading are the following: Added oil bath air cleaner. Changed out ignition components. Changed out cooling system hoses and thermostat. Ambient temperature around 32F vs. temps in the 50 to 60 range.

My thinking is that possibly one or two things have taken place. One would be that since I have been running the engine that has sat idle for so long, maybe it is in the phase of self destruction. The other thought, could it be possible that the oil sending unit is on it's way out, or reading differently since the drop in outside temperatures?

Thanks for any and all help.

Tom L.

 

read with mechanical gauge

 

 

Use a mechanical gauge to verify first .

 

There was work done by a member (Brain??) a few years ago on his 226 I6's oil pressure. His experience with gauge readings sound similar to yours. In my own case, pressure ranges from 45 to zero depending on engine temp - for the past seven years.

Certainly, a mechanical gauge could clarify the situation.

 

The gauges on these trucks work on a thermal principle, little heating coils wrapped around a bimetallic strip. Cold weather can affect their readings, until everything warms up.

What oil are you running? if it's real thick stuff, the presure relief may be opening until it warms up.

 

I'll speculate that the varnish and sludge from sitting for so long and maintaining clearances is being "washed away" and going into solution with the new oil, which is probably a detergent? I seriously doubt it's going to self destruct, they have ways of letting you know if they are. As stated by others, verify with a mechanical gauge, but don't get your hopes up too high. 5-10 psi @ hot idle is ok. It's not doing any real work.

 

Thanks for the input.

I am running 10w30 Valvoline which is a detergent oil. I had also added Seafoam to the crankcase and fuel. I am thinking the same as others that sludge is starting to let loose and plug things up. I am going to change out the oil and cartridge filter to 30w Castrol and see what comes out on the crankcase. I assume that if I have sludge building up that I need to remove the oil pan and clean out the oil pump?

The information on the type of pressure sender and it's operation that Ross gave certainly makes sense. Hopefully today, the temperature will come up and I can see if there is any difference in the readings.

For now I will try a mechanical gauge and dump the oil and see if anything improves. If no improvement, I guess I should take down the pan and see what I've got.

Tom L.

 

Well today the temperature outside came out of the low 30's to a high of 57F. Started up the truck and within a minute or so the oil pressure was reading backup to where it was before the problem of lowering oil pressure. However, after running and driving a mile or so, it went back to the previous low readings. When I went to put it back in the garage, it went back to the high readings again. So, I am now thinking that the oil pressure sender maybe giving me an erratic reading. Or, possibly sludge running around causing erratic readings.

I just dropped the oil and it looks pretty clean. Trying to decide if I should drop the pan, or maybe at least the inspection cover.

Can you get to the oil pump screen to clean it out without taking the pan down? Would it be worthwhile to fill the crankcase with diesel fuel or kerosene and let it soak overnight before putting in a new cartridge and oil? Or, am I just kidding myself and it is time to start taking down the pan and seeing what I really have going on?

Thanks for any and all help.
Tom L.

 

 

I agree with BigWin, a good accurate gauge is the first step. But it can't hurt a thing to drop the clean-out on the pan. You can remove and clean the screen without pulling the pan. But if the whole pan is full of gunk, pan removal is the only course of action. Soaking with kerosene or diesel is likely to just allow sludge to circulate where you don't want it to go, if there is a lot of it.

Usually when the screen is plugged, it affects high-RPM pressure more than idle pressure.