Hey all, My 88 f-250 5.8 is dry starting... I think, If i let her sit for a day or two and start it i hear a clunky type noise hard to explain but after 1-2 seconds it stops so i think the oil is draining back into the pan. But i have good oil psi, 50psi according to my gauge on a cold start but when she warms up it drops to 20-30 psi and if i drive it drops to below 10 when i stop at a light or something but i think that's my gauge cause i can flick the glass and it jumps to 40 psi. I was just wondering if that is my problem and what is causing the oil to drain back to the pan.

Thanks for the help!

 

What brand of oil filter are you using?

 

make sure you are using a motorcraft oil filter not a fram

 

That is the reason that Ford went to gauges that do not move. The first thing to do is make sure you have a reliable oil pressure sender and gauge. The cheap ones in parts stores are not as reliable as a brand name. Flicking the gauge and the pressure goes up is a sure sign of a failing unit.

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I am using a Motorcraft filter, When i bought the truck it had a fram so i thought that was causing my problems. The previous owner (Bought the truck new) put a 0-100 psi. old auto meter mechanical in it. I guess i should buy a new electric auto meter. But what could cause my dry starting? Oil pump failing? The truck only has 68,000 original miles on it.

 

You could have a lifter or two that are bleeding down. Can you be more accurate with the description of the start up noise?

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could be numerous things if possible record the sound in a video and post it through photobucket

 

i don't have a camera capable of recording but it is a rough clunk clunk clunk for a second or two with the speed of the engine. In a way it almost sounds like a knocking valve. But if it were a valve wouldn't it do it all the time? the motor is clean as can be no leaks anywhere.

 

What oil? what viscosity? 10w-30? thats what Id use in that engine at least. Might try 10w-40..

 

I am running Mobil 5000 (but i change every 3). 10w-30 with a motorcraft filter. Do you recommend 10w40 on the next change?

 

I got the same sound, had it for ten years now. I use 5w-20 oil and motorcraft filters and still have it. Someone once told me that it's piston slap where the piston is loose in the bore when first started the expands to fit the bore after running it awhile. Is this bull? I don't know. Just make sure the sound goes away after a few seconds.

 

A lifter that bleeds down will sound more like a sharper clicking sound until that lifter pumps up, not a clunk sound. If it is duller sound it could potentially be bearing or piston related.

Also your oil pressure gage is taking pressure right near the oil pump, the internals of the engine can be slower to react to the pressure. A good filter like the Motorcraft has an anti-drainback valve to help dry starts. The 5.8 filter sits horizontal, so it could be as simple as your filter drainback valve is leaking.

 

If I had that problem in a push rod motor yes I'd try a heavier viscosity.

 

I will up the viscosity on the next change.

srfd44 said it could be piston slap and he has had this problem for ten years so maybe it isn't to bad. I was just worried cause i am out of a job so if my motor blew it would be a long time before i could fix it.

Thanks for the help all.

 

After running to town i got back home and crawled under my truck and i can hear the oil draining back into the pan so i don't think it is the viscosity of my oil causing my problem and the filter and oil was changed 1k ago with mobil oil and a mc filter so i also don't think the drain back valve is leaking so what else could it be? Is there a device in the oil pump that holds the oil in the engine?

Thanks for your help.