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No/Slow oil pressure in cold weather - temporarily fixed by new filter..what's up?

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Big6ft6

1/2 ton status
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Location
Madison, WI
91 TBI 350 in k2500 175k miles. Uses oil (fouls 1 plug but no blue smoke), good compression in all 8 cylinders. Here are the symptoms of my oil pressure issue.

  • In cold weather, when I start my truck the oil pressure gauge takes a long time to show ANY pressure. (Like 5 minutes!:eek1:).
  • When it finally starts to register it is slow to come up and doesn't quite reach normal full pressure, but close.
  • When pressure first starts to register, for a short time pressure will actually drop with engine rpm (drops to zero)..but once warm, pressure increases with engine rpm as you'd expect.
  • Once warm, if I run into a store or something when I come out and start the truck, pressure is instant.
  • If I change the oil/filter, the problem is instantly fixed. Even from a stone-cold start I get instant, full (higher) pressure right away. But the fix is only temporary. After a few hundred miles,...I am back at the same spot as long as it is cold weather.
  • I've tried many brands of filters.
  • I used a mechanical gauge at the port above the filter to confirm pressures and rule out faulty gauge/sender.
  • I cut one of my filters and noticed nothing, but I didn't really know what I was looking for.
  • I did remove the factory oil cooler and oil cooler section, so this required a different filter mount plate that I put on. Since filter is now vertical I have to use the shorter filter.
  • In warm weather I don't notice this pressure problem?

Ideas? Thoughts? Looking for the 350 engine gurus out there to teach me would could possible be going on..
 
I'm thinking sludge at the bottom of the pan is restricting the oil pickup. Hot oil can probably flow past the restriction easier.
 
I'd be dropping the pan as well.

I have cleaned up a couple of top ends, obviously everything runs to the pan afterwards, and it has always caused oil pick up problems. Ended up dropping those pans and always found debris and crap in there plugging up the pick up tube.

My '89 was pretty sludged up when I finally tore it down. Never had any oil pressure issues with it though. Bad choices in oil brands or or change intervals or something from previous owner I'm guessing.

Mine also used a bit of oil and fouled a spark plug over time. It does smoke, it's just not as visible as you think. Usually at start-ups and higher rpm driving.

Drop the pan, you'll find out more info from that and while it's down, swap out the pump.
 
thanks guys that is a good thought, but why would the problem go away with a new filter?

I will plan a pan drop when the temps finally get above zero here in Wisconsin. Probably a smart idea no matter what. It would be cool to get a good look at the bottom end anyway. I've installed a handful of complete engines, but never really pulled a pan on an engine that I've been running in one of my vehicles.
 
It sounds like the engine hasn't suffered any damage,made any clicking,ticking or knocking noises--so I wouldn't be too worried about the weird gauge action...evidently it IS getting pressure to all the bearings and lifters,maybe the oil passages to the sending unit are all sludged up...

You say you used a mechanical gauge in the port above the oil filter to confirm pressure--did it act normally there,even at a cold start?..if so I'd guess it was a partial blockage in the oil passage feeding the sending unit (where I assume you have a mechanical gauge now plumbed into?)...

Another possibility is the oil pressure releif valve in the oil pump might be bleeding off excess pressure when the oil is very thick and cold,and as it warms up and thins out it starts reading normally...there are also by pass valves in the oil filter ports in the block,and might be some in the oil cooler ports,that allow oil to still be fed to the bearings ,etc,should an oil filter plug up or the cooler or its lines get blocked up,those may be sludged up or sticking...

It probably wouldn't hurt to drop the pan someday and put a new oil pump,pickup screen and a metal drive collar on it...a friend of mine had a 283 years ago that had a weird oil pressure problem,the gauge read all over the place at times,and sometimes acted normal--when it acted weird,you could hear the lifters start tapping,then suddenly they would go quiet,and the gauge reading increased...

Years later,when we pulled the engine out to swap it into another truck,he took the oil pan off it--the pickup tube was loose in the oil pump,the screen was partly blocked up with nylon cam gear teeth,and the nylon drive collar on the oil pump shaft was missing,we found it in the pan in peices,stuck in sludge at the bottom...evidently the drive shaft for the pump would slip out of the distributor shaft that drives it and let it stop pumping every so often,we assumed...after putting a new pump in it and a steel collar,and a new pickup tube,it had normal oil pressure again all the time...he also put new timing gears (steel cam gear) and timing chain in it while it was apart too..I was very surprised the cam lobes and lifters and bearings looked ok still!..
 
Diesel,

Thanks. Appreciate the good thoughts. The mechanical gauge showed zero pressure as well, so it confirmed the readings at my dash gauge. Also I took off a valve cover and watched the rockers. There is no oil at the rockers until the dash gauge registers. So unfortunately I'm not at all confident that the bearings etc are getting oil during this period of no gauge pressure.

Last winter swapping the filter took care of it for the little I drove it after that. but this winter I've driven her more and it has been WAY colder all winter. I've changed the filter already once in November only 500 miles or so ago and it is back. I think I'll try and change the filter again to see how much time it buys me keep closer track of miles.

I'm really curious to drop the pan and see what I find.
 
If your showing zero pressure for more than a few seconds,that doesn't bode well...but if things were starved for oil this long ,you should be hearing bearings rattling or the lifters ticking too...usually a bearing with no oil pressure or one thats loose will rattle like a woodpecker when the engine is first started cold in the morning,and may do it after its hot as well...then quiet down after some oil pressure reaches it..

If the oil is too thick for the temparatures it will be sluggish to pump up to the top end until it warmed up some too...but unless your running SAE 30 or 15w-40 ,20W-50 in frigid conditions, thats not likely the cause I'd say though...

Maybe you could try using a larger oil filter,and see if that helps any..on my older 350's I used to put a Wix 51794 two quart oil filter on my trucks,that added a quart of oil to the capacity and helped it run a bit cooler,and I was not worried about having to change the oil at 3000 miles as much..

(I'm going by memory on the filter #,so make sure its correct before using one if you decide to try that!)...some "cheap" filters are constructed quite shabbily inside,especially Fram's,I would not use them unless nothing else was available after seeing a cutaway view of one compared to other brands a salesman showed me at the parts store..

If parts have been oil starved for a long time,you'll probably find a lot of things inside the engine you wont like..worn cam lobes,bearings,etc...but I've also seen some engines in newer vehicles,mostly Jeeps and Chryslers (the 2.7 v6 especially) have oil pump screens completely clogged up with sludge that came in my friends shop clicking and knocking,---after they first started they were quiet,but slowly lost pressure as they warmed up,then started making noises---and the customer wanted him to "fix it"...

He suggested a used engine being a better option than pulling the pan,cleaning out the GUNK that was like tar!-- and hoping a new oil pump and screen "fixed" it,but he did just that at their request,and to our surprise,once the engine was buttoned back up,they not only had good oil pressure again,they actually quieted down after a good 10-15 minutes of running time..so far they are still running ok!..maybe you'll be lucky too..
 
Looking inside an engine that has been maintained with say good oil or even better Synthetic and one that has been not maintained well or used cheap oil is amazing! One will look clean, like metal with some oil on it and the other? Well 1/4 inch of sludge on everything!

Years ago.... well even today some people swear Synthetic ruined their engine or seals. Which is not true. But it cleans so well it does start to breakdown all the sludge from cheap oil.

There was a website with pictures... now gone... that showed a SBC under valve covers that was horrible! It was built up so heavily it almost looked solid? Guy put Synthetic in and changed the filter every 500 miles and cut open filter to show the sludge. After 6000 miles the filters were getting cleaner and valve train under valve covers was looking way better.

How bad did it look under your valve covers?

Be sure to use a Wix or NAPA Gold (which is Wix) filter. All filters or engines are supposed to have a bypass so if filter is clogged the engine will still get oil. I wonder if your changes to oil cooler and oil filter adapter did something bad?
 
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So I did a little test today. I went out to my cold truck, and changed the filter without changing the oil. I just unscrewed the filter and threaded a new on on.

Totally fixed...as soon as I started the truck I had instant great pressure. So this rules out the idea that when I drain the oil, the flow of oil is moving sludge away from the pick up.

The problem seems to be isolated to the filter, and I assume it is getting clogged up. I have run some higher detergent oil/engine cleaners through, so maybe I have loosened up enough stuff that my filters are clogging quickly.

If this is the case, why doesn't the filter bypass allow oil pressure? Should the bypass be allowing the flow of oil past a clogged filter?
 
Currently using a AC Delco PF454. I have to use the shorty because I took out the oil cooler and now the filter mounts vertically. The regular filter is too long when mounted vertically and potentially interferes with front drive shaft when suspension is under compression.

I noticed in the specs for the Wix 57099 (Wix equivalent to PF454) it says there is no bypass valve. Is the bypass valve normally in the filter? I thought the engine block had a bypass oil galley/spring?

Thanks for the link Eagle. I will check it out.
 
Never heard of a small block with a bypass in the filter. Anti-drainback yes, but as you note, the bypass is in the filter adapter.

Only even halfway educated guess I can make is that perhaps the bypass in the adapter is having problems. Might just pull the filter, then remove the adapter (edit: and see if it's working properly). You replaced it, were you having this problem before you pulled the cooler adapter?
 
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Big6ft6 said:
Currently using a AC Delco PF454. I have to use the shorty because I took out the oil cooler and now the filter mounts vertically. The regular filter is too long when mounted vertically and potentially interferes with front drive shaft when suspension is under compression.

I noticed in the specs for the Wix 57099 (Wix equivalent to PF454) it says there is no bypass valve. Is the bypass valve normally in the filter? I thought the engine block had a bypass oil galley/spring?

Thanks for the link Eagle. I will check it out.
Click to expand...
Bypass should be in the adapter for oil filter on engine. There's a drain back on good filters... I think I misworded above and caused some confusion, fixed it and sorry.

What kind of pressure do you get after a highway drive? (You know fully warmed up oil).

Is it making noise when no pressure?
 
By "vertical" I assume you mean the filter is upright,with the threaded base towards the ground?...the fact you changed the filter & adapter does throw another factor into the equasion..

Filters mounted that way should have an anti-drainback valve,so the filter wont be empty after the engine was off awhile,otherwise it will take a few seconds to refill it upon starting and that "lag" can contribute to bearing wear and other parts being scuffed up till pressure builds back up...perhaps the small capacity filter gets sludged up quickly and makes a restriction,so oil has to resort to going thru the by pass valve in the engine?..

Also the oil pump pressure relief valve might be forced to dump some of the pressure off by letting oil dump back into the pan,so things wont blow apart..(I've seen oil filters pop like firecrackers when an oil pump's pressure releif valve failed to work,according to my WIX catalog,its possible for an oil pump to make over 300 lbs pressure easily if not "limited" by a pressure releif valve!..)

Some filters do have by pass valves,as do most engines ,the ones in a small block will let SOME oil flow thru the oiling system when a filter plugs up,but not the full amount it normally would get probably..so instead of getting say,40 lbs,you might get only 25,enough to keep it from seizing,but not optimal either...

Another question,when you removed the oil cooler,did you simply plug off the ports in the block--or make a loop of tubing or hose to bridge them together?..I used 3/8 copper tubing to join the two cooler ports on my 6.2 because I was told by a few guys that it "might" cause oil pressure reduction if I simply plugged them off--others said they plugged them and the trucks are still running strong years later..I didn't want to risk it,so I looped the ports together...my oil pressure came up about 5-10 lbs after I "deleted" the cooler..
 
He already said he removed the cooler adapter, which has the ports on it making it a setup identical to early setups before coolers we're added, no ports to loop cooler lines to from the actual block. And he means vertical in the same way. IFS trucks have a weird adapter that kicks the filter out sideways to prevent any interference with the driveshaft, which is also on the drivers side. Vertical, meaning screwed straight onto the block, old style.
 
When removing the oil cooler adapter though, the smaller thread only adapter is it's replacement, to be able to thread the oil filter to the block.
 
Yes 4xcrazy, you've got it. I completely removed the oil cooler section from between the filer and the block and mounted a traditional filter plate. So now I'm just screwing the filter straight on to the block like old school, with threaded filter base up towards the block. Maybe I should put the cooler plate back on and just run a hose between the ports or plug them off, then i can use OEM filter still. This would rule out my screwing something up by taking off that oil cooler plate.

Eagle: Fully warm highway driving the dash gauge shows 17psi or so (It is a little more than half way to the 30). I remember when I used the mechanical gauge last winter that the dash gauge reads low by a healthy amount. But the mechanical gauge did read zero when the dash gauge showed zero.

No, I hear no noise when I'm experiencing the zero pressure situation. This is weird since it has happened quite a few times now, I'd think if there was really no pressure I'd have messed something up running a 173k mile engine for 5 minutes with no pressure a dozen times when it is below zero temps. But I have visually confirmed no oil at rockers during these periods and no pressure using a mechanical gauge at the oil pressure port near the filter...? Is that oil port above the filter a true representation of engine oil pressure?
 
When I first bought the truck I didn't know where the oil was going (It 'uses' about 1qt in 300 miles) and I thought that it was leaking into the radiator so in my excitement of thinking I solved it I pulled at the oil cooler stuff off.

At the time I didn't realize that I could've left the cooler plate between the filter and engine and just plugged the hose ports.
 
I would think it's safe to say, that you have eliminated that question about it going into the radiator, an obvious visual inspection inside the radiator would have worked too though, but also if oil were going in, then water should have also been getting into the oil as well.

I would hook it back up if you still have everything, nothing wrong with helping keep the oil temps under control.

did you have this problem before the cooler stuff was removed?
 
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