Chevy Silverado 350 V8- no oil pressure?

[Johnshan1]

Hey everyone, latley my oil pressure has been dropping to zero when driving for a second or 2, the idiot light comes on and then it goes back to 40-60 psi. Since it made no noise and ran great I assumed it was a bad sending unit.<br /><br />Well tonight I got off the highway and the pressure dropped to zero again and stayed there- I heard tapping noises, I put it into N and gave it a quick rev and it shot back up to 40 psi and the ticking went away.<br /><br />I got home and changed the oil and filter, which had 5,000 miles on them. The problem is now gone, I have 60-80 psi when cruising and 40 psi at idle steady.<br /><br />What do you guys think happened? Clogged filter or what? Makes me nervous, it has 170,000 miles on it and has always had regular oil changes at 3,000 miles this past time was the longest I had ever gone without one (5,000 miles).<br /><br />I plan to cut the filter open and see whats inside it tommorow night.<br /><br />Thanks for any ideas<br /><br />-John

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

By the way it also burns no oil between changes, and was full when I changed it tonight.

 

[LubeDude]

Re: Chevy Silverado 350 V8- no oil pressure?

Wasnt a Fram filter was it??????

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

No way would I use one of those!!!<br /><br /><br />It was a Purolator filter- I usually use AC Delco filters, thats what I used this time around. I dont know if Purolator is any good or not- but I have not heard anyone bash them.<br /><br />-John

 

[John Carpenter]

Re: Chevy Silverado 350 V8- no oil pressure?

Had this exact same problem a couple of years ago. Oil pressure would come and go...happened every few months & went away quickly. I too thought it was a bad guage or sending unit. Cost me an engine.<br /><br />Have you by any chance recently changed to a "high milage" oil? I had and the increased detergency broke loose all sorts of sludge that clogged the intake screen on the oil pump. When we pulled the pan, the 3" diameter intake screen had an opening about the size of a pencil for the oil to flow through. I would recommend dropping the pan to check it out...might end up getting out cheaper than I did

 

[dolluper]

Re: Chevy Silverado 350 V8- no oil pressure?

Good call on the pickup or just the oil pump getting worn might be worth a peak<br />also check the drains in the heads that they aren't cruded up,alot of short trips and infreqent oil changes causes the drains to crud over not your case I don't think

 

[DJ]

Re: Chevy Silverado 350 V8- no oil pressure?

Oil pressure is hydraulic. It doesn't just come and go unless:<br /><br />1. There is a restriction that is "moving", eg, sludge.<br /><br />2. Low oil level causing the pump to draw air.<br /><br />My vote goes for something moving around the oil pick up area.

 

[sangerwaker]

Re: Chevy Silverado 350 V8- no oil pressure?

Buddy of mine had similar problem on his Ranger. Turned out to be pieces of the neopreme oil pan gasket were floating around in the oil pan and clogging the intake screen.

 

[markvan]

Re: Chevy Silverado 350 V8- no oil pressure?

I can second what sangerwaker is saying I had the same problem a number of years ago, drove me nuts trying to figure it out, finally dropped the oil pan and wow pieces of gasket material, cleaned it up, put her back together and never had a problem since

 

[LubeDude]

Re: Chevy Silverado 350 V8- no oil pressure?

All these are good replies, The pickup screen would have been my next place to start. Chevys are not on the list of sludge monsters and this is a rare problem in 350s. The pan is not that easy to get off, you will likely have to unbolt the engine mounts and jack the engine up somehow to remove the pan. Any oil filter can fail though. how is it now that you changed the filter?

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

Thanks guys for all the info, im going to drive it a bit more and see what happens- since I changed the oil and filter last night my oil pressure is steady at 60 psi when driving just like before, at idle its at 40 psi steady, I have had no more issues with a loss of pressure.<br /><br /><br />Before if I went to pass or merge onto the highway, the oil psi would actually drop to 20 psi and hold there until I let off, at which point it would goto 40 psi and dance around.<br /><br />But again it seems 100% now that the oil is changed.<br /><br />-John

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

Well I took the old filter apart, nothing seems to be clogged or any different from a normal used filter. I bet your right on with the oil pump pickup being clogged, maybe its time for a new truck.

 

[LubeDude]

Re: Chevy Silverado 350 V8- no oil pressure?

How many miles on this truck? Also, have you owned it sense new? What oil are you using, and what intervals have you changed the oil? Have you always changed at about 5,000 Miles? Have you recently changed brand of oil?

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

The truck has 170,000 miles. I have owned it for 50,000 miles and have always changed the oil every 3,000 miles. This last time I used Supertech walmart oil 5w30 usually its castrol this last night I used havoline.<br /><br />When i bought the truck it didnt have a hitch but it had a ball on the bumper and a wire harness. <br /><br />When I bought the truck I put a 7 1/2 foot snowplow on it, so basically I have run the truck hard but maintained it well. It was in great shape when I bought it with original ball joints, tie rods, ect so it wasnt beat on as far as I can tell.<br /><br />-John

 

[Bob_VT]

Re: Chevy Silverado 350 V8- no oil pressure?

It would drop when you got on the pedal? That is an indicator that you are low on oil by about a quart. I had an Alfa Romeo that would do the same exact thing and that was a big signal to check my oil.<br /><br />Bob

 

[Johnshan1]

Re: Chevy Silverado 350 V8- no oil pressure?

When i checked the oil it read full on the dipstick, cold and hot motor same reading.

 

[Realgun]

Re: Chevy Silverado 350 V8- no oil pressure?

The oil bypass on the filter was beginning to fail for some reason. You should be fine. But just keep an eye on it.

 

[LubeDude]

Re: Chevy Silverado 350 V8- no oil pressure?

I dont think you have a sludge problem, not to say something might be running around in the pan though, My bet is with Realgun on this, just keep an eye on it. Even though the relief valce on Small Block Chevys is in the oil filter adapter and is relacable. Like I said before, those 350s are not known to sludge up with decent maintenance.<br /><br />At least youre not blaming the SuperTech oil, Actually its a decent oil for the money and surely wont cause any harm.