Chevy 350 oil problems - Non-Marauder (in case you were wondering!)

[Breadfan]

My folks have a '95 Suburban with a 5.7 TBI V8. It has 160,000 miles on it, and has a few issues, but ran well. They haven't been driving it, and it's sat for about a year. A few weekends ago, on a whim, I jumped the battery and got it running. It ran pretty good, so the next weekend I did an oil change on it.

I had noticed prior to doing the change, while letting it idle, that the oil pressure seemed to be jumping around from 70-90. At first I thought it might just be a weak battery if the gauges were electronic. I then thought perhaps it was something like sludge clogging an oil passage.

So I did an oil/filter change. The oil that came out seemed ok, so I didn't think to much of it.

Today I started it up again, and it sounds like a knock has developed in the engine. The oil gauge was back to it's old trick. I only ran it a minute or so, it did get a bit quieter but the knock was still there. I'm pretty sure it's a lifter noise.

After shutting it off, I popped off the oil fill cap and reached in, I was able to feel a rocker arm but it didn't feel very oily...I'm also pretty sure on these engines the oil travels up the pushrod.

So...I'm wondering if I have a clogged oil passage and perhaps was running part of the motor dry. Of course, it's also possible some damage has been caused, but I'm hoping an older Chevy 350 can take a bit more abuse than that. :)

At anyrate, anyone have any ideas? Is there anything I can run in the oil, like Seafoam, to clean the oil passages? Any other issues with these motors that could cause this?

I've got tomorrow to mess with it, so if I can do anything I'll give it a go. I hope it's smoething that can be remedied without engine removal, this truck still has some life in it.

[cyclopsram]

Just dump in some engine cleaner and run it for a while... I usta use Rislone...or some ATF...then change oil and filter again... Those engines will run 100000 miles with the lifters clacking and 20 lbs oil pressure...

[jgc61sr2002]

What grade of oil did you use?

[Breadfan]

5w30 oil was used, non-synthetic Valvoline.

I was thinking of hitting the parts store tomorrow for some engine flush or Seafoam.

[finster101]

1. Use 20w50. It is not a Marauder do not treat it as such.

2. Find "Wynns Tuneup Treatment" Do not put ATF or some other crappage treatment in it.

You have a higher mileage engine whose tolerances were no that close to begin with. Yes the oil is fed up the pushrods however if this has sat for a while it will take some time for it to get up there the lifters take a little to get pumped up, and well just be patient. drop the 5w30 and put the 20w50 in start it up and let it idle. Don't blip the throttle or any of those other fun things to do, just idle. And that thing did not have 90 psi siiting in the showroom floor. Suspect the guage.

[Blackened300a]

We had the same engine in our service truck and it would run on nothing but 10w30. We also went a year without changing it and almost 10K miles without a single issue. Its hard to kill a small block chevy. Just throw some engine cleaner in there and that should clean the passages out and let the oil to the top.

[my_rodder]

Cut the oil filter/s open and look for bearing material. Also, run your fingers through the old oil, looking for debris or metal 'sparkles'.
If possible, run some diesel fuel through the oil system by removing the distributor and spinning the oil pump with a drill and a SBC engine priming tool.
Check the oil pan for dents, and maybe replace the oil sending unit (or hook up your own mechanical gauge).

[RCSignals]

You could try some Marvel Mystery Oil.

[Breadfan]

Well, yesterday I put in 2 cans of CRC engine flush/oil system cleaner, and ran it for about 10 minutes. The noise actually went away fairly quickly and was less pronounced when starting it this time than it was the day before.

After that I put in fresh oil and installed a fresh filter.

The noise appears to be gone. I did notice that after letting it sit a few hours and starting it, I heard a bit of noise for about half a second, but it quickly vanished and the truck ran smoothly with no engine noises.

I'm thinking I may be OK, perhaps this thing just needs to be driven and get some hot oil cycling through it more often. That was one reason I've been working on it - cars need to be run, sitting for extended periods and they magically breakdown. :)

Oh, I ran a bit of Seafoam through the throttle body, and put the rest of the can in the crankcase after putting in the fresh oil.

The oil gauge does still seem to fluctuate, but it does stabilize at times. Also, when the oil got hot the pressure dropped and held steady around 40psi.

I think it may have a sender that's on it's last legs...

[Breadfan]

Just an update, I stopped by there this weekend and started the 'burb again. I heard the slightest bit of noise for about 1/10th of a second but aside from that it was running great!

Sounds like the flush did the job.