J-money

So I changed the oil today on my 92 RS 5.0L. Immidiately after I cranked it up I noticed a knocking noise from the engine. I usually ran 10w-40 synthetic in the engine but this round I put 10w-30 synthetic in it. Has anyone else ever had this problem before? Im pretty sure the knock is coming from the bottom end. Its never done anything like this before when I've changed oil. Im thinking of just putting some regular 10w-40 in it tomorow to see if it goes away. Any other suggestions or is it about time for me to hunt down a knew engine for this thing?

Stevolwevol

iTrader: (1)

Changing oil viscosity will no cause a knocking sound as you described, and changing back to 10 40 wouldn't make it go away. Does the knock go away after the engine runs a bit?

Edwardgp

I always unhook the distributor and spin motor with starter until I get oil pressure, seems to work for me. Edward.

paulo57509

How's the oil pressure?

You might hear some knocking upon start up immediately after a oil and filter change. But it should only last until oil pressure is built up; a few seconds at most.

Viscosity change shouldn't have affected anything. How about the oil filter? Did you install the same brand of filter that was removed?

J-money

Yeah when I first heard it I was like"it will go away in a few seconds". But it didnt fade off after letting it run for a few minutes so I just now went to the store and bought some 10-40 oil and dumped back in it. It still made a little noise but was noticeable quieter. after letting it run for awhile I could only hear it if I let it idle in reverse. So I took it out for 2 test drives, the first which was easy on it and the second I got on the throttle alot. Now I cant hear the sound at all even in reverse?
So I really dont have any clue what the issue was other than maybe the oil. But Ive never had this thing give me issues when changing the oil before.

J-money

And no I went from a mobil 1 oil filter to a bosch.

Stevolwevol

iTrader: (1)

Well you can bet it's not a spun bearing which should be a relief. I feel a little relief myself. paulo asked about your oil pressure. How is it when the oil is good and warm?

J-money

Yea I cant imagine that its anything to awful bad since it faded away. and Im not sure on my oil pressure honestly my gauge doesnt work right. It started acting up a few years ago and now it only registers when it is cold. after it runs for a few minutes it quits working. I really need to change the oil sending unit out especially with the mileage mine has.

Stevolwevol

iTrader: (1)

Yeah you need to know your oil pressure. If your oil pump is flying south, you could be in for a seized engine.

J-money

how hard is it to get the oil pump off a 92 305 anyways? I've been wanting you pull the engine and rebuild it for some more power for a long time, just cant seem to get the money saved up.

paulo57509

This is a definite red flag. You need to confirm that there is oil pressure at operating temperature and that it's not just a sending unit/gauge problem.

Edwardgp

J-money

I will put a new gauge in when I get paid again hopefully, until then I'll just drive the cavalier around. I think I have a small oil pressure testing kit from harbor frieght tho. I will check and see if I can use that to test it. If it does have low oil pressure when warmed up is there anything else you guys would recommend changing other than just the oil pump itself?

Edwardgp

I am sorry to tell you this but you could [I am not saying for sure] need new crank and rod bearings.

sofakingdom

iTrader: (1)

That's WORK. Why would anybody want to do THAT??

How about, just pour a quart of oil into the filter (through the big hole in the middle ONLY, until it's full) before you put it on?

However all that may be...

Any "knock" you may be hearing now IS NOT due to the oil change (not the viscosity, not the synth, not anything else) and WILL NOT go away by changing the oil again (not to thinner or thicker, not to dino juice or anything else). If it's REALLY knocking, it has mechanical issues, and did before, and will continue to do so; the fact that you noticed it shortly after changing the oil is pure coincidence. But if the oil pressure hasn't changed and the engine runs the same, write it off to timidness and lack of self-confidence, and drive it anyway. After all... it'll either blow up or it will last, and none of the rest of that "worry" and "Cavalier" and all that other crap will change it in the slightest.

If your gauge isn't working right, change the sending unit. Move on. Don't waste your time on a "mechanical" gauge until you've already PROVEN the stock one is beyond resuscitation.

"When in doubt, swap it out".

Oil pumps in this type of motor basically DON'T go bad. Don't even let the thought disturb your peace ever again.

J-money

Update: Put my new oil pressure switch in today after fighting with the old one to get it out. anyway now my gauge is working right again its showing about 55psi when the engines cool running down the highway and about 35-40 when its cool idleing. When its warm its about 25-30ish idling and about 45-55ish going down the highway at 2200 rpm. Its showing alot higher than I expected with the mileage its got on the engine. And its hasn't made any more freaky noises and is still running decent.

So Im hoping this old thing will last me a few more years before its rebuild time.

sofakingdom

iTrader: (1)

Common sense and clear thinking will outscore panic, every time.

J-money

maybe... but I swear that thing did make some strange noise from the bottom end. Every one standing in the yard heard it as well and thought I had forgotten to put oil back in. oh well I'll just keep a close check on everything and hope for the best. Thanks everyone for the help.

TreeFiddy

Several oil changes ago, mine knocked a bit on first startup too. Lasted a few seconds, nothing in the many years since. Put it down to the oil passages in the block and crank being empty, due to me having drained the oil