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I have a 1992 Toyota pickup with 90,000 miles. It has always been taken care of. One day I noticed a knock, which was barely noticeable. You couldn't even hear it with the heater on but it progressively got worse. It ran to the point where it's louder than the engine in a matter of minutes but hasn't gotten any louder.

Since then, I've driven it less than 8 miles. I have been told by multiple people they think it's a rod knock but the knock will cut out for around a second at odd times, like when you come off the gas and push in the clutch.

I may be wrong, but wouldn't a rod knock be continuous? At the same pace, after we took it to a professional mechanic, (who did nothing after two weeks but listens and say they thought it could be rod knock) I picked it up and drove it 2 miles home. It's developed almost three other knocks, so I guess I could have spun other bearings.

I let it run for awhile. At first oil pressure was normal and then after about 10 minutes oil pressure dropped significantly. When I revved it, it would bring oil pressure back up but only for a little.

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  • What is the history of oil changes for this car? ( every 5000 miles or so without fail?). History of no coolant ( oops , missed that leak) over heating?
    – zipzit
    Commented Apr 6, 2018 at 3:25
  • I added punctuation to your post to make it easier to read. Hopefully I didn't inadvertently change the meaning of anything.
    – CharlieRB
    Commented Apr 6, 2018 at 13:26
  • Do you know what part of the engine the knock is coming from (top, bottom, front, rear)? Also, what was the oil pressure and what was it when it dropped "significantly"?
    – CharlieRB
    Commented Apr 6, 2018 at 13:32

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From what you have described, sounds like you have a spun main bearing. Obviously that is a guess. If you read what @Paulster2 wrote in his this answer, it helps explain a lot about the oil pressure fluctuation.

wouldn't a rod knock be continuous?

Not necessarily. This will depend how bad the bearing condition is. As the gap continues to open, there will be more slop for the rod to move around. Each time the cylinder fires, it will slam the gap shut. In some cases, you may not hear rod knock unless the engine is under load or the engine RPM is increased.

My advice to you is not to run the engine anymore until you get it repaired. Every time you run it, you take the chance of damaging more components and the cost of repair climbs.

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