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My one owner(me) 1996 Silverado with 5.7L 350 8 cyl. 2WD 286000 miles I took it in to get the heater core replaced after I smelled and found coolant in the cab floor (not the first one I've had to replace but it has been a couple of years ) I had no other issues that I knew of but as soon as I picked it up the service engine light came on and I saw no oil pressure. I took it back and asked if they would check it. They told me it was nothing to do with what they worked on but would check it. When I went back they said I needed a new motor. I drove it 50 miles home. It did not over heat or make noise but it still showed no oil pressure. I took it to a local guy who had recently changed the rotor, distributor cap, wires, and sensors, and oil, and he replaced the oil pump and put a mechanical gauge on the dash. After I picked it up before I got home the check engine light was on again. I took it back and he just said he didn't know what it was unless maybe the computer. So I took it to another guy and he tells me that it had spun a bearing and the only option is to replace the motor. Then another guy says he can replace the bearings and it's not big deal parts plus a hundred or two for labor. I still have no lifter noise, no knocking, maybe a miss at idle if I listen hard, I'm not sure. Can anyone tell me something different?

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My guess is that at 286K miles, the motor is getting tired. And replacing bearings is probably just a band-aid at this point.

 

This is why some recommend you replace the motor. Think of how irritated you'd be if you spent the money to replace the bearings (cam I assume) and then something else goes. It's your money, but you may be chasing an endless list of worn out parts.

 

I'd replace the motor, but that's me.

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My guess is the oil pressure sensor is not communicating with the computer and that's why you're getting the check engine light. If the mechanical gauge is showing pressure at speed then you've got oil pressure and you should if you got a new oil pump. If it has oil pressure at speed and the pressure goes to or near zero at idle, the bearings can't hold pressure at idle and that means they are badly worn which you could expect at that mileage. If you've got 10 - 20 PSI at idle on the mechanical gauge I would double down on the sensor/computer link. In that case it could be the sensor (replace it), the connection between them (trace it out and repair it), or the computer (reset it first and if that doesn't help it may need replacement. you might try just disconnecting it and reseating the connections).

 

That part about resetting the computer reminded me of something on my 94 GMC Sierra. I left the driver's side window cracked at top because it was a hot summer day and we had a heck of a storm that came through. When I opened the door the next day there was a lot of water on the floorboard and, on mine, the computer was under the seat on the driver's side. I got some wierd messages out of it and the truck was fairly new at the time. I pulled the computer out, took the cover off, and blew it out with light compressed air (10 PSI) and hit it with a hair dryer to make sure it was good and dry and did the same thing with the connectors. When I put it back in everything was OK. I'm still driving it today. What made me think of it was your leak from the heater core but that's on the other side of the transmission tunnel so I doubt that's it because I don't think the water could get to the driver's side.

 

If you've got a long steel rod, say 3 feet or so, place one end somewhere on the lower part of the block and cup the other end with your hand and around your ear. If you've got a spun bearing or worn bearings you might hear a thumping sound coming from end of the rod by your ear. It's a poor man's engine stethoscope. If you do hear the thumping sound, it's time for a new engine pretty soon.

 

If all of that doesn't turn up anything just keep driving it until something really gets your attention. That, however, may leave you stranded somewhere if it goes all at once.

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  • 2 weeks later...

Correction: the part about the computer getting wet in the earlier post must have been some other car I had. I rebuilt the dash in my 94 Sierra last weekend and the computer is in the far right side of the dash, to the right of the glove box. So it's possible the leaking heater core sprayed water up there depending on how it was leaking. Or possibly hot water vapor condensed on the case and ran into it. It also may had been jostled around when they replaced the heater core so check the connections. The easiest way to check it is to remove the glove box.

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