I have a 1999 4.3L with 135,000 miles. I had the intake manifold gasket changed 1,300 miles ago because coolant was in the oil. At the time of the change I sent an oil sample into be tested and it came back with high levels of coolant in the oil of course and 10x the amount of lead, cooper and tin. My suspect that dexcool was attacking the bearings, cylinders and interals was correct.

After the intake gasket change, new oil and filter was put in and switched over to green coolant and got rid of using deathcool. I ran that oil 500 miles and changed it and the filter again. Ran the new oil for 800 miles and changed yesterday with new oil and filter. I have been using Valvoline dino 5w-30 and a PF52 AC delco filter all along 135K on the truck.

When I changed the oil last night I decided to go with Valvoline Max Life non-synthetic for high mileage engines figuring I'll let this run for 3K miles to the next change. I also swithced up to a Mobil 201 filter because I've had good success with them in other trucks.

Ok...the title of the story...Today, I notice the oil pressure gauge dipping below 20psi at idle. I know the range from 20-40 is normal and at higher RPMs it was running near 40psi. After about 1/2 hour of in-town traffic, I got on the highway and started to notice engine knock. Not lifter noise but a deeper knocking sound. As I headed to the nearest exit the pressure started to drop rapidly and finally was down near 5psi at 50mph. I pulled off the ramp and into a gas station and it was knocking really bad by now. Oil pressure near 2psi. I shut it off as soon as I pulled in and checked the dipstick. Dipstick is Grey and smoky with metal shavings on the it. No fluid leaking under it after waiting an hour for a tow. Had it towed to my local shop and walked home in disgust. I figure a spun bearing or broken rod. Rebuild the bottom end or swap out completley?

Any thoughts or comments welcome to a bummer of a day.

 

I know it may be a stupid Q but did you put the drain plug back in? Even oil change places forget. Just double check, You never know.

 

Yep. it's there. I thought of that too. Plus I checked this morning before leaving for any signs of leaks overnight and checked the dipstick to make sure it was 4.5qts. In fact, the dipstick was so clean with new oil this morning I had to check it 3 times to see the full level on the stick.

Thanks for the advice, I wish it were that simple but then I'd feel really stupid if the plug was left out. Now I'm just pissed.

 

Yea, I hear ya! As for your rebuild/replace Q. Its up to what you wanna spend. Check some salvage yards for 4.3, 4.8, 5.3, and maybe a 5.7. See what they want for them and then go see what a rebuild will cost.

 

swap it out with a new engine!! do not roll in only new rods and mains!!! trust me i've rebuilt diesel and gas engines where coolant mixed with the oil and believe me it takes EVERY bearing and thrust bearing and/or washers. Just because the cam turns half the amount of revolutions of the crank doesn't mean s***!! and don't forget about the balance shaft bearings, they all look the same that beautiful fine polished bare copper surface you can be sure of that. i've had engines to rebuild that when i dropped the oil pan the oil looked like thick gray house paint and the water never separated from the oil for over a month, and you need to get every bit of that sludge outta there, so i would definitely swap it out with a reman, you get a warranty and it will be waaaay faster than a total rebuild and piece of mind knowing every journal, oil galley, and ports have no hidden metal flake that you may have missed just waiting for a brand new bearing surface to etch.

Then your right back where you started!!!!

Good Luck!!!

 

Couldn't be further from the truth. Regular coolant would have caused wear on the bearings as well. The damage was done by allowing the coolant to be in the oil. You can blame GM's crappy stock gaskets for that. But think whatever makes you sleep better at night. Hopefully when you put it all back together, you will use the updated metal framed intake manifold gaskets.

It is probably going to be cheaper to swap the engine than rebuild it.