I have a 1995 Chevy k1500 4x4 with a 350 v-8 that has 95,000 miles on it. I've always ran 5w30 in the winter and 10w30 in the summer. Well last winter (while using 5w30) it would knock loud after start up, but not ever time, about 1 out of every 6 times I'd start it. This would only happen after sitting aleast for a couple of hours. It would knock very loud until I'd pull out onto the road and put some load on the engine. The oil pressure was fine and would pump up fast every time. I changed the oil twice and flush the engine (which was already very clean under the rocker covers) with no change in the problem. So I changed oil again, going back to 10w30 and the problem is gone. I'm guess I have a lifter that was bleeding off with the thinner oil and is ok with the thicker 10w30. And guesses?
engine knock and oil viscosity
- Thread starter Doc Holiday
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Doc Holiday,
I am no expert, but this sounds like the ADV on the filter is malfunctioning. A simple filter brand change might solve your problem. I always had good luck with Napa(Wix)filters. Just a thought.
I am no expert, but this sounds like the ADV on the filter is malfunctioning. A simple filter brand change might solve your problem. I always had good luck with Napa(Wix)filters. Just a thought.
tried several filters...none helped...only changeing to the 10w30 stopped it....thanks though...the filter was my first place to check.
Doc I had the same problem with my VR6. I changed to 0w30 GC and had terrible startup knock (especially if it sat around for a few days). I've since drained it and now have thicker mixture of M1 ~ 10w-40 and the problem has disappeared. I think some of the thin 0w-xx and 5w-xx oils don't stick to the internal parts for very long, and drain back to the pan.
Are you calling valve clatter knock?
If your engine "knocks" it is already damaged and won't hold on much longer.
A noisy start and engine knock are not the same thing.
If your engine "knocks" it is already damaged and won't hold on much longer.
A noisy start and engine knock are not the same thing.
JTK
$100 Site Donor 2025
How's your oil pressure? This sounds like piston slap to me. I had a 1998 chev K1500 with a 4.3L that would do the same thing.
G/luck
Joel
G/luck
Joel
its not piston slap...its a lound knock that sounds like a rod will fly threw at any second. And if it were badly damaged, it wouldn't just stop with the 10w30. I've had cars with piston slap...they would have a "light" knock until the engine warmed up. This loud knock stops after the engine is under a load. And I had lots of oil pressure.....thats why I was thinking a lifter that is "bleeding off and sticking" after it has set all night......I can't make it do it with 10w30.......
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