I have a '01 GMC Sierra with a 5.3. It only has 5x,000 miles on it and runs great. Here's my question. When I start it cold, it's quiet for a few seconds and then it begins to knock. It's a metallic knock, directly variable with engine RPMs. Within 60 seconds or less it's gone and will not return. This is more prominent in cold weather. I don't believe it's piston slap. I don't think piston slap goes away this quick. It's also an on/off type thing. When it quits, it quits. It doesn't just gradually fade away. I'm currently running Mobil 1 5w30. The worst it's ever been was with Amsoil 5w-40. My personal feeling is that it's oil starvation somewhere in the valve train, perhaps a lifter that bleeds down. As soon as oil hits it, it shuts up immediately. That would also explain why the 5w-40 was worse. Oil filters are Wix.
Engine Knock??
- Thread starter blsnelling
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That actually does sound like piston slap IMO. It kind of slowly sets in after you start the engine and then slowly goes away, sometimes within a minute. It usually doesn't just immediately start knocking like a loose bearing or something.
BUT, if you have an aftermarket cam in it, the cam and valvetrain would be the first place I'd look!
BUT, if you have an aftermarket cam in it, the cam and valvetrain would be the first place I'd look!
Try a different brand of oil filter, maybe an AC Delco, and see what happens. It'll only cost you a few bucks to see.
I had an old Monte Carlo and it developed some start up noise. Since the car had over 200k on it, I figured the end was near. However, I switched brands and tried an AC Delco oil filter and the noise went away immediately... and drove the car for another year+ after that, so it wasn't any sort of mechanical issue.
I had an old Monte Carlo and it developed some start up noise. Since the car had over 200k on it, I figured the end was near. However, I switched brands and tried an AC Delco oil filter and the noise went away immediately... and drove the car for another year+ after that, so it wasn't any sort of mechanical issue.
I knew someone was going to mention the cam
It had the same behaviour before the cam was replaced. The rockers and lifters are stock, as is the oil pump and timing chain/gears.
AMSOIL's website has these recommendations:
Engine Oil
Grade 1......API*
Series 2000 Synthetic 0w30 Motor Oil
SAE 5w30 Synthetic Motor Oil
SAE 5w30 XL Synthetic Motor Oil
Series 3000 Synthetic 5w30 Heavy Duty Diesel Oil
Above 0°F......10W-30
I think you figured out the problem with the 10W40 Amsoil European oil being too thick for this application. Maybe try the 0W30?
Engine Oil
Grade 1......API*
Series 2000 Synthetic 0w30 Motor Oil
SAE 5w30 Synthetic Motor Oil
SAE 5w30 XL Synthetic Motor Oil
Series 3000 Synthetic 5w30 Heavy Duty Diesel Oil
Above 0°F......10W-30
I think you figured out the problem with the 10W40 Amsoil European oil being too thick for this application. Maybe try the 0W30?
This knock doesn't slowly fade. It just stops. That's why I didn't figure it was piston slap.
I have the same truck, 01 Sierra 4X4, 5.3L engine with 68K miles. The cold start knock shows up on a sporadic basis in my engine, normally about 10-15 seconds after a cold start-up and is about 10 seconds in length before it fades away.
My comment is that some oils, such as M1, will tend to magnify or transmitt the sound more clearly.
Sometimes I will hear the noise at back to back start-ups, other times I will not hear it for 2 weeks or more.
Since it is sporadic, it makes me think it is related to which pistons end up at TDC when the engine is shut-off. Or the o-ring on the oil pump is not sealing & affecting start-up pumping flow.
I noticed a comment on a GM truck forum that parking downhill-uphill will make a difference & I always make a point, at work, to park on the side of the lot where the nose of the truck is facing slightly downhill, as I definitely have experienced more noise with the nose pointed uphill, such as in my driveway.
Other than that issue, the truck rides smooth & runs strong, probably the best pick-up I have owned over the last 25 years.
My comment is that some oils, such as M1, will tend to magnify or transmitt the sound more clearly.
Sometimes I will hear the noise at back to back start-ups, other times I will not hear it for 2 weeks or more.
Since it is sporadic, it makes me think it is related to which pistons end up at TDC when the engine is shut-off. Or the o-ring on the oil pump is not sealing & affecting start-up pumping flow.
I noticed a comment on a GM truck forum that parking downhill-uphill will make a difference & I always make a point, at work, to park on the side of the lot where the nose of the truck is facing slightly downhill, as I definitely have experienced more noise with the nose pointed uphill, such as in my driveway.
Other than that issue, the truck rides smooth & runs strong, probably the best pick-up I have owned over the last 25 years.
Tell me more about this o-ring on the oil pump. The oil pump is really easy to get to on these engines. Especially since I installed e-fans.
I doubt it's the pick-up tube o-ring since I have good oil pressure.
If you go to the pistonslap.com website, you'll find a link to a TSB on cut o-rings.
Another item I should mention is combustion chamber deposits. Part of the blame for cold start knock is placed on the low daylight dimension between the upper ring & the cylinder dome.
I'm not very consistent with my fuel power treatments, as I'll add it for 1-2 tanks and then get busy & forget about it for the next 2-3 weeks. So I may have varying levels of deposits in the cylinder dome area.
Again, for me it is a bit of a puzzle, as the noise tends to come & go and I haven't been able to pin it down with any of the combinations of variables.
Another item I should mention is combustion chamber deposits. Part of the blame for cold start knock is placed on the low daylight dimension between the upper ring & the cylinder dome.
I'm not very consistent with my fuel power treatments, as I'll add it for 1-2 tanks and then get busy & forget about it for the next 2-3 weeks. So I may have varying levels of deposits in the cylinder dome area.
Again, for me it is a bit of a puzzle, as the noise tends to come & go and I haven't been able to pin it down with any of the combinations of variables.
If it were carbon deposits, wouldn't the noise begin immediately when the engine started?
Have you hooked up an accurate mechanical oil pressure gauge to check on oil pressure during the event?
No I have not. I did install a Bosch Premium oil filter last night. We'll see if that has any effect on it.
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