I don't have an engine prone to piston slap, and I've read and listened to a bunch of the reports on the GM issues. It makes me wonder if one could definitively tell cool engine lifter tick from piston slap, with or without a stethoscope. From all of the online descriptions and recordings of piston slap they may not be easy to tell apart.
How to tell piston slap from lifter tick?
- Thread starter Craig in Canada
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In my experience, depending on the stage of wear, both can sound exactly alike. Just keep driving and the reality will manifest itself over time.
If you still can't tell the difference after 3-4 years or 40,000 miles, it's a lifter.
If you still can't tell the difference after 3-4 years or 40,000 miles, it's a lifter.
To my ears piston slap has a much lower frequency sound than does lifter tick.
Once you have heard both they are easy to tell apart. Piston slap really sounds like a knocking, whereas lifter tick sounds more like a "tick" hence the name.
In addition, some cars can have both, or exhibit one or another depending on various conditions.
Lifter tick will usually start as a slight tick a few seconds upon starting the car in the cold and quickly goes away and develops into something that happens all the time. Piston slap may start off only when the car is hot, or when cold, or anytime really.
Lifter tick will usually be helped by thinner oil. Piston slap will usually be helped with thicker oil.
Once you have heard both they are easy to tell apart. Piston slap really sounds like a knocking, whereas lifter tick sounds more like a "tick" hence the name.
In addition, some cars can have both, or exhibit one or another depending on various conditions.
Lifter tick will usually start as a slight tick a few seconds upon starting the car in the cold and quickly goes away and develops into something that happens all the time. Piston slap may start off only when the car is hot, or when cold, or anytime really.
Lifter tick will usually be helped by thinner oil. Piston slap will usually be helped with thicker oil.
Pull the plug wire or injector connector to each cylinder one at a time, knock/slap goes away then you found it. This will diag which one is slapping, or if there is no change while doing that you might have a lifter or exhaust tick.
Thanks everyone for contributing.
The engine in question is a 1998 BMW M52 (2.8L I6) that's extremely well cared for and has about 127,000km on it. The noise in question generally only occurs when the engine is partially warm. In the summer, coolant temps ~30-50C may do it. In the winter it's a similar range but cooler. Let's say from about 30 seconds after start to 120 seconds, or when restarting while still lukewarm but significantly below operating temperature.
Last summer I decided to ARX it, partially for the heckuvit, partially to see if I could silence this assumed lifter. The car previously ran on M1 0W40 and the tick was audible but didn't stand out. I used Esso XD-3 15W40 HDEO as my ARX clean and rinse oil. Immediately the tick became prominent, not because it got louder but because the rest of the engine got so much quieter. I'm a believer in the M1 noise issue now, BTW.
Part way through ARXing, I noticed that this sound was coming and going. TICK TICK TICK tu tu tu TICK tu tu TICK TOINK. I figured maybe ARX was working. By the end of ARX it was much quieter. Nothing was ever really evident far off of idle or when thoroughly warmed up.
I now use GC w/ LC-20. It's winter here, so I don't spend a lot windows-down time but the other day I noticed that the tick was noticeably clearer again, and possibly happening for a longer time in a wider range of temperatures. With the way it consistently occurs in certain temperature ranges I starting wondering about piston slap as a possibility, although it's only one cylinder doing it, which led to my question.
I may try the injector disconnection method to try to find if it is slap or lifter. I didn't like the plug disconnection method because of fuel washdown. It might be tricky to get through the whole process while the sound is clear and before it stops on its own.
Cheers,
C
The engine in question is a 1998 BMW M52 (2.8L I6) that's extremely well cared for and has about 127,000km on it. The noise in question generally only occurs when the engine is partially warm. In the summer, coolant temps ~30-50C may do it. In the winter it's a similar range but cooler. Let's say from about 30 seconds after start to 120 seconds, or when restarting while still lukewarm but significantly below operating temperature.
Last summer I decided to ARX it, partially for the heckuvit, partially to see if I could silence this assumed lifter. The car previously ran on M1 0W40 and the tick was audible but didn't stand out. I used Esso XD-3 15W40 HDEO as my ARX clean and rinse oil. Immediately the tick became prominent, not because it got louder but because the rest of the engine got so much quieter. I'm a believer in the M1 noise issue now, BTW.
Part way through ARXing, I noticed that this sound was coming and going. TICK TICK TICK tu tu tu TICK tu tu TICK TOINK. I figured maybe ARX was working. By the end of ARX it was much quieter. Nothing was ever really evident far off of idle or when thoroughly warmed up.
I now use GC w/ LC-20. It's winter here, so I don't spend a lot windows-down time but the other day I noticed that the tick was noticeably clearer again, and possibly happening for a longer time in a wider range of temperatures. With the way it consistently occurs in certain temperature ranges I starting wondering about piston slap as a possibility, although it's only one cylinder doing it, which led to my question.
I may try the injector disconnection method to try to find if it is slap or lifter. I didn't like the plug disconnection method because of fuel washdown. It might be tricky to get through the whole process while the sound is clear and before it stops on its own.
Cheers,
C
GM 5.3L piston slap is much louder than a lifter tick. Not a loud as a bent connecting rod or bent pushrod but almost. One way to really distinguish with this engine is in warm weather and on start up. When the engine has sat for 6-8 hours plus and all the oil is back in the pan on start up you will get lifter tick but not very much piston slap if it's over 70 degrees out. Plus if you use 10w30 or 10w40 it will leave enough oil film on the cylinder walls to prevent slap almost completely.
Could this be friction gear noise? Or even just the fuel injectors making noise? I know the Bosch fuel injectors on the VW made a considerable amount of noise from day 1 to when i sold it 10 years later.
Piston slap to me is much deeper and louder. It also seems to go away when the engine warms up.
I agree it's probably a lifter, but I needed to educate myself on what the difference really is, since based on online sound samples (yes, I know they are of the highest reference quality
there are some things in common.
Yes, I can't rule out a REALLY noisy injector, but since it happens in specific temperature conditions I am inclined to feel that it's something more closely related to the block temperature and an injector which would still have a flow of very cold fuel through it for a significant amount of time after startup (in winter).
Craig.
Yes, I can't rule out a REALLY noisy injector, but since it happens in specific temperature conditions I am inclined to feel that it's something more closely related to the block temperature and an injector which would still have a flow of very cold fuel through it for a significant amount of time after startup (in winter).
Craig.
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