Piston Slap and EP Additives

[DeepFriar]

I have a 2004 Buick Rainier (don't ask) with the aluminum 5.3L, LM-4 V8. They're known for enough piston slap noise to convince you, no doubt about it, the crank is about to knock enough to tear out the bottom. *Everybody* says, "don't worry about it, it's just the way it is". But.... I was out of town and had time on my hands, i.e., needing some time away from relatives, and I dropped into a quick change place and told them to just use 5-30 PYB and out the door. Two things: normal use is 5-40 Motul (mostly PAO I assume) and the piston slap is there but only about 25-30% as loud. Secondly, it occurs to me that there may be some washoff of one add package for the new one and it has not had time to *deposit* the new package. But the other concern is the possible change of HTHS has had the most effect. Bearing in mind that the slap will never completely go away:

Would piston slap in an aluminum motor be *helped* from a wear standpoint by going to and sticking with a very high moly like RL or similar? Or,

Would staying with an oil with goodly HTHS be enough to reduce the noise AND limit the wear? In other words is expensive, high moly RL or similar indicated or should I just stay with (the much less expensive) Motul?

Even if *they all do it* that absolutely gets my attention on cold start! It can still be lightly heard at idle when warm. What say?

Cheers and thanks.

 

[CT8]

Try some oil and see.

 

[DeepFriar]

But I won't be able to *see* if the moly is laminating like I hope. Yes, some future UOA may tell the tail. As I said, some remnant of the noise will always be there based on past experience. I was just looking for well informed opinion from all my fav oil friends. And speaking of cold starts, how are things in Idaho this week? ...€

Cheers

Larry

 

[PeterPolyol]

Had a recent revelation that what I thought was piston slap for many years in our 3500 V6 is more than likely sloppy lifters. Just a heads up these GM pushrod engines all use the same lifters, and on a few occasions I've heard replacing the HLAs solved the problem. Nonetheless, I've ran SAE40 in it trying to eliminate the "pistons slap", but it turned out it was the absolute loudest, regardless of ambient temperature.... it "slapped" louder on SAE40@21C (room temp) than conv. 5W20 does at -20C!
As with all these engines, the noise goes away in relatively short order, no matter what's in the crankcase. Not to say that your issue is lifters, but I can't help wonder how many of these grotesquely-knocking GM push rodders are just sloppy cold lifters.

But to the OP, over the years I've tried many oils and additives, esters, moly etc... never found anything that eliminated it. YMMV

 

[DeepFriar]

Thanks Peter and you raise an interesting issue. The pre-AFM engines in the early 2000's had what I would call a detective EGR system. The path back out of the valve cover was poorly positioned, wrongly shaped and caused too much oil to be fed back into Cyl 1. This caused ring contamination with attendant wear and general gunking up. I've wondered how much of that accounts for *slap* as well. While changing over to the 2007 valve cover *fixed* that there is still an unknown 120K miles of unknown consequences. That being said, my knocking seems to be of lower sound frequency and lower down in the motor than a valve. That's why it scares me. And BTW I have seen exactly what you describe about the different oils. Another reason I was asking the original question.

Thanks again

Larry

 

[PeterPolyol]

Do you have a boroscope you can stick down the Cyl1 spark plug hole to check for any anomalies like lapping grooves or excessive carbon? Could help eliminate/implicate the EGR effect... our 3500 is a quirky one; only 2 of the 6 pistons have piston oil squirters! Such a GM thing to do.... perhaps it's to address uneven bearing discharge (splash lube), who really knows lol.

On the real, I'd stick with 5W30 from now on. What we logically expected to happen with a thicker oil film, higher HTHS, more cusioning etc has yeilded an inverse result.... more viscosity = more noise.

 

[DeepFriar]

Good idea. No I haven't looked with a scope and I had to be away when the guys changed the valve cover to 2007 type so I wasn't there to ask. But that was nearly two years ago. You're right, time for a look. That is one weird fact about the viscosity. I saw it too. But going to a 0-30/0-40 didn't seem to help and different *heavyweights* were variable too which th is what got me wondering about add pack washoff. I'm old school and terrified (j/k) of any x-20. I guess my thought process had been - darn the noise, if I can get needed protection via the super high EP types then I'll go that way. The search continues. Next up - 5-40 T6.

 

[CT8]

Originally Posted by DeepFriar
But I won't be able to *see* if the moly is laminating like I hope. Yes, some future UOA may tell the tail. As I said, some remnant of the noise will always be there based on past experience. I was just looking for well informed opinion from all my fav oil friends. And speaking of cold starts, how are things in Idaho this week? ...€

Cheers

Larry

You won't see the moly laminating even if you took the engine apart. Moly doesn't laminate. Try the oil and see if it cushions the parts . That is all you can do and the cost is less than an engine rebuild. Idaho is cold and rainy

 

[Rat407]

I have it in my 2002 Silverado with 186k miles on it. Tried all kinds of different weight oil and it never changes.

A friends 2003 Silverado and anothers 2005 Suburban have it, they both have 365k and 353k miles. They have put nothing but the least expensive oil in at 5k to 8k oil changes. Noise still there.

So if you find a good product that quiets the noise let me know. As for longevity, it isn't a concern.

 

[krismoriah72]

Originally Posted by Rat407
I have it in my 2002 Silverado with 186k miles on it. Tried all kinds of different weight oil and it never changes.

A friends 2003 Silverado and anothers 2005 Suburban have it, they both have 365k and 353k miles. They have put nothing but the least expensive oil in at 5k to 8k oil changes. Noise still there.

So if you find a good product that quiets the noise let me know. As for longevity, it isn't a concern.


I hate to even post this but I have gotten rid of my startup noise in my 2003 Suburban 5.3. I got it with 212K miles with a distinct slapping at startup that lasted about 5-10 seconds. I attacked the noise from a few different angles so i am not sure if one or all did the trick.

First thing i did was add Liqui Moly Pro-Line Engine Flush to the oil.. then I did a Mopar Combustion Chamber Cleaner cycle thru the intake. I followed the instructions and used the whole can and let it soak with the engine flush and the combustion chamber cleaner soaking. I dropped the oil after a few hours and changed with Rotella 5w40 and a PF46 filter.. and added a can of Liqui Moly Hydraulic Lifter Additive. I then took it on a spirited drive as per the end of the combustion chamber cleaning cycle.. The startup noise has not returned.

Edit.. i had Redline Si-1 in the tank also.

I have had to replace a couple of oxygen sensors since I did that chemical overdose after about 2500 miles.. perhaps it was coincidence.

 

[Trav]

The Cadillac N* was famous for this racket at cold start but it was not piston slap in most cases it was carbon buildup. It may be slap but its worth trying to rid the engine of excess carbon.
Get two bottles of top engine cleaner for a V8, one of these will do.

https://www.amazon.com/Genuine-Toyo...mp;psc=1&refRID=8RB4AR1YNC005NEMNM9D

https://www.amazon.com/Subaru-Genui...4&keywords=subaru+top+engine+cleaner

T into a vacuum source and manipulate the flow by kinking the hose with the engine running at 2K RPM, shut the engine off let it cool and remove the plugs. Spray this into each cylinder, soak it down good..

https://www.amazon.com/Genuine-Chrysler-Accessories-4318001AD-Combustion/dp/B00BV4D97K

Let it sit overnight then tighten the plugs and fire it up, warm it up and run it hard for a few min. The N* engines I did this way were quiet as a church mouse the next cold start and remained that way. If it is slap, forget it nothing with help it much.

 

[slo town]

We have a Honda with the K24 motor. It has some really nasty piston slap when cold. When I first take off down the street sometimes I swear I can feel the knock in the pedals. Anyway, I have experimented with 4 or 5 different oils, including Redline. Nothing has made any difference with our K24. Anymore, I've taken to let it idle for a minute or two after a cold start. But still, it takes 5 minutes of drive time before the knock starts to lessen. I should add that it uses about 1/4 quart per 5k OCI. Not bad for 185k miles. We bought it new.

FWIW,

Scott

 

[DeepFriar]

Hey Trav. Well that's good news to these ears! Thank you sir.

 

[A_Harman]

My Camaro has had cold start piston slap since I bought it new.
I have run a lot of different 30-weights over the years, and none of them affected the noise.
I have found that if I rev the engine to 1700 rpm, the noise goes away. Maybe it's more oil spraying on the cylinder walls, or maybe it's the pistons don't have time to rock in the bores.
But once the engine runs for a few minutes, the piston slap noise goes away at idle.
The engine noise is quietest after I come in from a good thrash on a racetrack.
I wouldn't worry about longevity; mine's been noisy for 270k miles.

 

[sweezy722]

I had a 1998 350 engine I drove for 17 years with what I thought was piston slap. After 17 years and 250K miles it bent a valve on the passenger bank. I replaced the valve and new springs for the passenger head. It engine has been quiet ever since.

 

[JustN89]

Originally Posted by DeepFriar
I have a 2004 Buick Rainier (don't ask) with the aluminum 5.3L, LM-4 V8. They're known for enough piston slap noise to convince you, no doubt about it, the crank is about to knock enough to tear out the bottom. *Everybody* says, "don't worry about it, it's just the way it is". But.... I was out of town and had time on my hands, i.e., needing some time away from relatives, and I dropped into a quick change place and told them to just use 5-30 PYB and out the door. Two things: normal use is 5-40 Motul (mostly PAO I assume) and the piston slap is there but only about 25-30% as loud. Secondly, it occurs to me that there may be some washoff of one add package for the new one and it has not had time to *deposit* the new package. But the other concern is the possible change of HTHS has had the most effect. Bearing in mind that the slap will never completely go away:

Would piston slap in an aluminum motor be *helped* from a wear standpoint by going to and sticking with a very high moly like RL or similar? Or,

Would staying with an oil with goodly HTHS be enough to reduce the noise AND limit the wear? In other words is expensive, high moly RL or similar indicated or should I just stay with (the much less expensive) Motul?

Even if *they all do it* that absolutely gets my attention on cold start! It can still be lightly heard at idle when warm. What say?

Cheers and thanks.

Not the same engine, but I've got a GM 3.4L V6 that has some pretty noticeable piston slap. I tried a high moly oil (Schaeffers 5W-30) and it was much more noticeable than the previous run of Castrol Magnatec. HTHS might make a difference, but I don't think moly does.

 

[Virtus_Probi]

Originally Posted by Trav
The Cadillac N* was famous for this racket at cold start but it was not piston slap in most cases it was carbon buildup. It may be slap but its worth trying to rid the engine of excess carbon.
Get two bottles of top engine cleaner for a V8, one of these will do.
https://www.amazon.com/Genuine-Toyo...mp;psc=1&refRID=8RB4AR1YNC005NEMNM9D
https://www.amazon.com/Subaru-Genui...4&keywords=subaru+top+engine+cleaner
T into a vacuum source and manipulate the flow by kinking the hose with the engine running at 2K RPM, shut the engine off let it cool and remove the plugs. Spray this into each cylinder, soak it down good..
https://www.amazon.com/Genuine-Chrysler-Accessories-4318001AD-Combustion/dp/B00BV4D97K
Let it sit overnight then tighten the plugs and fire it up, warm it up and run it hard for a few min. The N* engines I did this way were quiet as a church mouse the next cold start and remained that way. If it is slap, forget it nothing with help it much.

Subaru sells a special tool for introducing their cleaners through a vacuum line if you care to track one down and shell out for it...took me a bit to find one, ended up ordering it from a dealer in Colorado (believe it was the Heuberger seen in Trav's link).
I have found it to be very handy for that kind of cleaning process...they actually sell two types of cleaner, the Carbon Clean and Top Engine Cleaner. The former has an overpowering bleach smell while the latter has a typical hydrocarbon stench.

 

[aquariuscsm]

My 2nd 3000GT had piston slap ONLY with Castrol Syntec. Dino oil,it was smooth and silent!!

 

[Snagglefoot]

Originally Posted by aquariuscsm
My 2nd 3000GT had piston slap ONLY with Castrol Syntec. Dino oil,it was smooth and silent!!


And certainly this is believable, but maybe the real truth is the following:

" My 2nd 3000 GT had a piston slap only with motor oil that had a Kv 100 of X. With a Kv 100 of Y, it was smooth and silent!

It would be handy to know the weight and Kv 100 and Kv 40 numbers of those two motor oils.

 

[aquariuscsm]

Yeah that was so long ago. It was the old bottle Syntec 10W30. That car hated that oil. It gave it piston slap whether on cold or hot startups. I wonder what the additive makeup of that old (it was either SL or SM rated Syntec) Syntec was?