Piston slap
Thread Starter
Junior Member
Joined: Feb 2007
Posts: 33
Likes: 0
From: So Cal
2000 E55 Designo Silver; 2007 BMW 335 hardtop convertible and 2016 Audi SQ5
Piston slap
The previous title of my post was about the need to replace lifters.
Background info: My 2000 E55 engine developed a klacking noise at start up from a cold engine. The klack goes away after about 1 to 2 minutes of idling. The dealership said it was lifters, but first try to clean out the injectors. That was done without any result. At a cost of over $1,200, the lifters were replaced. The klack was still there. Then a cleaning of the engine with some type of fluid was done. Still klacking. Next the timing chain tensioner was replaced. No change. Next the solution was to change the timing chain. However, with only an 80% chance that would solve the klacking, I put further repairs on hold.
Piston slap: I had my retired airline avionics tech brother-in-law listen to the klacking last week and he said it sounds like piston slap. I never heard of piston slap, so I researched it on the internet/youtube. The sound I hear on my E55 sounds just like some of the engines with piston slap on youtube videos.
I read that the cause of piston slap is due to a piston being smaller than the cylinder and thus the piston hits the sides of the cylinder causing the klack until the engine heats up and the piston/cylinder expand.
Uncertain: The klack started at about 103,000 miles. The engine is now at 107,000. I don't understand why it started. The car has been faithfully maintained.
Plan: I don't intend to fix this problem as the fix, from what I read, would be an engine rebuild. I can't imagine the cost for that. I'll just let the engine idle for a couple of minutes at cold start up before driving.
Comments?
Background info: My 2000 E55 engine developed a klacking noise at start up from a cold engine. The klack goes away after about 1 to 2 minutes of idling. The dealership said it was lifters, but first try to clean out the injectors. That was done without any result. At a cost of over $1,200, the lifters were replaced. The klack was still there. Then a cleaning of the engine with some type of fluid was done. Still klacking. Next the timing chain tensioner was replaced. No change. Next the solution was to change the timing chain. However, with only an 80% chance that would solve the klacking, I put further repairs on hold.
Piston slap: I had my retired airline avionics tech brother-in-law listen to the klacking last week and he said it sounds like piston slap. I never heard of piston slap, so I researched it on the internet/youtube. The sound I hear on my E55 sounds just like some of the engines with piston slap on youtube videos.
I read that the cause of piston slap is due to a piston being smaller than the cylinder and thus the piston hits the sides of the cylinder causing the klack until the engine heats up and the piston/cylinder expand.
Uncertain: The klack started at about 103,000 miles. The engine is now at 107,000. I don't understand why it started. The car has been faithfully maintained.
Plan: I don't intend to fix this problem as the fix, from what I read, would be an engine rebuild. I can't imagine the cost for that. I'll just let the engine idle for a couple of minutes at cold start up before driving.
Comments?
MBWorld Fanatic!
Joined: Jan 2007
Posts: 1,152
Likes: 29
From: Sydney, Australia
190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
It sounds like carbon build up on the piston crowns. Very commonly misdiagnosed.
Basicly the clearence between the piston crown and the bottom of the cylinder head is very small on the N/A 55 engines, particualrly the later 11:1 compression engines, and they can get a buildup of carbon which will make contact with the cylinder head each time the piston gets to top dead center.
The carbon is hard when cold at to makes the conrod bearing "bottom out" making a noise both near the sump and at the heads at the same time. When the engine warms up the noise will deminish and most likely won't be heard when hot. The noise will reoccur when the engine cools again.
Various upper engine cleaners can help but they are mainly designed for cleaning intake valves, not piston crowns. The best way to clean the crown is some hard running.
Warm the engine up gently, get it to full operating temp for at least 5-10 mins and then give it maximum engine load in the upper rev ranges (4k rpm+) for an extended period.
Obviously local conditions will dictate how you achieve this, it's a little harder to do in a E55 then a C200. My suggestion would be to do it on a quiet highway at night, using full throttle runs from 15kph/10mph in 1st gear to redline in 2nd gear then slow and repeat at least 10 times. Dont hold it back using the brakes.
Continue driving for another 10mins an then see how it sounds the following day.
Basicly the clearence between the piston crown and the bottom of the cylinder head is very small on the N/A 55 engines, particualrly the later 11:1 compression engines, and they can get a buildup of carbon which will make contact with the cylinder head each time the piston gets to top dead center.
The carbon is hard when cold at to makes the conrod bearing "bottom out" making a noise both near the sump and at the heads at the same time. When the engine warms up the noise will deminish and most likely won't be heard when hot. The noise will reoccur when the engine cools again.
Various upper engine cleaners can help but they are mainly designed for cleaning intake valves, not piston crowns. The best way to clean the crown is some hard running.
Warm the engine up gently, get it to full operating temp for at least 5-10 mins and then give it maximum engine load in the upper rev ranges (4k rpm+) for an extended period.
Obviously local conditions will dictate how you achieve this, it's a little harder to do in a E55 then a C200. My suggestion would be to do it on a quiet highway at night, using full throttle runs from 15kph/10mph in 1st gear to redline in 2nd gear then slow and repeat at least 10 times. Dont hold it back using the brakes.
Continue driving for another 10mins an then see how it sounds the following day.
