ackerman71

I have recently posted some threads re: a tapping noise in my engine. The car is a 2001 with 114.000 miles. The tapping noise speeds up with acceleration, and almost disappears once reaching 60 mph. Very loud and embarrassing.

Took to a mechanic and the tapping noise was diagnosed as a bad lifter. The shop could not get me in to replace lifters for atleast another week. In the meantime they suggested changing the oil to see if this helped. It did quiet it down for a couple of days (never completely gone, just not as loud). The mechanic did say the car was low on oil. I also noticed that it was going through more oil than usual.

After about two weeks the car went to another mechanic who specializes in European cars. He removed the valve cover and also diagnosed as bad lifters on the left side. He recommended replacing all 9. We did.
Car was scheduled to be done yesterday. By noon, no calls. We called and he informed us that the tapping is still there!!!! Now he is saying it sounds like an internal noise. We just paid $950 to get our car and left with the same noise we went in with.
Does anyone know what else this could be? Any advice is greatly appreciated.
Thanks.

Hirnbeiss

Piston slap?

ackerman71

Boy I hope not. Does a piston slap sound like a lifter? The tapping does not sound louder at start up, if anything louder once it warms up. Is this normal for piston slap?
Thanks.

Hirnbeiss

Actually I remember a thread on another forum that piston slap is rare on the M112, but that bad motor mounts can cause a similar sound. I would check there first.

Bossman121

Bad plug wires make a lot of noise. More like a ticking than a metallic noise though. I had my plugs change and then had a loud ticking noise. 2 mechanics said I needed lifter work. The third mechanic said bad plug wire on cylinder 5. Bought two new plug wires, tapping gone.

ejsheltra

Piston slap would sound like a diesel at start up and eventually get quieter as the motor came up to operating temp. This is typically found on high compression motors running 11:1 or higher forged racing pistons like Jahn's for example. The tolerances are larger to compensate for heat expansion unlike a cast piston. In your case I doubt very much (read 90%) that you have piston slap. Check all your electrical connections to and from the coils, especially to the plugs. Make sure they are all connected tight and sitting at the same height. Oil in the M112 motor is recommended as Mobil One full synthetic 0-30 or 0-40 at 8.5 quarts with filter. How many miles on the car and what kind of driving? Possible timing chain noise, although unlikely? Get an engine stethoscope and check from where you hear the noise at idle. More detail is needed otherwise just guessing. Unless engine has been run real hard and poor maintenance and low oil I would have never thought lifters. M112 motor is all roller tappet and double roller timing chain set up and very quiet. Give us more details before going back in and getting pic pocketed for your hard earned dough.

ackerman71

The car has 114,000 miles. I did notice about 6 weeks ago the car was going through a lot of oil. I had an oil change in mid-january, after about 3,000 miles the car was 2 quarts low. Since then I have had another oil change adn frequently check the oil. Second oil dealer change done at dealer and they said the oil filter had not been replaced at last oil change (A Jiffy Lube change when I was out of town). Could this cause any damage?

This is interesting. In early March, the car would not run. Had misfire in cylinder 4,5 and 6. We had the spark plugs changed at that time. Car still would not run. Later diagnosed as bad catalytic converter on left side. Car was towed to shop to have catalytic converter replaced. This is when I first heard the ticking. The day the car was picked up with catalytic converter the ticking was present. It does not go away, regardless of whether the engine is warm or cold. Now I question the lifters. This could very well be related to spark plug wires or coils.

Hirnbeiss

Another item to bear in mind is a small exhaust leak. Since you said the noise started when they changed the cats, it's possible they left a leak somewhere.

As to the oil usage, first see how much is due to oil leaks. With the belly pan underneath as a catch-all, you can often convince yourself that you have no leaks. I have about the same mileage, and mine has become leak happy at the valve covers and valve cover vents.

If it's not leaking, then get a compression test done before paying for any other work. If any cylinders are low, make sure they also check the compression wet.

martz

as previously stated by Hirnbeiss " exhaust leak"
could possibly be a cracked or missing bolt on the exhaust manifold. Does the ticking disappear or lessen when engine reaches operating temp? if so check your manifold.

ackerman71

It has been some time. You guys have always been so helpful. Still having problems with the Mercedes. Have not driven much but really need the car.
Went back to dealer who has now diagnosed as piston slap. What would cause the pistons to go bad? The car only has 114k. They say we need a new engine. Has anyone ever installed an engine in the e320?
Also, what would be involved with motor mount? Could the problem be misdiagnosed? Has been before with the lifters.
Thank again for your feedback.