New tick or knock… Any ideas?
 

Hello Benz fans

I have had a ticking lifter that I intend to replace soon but I have a new noise. It sounds like a lifter but louder. It only seems to knock when I am on the throttle. At idle or coasting it goes away. I changed the oil to 10-40 over the weekend and although I don’t see any milky white, the coolant seems to be just slightly lower. The oil on the dipstick is bubbly. I drove 2 miles and it was very bubbly and after 12 miles it was less bubbly. I am not looking forward to pulling the heads. Anyone have any ideas?

When coolant and oil mix it's rarer than rare that the heads don't have to come off. Maybe start with a leakdown test to see where you stand.

Sixto
95 S420
87 300SDL

Yeah, I know if I have coolant in the oil, a head gasket (or 2) will be needed. But what would cause the noise? I suppose I have to start by pulling the valve covers.

If I had to guess I'll say that the reduction in oil pressure because of the contamination is causing the lash adjusters to not pump up sufficiently.

Sixto
95 S420
87 300SDL

Bubbly oil on the dipstick is sometimes caused by "frothing". This occurs if TOO MUCH oil is poured into the engine..ie..during an oil change, which you just did.

Check your oil level on a flat surface after the car has been at rest overnight.

I wouldn't push the blown-head-gasket-panic-button just yet.

My 2 cents.

I checked the oil level (4 times in 2 days) and it is just over the center between the marks. After sitting a few hours there are no bubbles and the level is normal. It does not appear to be over full. I wonder why it would foam if not over-filled. I also can't confirm the coolant is getting into the oil. I will drive it a little more and see if the coolant goes down or there is milk in the oil. I am panicked and afraid to drive it.