Have a '90 300E Base SOHC 6 3.0 engine. Engine has 200k on it and head was redone by a good shop at 150k. Engine has always tapped for 5 or 10 seconds when you start it cold, then quiets and that's it. Oil is changed religiously every 5k with Syntec 5W-40. It runs like a charm. Daily driver.

Two days ago it started tapping on and off when driving it. Taps the same whether driving or idling. Pressure gauge shows plenty of oil pressure. Oil level is full and oil condition is clean and fresh looking. Noise comes and goes. Sometimes it is persistent, sometimes lasts only a few secs. TONE of noise changes as well, sometimes is a solid sounding "clack" sometimes has more of a ringy tone to it. Always emanates from under the valve cover. Even though the pressure appears to be fine, a peek inside the filler cal lead me to believe that the valve train, while not dry, appears that it may be drier than it should be. Again, pressure indicator is showing 3 bars running and 2 at idle.

I am thinking that I have a lifter(or maybe 2 ?) collapsing But this is actually quite a sudden development. I am also wondering if I have a sudden oiling problem to the top of the engine.

Anyone ever experience this before with a 3.0 SOHC ? Any one have any input or ideas? All input is welcomed.

 

148 looks and not one response eh? Really ?

 

I use 0w40 mobil 1, and the one and only time I used 10w40 mobil 1, my lifters leaked down every day, just a racket every start.

Pop the valve cover and see ... loose rocker or oil tube, worn camshaft, broken spring, clogs or an oil tube's bolt swimming around. If everything is solid, try different grade oil, if that doesn't fit it, maybe lifters? If still noisy, could be the bottom end.

I think I just named every metallic part in the top end. A ringy clack sounds like metal to me. Find out whats clacking and get back to us!

 

I have heard that this could be a flat spot on the valve stem. As it rotates in and out of good alignment it clicks. I was also told not to worry about it, that its fine and not worth taking the head off till it burns a lot of oil. M103's have poor valve geometry and it creates wear on the valve guides. When your car smokes blue on startup then its time to fix it.

-Mike

 

Well, we ordered a couple of lifters. We got the lifters in and pulled the cover last night. It was apparent right away that there is no oiling problem--LOTS of oil volume and pressure both. Oil rail (tube if you like) is pristine clean and was tight. All rocker arm carriers are tight. All lifters are pumping up....and at about the same rate. There is no apparent slop in the rocker clearances. We didn't put a feeler gage on them, but it is pretty obvious that there is nothing loose or sloppy. The top end is clean as a newborn. No sludge or crap anywhere, just clean and pristine mechanicals and oil. You'd think the engine had 30k, not 200k on it.

Four key things we observed: 1) the tapping does not occur when the car is started after sitting and gets fully cold. We had to wait for it to warm up before the tapping started. 2) Once it starts it moves around...one will tap, then stop, then another taps, then stops, then a different one, etc. Never two at a time, and never on the lower end of the head, only the valves along the top (closest to the air filter) of the head. 3) The last time we changed the oil (maybe 5 weeks ago) we used Valvoline synthetic because it was on sale, however I can't recall the weight they had. I have always used Castrol Syntec 10w-40 in this motor. This oil appears quite thin or watery.

I bought 6 quarts of Castrol Syntec 10w-40 (per MB recommended oil wight chart for this motor)and a filter. I really have a hard time believing that 4 or 5 lifters suddenly all took a crap all at once. There is no evidence of poor oiling ANYWHERE, and everything is tight. There is tons of oil flow, and the pressure is good. The mechanicals are clean as hell and so is the oil. We are kind of baffled, but are now thinking it may be an oil problem, either the wrong weight or just doesn't like the Valvoline. My Porsche has a similar issue if I use certain oils in it - the lifters drain when it sits and it taps. Put the same exact weight Mobil 1 or Royal Purple in it and it stops doing that immediately.

I'll let you know how I make out......

 

Another guy on another board posted:
"Make sure the noise is not from the belt tensioner shock. Its right next to the engine and the bushing wears which allows forward/backway play and it will make noises that sound like its coming from the engine. Grab it and if it moves back and forth, either replace the shock or put two washers on either end and retighten so it does not move anymore."

We may have a winner here. We had just finished replacing the upper radiator hoses, thermostat, and belt a few days before this all started. The tensioner gave us fits when we reassembled, but we thought we got it "fixed." Thinking back, the wife did complain that the belt was squealing some, and we were going to look at that before this "tapping" started. We have concentrated on the tapping since then and not even looked at the belt or tensioner....

...until last night that is. Sure enough, the belt tensioner isn't working. We were able to move it back and forth and make a tapping sound by hand, so at 1000rpm......well, you get the idea.

Parts on their way to completely replace the tensioner assembly and all peripheral parts. Hope this is it. More to come.....

 

Belt tensioner assy replaced. Correct oil put in. Still tapping. Still coming and going. Still "moving around." HAS to be lifters.

Trying one more thing before I replace 12 lifters.....will run a bottle of Gunk engine flush through it and change the oil. Maybe I've got some crap in an oil passage somewhere......

Still have a hard time believing that I have 2 or 3 lifters that all of the sudden decided to take a dump at the same exact time.....on the other hand, they DO have 200k miles on them ......

 

Well fellas, sometimes all you need is a bottle of engine cleaner and 10 mins of time........:laugh4:

Started her up and put in a bottle of Gunk Engine Flush. Can says put it in a cold engine and let run for 5 mins. I put it in a cold engine and let her run for about 10 mins.....wanted to give it every chance to tap. Twice I heard it j-u-s-t s-t-a-r-t to tap a little and stop right away. Then I heard no more offers to tap. Shut her down and changed the oil....Castrol Syntec 10w-40, and been running it around for two days now without a hitch (or a tap). Mind you....the inside of the engine looked beautiful to start with. Would not have even thought I needed to flush it.

It is also running smooth as silk....much smoother than before all this. Not sure if the new distributor cap and rotor I put on while I had all this apart anyway did that, or if the engine flush did.