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Knocking Bimmer

Q. Vince, Lengthy email but please respond, I'm desperate and anxious.

I own a 1995 BMW 318ti Club Sport (with M3 suspension), 1.8litter, 5 speed manual, Fuel injection., ABS, P/S & A/C no cruise. Current Mileage is 82,000 miles. I bought it used at 26,000 miles. In 1997, at about 37000 miles I noticed a very, very faint knock when accelerated (at idle) to 2000 rpms. I brought it in and the dealership reported they heard no noise. Yet I continued to hear it. I brought it in to a different dealer at about 52,000 miles when the knock became just "slightly" more pronounced. Still after diagnostics, the dealer reported nothing wrong could be found.

Now riding at near 82,000, I can hear the knock while in the car. This became audible inside the vehicle at about 65,000. The sound is very, very difficult to distinguish when standing outside of the car because the engine has always had loud peripheral noise. But in the relatively sound proof cabin the knock is audible. And it is a solid type noise even if it isn't loud enough for "say" a casual passenger to notice and comment on. I really have to listen while accelerating to hear it....

My experience with knocking engines goes back to a 1976 Cutlass Supreme that no more than a couple of weeks after hearing a faint knock, the loudness escalated quickly and the engine basically was ruined because of rod bearings. I'm accustomed to hearing about Bimmers lasting well into the 100 Grands but I don't feel very fortunate about mine. Now being that this noise has been around for almost 4 years and 50,000 miles, I tend to believe that this isn't the same type of catastrophe I experienced with the Cutlass. One would think that worn bearings would completely give out very soon after the initial worn bearing knocking begins. Yet I cannot afford to "put it in the shop" for major repairs so I'm really beginning to worry.

The engine has good power at high speed and continues to perform within the 80-100 mile per hour range. I frequently travel long distance at high rates of speed (65-85 mph). Gas mileage and Oil consumption as never "noticeably" changed. Also, the knock drowns (maybe because of loud peripheral noise) out at approx. 3000 rpms. The knock really never gets louder as I accelerate and isn't generally heard before 2000 rpms.

My question to you is, do you think this is drive train related? I mean crank shaft, cam shaft, rods, bearings.... Can worn bearings or other rod and crank shaft components begin to fail and continue to perform for nearly 50,000 miles?????

Also, what would your comments be on a do-it-yourself replacement of rod bearings and possible crank shaft replacement? If I were to rate my automotive expertise on a 1 to 10 scale, I'd be a 6 on traditional American car engines (carb., V8, 350 Olds).

Thank You Very, Very Much.
Rick

A. Rick, you have a problem with that engine. That knocking noise is a definite indication of lower end problems. The only reason it's lasting as long as it has is that a BMW engine is built a lot better than a GM engine. I had a friend who has a 1987 Toyota Camry that had an engine knock. It went about five years before the engine failed. The last six months of that driving was at 90mph+ (I'm not saying I ever drive faster than the posted speed limit) on a 160 mile round trip five days a week.

The thing is it's getting worse and it will reach the point where one or more of the connecting rods will leave the engine. Most technicians will give a knocking noise such as you describe a cursory examination. They will not drop the oil pan and inspect the lower end properly.

At this point, I would drop that oil pan and look at it very closely. At this time you may be able to just replace the rod bearings and that will fix the problem. The rod journals will need to be measured for wear, but I have been very successful at replacing rod bearings even with a loud knock.

Don't put it off, get it taken care of ASAP.

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