Questions and Answers
BMW Turbo Diesel Valve Noise
Q. When I first looked at the car before buying it, I was aware of a knock/tapping noise from the engine. It seemed to be originating from one cam follower, so I went ahead and bought the car. When its service was due, I asked the local main dealer to investigate this noise. They told me that it was a defective hydraulic cam follower and I gave the go-ahead to replace the set of 12.
Guess what? The noise was still there, albeit slightly quieter. Over the next few weeks, the noise returned to the level it was when I got the car. It has not got worse. The noise does not seem "heavy" enough to be a bottom-end problem. From a cold start, the noise is muted after about three seconds as the components receive oil. As the engine warms and the diesel-clatter dies down, the noise again becomes more noticeable. It does not seem load-dependent to a great extent, it is maybe slightly quieter at zero throttle over-run around 2,000 rpm. Any ideas?
There is also a minor diesel injection problem. (Also since I've had the car). Could the two be related? The engine starts well from cold (ie when the glow-plugs operate), but when warm can take about 15 seconds of continuous cranking before firing. A cloud of smoke is emitted when the engine does fire, so it is getting fuel. My guess is that the fuel pressure could be low, or the injectors are not spraying as finely as they should. I plan to take the car to a Diesel Injection specialist to have the pump and injectors tested.
As for history, there is a full service history, but I have no record of any work being carried out on the engine. Looking through the oil filler, the engine is remarkably clean internally. There are no external oil leaks and I do not need to add any oil between services (about 6,000 miles) I replaced the injector leak-off pipes about 12 months ago, a smell of diesel fuel was pinpointed to a perished pipe.
I'd really like to obtain a service manual for this engine. I've tried almost everywhere without success. Will I be able to obtain one from a main BMW dealer?
BMW 525tds, 1994
2.5 turbo-diesel, intercooled (M51)
Manual
Mileage about 235,000.
Diesel Electronics
ABS Fitted
P/S and A/C (A/C faulty) but no cruise.Thanks,
SimonA. Well Simon, I'm going to go out on a limb here and guess this is not an American model BMW. There hasn't been a diesel powered BMW in the US since 1986.
Those have manually adjusted valves and I'm wondering if anyone bothered to try adjusting them? I have seen many rocker arms replaced because of a mal-adjusted valve. So I would do that first. Valve clearance for intake and exhaust should be:
Cold .012 in (0.30 mm) Hot .014 in (0.35 mm) NOTE: BMW provides both hot and cold valve clearance specifications but does NOT recommend hot valve clearance adjustment.
For some reason finding BMW and Mercedes service and repair manuals is very difficult. I would try Auto Repair Manuals.com and see if they have it. If not, you should be able to get one from BMW>
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