Low pressure on several cylinders in a BMW – what is the cause and how to fix it?
BMW driver’s question
I am writing to you about the repair or overhaul of the M52B28 engine. A 1996 production engine and therefore a single Vanos. I recently measured the compression and discovered errors on two cylinders.
On one the pressure is 9 bar, and on the other 5-6 bar. The rest of the cylinders 15-16 bar. The engine has an undetermined mileage – on the clocks there is 212,000 km of mileage, but it is known that with a car of this year it is unlikely. I am anxious to overhaul this engine. I would like to know what are the price ranges. I have the possibility of dismantling the engine.
The problem was with a 1996 BMW E38 728i with the M52B28 engine, but it can happen in other models as well.
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Response from BM Cars service
In the case of lack of compression on two cylinders, there are few repair options. A common repair involving only the replacement of piston rings may slightly improve compression, but before that, a thorough inspection/measurement of the cylinders and visual inspection of the cylinder head is necessary. If there is damage to the cylinder head or cylinder spinning, replacing the rings alone, will not help much.
It may be necessary to replace the cylinder block. It is also necessary to check the condition of the valve seats and valves, as lack of compression can also be caused by damage to the valve plug or seat.
In any case, the repair costs are economically unviable. A repair done according to the rules and technical documentation will exceed the value of the vehicle many times over. The only economically reasonable method of repair is to replace the engine with another efficient one.
For an accurate diagnosis, it is necessary to carry out additional inspection activities.
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