ENGINE REBUILDERS PTY LTD
7 BARRETT STREET, FLEMINGTON VIC 3031,
TEL: (03) 9372 3111, FAX: (03) 9372 3122
ACN: 006 798 492 ABN: 74 006 798 492
TECHNICAL NEWSLETTER 26/03/2010
BMW M52 THROUGH M54 SERIES ENGINES THERMO-FAN CONTROL.
PROBLEM:
This 1997 BMW, M52 early 6 cyl DOHC, engine came in with a complaint that the radiator was losing one litre of coolant every week with no apparent evidence of the cause. The mechanic tested the coolant system and could not fault it. Road testing indicated that the thermo fan was operating but the temperature came up when driving in slow traffic.
Back in the workshop, the fan system was again seen to be operating and again this part of the coolant system was by-passed to investigate other areas. Still the temperature was going up when in traffic.
CAUSE:
The BMW radiator has an electrical switch 100 mm below the header tank on the driver’s side. This switch controls a THREE stage fan control: slow, medium and fast. This switch had a fault that disabled both the medium and fast modes of the fan speed control.
CURE:
Replace switch.
It is also relevant to understand the mechanic’s input and the technical data reference used by this particular technician in his approach to analysing the fault. Firstly he had an understanding of fault diagnosis and secondly he had the resources in the BMW data available from U.S.A. via the internet. Cost for the full set of BMW CD’s was around $500.00.
He advises that two switch designs have been found across this series of coolant systems: one where the switch has direct contact with the coolant; and a second design that only has contact by thermal transfer from the radiator body, not the coolant.
It is also relevant for each of us engine reconditioners to be up-to-date with the engine bay controls that affect our work.
H.J