Always the Little Things
Clogged Body Drains
By Mike Perkins
Owner - Bavarian Machine Specialties
An easily preventable problem centers on
clogged body drains (the small drains that allow rain and carwash
water an escape from the body). Drains in the cowling area, sunroof,
and convertible top storage compartment are seldom inspected and
without attention they can lead to a major calamity. Those who park
outside, especially under trees, beware: leaves and debris are easily
trapped in key drainage areas, and if allowed to decompose, will
completely clog the drains.
If you have an E34 (5 series from 1989-1995)
and allow the cowling drains (those at the base of the windshield
under the hood) to clog, expect soggy front footwell carpets after
a hard rain as the water winds it's way through the heater box seal
and into the car. If this condition goes undetected your soggy carpets
will not only mold, there is a good chance your air condition control
unit and wiring will corrode and fail. Imagine a moldy, non-airconditioned
car simply due to leaves in the cowling drains.
Clogged cowling drains result in a different
disaster for E36's (3 series from 1992-99). Rather than flood the
passenger footwell area, the water instead flows to the area housing
the engine management control unit (DME) which, at best, causes
a non-start condition until the unit dries (or at worst a totally
"fried" DME). Perhaps you or one of your friends have
experienced a non-start after running your 3 series through a car
wash (check those cowling drains).
Surprisingly, sunroof drains are notorious
for clogs. A clogged sunroof drain leads to soaked headliners and
or ruined leather seats. A quick check of the drains leads can be
performed by pouring a small cup of water into first one corner,
then the other corners of the sunroof channel. If clear, you will
see the water pool beneath the car behind both the
front and rear wheels. If you find a clogged drain be careful using
compressed air to clean the blockage: sunroof vent tubes are pressed-on
to plastic tubes that can pop off if the clog is stubborn.
Clogged drains in the convertible-top storage
areas of E36's are also problematic. One customer of ours regularly
parks beneath a live oak. After a week out of town (when it rained
heavily) he returned to find a thoroughly soaked back seat and two
inches of standing water in the footwells. Initially he he thought
the convertible top leaked, but upon inspection the culprits were
completely clogged drains in the convertible top storage area. As
the storage compartment filled with water it overflowed into the
backseat and onto the floor.
Air Flow Blockage
Clogs present a different problem on all E39 (5 series from 96-03),
here having to do with air conditioning and engine cooling. These
cars tend to trap road debris into the lower air conditioner condenser
area. Paper, leaves, and other road debris collect between the auxiliary
fan and condenser causing a number of heat dissipation issues. The
clogged condenser area creates super heated air that affects radiator
cooling, auxiliary fan operation, and eventually air conditioner
compressor life. A good cleaning of the condenser once every couple
of years will help alleviate these potentially expensive situations.
Paper, leaves and other road debris cause problems with BMWs from
the late 1980s that have an alternator cooling duct (especially
those with low inlets). Pop the plastic cover off the back of the
alternator some time and you will think some rodent built a nest
in your alternator. We have found all manner of paper, twigs, leaves
and even cigarette butts crammed into the back of the alternator.
The ducting acts to cool the alternator's diode plate and is needed
especially on later model cars with higher amperage alternators.
Heat build up has become such an issue that BMW engineers have tried
water cooling the alternator, as on M62 engines. Unfortunately,
in my experience the only time the alternator cooling duct is cleaned
is after an alternator failure and the expensive new alternator
final clogging problem for now: as everyone knows, the most efficient
way to operate the air conditioning system in the hot, humid, Texas
climate is in recirculation mode. However, be aware that on all
E38 and E39 models (7 series from 1995-2001 and 5 series from 1996-2003)
this can lead to a clogging problem with the integrated heating
and air conditioning system (IHKA) internal recirculation filters.
These IHKA filters are not to be confused with the external air
microfilters (which should be replaced at regular intervals as part
of routine service). When the IHKA filters become clogged, they
impede air flow through the air conditioning system including the
blower motor and final stage. If no attention is paid to the IHKA
filters, the result will be a 12 hour job to remove the dash and
replace a burnt out blower - all for the sake of two small filters.
When you replace these original filters for the first time, especially
if you have a pet that travels in the car, wear a mask and gloves
because it won't be pretty. You won't believe what you've been breathing.
published in the BMW CCA Houston Chapter Newsletter