2019-04-01 BMW Car

APRIL 2019 75

WORKSHOP WISDOM

Two minutes with a wire brush and our swirl flaps

were fully cleaned up. After this mileage, they

showed no signs of distress. We could have just

cleaned the manifold out with a small wire brush and

brake cleaner and reassembled it. But would you

ever fully trust it after that?

The inlet manifold can now be removed. Take care

and remember about strained electrical connectors,

but it’ll slide off the lower studs easily. Don’t tip it

upside-down as the bolts or sleeves might drop

out. Plug the inlet ports with clean tissue and, on

reassembly, fit these seals – use grease to stop them

from dropping out.

The new alloy blanks are fitted to the manifold using
the existing screws. They have rubber O-ring seals
and are a good, snug fit. Always check which ones
your car has; as a rule, the M47N has the smaller,
22mm blanks, but you might want to order both and
send the other set back once the job’s done.

You can see 160,000 miles-worth of EGR gunge
on the swirl flaps. These have never been looked
at – half the problem is EGR grunge making them
sticky and putting a strain on the tiny Torx screws. I’ll
remove them and see what they’re like.

Under the manifold, you will see the vacuum capsule
for the swirl flap actuator. It has a vacuum hose
entering from the left, and a connector on the right.
Disconnect them both. When dismantling, always
take photographs and take notes of hose routing.

Once the blanks have been fitted, clean out any

excess carbon from the ports with an old spoon and

brake cleaner, then refit the manifold using grease to

‘glue’ the orange rubber seals in place. Check all the

vacuum hoses and replace one by one with proper

BMW parts before the manifold is fitted.

Once the manifold is back on, double-check

everything – vacuum hoses, connectors and that

10mm dipstick tube securing bolt. Once the engine’s

fired-up and running OK, start to clean up the engine

bay, carefully removing the leaves and general

debris. I’ll be explaining the procedure for doing all

this in a future feature, as debris build-up can cause

major problems.

The swirl flaps are removed by undoing these two,

small Torx screws, after which they can be prised

out with a screwdriver. The metal linkage can just be

seen here, and it can be unclipped with a screwdriver.

The operating capsule is removed to access the last

swirl flap, but must be refitted afterwards.

The manifold can now finally be unbolted, starting

with the upper 10mm bolts that secure the manifold

to the cam cover, followed by the 11mm lower nuts.

On the rear bulkhead, you’ll see a plastic extrusion

with three, 10mm bolts. Remove this to provide more

clearance. Use a dab of grease on the socket when

reassembling, to stop the bolt dropping out.

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