How to remove Lotus Elan M100 inlet manifold

Lotus Elan M100 Inlet Manifold Gasket Change

Allow about 4-6 hours to do this yourself if you haven’t tackled it before.  It isn’t difficult, but access is very tricky to some bolts and putting it back together takes a little longer than taking it apart for this reason.

Upper intake plenum / manifold

Tools required:

I have a standard 150 piece Halfords ‘Professional’ socket set,which provided almost everything needed.  Add to that a 23mm spanner (for the EGR pipe), a Stanley knife blade (for cleaning old gaskets off the manifold parts), a pair of wide pliers or Mole grips and a small ‘terminal’ screwdriver.  Oh, and sanity is saved by a magnetic retrieval tool.

Preparation
Disconnect battery (saves dropping things on starter motor / alternator connections causing fire)
Remove induction hose to throttle body
Unclip throttle cable from breather hose
Remove throttle cable from bracket on manifold
Disconnect throttle cable from throttle body

Across rear of manifold
Remove 4x 10mm bolts holding fuel pipes to upper manifold
Remove jubilee clip and disconnect brake servo feed from manifold
Disconnect two vacuum lines (lower to reservoir for inlet changeover, top to bulkhead)

Timing belt end
Remove boost gauge hose
Disconnect fuel pressure regulator hose at manifold
Remove breather connection
Remove 2x 10mm earth connection bolt from end of manifold flange
Disconnect hose to MAP sensor at right angle adaptor (release hose clip with wide pliers and slide down pipe first)

Upper manifold
Remove 4x 12mm bolts holding throttle body to upper manifold
Part throttle body from manifold to access egr pipe union
Remove EGR pipe (23mm union) from diaphragm/valve assembly

Remove 12mm nut at timing belt end of flange

This works for top row bolts (3/8 inch drive to 12mm socket)

Top row bolts just visible

Top row nut to be removed, note earth connections also have to be removed

Remove 3x 12mm long bolts from top row

Remove 4x 12mm short bolts from bottom row
Now remove 2x 12mm bolts from engine to manifold brace at throttle body end
Remove 1x 12mm bolt from timing belt end engine lifting bracket at manifold
Disconnect EGR vacuum connection (goes to upper connection on inner wing mounted solenoid valve)
Remove 2x 10mm bolts holding throttle cable bracket to manifold
Part manifold upper and lower parts (I had to tap with a block of wood)
Remove upper manifold by rotating slightly forwards while pushing the bottom backwards to clear the two end studs

Lower manifold / injector housing
Remove 2x 10mm bolts golding fuel injector wiring conduit to injector housing
Remove 2x 11mm bolts holding fuel rail to injector housing
Unplug 4x injector electrical connectors (retain spring clips!)
Detach fuel rail from injector housing by wiggling and pulling backwards, leaving injectors attached to rail
Hook fuel rail over rear engine compartment rubber to give better access
Disconnect 4-pin plug from idle valve
Remove 12mm nut from timing belt end engine lifting bracket and remove bracket
Remove stud from timing belt upper row (5mm socket)
Remove 12mm nut from stud in upper row at gearbox end
Remove 3x 12mm (shorter) bolts from upper row
Remove 4x 12mm (longer) bolts from lower row
Disconnect idle valve pipe from throttle body and injector housing (easiest at throttle body)
Disconnect loom connector to vacuum solenoid for inlet butterfly control
Remove injector housing complete with inlet changeover solenoid, vacuum reservoir and diaphragm actuator

Clean all mating surfaces thoroughly removing all traces of the old gaskets before reversing the instructions above to put it all back together again.  Inlet manifold bolts (both parts) should be torqued to 13 ft lb, but good luck getting a torque wrench in there to do the upper manifold top row bolts.

I will post photos of my car shortly from when I did this job, which will help with parts identification.

Feel free to contact me if I’ve missed anything, as is always the case, there are other ways of tackling some parts and it may not be necessary to remove some parts, but doing it the way I did allowed me to clean it all up well before it went back together.