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Last updated:
Saturday, January 14, 2006 08:44:25 AM
Warnings for head gasket replacement (from various sources)
New items at the end of the list.
- The head will warp or is already warped, when breaking the head bolts,
go slow & evenly; if it takes 50ft/lbs to break them free -- they were not
re-torqued regularly.
- Check head for cracks -- More common in earlier year m30 engines.
- Use the special 3mm head gasket if you do more than a slight milling of
the head.
- Use new head bolts, clean out the threads and ANY water before torquing
-- torque down as specified, slowly, in order & the final 35degree torque is
required.
- Replace the chain tensioner & bleed
it properly. (How?)
- At the very lease do a valve job w/ new valve guides
& seals
& 3 way grind.
- Port / polish the head. (I've heard mixed things about this
A)
it adds horsepower,
B) it does little but waste money.
I'm not willing
to start going nuts with headers, improved air intake, new exhaust &
high-low
injectors -- the "system" is a can of worms if you start mucking too much
with one part and not the rest)
- Bolt the cam cover to the head when resurfacing to make sure they are
surfaced to the same depth.
- Replace the timing chain (Can this be done easily when removing the
head?)
- Rebuild the head. (Note: I'm not up for this cost wise, and when I've
done head jobs before; I always seem to blow out the bottom end soon
thereafter)
- Replace the valve stem seals.
- Put
new cam & rocker arms on.
- Check the cam for wear, replace cam & rockers if needed
- Anything
over 100k miles should have the: (All can be done w/o the motor out but it's
not easy) (This is getting into a time / money constraint.)
- pistons pulled
- oiling holes cleaned
- new rings installed
- cylinders de-glazed with a dingle-berry hone
- cylinders cleaned
- then the crank bearing shells replaced.
- Oil pump relief valves get troublesome, so consider it
before re-using your old pump.
- Never use the "CORK-style" pan gasket.....not even the new
bonded ones...
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- Rocker
arms, camshafts and rocker shafts can be inspected and re-used.
- Steam/coolant
ingestion into the combustion chambers will get up the valve guides and may
require replacing the valves and guides.
(Note: We adjusted the valves,
but didn't see any evidence of bad guides/seals.)
- If
you "split" the timing chain while the cam sprocket is still in place, it's
very easy to tie the new chain to the old, and pull it thru once the head is
off. Removal of the bottom timing cover is very difficult! It
requires special tools.
- If
the gaskets are not leaking, leave it alone as the chain guides are capable
of 500k miles.
- Install a new cam sprocket.
- Clean and Bleed the cam chain tensioner.
- Be very careful about getting both the crankshaft and camshaft to TDC on
install.
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- The
new style M30 heads as so good that I frequently have them skimmed with just
a couple thousandths of an inch removed....... .3mm = .012 in (FINALLY
some GOOD news!)
- See
All About the Cam Tensioner.
- Cam
Removal w/o the special tool.
- First
Hand experience with similar symptoms, re-enforces what we "plan
to do"....
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