Conference terri::cars_uk

    
    Piston rings, head gasket, valve guides + valve stem oil seals.
    
    Solutions.
    
    Pistons rings. Engine rebuild. Rebore perhaps with oversize pistons
    		   plus new rings. New end bearings et cetera.
    
    Head gasket.   Head off and refit new gasket. Also check the valve
    		   guides and rebore if required then fit valves with
    	           oversize stems plus new stem seals. DON'T have the
    		   valve guides "knurled" as this leaves a thread running
    		   through the guide itself. I had it done on a Ford OHC
    		   before and it ruined the cylinder head.
    
    JN.
    

JN,

I agree with problems and actions,  however are these possibilities for my engine
or worn engines in general?

I cannot reconcile bore wear with such high compression... or perhaps you can 
tell me otherwise,  it sure puzzles me.

_Richard

    
    
    
    With the the compressions being so good then that would perhaps 
    eliminate the piston rings being on their way out. If they were 
    playing up you would certainly notice exhaust smoke and oil 
    consumption.
    
    If the oil stem seals were gone and you have worn valve guides
    this would not effect compression which is measured during the
    combustion stroke, ie, both exhaust and inlet valves are closed.
    
    The only way to really tell if you have worn valve guides is to
    wip the head off and waggle the bottom of an open valve. There should
    ONLY be a barely detectable movement. Any more than that and its
    a stem rebore plus oversize valve stems. Sleeves can also be fitted.
    
    I don't know what car you have, the engine et cetera, but there is
    a tool that allows you to replace stem seals and valve springs et
    cerera without taking the head off. The Ford OHC stem seals lasted
    about five minutes and a friend of mine became rather cheesed off
    with having to take the head off for such a simple job.
    
    You can obtain a good idea of their state by taking off the rocker
    box and looking at the seals near the valve tops.
    
    The ideas I gave in the previous note are for both possibilities.
    
    JN.

    I seem to recall that a way of differentiating between piston ring wear
    and valve guide wear is to measure the engine compression, drop a
    teaspoon of engine oil into each bore, then measure the compression
    again. The change in reading (if any) indicates where the wear is most
    likely to be. I don't remember the details - perhaps someone can
    enlighten us ??
    

The oil in the cylinder trick is a good old standby for testing the rings,
I must admit to not having tried it,  the compressions were so close to 
the original values as to make me think the rings were ok.

I tend to think it is the valve guides/seals.  The main problem is that the
guides are machined into the head,  and it will require a head removal and
overhaul to cure this,  oh well,  it's only money ;-(

BTW: The engine is Opel 3.0 CIH engine,  all cast-iron and V. Heavy!

    Old Engines :-
    
    My Alfa V6 has just recently passed 100,000 miles.
    
    It has had a fair amount of work done and is now in very good health.
    
    
    It was smoking quite badly at tickover - because of very worn valve guides.
    
    As a result of the play in the valve stems, two of the valves ended up
    with damage (chip on one, crack on another) due to not seating properly.
    
    There was some bottom-end rattle - worn bearing shells.
    
    In fact, one of the shells had worn, then stuck to the crank journal
    and started to spin in the big-end of the con-rod !
    
    Piston liners (bores) were scored, rings were worn, piston skirts had
    been scuffed, one piston had a slight chip at the edge of its crown.
    
    
    Plenty of work, but the sort of thing you can expect with high mileage.
    
    The work on the engine involved the purchase of :
    
    	New pistons and liners (other engines may need a re-bore)
    
    	New valve guides (again, other engines may need more work)
    
    	Two new valves (only the damaged ones, stems on the others were ok)
    
    	New crankshaft bearings, plus one new con-rod (with engine in-place)
    
    The oil pump clearance was checked and adjusted, cams appeared fine,
    core plugs and other 'odd' items were untouched.
    
    
    Now, the engine just needs to be run in...
    
    I've already covered 700 miles (since last week) and have had the
    heads re-torqued and an oil change (now using synthetic oil).
    
    I wonder how many more miles I can keep to 'restraint' with this engine ?
    
    One more week and I guess it should be happy to pull high revs again,
    but I don't hold it at the red-line anyway (I change up)  :-)
    
    J.R.

Is the engine burning oil ?

The blackness of the plugs could just be an over rich mixture, not
necessarily oil being burned ...

    
    RE: Oil in cylinder trick. There's not much detail to give except
        just calulate the difference between compressions when you've
        taken the new readings after putting a drop of all in.
    
    JN.

    When you put oil in the cylinders you improve the seal between the
    rings and cylinder walls. If the compession is still bad then it is the
    valves guides that are worn.
    
    Andrew

Over rich mixture,  could be,  however I would have though that it would have failed
an MOT,  (last week) on the new emission test. The plugs are definitely oily,  not
just sooty.

It does consume oil,  always did,  however it consumes much more now.

It is beginning to sound bad for the cylinder head/valves etc...

BTW:  Recently correctly diagnosed burnt valve using compression tester and oil, the
value was down from 170 to 40psi and oil made no difference.

How much did the Alfa engine rebuild cost?  (If that is not too personal a question?)

_Richard

My wife's XR3i (c 60,000 miles, 1987) failed one recent MOT on brakes but not 
on emissions. Our tame mechanic couln't find anything wrong with them, so I 
took it to another garage one day later, who passed the brakes .... but failed 
it on the emissions. Thus I had to pay c �26 for a 'crypton tune' .... then 
they passed it!
I reckon this emission stuff is potentially a very good money spinner for 
garages ... with the poor motorist at the mercy of rip off merchants 
everywhere .... so what's new?

    
    With the oil trick if the compressions improve then the rings
    are going downhill. If there is no improvement and the compressions
    were low anyway (I know they weren't) then its the valves.
    
    Is the opel engine the straight six that looks like the flat
    side of a bus ?
    
    JN.

Yup,  it is the six cylinder machine,  although I cannot recollect it looking
like the side of a bus!

It is the old opel 2.0CIH with two extra cylinders and extra pain in the wallet.

There have been numerous versions... 2.5,2.6,2.8,3.0  all gutless until you got
to 3.0 with balanced crank. ('83/'83)

_Richard

BTW: It is going to be sold soon,  I wonder if I can get away with new seals in
order to sell it?

Is the engine very smokey ? How much oil does it consume ? 1 pint per 5000,
1000, 100 miles ?

If your compression is as good as it seams, I'd go for the valve guides
or valve stem oil seals. Assuming it's not an OHC engine, and you are
about to sell it anyway, just change the seals ...

If you do decide to change the guides, then I would get an engineering
shop to do it for you, and look at spending UKL 100+ ...

Or just get an exchange head from a breakers ...

How would exhanging my head improve things ? ;-)

Seriously though, I think the seals are the best bet in this case,  they are easy to
replace as the head has rocker arms, with the cam along side, ie no push-rods.

It has never been smokey,  apart from once when I generated lots of vacuum by 
decelerating in a low gear,  I guess that almost answers the original question, still
it is nice to hear other opinions.

As for oil consumption,  never measured it,  just checked it every week and topped 
up every month, there is 1.5l between min/max on the dipstick, and I did approx 2500
miles per month, so it was never too bad,  I have noticed it get much worse since
the plug fouling incident,  so somethink is wrong.

_Richard

    re cost of Alfa rebuild
    
    I haven't got the final figure yet, but the pistons+liners cost �300,
    with the bearings about another forty, labour *about* 300 to do the
    work on the bottom end (involves removing both heads).  The actual
    head work has cost quite a few hundred on top of that  :-(
    
    Now that the engine is in good condition, I will definitely keep
    the car for some time (body is not rusting either, makes a change
    on an old Alfa).
    
    After all this expense (plus a new radiator) I do think that it
    is worth it.  In terms of enjoyment of the car, not in its value...
    
    J.R.

It's quite impressive the amount of oil an engine can consume when the
seals have worn out. However, it is usually associated with quite a lot
of smoke.

A classic sign of guide wear, and seal wear is when you start the engine
from cold. There is a lot of smoke. The reason for this is that when the
engine is left for some time, the oil runs down the guides and into the
engine through the valves which are open. When you start up, this burns
off ...

    
    Re -1
    
    This could explain the oil usage of my MR2. Though not old, (15 000
    miles) its using a fair amount of oil. People have remarked when following
    me that the engine blow out a lot of smoke from cold. 
    
    The garage where I get it serviced say that the MR is prone to use a
    lot of oil especially when driving quickly down a motorway. Most of my
    driving is round Basingstoke with the odd trip to Scotland and back.
    
    I spoke to the garage who supplied the car and enquired how much an MR 
    should use. They said "Why how much are you using?" I said I'm using about
    6 litres between services (6000 miles), he did a bit of arithmetic and said
    thats about 450 miles a pint you should be getting about 700 to 800.
    
    Needless to say I'm going to insist the servicing garage look into the
    problem next time 'coz Mobil 1 isn't cheap!!!!!. (Maybe something wrong
    with the valve guides)
    
    Anybody else out there having problems keeping oil in a MR2?
    
    
    POL.
        

Maybe you should change gear *before* you hit the rev limiter some time!

Remember telling us all how you drove? 8-]

Steve.

    
    re -1
    
    Steve,
    
    But thats what its there for isn't it? Once you hit the rev limiter its 
    not going to go any higher so you may as well leave your foot on the
    accelerator whilst changing up!!!!!!!!!!!!!     8^)
    
    
    POL.
    
    P.S. I don't remembering it smoking when I tried this

    
    Moving on. I have an older diesel Golf ('80 vintage) which although
    functioning well, even though it's coming up to the 200k mile marker, has
    a small problem. That is an oil leak, which I guess most cars suffer
    from irrespective of mileage. This, however, is coming from around the
    cylinder head gasket (from face only) and is only leaking to the
    outside world. [No water oil mix or other such probs.]
    
    Question is does one go for a total head rebuild and cylinder head
    gasket replacement or simply the later to save money? As I said I have
    absolutely no running problems or extraneous kncking noises so must
    assume normal compression and little wear of camshaft, valves etc.
    
    Thoughts here? Ta
    
    Ian
    
    PS. The refurb shop I spoke to said �300 gets me a replacement head
        which is about as cheap as a total refurb to my unit...