thanks for reading. I am seeking some feedback on a problem I have had twice
this year on my Volvo Penta MD17C diesel. the engine is in good shape with
under 1500 total hours. it has been overhauled and serviced etc. well this
year In early june I had a pushrod (on the intake valve) fail on cylinder #2
and the exhaust valve pushrod was bent. New pushrods were installed and valve
clearance and timing checked etc. Well, today I started the engine and it was
sounding like backfiring and I checked and exhaust was belching out the intake
of cylinder #2. turns out the pushrods are bent again!?!?! my mechanics are
stratching their heads. I am puzzled as to why this is happening ( timing?,
fuel?, ). BTW, it seems to happen after the engine has sat for awhile
(months) and during cold weather starts....

please post reply here, this is a no email address.....thanks...

I would suspect a bent or sticking intake valve stem, which could be stiffer
when the engine is cold or been sitting for a while.

I think it is time to pull the head and do a valve inspection and grind and
reseat. At this time you should look for anything in the cylinder that could
be causing this. You could also see if the valve has been hitting the piston
top. I don't remember if these pistons have a indentation machined into the
top for valve clearance but if they do, it is possible that it is filled
with carbon deposit.

I'm looking at a MD2B piston here and it has no valve notches but does have
deep combustion chamber in (near) the middle of the piston tip. Could it be
possible that something has been sucked into the engine that is now riding
around in that chamber and is sometimes interfering with the valve head
clearance with the piston top.

This is a nice little engine and well worth the shop time to resolve this
problem.

--
My opinion and experience. FWIW

Steve
s/v Good Intentions

Sounds like injection timing is jumping. Valve trains don't
appreciate it when injection happens into the hot, compressed air
while cams are trying to open valves. The explosion will easily bend
valve stems.....and make that backfiring sound as the valve is
partially open. Of course, once bent, the valve can't fully close so
there's lots of blast-by if it has enough heat and compression left to
fire the injection....which it probably does with the pre-heaters
setting it off....



On 29 Oct 2003 20:18:44 GMT, (Spamfreedom) wrote:

thanks for reading. I am seeking some feedback on a problem I have had twice
this year on my Volvo Penta MD17C diesel. the engine is in good shape with
under 1500 total hours. it has been overhauled and serviced etc. well this
year In early june I had a pushrod (on the intake valve) fail on cylinder #2
and the exhaust valve pushrod was bent. New pushrods were installed and valve
clearance and timing checked etc. Well, today I started the engine and it was
sounding like backfiring and I checked and exhaust was belching out the intake
of cylinder #2. turns out the pushrods are bent again!?!?! my mechanics are
stratching their heads. I am puzzled as to why this is happening ( timing?,
fuel?, ). BTW, it seems to happen after the engine has sat for awhile
(months) and during cold weather starts....

please post reply here, this is a no email address.....thanks...


Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"

Larry W4CSC wrote:
Sounds like injection timing is jumping. Valve trains don't
appreciate it when injection happens into the hot, compressed air
while cams are trying to open valves. The explosion will easily bend
valve stems.....and make that backfiring sound as the valve is
partially open. Of course, once bent, the valve can't fully close so
there's lots of blast-by if it has enough heat and compression left to
fire the injection....which it probably does with the pre-heaters
setting it off....

Oooohhh my gawd ...


Rick

Spamfreedom wrote:

BTW, it seems to happen after the engine has sat for awhile
(months) and during cold weather starts....

It sounds like you run the engine infrequently, at low loads and it
never really gets hot ... is this close?

If that is the case, you probably have carbon deposits on the valve
stems and lack of lubrication, particularly when starting cold, can
cause the valve stems to stick and bend the pushrods.

You can avoid a lot of this by making sure the engine gets up to
operating temperatures when loaded and then idles for a few moments
before switching off so that oil cannot carbonize on the hot valve stems.

Rick

Good points Rick.

I know the MD series engines have very limited oil lubrication going to the
top end. One of their problems is rusting valve springs. This, according to
Volvo, is due to short run times that doesn't provide enough oil or temp. to
eliminate moisture condensation in the area of the valves, springs and
rocker arms.

I had a valve spring break, due to rust pitting, while in Baja '89, and
found that there had been another boat in the same area that had experienced
the same problem.. My valve dropped into the cylinder and was jammed back
into the valve seat, cracking the passage into the water jacket... Had to
replace one cylinder head.. Also, I was later shown service bulletins
regarding the rust problem in the valve gear area.

The MD17C may suffers from the same rust, condensation problems as the other
MD series engines.

Like Rick says, start it often, run it long enough to get the oil hot and
circulating to all parts (and this should help to eliminate moisture in the
valve area).


--
My opinion and experience. FWIW

Steve
s/v Good Intentions

Steve wrote:


The MD17C may suffers from the same rust, condensation problems as the other
MD series engines.

Hadn't considered that aspect but it makes a lot of sense ... rusting
would cause the same symptoms as carbonizing, valve stuck closed, bent
pushrod. Same cure in any event so either bird with the same stone 8-)

Thanks for adding that little piece of info.

Rick

BTW, it seems to happen after the engine has sat for awhile
(months) and during cold weather starts....

It sounds like you run the engine infrequently, at low loads and it
never really gets hot ... is this close?

If that is the case, you probably have carbon deposits on the valve
stems and lack of lubrication, particularly when starting cold, can
cause the valve stems to stick and bend the pushrods.

well.....I am in the great lakes.....lake michigan actually.....the boat is
hauled in winter....the last few months have been busy and I was not able to
use the boat much unfortunately.....I did go there and start the engine monthly
and I would let it idle for 10 minutes or so then run at 12-1500 rpm for a half
hour.....and even put under load for a few minutes....I thought I was doing
things right, but now I am not sure....maybe wrong oil?...(Rotella T
10W30)....I did put some "power service diesel treatment" in the fuel when I
filled up on monday (and ran the engine for a good hour)...when i started it
wednesday, blam, the problem was there (missing, spitting out intake,= bent
rods)....I took the vavle cover off #2 and all looked fine, no rust or
such,.....I think I must pull the heads (even though I have a whole 6 inches of
clearance in the engine room above the engins...yippee)

So how do I avoid this?.....during the wisconsin winters, I do go down and hand
crank the engine a few spins to move oil.....and I fogged the engine with oil
and ran the oil/dsl mixture thru fuel system etc.....following the manual....I
do need to pull the injectors off this year for cleaning (I didn;t last
year....bad?).....

funny thing is that I do have 2 spare push rods......my last mechanic said he
canl;t get them for one month.....BUT I (and google) was able to find some and
order extras within one day....they were only $20 a piece, cheap spare IMO....

Hey I really appreciate the feedback so I can discuss it with a mechanic (after
I find one that seems to know what is going on....amazing how easy I can stump
some of them with my limited knowledge after reading calder's book).....thanks
again for the great feedback....

As I have mentioned in here, in other posts, I'm on my second boat with the
MD2B. Not an expert but I have experienced some problems with the engines
(no more than you might with other makes) but I have sorted them out myself
with the aid of the manuals and Volvo service bulletins and user articiles.
As a result, I have a higher degree of confidence in the Volvo MD series
than most around this group.

One of the biggest complaints I have had in the past has been the high cost
of simple parts, like gasket, etc. Major parts are expensive as well but now
that there are so many being replaced there are plenty of use parts
available.. I even found a fellow at the boater Swap Meet that had his
cruising spares for sale at a bargin price.

A fellow from Europe contacted me once to let me know that the MD series
engine are still available new in Northern Europe and sell for about $3500
US for a MD2x..

Just one final tip regarding the marginal oil circulation in the valve area
when the engine is cold or shot run... When ever I add oil to my engine, I
do it throught the plugs on the valve cover. These plugs were intended for
adjusting the compression release, but work better for adding oil than the
regular oil fill. Doing this totally floods the valve gear with fresh oil.


--
My opinion and experience. FWIW

Steve
s/v Good Intentions

Spamfreedom wrote:


So how do I avoid this?.....during the wisconsin winters, I do go down and hand
crank the engine a few spins to move oil.....and I fogged the engine with oil
and ran the oil/dsl mixture thru fuel system etc.....following the manual....I
do need to pull the injectors off this year for cleaning (I didn;t last
year....bad?).....

Leave the poor thing alone in the winter 8-) ... unless you have an
engine preheat system with prelube all you will do by turning it over
will be to introduce cold moist air to the cylinders, wipe what little
cylinder lube remains, and rub dry bearing surfaces against each other.
You will not move any oil except for that which you are far better off
not moving.

If you are going to pull the injectors for testing and calibration then
you can go ahead and squirt some preservation oil in the cylinders. You
don't have to pull the injectors each year unless you have good reason
to suspect problems with them. They can and should go for years with no
attention at all.

If you do not have any signs of rusting under the valve covers or on the
springs as Steve described then your problem with the pushrods is most
likely carbon deposits on the valve stems. They can be the result of
your unloaded runs, people think that is good for an engine and it
simply isn't as you have discovered.

If you find rust on the underside of the top of the valve cover, check
carefully for rust on the valve springs and stems. If you find any, take
an oil can with some diesel and squirt on the springs and stems. Wipe
off what you can and refer to the hammer mentioned in the next paragraph.

It is a credit to the design and construction of diesels that they
survive the best efforts of users to destroy them with kindness. Do not
give it short runs during the layup, do not turn it over unless it is
preheated and prelubed, in the Spring remove the valve cover and check
for condensation on the underside, squirt some light oil on the rockers
and valve stems. If you are really worried about sticking valves, tap
the closed valves with a soft faced hammer to see if they are free ...
they will feel "springy" if they are, solid if they are not and a few
taps and a drop or two of diesel on the stem should free up the stuck
ones. Do the same hammer test on the other valves, some will be partway
open or all the way open, you can rotate the engine to allow the open
valves to close to ensure they are free.

Rick