Brokenness valve springs

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richardsnowstar

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Help! I have a Bukh 36 in my boat and yesterday it made a strange noise while motoring. I immediately put the engine in neutral and went to investigate. The engine vedy quickly stalled. Tried restarting and still got a strange noise and it did not start.

Today I took the rocker cover off and found that the exhaust valve springs for cylinders 1 and 2 were broken.

Last year I had a water pump problems and got water in the oil. After the water pump was fixed I changed the oil 3 times to flush out the emulsified oil. Despite this there was a lot of emulsified oil on the head.

My questions are . .. What would cause 2 valve springs to go at the same time?
Is it related to the emulsified oil?
What do I do now? Replace the springs only or take off the head and check all is well with the valvess and pistons?

Any advice would be appreciated.

Edit: Title should have been "broken" valve springs. Posted by mobile!
 
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It can very well be.Just a bit of surface rust is enough to cause a valve spring to brake.You should (as in must) replace all the springs because they've all been exposed to water.Hopefully there won't be much damage to the cylinder head or pistons but you'll have to dismantle and see.When the valves dropped they may have touched the pistons and may have been bent.The valve guides will need inspecting as well.
 
richardsnowstar said:
Help! I have a Bukh 36 in my boat and yesterday it made a strange noise while motoring. I immediately put the engine in neutral and went to investigate. The engine vedy quickly stalled. Tried restarting and still got a strange noise and it did not start.

Today I took the rocker cover off and found that the exhaust valve springs for cylinders 1 and 2 were broken.

Last year I had a water pump problems and got water in the oil. After the water pump was fixed I changed the oil 3 times to flush out the emulsified oil. Despite this there was a lot of emulsified oil on the head.

My questions are . .. What would cause 2 valve springs to go at the same time?
Is it related to the emulsified oil?
What do I do now? Replace the springs only or take off the head and check all is well with the valvess and pistons?

Any advice would be appreciated.
Click to expand...
My understanding is that water in the oil or even condensation can cause rusting of the springs. This leads to the springs cracking and breaking.... Its a reason why you should not run an engine frequently without getting it up to full working temperature.

If the valves have dropped they will almost certainly been hit by the pistons.



I would take the head off and fully service it with all new springs and new valves where needed. A good chance you'll need a couple of new pistons as well and possibly a new head.

I have seen the result of this happening to a Volvo MD11C. Not a pretty sight at all. One valve had been hit, the head broken off and hammered back into the seat.
 
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You'll have a struggle replacing valve springs without taking the head off...

I don't know the Bukh but if its a conventional layout check you've got all the bits of the spring and the split collets - make sure none of them has fallen into the engine or its a much bigger job to fish them out.
 
MASH said:
You'll have a struggle replacing valve springs without taking the head off...

I don't know the Bukh but if its a conventional layout check you've got all the bits of the spring and the split collets - make sure none of them has fallen into the engine or its a much bigger job to fish them out.
Click to expand...

Are you a "conventional layout",because you sound like what the Dutch call a "kutteliktje" which means an expert on certain devices,but perhaps not precisely what the OP was asking,all the best x
 
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richardsnowstar said:
Thanks for the comments. Will remove head. Any suggestions regarding getting rid of the emulsified oil?
Click to expand...
It depends on how bad it is.I once dismantled a Bukh 20 that had had a ruptured liner allow water in the sump.The resulting goo was so thick that it took a long time with a compressor and loads of parafin to shift.If your oil isn't too bad maybe flushing oil will do it.
 
30boat said:
It depends on how bad it is.I once dismantled a Bukh 20 that had had a ruptured liner allow water in the sump.The resulting goo was so thick that it took a long time with a compressor and loads of parafin to shift.If your oil isn't too bad maybe flushing oil will do it.
Click to expand...

The oil in the sump is fine. I wasn't sure if flushing oil would shift the "mayonnaise".
 
Emulsified oil in the head can be caused by as simple a problem as a blocked breather pipe. It appears as a "mousse" clinging to the rocker cover and at its worst, the rockers themselves. It was a typical problem associated with the BMC A and B series engines.

Marine diesels run cooler than vehicle engines, even FW cooled marine engines, so condensation is a likely cause too, again usually made worse by poor crankcase and engine "breathing". I would check the brathing arrangements for the engine and change the oil and filter, then watch to see if this is a effective cure.

Valve springs have a hard life and rusting creates stress concentrations which can cause premature failure. +1 the Top end overhaul.
 
richardsnowstar said:
My questions are . .. What would cause 2 valve springs to go at the same time?
Is it related to the emulsified oil?
What do I do now? Replace the springs only or take off the head and check all is well with the valvess and pistons?

Any advice would be appreciated.

Edit: Title should have been "broken" valve springs. Posted by mobile!
Click to expand...

Yes this seems to happen on old Volvo's and Bukhs from time to time. The sea water seems to start some sort of reaction in the tempered springs. Usually it is the plunger springs in the fuel pumps.

You would be wise to replace all the valve springs and service the Bosch HP injector pump and ask for new springs to be fitted to avoid a future problem.

Some boats get sea water contamination and have non of these problems whereas some with the same engines experience broken springs following after the clear up of the contamination.
 
Corrosion pitting is a well-recognised initiation point for fatigue fracture. I would assume that your springs have failed torsionally with a smooth-looking fracture face? It also is typical that both failed together, having seen the same number of cycles.
 
The current plan is to replace all valve springs, replace the springs that hold the rockers in place, replace a bent push rod and replace one valve that has damage on the top where it touches the rocker. The damaged valve also seems to be the one that went first as there is certain amount of polishing on the valve end and the corresponding top of the piston. Because the valve is square on to the piston and there seems to have been minimal contact I am not planning to replace the second valve that had a broken spring. I will also take the opportunity to get the head cleaned ultrasonically to open up the waterways as they are currently about half their original size.
 
richardsnowstar said:
The current plan is to replace all valve springs, replace the springs that hold the rockers in place, replace a bent push rod and replace one valve that has damage on the top where it touches the rocker. The damaged valve also seems to be the one that went first as there is certain amount of polishing on the valve end and the corresponding top of the piston. Because the valve is square on to the piston and there seems to have been minimal contact I am not planning to replace the second valve that had a broken spring. I will also take the opportunity to get the head cleaned ultrasonically to open up the waterways as they are currently about half their original size.
Click to expand...
Check that the valve guides are within spec while you're at it.I'd replace the other valve just to be safe.It could be very lightly bent . The seats could benefit from lapping or recutting .
 
I'm well known as a tightwad sailor, however, replacing only one valve is an economy too far. The cost of the top end overhaul "consumables" is too high to risk it even if you're doing all the work yourself. If you can't get a decent seat/valve grind, have the seat recut. It really is a false economy to do anything else. Don't forget to torque the head down again after about 50 hours running, too. It's an expensive lesson f you don't.
 
I must admit I would check the condition of all the valves and valve seats and seriously consider replacing all the valves as well as the springs.
 
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