New Yanmar catastrophic failure

Is not the Yanmar 4JH57 a Common Rail electronic diesel engine ?

 

can not happen on that diesel

 

Thanks boys
Yes, been up to my elbows, we launched a couple of weeks ago after 18,000 hours building. And miles to go before i sleep

A guardian angle has appeared in the form of a kind mechanic who has a lifetime of diesel experience

In a moment he had the valve cover off and discovered two stuck valves. His boroscope seems to reveal no piston or cylinder wall damage. The clatter clatter was two bent push rods.

Like a heart surgeon he gently moved the pistons up by rotating the engine with a 22mm socket on the pulley nut.

Tap tap down with a nylon mallet, push back up with the piston. After tapping down and pushing back up with the pistons he freed both stuck valves.

Fate continues its magic: although there are no push rods in Australia, lightning just struck a new motor in Sydney and its push rods have been extracted and express posted.

Our guardian angel is confident he can sort it

In conclusion...all through this long difficult project i have been amazed by the guardian angels who appeared and help. The moral is go for it, do big stuff, take calculated risks and somehow you get there.

 

great, please make sure that the exhaust is not open to the sea, salt air can eat valves

 

Thanks for the update, I feel better knowing Xmas miracles still happen.

 

You have not stated root cause or I’m too daft to decipher.

 

As I understand it, two valves were frozen shut and when the engine was cranked the pushrods bent trying to open the valves.

 

I get that, but what causes the valves to ‘stick’?

In a conventional engine; the springs pull down really hard, so in order for them to be stuck up or down against the shaft, some error has occurred, as in open exhaust and corrosion, or the lubrication system failing.

So, root cause is not a stuck valve, but the reason the valve was stuck.

 

Sorry about my last post, bit too philosophical.

Now to business: the root cause of stuck valves. I installed two new Yanmar 4jh57 about three years ago while building the boat in my back yard. Very careful design went into the exhaust system. Many of you contributed.

I test ran both engines for few minutes using fresh water. Impellers ok, water out through exhaust ok. Both ran smoothly. Inevitably some water remained in the long horizonal cylindrical Vetus muffler that is about 300mm below the elbow.

This muffler has three baffles. So maybe the first compartment seals in a humid atmosphere. Cold nights, possible condensation on two exhaust valve stems.

This situation could happen to any engine left unused, and it does not. After two years of Covid travel ban, the Perkins in my old boat started with a few cranks. Also the identical new starboard Yanmar engine runs smoothly

Therefore do we conclude the Yanmar valve stems were sub standard.

 

Glad you got it figured out.

Lots of possibilities for the stuck valves, but I have to wonder if you were only operating the motors for a few minutes on occasion, if the oil temps were ever able to get high enough to allow for good lubrication of valve stems.

I just dealt with some stuck valves on a motor.

The culprit was a rubber insolation gasket that had turned to goo from ethanol fuel.

The gasket goo dropped down the intake runners where it burned off creating a sticky smoke that coated the tops of the pistons, combustion chambers, valve faces and stems.

The stems got so sticky in the guides that the keeper grooves on the valve stems were beat out.

Fortunately I discovered the issue before any valves or seats dropped.

 

A comment or question?

Make sure to change all engine oils…

 

Good news
The guardian angel straightened the push rods and after testing with handcranking (22mm socket on pulley nut) it started with the starter motor. Then we ran the engine at low revs until temp got up, about 45 mins. Now just waiting on the new push rods. Looks like all is well.

Still do not know why two exhaust valves stuck. The heat exchanger, exhaust elbow and muffler have been removed and no signs of damp or corrosion. The mystery remains.

Conclusion... Yanmar could maybe issue a warning about letting sleeping engines lie

Thanks for all your helpful advice
Michael

 

Diesels need load and heat per most conventional wisdom. You offered neither on short runs or crankovers.

Some soot or carbon build up or even the fuel not cooking off can cause it.

Yanmar is not at fault. Be a wise captain and own it.

 

Hear Hear!
45 minutes at idle with no load does not constitute a full warmup, and can cause further damage.

 

This is a terrible warm-up regime for a diesel.

It's a good thing you have a guardian angel, you're going to need it.