Blown Head Gasket on Yanmar 4JH ?

[Conch Cruzer]

I was three hours into a 20 hour passage to Panama when the engine started to overheat. This is my first experience with that problem. We sailed back into Cartagena and tied up to a dock. I did some checks today and found water in the cylinders. At that point, I decided to disassemble the engine and remove the head, thinking it's either a head gasket or cracked head.

Is there anything else it could be? If it was a leak in the heat exchanger, it wouldn't be letting water into the cylinders. I think it's most likely a head gasket, but what would cause that to suddenly blow out after 1700 trouble-free hours?

Any ideas?

Thanks,
Dan
S/V Eventyr

[Inthewind]

How did you know that there was water in the cylinders? Did you pull the injecters out and turn the engine over and water shot out? Did this problem with the water happen when the engine was running? A small amount of water in the cylinders could cause the engine to lock up. It would have had to get extremely hot to crack the head,did your alarm go off or did you see it on the temp guage? How does your exhaust elbow look? Has it ever been changed? Do you have an anti-syphon valve installed on your engine? Did the engine shut down on you or did you shut it down. Have you ever changed your water pump impeller? Sorry to hear about your problem?

[Alan Wheeler]

So seeing as you are asking for other possibles, does that meant the head gasket looked OK??

[Conch Cruzer]

The head gasket didn't show any clear sign of failure. In fact, it looked ok to me.

I shut the engine down myself. It didn't go above 230 or 240 on the gauge and the alarm didn't activate before I caught it and shut it down. There was a lot of water in the cylinders when I pulled the injectors, they were full. However, I was filling the engine with water yesterday morning while it was shutdown. Wherever the leak is, it was going through there and into the engine just under the static pressure of the heat exchanger being full.

I only shut down for a few minutes at sea to let things cool off and refill the water and check the oil. Seeing the water disappear as I put it in, I decided to crank the engine immediately and keep it running at idle until I was back in port. This worked well for me. I had to add water every half hour, but I had the engine available to maneuver through the channel and into a slip at a local marina.

I'm thinking now about the possibility of having a leak in the exhaust manifold between the gas and water sides. That's making more and more sense. Any thoughts on this?

Thanks Again,
Dan
S/V Eventyr

[Inthewind]

It would seem to me that it would not be the exhaust side causing your problem. You are pouring water in the fresh water side, the exhaust is cooled by raw ocean water. When the engine was very hot,did you pour cold water in? Did you hear any cracking if you did that?

[AnchorageGuy]

In the Yanmar the fresh water coolant and the exhaust manifold share the same piece of equipment. Most engine manufacturers are going to this set up. But I am still not sure how the fresh water is getting into the cylinders. Raw water can enter through the exhaust by a few different methods. If the exhaust manifold is cracked I would think it would pressurize the fresh water system and force the water out of the tank while running. We are dealing with just that problem right now, we think.

[Conch Cruzer]

I pressurized the exhaust manifold/cooler assembly this morning and found a sizeable leak near where the mixing elbow attaches. With the cooler full of freshwater, the jacket around the exhaust manifold emptied into the exhaust and backflooded the engine/head with freshwater. With either intake or exhaust valves open, water was able to drain into the cylinders.

Yes, the exhaust is raw water cooled, but only after the mixing elbow. The exhaust manifold itself, as stated already, is integral with the cooler and thus is freshwater cooled.

Thanks all for the tips and help.

Cheers,
Dan
S/V Evenyr
Cartagena Colombia

[Alan Wheeler]

Good to hear. I was going to say that was probably the problem. It is not a new concept. My Perkins uses the same idea of the fresh water cooling the manifold.

[Extemporaneous]

I'm trouble shooting a similar problem although there are not a lot of fluids involved. I recently did an oil change and as always got an oil analysis done. Regardless of the oil looking perfectly normal, the oil analysis revealed glycol in the oil. I have in the past had to top up my glycol (I should have woken up then) with little signs of external leaks. So far I have had the oil cooler pressure tested and it appears fine. The exhaust manifold is now be tested but I don't have results yet. If it is not this, I guess the next steps will be checking out the fresh water pump and finally the Head gasket / block (hope it is not this).
The engine is a Westerbeke W46.
Any advice or comments on my approach?
Thanks.
Extemp.

[Extemporaneous]

Originally Posted by Extemporaneous

I'm trouble shooting a similar problem although there are not a lot of fluids involved. I recently did an oil change and as always got an oil analysis done. Regardless of the oil looking perfectly normal, the oil analysis revealed glycol in the oil. I have in the past had to top up my glycol (I should have woken up then) with little signs of external leaks. So far I have had the oil cooler pressure tested and it appears fine. The exhaust manifold is now be tested but I don't have results yet. If it is not this, I guess the next steps will be checking out the fresh water pump and finally the Head gasket / block (hope it is not this).
The engine is a Westerbeke W46.
Any advice or comments on my approach?
Thanks.
Extemp.

Just got a call that my exhaust manifold checked out fine.
Looking at the manual and diagrams of the fresh water pump, I'm not sure if there is place where a faulty seal could cause cross contamination between the oil and glycol. The pump is belt driven.
Do any of you know?
Thanks,

[Alan Wheeler]

I can not think of one thing that would give you glycol in the oil without some other major operational issue rearing it's ugly head.

[terrymccann]

Hi, interesting Yanmar analysis developed between the helpful parties there.
I've also got a Yanmar issue that concerns me and would love some expert assistance with my 4LH/HTE , please. I've just noticed emulsion under the oil filler cap and on the dipstick on my Yanmar 4LH/HTE, after last week's running the motor alongside to charge batteries?
I usually run the engine under load each week while I'm busy with the refurbishment of the boat and only use good quality Shell lubes. Any suggestions as to the problem... the water temp has remained cold and I've been watching the gauges, as well as feeling the exhaust water temp and there's definitely been no overheating at any stage.