Yanmar 3ym30 raw water inlet gasket failed. Help?

[[3889]]

If the gasket on the above fails (arrowed in pic) will both raw water and coolant leak? I can see/ taste the raw water drip but the coolant level has also dropped and the bilge fluid has a pink tinge. Is the coolant loss likely to be a separate fault?

 

[prv]

I don't know the YMs so well, but I'm guessing that's the end plate of a heat exchanger? Quite possible it would be letting both leak, yes.

Pete

 

[[3889]]

It is the heat exchanger, thanks for reply.

 

[RichardS]

The sea water and coolant are kept separate and stopped from leaking out by two rubber O rings at each end of the heat exchanger. The four O-rings are indentical.

Perhaps some corrosion has occurred around one or more of the O-rings which is allowing fluid to leak out and/or mix. I would be surprised if the O-ring is broken but it might not have been fitted properly and has been clamped slightly out of position, in which case it will probably be ruined.

The O rings are £7 each so you might need to be prepared with at least two of them for the leaky end.

Richard

 

[[3889]]

Thanks. The leak started when I inadvertently slackened one of the 3 retaining hex bolts, in the belief that it was the raw water drain bolt situated nearby No amount of pinching up will stop it so I assume there is damage to the gasket / o rings. Am I right in thinking I will also need to replace all engine coolant when I remove the end plate?

 

[RichardS]

Thanks. The leak started when I inadvertently slackened one of the 3 retaining hex bolts, in the belief that it was the raw water drain bolt situated nearby No amount of pinching up will stop it so I assume there is damage to the gasket / o rings. Am I right in thinking I will also need to replace all engine coolant when I remove the end plate?

Ah - I guess that the O-ring has shifted slightly out of position and you have now trapped in against the flat face of the spacer. As you say, you will never stop it by further tightening.

I would drain the coolant out from the lower drain in the bottom hose but save it as you can reuse it if it is not due for replacement unless salt water has got into it but as the coolant level has been dropping that seems unlikely. A drop on your tongue might detect any salt but don't swallow it as it's not nice stuff.

As you will have to remove the end plate you might want to take out and clean up the core tube assembly. It is a job that should be done occasionally but ususally gets left until overheating starts to occur. It sounds as if you will need at least one new O-ring although I would be inclined to order two just in case. The postage will be the same. Four rings would cover all bases but it depends on what you can afford.

I have two 3YM30s on my cat but only carry 4 rings as spares rather than 8 as that just seems to much outlay. I intend to do a heat exchanger inspection during the next few months. Some silicone grease applied to the O-rings on refit will help them stay in position and re-seal properly.

Good luck

Richard

 

[[3889]]

That's really helpful, thanks. Very reassuring to know what to expect when I take things apart.

 

[NickRobinson]

Is that well developed rust at 8pm to your arrow? There may be a pre-existing leak to your spannering the drain plug?

 

[[3889]]

It is but the leak started 8 weeks ago so has had enough time, I think, to rust the bolthead. I've only just got back to the boat.

 

[TradewindSailor]

You need to deal with it asap because the starter motor sits below it and the Bendix gear could sieze up. Certainly take the starter motor off and ensure there is no salt buildup and grease before replacing.