Yanmar 4JH5E slow coolant leak after alternator replacement

[karwas]

Hello,

I have recently replaced an original Hitachi alternator installed on my engine
with a new Balmar XT170.

As a part of upgrade, I have also replaced upper arm with Balmar adjustable
"Universal Belt Buddy". This required removal of the bolt from engine head,
and reinstallation with slightly (1/2") longer bolt, and a spacer 1/2" spacer:



To my surprise, there is a small leak of coolant from this place after installation.
I plan to use some "liquid gasket" to seal it, but it is strange that there is
leak there. After removing of the original bolt, there were no traces of any
sealant whatsoever, so maybe my new bolt broke through some thin wall,
and penetrated into cavity filled with coolant?

Any comments or advice how to fix this issue?

Thanks
Przemek (a.k.a PK)
S/V Festina Lente

[GordMay]

Greetings and welcome aboard the CF, PK.

I cannot imagine how coolant could leak from an alternator mtg. bolt-hole, so I'll be following, /w interest.

[Paul L]

Not sure on your model, but on the 4jh3 that bolt goes through the freshwater pump.

[GordMay]

Originally Posted by Paul L

Not sure on your model, but on the 4jh3 that bolt goes through the freshwater pump.

Thanks for pointing out my failure of imagination.

[Poeme]

Exact same upgrade, exact same "leak" on my 3JH5e. Just a weeping, a wet bolt...but all's well after install...curious...

[Scubaseas]

"so maybe my new bolt broke through some thin wall,
and penetrated into cavity filled with coolant?"

Yes. The bolt circled goes into a hole that is in the cooling system water jacket in the head. It also passes through the coolant pump. I could see coolant being there leaking on some engines and not on others. Just put thread sealer on the bolt and you should be fine. It's more likely just seepage from one of the two gasket faces under that particular bolt.

Look at the parts manual under "Fig.17. COOLING FRESH WATER PUMP" for a good diagram of what I am trying to say.

[Kd9truck]

I have the same motor (09), replaced my alternator 2 seasons ago with the larger stock Yanmar upgrade. No leeks but plenty of belt dust.

[karwas]

Thank you Scubaseas!

This is a perfect explanation. I was surprised by this leak,
because I haven't used any substantial force to neither
remove old bolt [35] nor reinstall new one, so I didn't expect to break
anything or penetrate through any metal walls.
But most likely, I must have disturbed the gasket [16] and cause a leak.
I will use Permatex gasket maker to seal non threaded surface
of the new bolt. Simple thread locker application is probably
not a best idea, as threaded part is inside cylinder head,
not water pump assembly. I will use some non seizing stuff on the thread,
because the new bolt is made of 316 SS.

Picture related:


I am also ordering a new gasket (https://www.dieselpartsdirect.com/ym12948642050)
which is not that expansive, and it will be good to have
in case I will develop further leaks from this place.

Thanks for all the advice!

I have some additional questions about grounding of the new alternator,
but I will start another thread about it.

Przemek
S/V Festina Lente