{Stus-List} Yanmar Heat Exchanger

Nauset Beach nausetbeach at optonline.net
Mon Mar 26 12:21:27 EDT 2007

Last Saturday I tried to remove the two end caps of the heat exchanger on my Yanmar 3GM30F to check and clear out any accumulated crud in the tubes.  7 of the 8 bolts were successfully loosened / removed.  The last refuses to budge.  Multiple coatings of PB Blaster, taps with a hammer - only to find that my apparently cheap 10 mm sockets [a  6 point and a 12 point] had not only rounded out themselves but also the head of the bolt.  Of course, this bolt is in a very awkward, inaccessible location which I cannot see other than with a mirror and the whole process was done by touch.

Aside from getting some decent sockets, any suggestions?  My 10 mm open wrench would not hold the bolt.  The bolt is somewhat recessed so putting a vice grip on it does not work - though possibly could put one straight on and put a wrench on the vice grip.  I obviously do not want to shear off the head of the bolt.  The other 7 bolts audibly cracked when they first started to move.  An easy guess is these have never been removed in the engine's 20+ year life.  

The good news, the tubes are mostly clear from the end I can see so am tempted not to try and force this.  I may just buy a wood dowel to rod out in place, flush out as best I can and hope any remaining loosened crud is flushed out by the raw water.

As an aside: I put the end cap I could get off in some vinegar to help remove some crud, and was surprised to see the interior of the cap turn pink - which would seem to indicate electrolysis.  According to the Service Manual there are no zincs on the HX.  I had been planning on filling the raw water side with vinegar and letting it soak for a couple hours as was discussed a couple weeks ago but am not certain that is such a good idea now.  Any thoughts?

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