Yanmar 3JH4E - How to Remove Cooling Stack from Heat Exchanger?

[carpetsauce]

I want to remove the tube cooling stack from the body of the heat exchanger on a Yanmar 3JH4E engine. I've removed both end caps but the tube stack won't budge.
Does the stack come out rearwards, towards the back of the engine?
Is there another fastener holding the tube stack in place that I've missed?
Does it twist? If so which way?
Should I protect the face of the stack with a piece of wood then whack it with a hammer?
Any jewels of experience from forumites will be gratefully appreciated.
Thanks.

 

[penfold]

Some tube stacks will go out either way, some have rims and will only go in one direction. Are both ends the same diameter? If so it should go either way.

 

[carpetsauce]

Thanks for your reply. Yes, both end caps are the same diameter and there doesn’t appear to be a step in the heat exchanger body at either end.

 

[penfold]

Some gentle encouragement with a hammer and a piece of wood is in order then.

 

[carpetsauce]

Thanks, in trepidation. If I trash the cooling stack its replacement won't be cheap.

 

[Rafiki]

I had the same problem with my Volvo D2-40 having disassembled everything I couldn't get the stack out despite hitting it with a hammer ( against a piece of wood), eventually I decided I really didn't want to damage it and gave up ! I instead used a very long and narrow screwdriver to poke through each tube where the raw water goes through - there were no obvious blockages - and all seemed very clear after more than 10 years , so I just put it all back together again. At least I know how it cames apart now and am pretty satisfied it's all clear. Typical days boating said the wife 4 hours driving and 4 hours maintenance and lunch on the deck !

 

[carpetsauce]

Thanks Rafiki,
My problem is that coolant water doesn't seem to be passing through the heat exchanger. When the engine is run and warmed up the coolant hose downstream from the thermostat gets hot, so I presume the thermostat is open. However the seawater outflow from the heat exhanger remains cold, as does the coolant hose downstream from the heat exchanger.
I'd earlier cleaned out the tubes in the stack and checked the strainer for weed etc, but I don't think that's the problem as there's plenty of seawater flowing through the whole system. I think I need to remove the stack to see what's preventing coolant water from flowing through freely. Not looking forward to this.