M35b head gasket replacement

[jgatherton]

AJAY is a 2000 mk II with an M35b.  Generally reliable, no starting problems, no overheating problems but a little more vibration than I would like from the engine/drive train when under medium to heavy load.
I have now noticed a weep of coolant at higher revs only(>2500) which seems to be coming from the interface of the head and the block, aft starboard corner.  No sign of coolant in the lube oil- yet, but I assume the head gasket is leaking and is in need of replacing. No evidence of head bolt movement on the paint.  I have not tried additional tightening.  I thought about doing a breakaway torque measurement and possibly re torquing but this is full of uncertainty, so replacing the head gasket seems the best course.  I don't want to tighten bolts, think I have solved the problem and generate bigger problems down the line.  But, perhaps I have missed something and all input would be gratefully received.

I have done a search on replacing the head gasket and I think it is something I can reasonably expect to do but all help on the following would be appreciated:

Best supplier for head gasket kit.  Kubota part numbers, or take out a mortgage and go to the marine suppliers?
Additional items needed (liquid gasket etc).  There is always something, and Home Depot don't stock it.
The likely problems in disassembly and tips for dealing with same
Ditto on reassembly
The unexpected thing that usually comes up to bite us in jobs like this - there is always at least one.
What else should I take care of while I am stripping the engine to this degree.  Thinking PM here and exhaust system perhaps?

I did wonder if the head was warped.  The PO had not dealt with the cam shaft/water pump connection problem, failure occurred and I had the head taken off and that issue dealt with about 6 years ago by a local mechanic.  Perhaps the bolts were not torqued in the right sequence or to the right force in the rebuild, but that does seem a long time for the problem to manifest itself.  Again, any thoughts would be welcomed.  Not sure how I can check this.  It may be just a case of replace the head gasket and see if it fails again.  But, I suppose 6 years is not too bad!

[HowLin]

Could be you just need a re-torque on the head (best case scenario)...  but usually if there is a coolant leak it means the gasket is compromised - may have not been installed correctly be mechanic?

FWIW I was able to replace my camshaft on my Cat36 M35B without removing the head (removed front gearcase cover only).

[Ron Hill]

jga : I agree with Howard - I'd replace the head gasket and after about 3-5 hours running, re-torque the head bolts.

[lazybone]

There is nothing to be lost by trying a cold re-torque. 
If the head gasket had been replaced then it would be standard practice to re-torque the head bolts after 20 to 30 hours.
Remove a single bolt, clean threads, oil and torque to specs.
Follow the correct bolt pattern.  If doesn't work you will be no worse off.

[jgatherton]

Thank you for the input.  The new torque wrench arrives tomorrow so I will try retorque first.

Reading the service manual I see that there is a reference to an O ring in conjunction with the head gasket.  I have not seen this configuration before.  I wonder if I should get a new O ring as well as a gasket - if I eventually need to replace the gasket.  Any thoughts?

[lazybone]

I have no experience with your engine but there are some heads that use 0-rings in addition to the head gasket to seal the oil passages between head and block.
Just my guess.

[Ron Hill]

jga : I agree with Aldo - nothing to loose by trying a re-torque. 

However, if you don't get about 1/8 turn on a couple of head bolts, then a new gasket is in order!

My thought