Anything else to do when changing a head gasket?

   / Anything else to do when changing a head gasket? #1  

Lobanz

Bronze Member
Joined
Oct 16, 2011
Messages
99
Tractor
Kubota L3400, Kubota G5200H
[I'm definitely not an experienced mechanic, but I have changed a head gasket before, but that was a LONG time ago. Remind me of any gatchas?]

My Kubota G5200 HST (3 cyl diesel mower) is overheating. Seems like a common problem. Only seems to overheats under load.

Anyway, I DID see air bubbles in my radiator. AND it uses water (but haven't noticed any in the oil). AND I can see some faint smoke coming out of the radiator when still cool (just after starting it up). So I am about to change the head gasket.

Wondering what else to do while I'm in there doing the head gasket. Already thinking about the following:
  • Fan Belt
  • Radiator Hoses
  • Exhaust and intake gaskets and bolts
  • Valve adjustment
  • Head resurfaced
  • Coolant system flush and, obviously, new coolant.
  • [Already had radiator boiled out not long ago]
  • Any sensors that should be replaced?
  • Anything to check on water pump?
  • Can you reuse the head bolts? (Service Manual (pg 1-53) doesn't mention replacing them, so I assume reuse is OK.)

Any other ideas?

I have noticed that the coolant drain cock on the block is rusted shut. Wondering if the cooling passage is also clogged. Don't know how to check.

Does your G5200 have a radiator fan shroud? Mine doesn't, but the Kubota Parts Site shows one (search G5200, click open, go to Cooling System / Radiator and it's part 110, #15852-72330). They are about $55. Wonder if it would fit mine and if it would help.

Also, does yours have an coolant overflow bottle? Mine doesn't, but it has a tube coming out of the neck of the radiator. So I just wedged a aluminum can in the frame and stuck the tube in the can. Don't know if it helps.
 
   / Anything else to do when changing a head gasket? #2  
Not familiar with that engine, but I'd make sure that it isn't an "interference" engine before you have anyone start shaving anything off the head ...

(I'd also have it checked for warpage)
 
   / Anything else to do when changing a head gasket? #3  
Look for evidence the head gasket failed after apart. If you can not determine the head gasket failed, have the head checked for cracks.
 
   / Anything else to do when changing a head gasket? #4  
After head removal, and top of block cleaning it is advisable to check the top of block with a ground stock bar and a feeler gauge to ensure the top block deck is not warped. The manual should spec out the tolerance, but within 0.002" is good to go. Do the same to the mating surface of the cylinder head. It's much easier of course to have the head surface milled to spec, usually 0.005" will do. Also head gaskets for diesel engines may come in different thicknesses. You measure the piston at TDC, top dead center, take into account if any resurfacing of cylinder head was done, or top block deck resurfaced. Then calculate total difference. A chart usually tells you which head gasket to use. I'd bet all you need to do is check surfaces, then install new Kubota head gasket.
 
   / Anything else to do when changing a head gasket?
  • Thread Starter
#5  
So, if I use a straight edge (like an aluminum square or something, or I have a level with a machined edge), and it looks pretty good in all directions (less than 0.005"), then do I really NEED to get it resurfaced?

Also, do I really NEED to take off the intake and exhaust manifolds? Would rather not deal with breaking rusted bolts if I don't have to.

If resurfacing is called for, will the machine shop require that the manifolds be off? How bout the valves and such?

Good stuff. Thanks!
 
   / Anything else to do when changing a head gasket? #6  
You are not going to have a handy tool laying just laying about that has those kinds of tolerances. A straight edge is precisely ground to specs for measurement....not a general purpose level or aluminum T-square or any wood working tools for that matter.
Checking the block is not a bad thing to do and necessary if theres a sleeve height needed for gasket sealing (ie. wet sleeves).
No you don't have to take off the manifolds IF you can check the head yourself. Otherwise the machine shop will, and charge you for it. Valves? Shrug, are you sure everything is okay there? Nows the time on find out not a hundred hours down the road. So yes, check those seats, guides and put in new stem seals.
 
   / Anything else to do when changing a head gasket? #7  
I have never seen a Kubota block warp (doesn't mean they can't). I've always used a straight edge and a .002" feeler gauge to check. I would check the head for cracks. The most common place these heads crack is in between the exhaust valve seat and the pre-combustion chamber on #2 cylinder (typically visible to the naked eye). If the head is not cracked you should have it resurfaced, usually it doesn't take much. If it does require removal of a lot of metal Kubota makes an .008" head gasket shim to correct the valve to piston clearance.

Brian
 
   / Anything else to do when changing a head gasket? #8  
Just a smatter for my own info brain, do those cracks run into the water jacket or is an easy repair to keep the seat from coming loose?
 
   / Anything else to do when changing a head gasket? #9  
Just a smatter for my own info brain, do those cracks run into the water jacket or is an easy repair to keep the seat from coming loose?

Yes, they go into the water jacket and are not repairable. There are companies that say they can repair them, but I've never seen one do it successfully. If the head cracks the best thing to do is replace it.

Brian
 
 
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