Head gasket replacement - how to?

[agirlandhertractor]

I'm not really sure how you can get oil into the water from a blown head gasket on these tractors. You, no doubt, have a blown head gasket from the pictures but could there be two problems? Cracked head?

I agree, two separate issues, though maybe related. One is the loss of compression from the blown sealing ring between 2nd and 3rd cylinders. That explains why it stopped running, and why those two pistons/combustion chambers are damp with unspent fuel.

The other issue below your quote...

My reasoning: There is no pressured oil passages going through the head gasket- only an oil drain back to the crankcase. The pressurized head lubricant is provided by an external oil pipe. It seems to me that if the oil appeared in the water when you were using the tractor then the coolant would be hot and under some pressure. Any opening between the oil & water passages would cause water to push into the oil

Unless the sealing ring was compromised and allowed pressurized/partly spent fuel/exhaust to force itself into a nearby cooling jacket:

[agirlandhertractor]

Just dropped head off at the local machine shop. They said it absolutely needs resurfacing, but they will also check it for cracks.

[agirlandhertractor]

Head is finished. It was in fact warped. Surface looks perfect now. They had to remove injectors to work on it, and I started a separate thread for that topic.

Need to work on preparing the block gasket surface next.

[agirlandhertractor]

Did the machine shop elaborate on how much they had to remove from the head? You know there in very little clearance between the valves and pistons on these engines. I think with to much removal it could be possible contact could be made. Probably not, just something to be aware of.

I asked them about that. He said the only removed around .005 (five thousandths) of an inch.

[agirlandhertractor]

I don't have a pitch gauge in my shop. Anyone know the pitch of the cylinder head bolts?

EDIT: Cylinder head bolt threads on a YM1601/1601D are M12-1.50

[Norm]

If you clean the piston tops, are there already valve marks where they are hitting the pistons, or is it just in the carbon?

[agirlandhertractor]

If you clean the piston tops, are there already valve marks where they are hitting the pistons, or is it just in the carbon?

No metal to metal markings on pistons.

[agirlandhertractor]

The threads are M12-1.50, if anyone else needs that.


A little blurry but here's the head.

[agirlandhertractor]

I looked back over my records and noticed that the rebuilder I bought from (Fredricks fwiw) didn't check or replace any valve components (this when it had 600 hours on it). I've put another 400 hours on it since 2008, so it seems like a good time to do a full valve job while I have the head off (again). The pistons, rings, and con-rod bearings were replaced at 600hrs.

Just ordered new valve guides, seals and springs from Hoye. Will have a local machine shop lap the valves when the parts arrive, then I should be good to go.

[winston]

If lapping is all your going to do why not do it your self. All you need is compound and suction cup.


https://www.oreillyauto.com/detail/b/li ... ping&pos=1

https://www.oreillyauto.com/search?q=lapping+compound

[agirlandhertractor]

Head is cleaned up with new valve springs, guides and seals. As before the shop wound up damaging the lower precup chambers a few weeks ago, so I have new ones ready to install now. Hope to start reassembly tomorrow.

[agirlandhertractor]

Making progress. Next is to place the rocker arm assembly on, and slowly rotate crank to make sure I don't have any clearance issues from having the head decked.

[agirlandhertractor]

Had to step away for a week for a work conference.

Got the tractor started up today, she purrs like a kitten. Let it run for 10 minutes enough to get the engine warmed up real good. Will let it sit till cool before retorquing the head bolts and flushing any residual oil in the cooling system from the blown gasket.

[agirlandhertractor]

Re-torqued head bolts after engine block was room temperature again. A few of the inside bolts were absolutely needing to be re-torqued. The outer bolts were still in spec.

[agirlandhertractor]

Quick update...

I used the tractor in my yard for 30 minutes, then let it sit overnight. Checked head bolt torque a second time, and a couple of the middle bolts had to be cinched in just a smidge more (to 78 ft-lbs).

Since then I put several hours of moderate use on the tractor this weekend mowing 3 acres of mostly tall grass/weeds. Tractor worked hard, and is running like a top again. No oil residue in my (new) radiator overflow tank, tractor feels as strong as its ever felt.

When you do your head gasket job:

1. Chase head bolt threads in the block
2. Re-torque head bolts after warmup and complete cool down.
3. Repeat #2 as many times as needed until you aren't having to adjust torque anymore

I didn't do these steps last year, so I got to do the job twice. I've updated this picture based tutorial with these steps.