Anything else to do when changing a head gasket?

[andreiwright]

"Hi my head gasket just blown out and the oil just dripping everywhere. Where can I get a very cheap head gasket or can I make it myself? Rockauto is so far away from here.

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Visit our husqvarna t35 trimmer head at power mower sales."

 

[Lobanz]

OK. Got the head off the Kubota mower and the Yanmar tractor. Mower head at machine shop being pressure tested and resurfaced. Should be ready today and I'll take them the Yanmar head when I pick it up.

I DID NOT see anything that I could discern as leakage on either head gasket. On the Kubota, there were some random blobs of carbon where I wouldn't think there should be any -- like on the head and block, but not in a piston area -- more into the gasketed area. Here's some pics and videos of the Kubota head.

Anyone see anything that I don't?

Head before cleaning:


Block before cleaning:


Head gasket pic (pic a little dark):


Video of block and head before cleaning (if it doesnt work below, try HERE):

Video of block after cleaning:
(see next post -- it'll only let you have 1 video on a post)

 

[Lobanz]

Here is the block after cleaning (held phone sideways for some reason. If video doesn't work, try HERE):

BTW, instead of PB Blaster or Liquid Wrench, I used 50/50 acetone and Dexron AFT as penetrating oil. MAN OH MAN did it work! :shocked: I didn't have any trouble with any bolt I put it on. The exhaust manifold bolts and muffler bolts looked like they were welded on there by the devil himself, but they were some of the easiest bolts/nuts I removed. Just soaked them down periodically throughout the disassembly process and by the time I got to them, they were like butter. Very nice. Doesn't stay mixed well, so you have to keep shaking it.

 

[john_bud]

Yes, light oil and a highly volatile carrier to move the oil into the cracks and gaps. The commercial stuff uses a carrier that is much "safer".

The faster the solvent evaporates, the better it moves the oil.

 

[Coyote machine]

I just checked it when it was cold! :thumbsup:

How do you do it?

:rotfl:

How did it have bubbles if you were checking it cold?:confused3:

The videos are hard to read with the camera moving all around. The marking on the pistons are probably just a particular sized, all matched, #1 piston size.

Did you show us both sides of the head gasket?
All I could see is piston 3 seemed to have an area where there was no carbon, which can be a result of a leak blowing water by the gasket and getting burned up or blown out the exhaust.

Lots of leaks, as a result of cracks in head/block can be invisible to the naked eye, which is where magnafluxing can show evidence of hairline cracks, etc. I doubt you have any cracks though, probably just a failed head gasket.

Another possible scenario is when your engine gets hot gases of combustion bypass the head gasket near the combustion chamber and get into the cooling jackets in the head and overheat the coolant, resulting in the bubbles in the radiator. The hot gases of combustion have to escape to atmosphere to reach equilibrium.

 

[Lobanz]

How did it have bubbles if you were checking it cold?:confused3:

Yup. Had bubbles. Pretty consistent stream of them. One per second maybe. The Yanmar does have a water pump but not a thermostat. The Kubota does have a thermostat, but there were still bubbles in the radiator just after starting when it was cold -- about 1 per sec or so. The thermostat should be closed at this point, but perhaps air bubbles can still get past it due to pressure building up on the engine side of the thermostat. Dunno. It looked very similar to this video (entitled "Water Bubbling in Radiator - Still Cold"):

Did you show us both sides of the head gasket?

Ooops. Should have taken another pic. I still have it, can take better pics at lunch.

Another possible scenario is when your engine gets hot gases of combustion bypass the head gasket near the combustion chamber and get into the cooling jackets in the head and overheat the coolant, resulting in the bubbles in the radiator. The hot gases of combustion have to escape to atmosphere to reach equilibrium.

This has been my theory all along, except that it also does it when cool. Kinda wish I had access to a compression tester and leak down tester now so I would better know where to look. But it would have been another $150 in tools that I would very rarely used. And I knew I was gonna change the head gasket anyway.

I ordered all new gaskets, hoses, valve seals, fan belt, and a new radiator cap.

Should I go ahead and lap the valves or just leave them be and just change the seals?

 

[Lobanz]

Here's a strange symptom. Just before pulling the tractor in to work on it, I wanted to check for bubbles again. It was slightly warm having been driven from the barn to the garage. Took radiator cap off and it was full of white foam. See video below:

 

[rsallen]

You're going to have the springs and keepers off so may as well inspect the seats, but if they look good I wouldn't touch them with any lapping compound...........and don't mixing them up. If they or even one looks iffy......time for a valve job. That's machine shop work.
With the amount of coolant it appears to have gone through this engine I'd be somewhat surprised if a valve job wasn't in order.......

 

[Coyote machine]

Yup. Had bubbles. Pretty consistent stream of them. One per second maybe. The Yanmar does have a water pump but not a thermostat. The Kubota does have a thermostat, but there were still bubbles in the radiator just after starting when it was cold -- about 1 per sec or so. The thermostat should be closed at this point, but perhaps air bubbles can still get past it due to pressure building up on the engine side of the thermostat. Dunno. It looked very similar to this video (Deleted for posting purposes.)


If combustion gases are in the cooling system bypassing the head gasket or otherwise, they will present as bubbles or make the coolant overflow the radiator, (once up to temp, thermostat open) and rad cap off.



Ooops. Should have taken another pic. I still have it, can take better pics at lunch.

OK. But at this point it's going to be whatever it is, but you might as well show us the condition for analysis...



This has been my theory all along, except that it also does it when cool. Kinda wish I had access to a compression tester and leak down tester now so I would better know where to look. But it would have been another $150 in tools that I would very rarely used. And I knew I was gonna change the head gasket anyway.

For future reference: some stores, Autozone, etc. will lend out tools for this kind of testing to save their customers $ and to help them get the job done....

I ordered all new gaskets, hoses, valve seals, fan belt, and a new radiator cap.

Should I go ahead and lap the valves or just leave them be and just change the seals?

Might want to consider a water pump if they're not a lot of money. Could have tested it when it was still on the engine by looking for shaft play side to side or in/out. Could still do that by just bolting it up and looking for excess play in the bearing/shaft. Sometimes they will wear the fins as already mentioned, and though your's looks good from my house it's hard to be sure. Decide how long you will keep the tractor to see if a new pump might be worth being safe vs. potential of being sorry. If it fails soon after the head job then all your money may end up down the toilet. On the valve lap, it can't hurt and it gives the valves a once over for any issues. Plus what RSAllen said above...

Here's a strange symptom. Just before pulling the tractor in to work on it, I wanted to check for bubbles again. It was slightly warm having been driven from the barn to the garage. Took radiator cap off and it was full of white foam. See video below:

That's the DEVIL in the details, most likely combustion gasses in the cooling system, hence the bubbles when the t-stat opens and you have reached op temp. You sure you don't live in Georgia?!:laughing:

You're going to have the springs and keepers off so may as well inspect the seats, but if they look good I wouldn't touch them with any lapping compound...........and don't mixing them up. If they or even one looks iffy......time for a valve job. That's machine shop work.
With the amount of coolant it appears to have gone through this engine I'd be somewhat surprised if a valve job wasn't in order.......

What he said ^^^^^^ And when you're all done you'll have a good reliable machine again. I do strongly suggest you find a way to tax you equipment less when it's hot out. JMHO.

 

[Coyote machine]

GATES: Cooling System Flush: Cleaning Neglected Vehicles FULL Version - YouTube

FWIW, the above vid shows how water pumps are damaged by neglected cooling system flushing, and how contaminants in the coolant and water in the system can destroy seals in the pumps when left in the radiator, block and heater core, where applicable.