We want to help you replace your Yanmar tractor head gasket.
If you do not feel that you understand these steps, or can perform them safely, consult your tractor dealer or local mechanic. And as always check your owner’s manual to verify that you are following the proper steps according to your tractor’s make and model.
Replacing a head gasket may seem intimidating.
No need to worry. If you are willing to put in a little blood, sweat, and tears (and get your hands a bit dirty) --- we are going to get you through the entire process. AND save you a whole lot of money.
Time to get started…
1. Clean the engine. Make sure the upper portion around the head is as clean as possible.
2. Take pictures of the engine as you disassemble it. This will help you keep track of what goes where.
3. Drain the water from your radiator into a suitable container.
4. Remove the water pump and muffler. While it is not necessary --- it will make the head easier to maneuver.
5. Remove anything attaching the head of the tractor or engine. This includes radiator hoses, fuel injector lines, oil lines, and the wire to the temperature switch.
6. Remove the valve cover.
7. Remove the pushrods and rocker arms. Keep the parts in order so they go back to the same place. TIP: Poke holes in a cardboard box and push the pushrods into the holes to keep them in order.
8. Remove the head nuts or head bolts, depending on your model.
9. Lift the head off. Make sure all the bolts are removed. If it feels stuck --- evenly, and gently pry the head up. Do not pry anywhere near the sealing surface of the head gasket.
10. Dry off the spilled coolant. Put rags or paper towels into the holes on the block to prevent pieces of the head gasket from getting inside. (This includes the water ports, crankcase, and oil ports.)
11. Remove the head gasket.
12. Scrape off any remains from the gasket or any sealer that was used on the block and head. Use a razor blade, gasket scraper, and carburetor cleaner to get everything smooth and clean. Be careful not to scratch the sealing surfaces of the head or block.
13. Inspect the head closely for cracks. Use a feeler gauge and a straight edge to check the block and head to make sure they are flat.
14. Run a tap down each of the head bolt holes to make sure they are clean and free of debris. This will give you a more accurate head bolt torque. A dirty thread can lessen the clamping force of a bolt by as much as 50%.
15. Blow out the head bolt holes with compressed air. This will ensure there is not any liquid, dirt, or head gasket remains in any of the holes. This will also keep the bolts from bottoming out before they are fully tightened.
16. Remove the paper towels or rags from the holes in the block. Double-check that they are all out.
Great news! You are halfway there.
Now it is time to put it all back together.
NOTE: The head gasket will install dry. Do not use gasket adhesive or silicone. You can use “Copper Coat” which is like copper spray paint. It goes on in a fine layer and can fill in tiny imperfections.
Ok, it is time to finish the job now…
1. Line up the holes in the block with the holes in the head gasket. (Head gaskets on these tractors are not typically symmetrical. There should be holes on one side that are not on the other. This is how you know which end is up. It is common for the holes that the pushrods go through to look different than your old head gasket.
2. Set the head down on the gasket carefully and evenly.
3. Wipe a bit of motor oil on the bolt threads. You do not want oil dripping from them. This can fill the bolt hole, causing the bolt to bottom out. Never use fancy greases or antiseize. They increase clamping force which can cause broken bolts, stripped threads, and other issues. NOTE: Many of the Yanmar tractor “F” series use a “one-time” bolt that needs to be replaced each time. Other “YM” series use a stud or bolts that can be reused.
4. Start tightening the head bolts --- tighten to finger tight. Follow the Yanmar service manual’s torque procedure. NOTE: Use a good torque wrench that has been calibrated or tested recently. This is vital.
5. Put the pushrods back in the correct locations.
6. Set the rocker arms back on the studs and finger tighten.
7. Adjust the valves.
8. Clean out the valve cover. Use carburetor cleaner.
9. Remove the old valve cover gasket.
10. Put the new valve cover gasket on the valve cover. Use gasket adhesive to help hold it in place.
11. Re-install the valve cover onto the head.
12. Torque to the correct torque as specified in your service manual.
13. Reinstall the water pump, muffler, any wires, oil lines, and hoses that were removed. Fill the radiator with water.
14. Start the tractor.
NOTE: We recommend re-torqueing the head after the engine has been up to temperature and cooled back down. You should also re-torque it again after another hot/cold cycle until the nuts/bolts no longer move when they are torqued. This should lower the likelihood of another blown head gasket due to the new gasket compressing as it settles down.
If you have any issues or feel unsure about any of these steps --- consult your tractor mechanic. And as always, consult your tractor’s service manual.