I have a 1985 Case 485 tractor. Some years ago I changed the head gasket and oil control rings, but the head has started leaking again, it is only an issue when I am mowing the fields with a topper mower and it overheats after about 15 minutes. Last time I changed the gasket I put a straight edge on the head and it looked fine so I did not have it skimmed. Can someone tell me if when the head is skimmed do I have to use a thicker gasket or standard. Also I cannot remember if the head bolts are stretch or not, I suspect not.
Can you describe the leak ? Did you re-torque the head bolts after it was warmed up when you did the repairs ? Usually they should be tightened in a particular order. A service manual would have the procedure in it. When you remove the leaking the head gasket, the old one will show where the problem is. Unless the head has a crack in it. I never heard of a thicker head gasket other than a standard one. If you have the head skimmed (milled) it will raise the compression ratio. That could be detrimental to the life of the motor. I wouldn't do it on a diesel. Replacing the head would be my choice. The block (deck) could also be warped.
The sign that there is a leak for me is that the engine overheats and steam and water pass the radiator cap. I did the head gasket about ten years ago or more and cannot remember where I got the torque specs from, I do not have a service manual. I saw no cracks on the cast iron head nor sign of damage to the block, the oil control rings were totally worn, the previous owner, who I had just bought it from had no air filters fitted, I replaced both, the bores, big end bearings, crankshaft journals and pistons were in excellent shape. I don't think it had been used in a farm but in an industrial application. I do not remember re torquing the head bolts, maybe if I had known and retightened as you suggest the problem may not be happening now.
Sounds like it could be just a regular overheating problem. Check all the standard things first, check the radiator, coolant hoses and block with an IR temp gun to make sure it's actually overheating. Blow out the radiator and hydraulic cooler (and in between the two if it has the swing out cooler). Check the thermostat for proper operation. Make sure the water pump is still good, they can and do wear out. Make sure the hoses are in good shape, they can collapse internally and restrict flow. Check or replace the radiator cap, sometimes they just get weak and start leaking/letting pressure off well below the specified pressure. What size topper mower (rotary cutter?) are you running and how heavy is the grass, how hot is it outside? They 485's were only a 40hp tractor, could have some marginal cooling issues and just overloading the tractor.
Well I don't have an IR temp gun but I did fit the tractor with a temperature gauge, when it overheats the temperature goes to 110C or more. I have had the radiator off and hosed the block of silt. Not sure where the thermostat is or I may have just forgotten. As far as the water pump is concerned I am not sure how to check it, but I did notice that the fan belt was rather loose, that could have contributed to it, I will tighten it and try it out to see if there is a change, my only previous experience of failing water pumps it when the seal goes and it leaks, it is just an impeller on a bearing, there are no signs of a leak on the pump. My topper is a twin rotor 6 foot with an offset cut option.
Yes, tighten the fan belt first and see if that helps. Check the thermostat next, it's in a right angle elbow with two bolts, hooked to the upper radiator hose. Pull it and test it for proper operation in a pot of water on the stove. I think it is a 180*F thermostat, so slowly start heating the water and it should be open by that temperature. Or just replace it, not that expensive.
I did tighten the fan belt, went out and did a bit more mowing but it boiled over after about 20 minutes. I am going to completely remove the engine cover and do a bit more mowing so I can see better what is happening when it overheats. I will have a look at the thermostat. In the distant past there were two different types of thermostat, one which might fail closed and on which would fail open, I thought that modern thermostats would for safety fail open rather than closed, I will see. Thank you for your input.
It is not unusual for fan belts to develop a hard glaze on them. They will then slip no matter how tight they are. I don't think serpentine belts have that problem. Have you removed the radiator cap and looked for bubbles in the coolant ? that would indicate a leaking head gasket or cracked head.
I have removed the engine covers and the discharged coolant contains quite a bit of sludge, and I suspect that there may be a lot of sludge in the radiator that I cannot remove so I have bitten the bullet and ordered a new radiator. I will flush the block again. Someone mentioned retorquing the head bolts after a short period, well the period may not be short, but if someone could advise me of what that final head bolt torque should be, I would just have to remove the rocker cover to retorque them all so they are correct and even.
Apologies for the delay, internet has been down. Received new radiator, some were priced as high as more than 600 euros but I got one for 300 delivered. Fitted the radiator, checked thermostat, flushed block again. Did two hours of mowing and the engine temperature stayed around 90C. What a relief. Thank you for your help.
Thanks for the update and glad you got it fixed.