Farmall M has intermittent miss

Chadd · Jun 25, 2008

Our Farmall M overheated out of the blue standing and idling a day or so ago. I added coolant and it only took a quart to bring it above the mesh in the radiator. It no longer overheats, but now it looses cylinders as it warms up. When I start it up, it will run on four, but has a miss. As it gets warm, cylinder 3 cuts out. Then after a while, another cylinder seems to quit. I did a compression test, and it had 85, 90, 68, and 88 psi on cylinders 1 through 4. It has the low compression Kerosene head (6336DD) When I turned it over to reset valves I swear could hear air blowing out on 3 and 4 through the pushrod holes in the head. Also, I see bubbles when I look in the radiator. I am guessing either a cracked head or bad head gasket. Do you think I can get away with just a headgasket, or is the compression low enough on all four that it should get a full rebuild?

Chad

El Toro · Jun 25, 2008

You need to get the head magna-fluxed for cracks if the head gasket doesn't show any signs of being blown. The overheating may have caused that if its cracked. Hal

rustyfarmall · Jun 25, 2008

It's not so much that the compression is low as it is that the compression readings are very uneven. Your best bet is to remove the head and take it to a reputable machine shop. They can tell you if the head is cracked, might be able to repair it, and can give it a valve job. You will be amazed at how much better that ol' M runs.

Dave BN · Jun 25, 2008

I curious why it over heated in the first place. And what makes you think it over heated? They sometimes feel, sound and smell hot even when they are ok. Were you working it hard just before this? Have you adjusted timing recently? Is the fan belt tight and in good shape? One quart low on fluid shouldn"t cause overheating if it was just idling. You need to figure this out before you repair the engine and then damage it again. Dave.

Chadd · Jun 26, 2008

I am pretty positive it overheated. When I walked up to it, the temp gauge was pegged at the end of the hot range and then the radiator cap started to unseat and relieve the excess pressure from the boiling. It had not been worked hard. I started it up to move a haybine, moved it, and then let it sit and idle for 5 minutes while I got some oil back in the oil can. It ran for all of 20 minutes The fan belt is 1 year old and is nearly tight enough to turn the motor over with. I can look right through the radiator, so the fins aren't plugged, and it is a 1 year old radiator that was filled with distilled water, so it isn't plugged internally. The water pump works, as I can see the flow when the tractor is running. Pretty much the only thing that I am left with is the thermostat sticking and then finally letting loose when it boiled. It has run on 2 cylinders for an hour and it has not reached run on the gauge since.

Farmall M has intermittent miss

Chadd

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El Toro

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rustyfarmall

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Dave BN

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Chadd

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