FD501V liquid cooled engine coolant leak

arch252

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I have a JD LX279 with a twin cylinder Kawi FD501V, liquid cooled. I noticed earlier this season some brief white smoke when I first started the mower. It would burn off pretty quick then run clean. I thought rings were getting bad but I did a compression and leak down test amd the numbers were all good.

I caught a whiff of the smoke and it smelled like coolant. One time before starting it I removed both plugs then turned it over and it spit out a few drops of coolant from both cylinders.

The season is about over so I'm ready to get into it and fix the leak. Can anyone tell me what I might be getting into? I'm hoping it's just a bad gasket. I'm assuming it's not a head gasket because it's leaking into both cylinders. Can anyone tell me what the likely culprit will be?

I'm comfortable doing the repairs, I replaced the crankshaft of this engine 3 years ago.
 

mechanic mark

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Purchase JD Service Manual for your LX279, very good investment & step by step instructions. Search websites for best price.
 

cpurvis

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If you're getting coolant in the cylinders, you probably have a bad head gasket(s), a cracked head, or a cracked block.

I'd guess the most likely suspect is the gaskets.
 

arch252

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I pulled both heads. No obvious cracks anywhere and no obvious defects in any of the head gaskets or manifold gaskets. I intended to remove the water pump but I realized it bolts in from the bottom and I would have to pull the engine off the mower and I'd really rather not do that if I don't have to. From what I can tell there is nothing in or around the water pump that would allow coolant into the cylinders. With no obvious cracks in any of the housings, I suppose my best bet is to replace the head gaskets and intake gaskets and see if that solves the problem. Are there any other diagnostic tests I can do to rule out any other problems?
 

Hammermechanicman

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You need a pressure tester with an adapter that fits your radiator to do a pressure test. Something like this
You pressureize the cooling system and if it doesn't hold pressure you look for the leak.
 

arch252

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Since I've now pulled the heads I think I'm past that point. I know there is a leak because I was getting coolant in the cylinders. Finding the leak is the problem.
 

bertsmobile1

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Usually the water sill scour the cylinder & head
So if one is oily and the other is very clean & dry, that is the bad side
 

StarTech

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Coolant leakage into cylinder is usually either head gasket or intake manifold gaskets. If intake gasket there may a little coolant in the intake valve area. Takes close inspection.

These heads can easily warp even when removing them as you were supposed to loosen the head bolts a 1/4 turn at a time in the same pattern as you torque them until they all are loose. I kinda doubt you did this.

Check for cylinder head warpage. Maximum allowed spec'd at .002". Also note following torque info.
FD440V-FD501 HEAD Specs.JPG

Can be check for using a flat pane of glass and very light weight oil. Also can flatten using the same pane of glass and very fine grit sand paper. If warp too bad replace the head in question.

Do not reuse the installed head gaskets.

Head 1 torque pattern
FD501 Head 1.JPG

Head 2 torque pattern
FD501 Head 2.JPG
Download the engine's service manual for info on re-assembly procedures.
 

arch252

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I've replaced both head gaskets, resurfaced the heads, replaced the intake gaskets and resurfaced the intake where it bolts to the heads. After sitting a day I cranked it with no smoke, no coolant being burned off as before, so I guess so far so good. I'm going to let it sit a week or two and check it again to make sure. The intake ports needed a good bit of sanding to smooth out, so at this point I'm thinking coolant was passing by the intake ports into the exhaust. We'll see.
 
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