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JD 4030 diesel - which head gasket

677 Views 2 Replies 3 Participants Last post by  Jim in NC
Hi all,
I have a 1976 JD 4030 diesel tractor. I replaced the head gasket about 5 months ago, had the head flattened, checked the block for flatness, torqued, retorqued after 20 min, torqued again after several hours. It ran fine for about 25 hours. Then I had water in the oil when I replaced the leaking radiator. My guess is the water system was able to build pressure since the hole in the radiator was no longer an outlet and the added pressure was enough to punch through the weak point.
The JD webpage shows two different gaskets:
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My JD dealer has no clue why two are shown. They see the same description as I what I see in the screenshot above. One could be for gas, the other for diesel. The shop manual mentions a thicker gasket is available. So it's possible one is standard thickness and the other is the 'thicker' one.
It's also possible I don't have a head gasket problem and it's something else. I couldn't see any obvious 'blow through spots' on the head gasket I removed. It seems likely to me it was the head gasket since it worked fine for the first 25 hours. The head was tested for leaks and passed (Magnaflux). I pressurized the oil cooler and over a 24 hour period saw no changes. I'm not sure if I should be looking somewhere else for a leak or if I just had the wrong head gasket to begin with.
If anyone has advice, I'd love to hear it.
Specifically: which head gasket? Last time I bought the first one on the list as it was more expensive and I guessed it would cost more to produce a gasket for diesel engine since the compression is about 4X that of a gas engine. But that's an assumption and could be in error.
Second: maybe it's not the head gasket and the leak is somewhere else. The oil is milky white and the 'dipstick level' went up an inch so my assumption is the water is getting into the oil because of a leak in the head gasket but could it be from somewhere else? Head gasket, oil cooler, head seem to check out. How do I find a leak in the block? Does it make sense it wouldn't leak for 25 hours and only start leaking under pressure? If the block is cracked, wouldn't it leak all the time?
Clearly I'm not a diesel mechanic. I'm open to any ideas you might have.
Thanks in advance,
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John Deere 4030 Technical, This John Deere 4030 Tractor Repair Manual contains top-notch pictures, circuit outlines, directions to assist you with working, support, indicative, and fix your truck. This record is printable, without limitations, contains accessible content, bookmarks, crosslinks for simple route.
The parts person may need your serial number to determine which headgasket to use.
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