'1986 F250 6.9L IDI HEAD GASKET - Diesel Forum - TheDieselStop.com
6.9L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 6.9 Liter In-Direct Injection Navistar engines.

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post #1 of 12 (permalink) Old 11-04-2018, 08:32 PM Thread Starter
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'1986 F250 6.9L IDI HEAD GASKET

I have a blown head gasket under one cylinder head or the other. Although I have looked into replacing the gasket’s I would almost rather swap the motor for a used replacement. Thoughts to consider?
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post #2 of 12 (permalink) Old 11-04-2018, 09:59 PM
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Can you get a rebuilt motor? And how much will it cost? Can you do the work yourself? If so I would do the gaskets and keep on rolling. We can help you do it yourself.

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post #3 of 12 (permalink) Old 11-04-2018, 11:56 PM Thread Starter
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I’m pretty sure I can handle the gasket replacement. I’ve been reading that it’s difficult while in the rig due to the firewall constraints, so probably pull the motor first(?) the gasket kit is available for $130. Also, aftermarket studs might hold up better if I don’t have the heads milled. It’s a pretty worn motor that could use rings and bearings too. I’m just not sure how far I want to chase it, and a rebuild is out of my reach $
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post #4 of 12 (permalink) Old 11-05-2018, 05:09 AM
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My $0.02, if I was pulling the engine for HG, and I knew the engine needed rings I would replace the rings while I had it out.

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post #5 of 12 (permalink) Old 11-06-2018, 01:27 AM Thread Starter
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UPdate: I happened upon a used, factory remanufactered 7.3 drivetrain w/ a 5-speed from a local Mini Cooper repair shop owner. Mileage is a little high, but seems a good motor. So, now I gotta figure out the swap from 6.9 to 7.3 along with 4 to 5-speed. I’m pretty stoked tho 👍🏻
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post #6 of 12 (permalink) Old 11-10-2018, 05:28 PM
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Nathan, I just finished replacing the head gaskets on my 1984 F250. I rebuilt and cleaned/painted the heads while I was at it. Anyways, I did it without pulling the engine. It IS do-able, although it was difficult. It's the 100 lb weight that was the problem; if the heads were aluminum, say, it would be no big deal. I had to be incredibly careful not to damage the new gaskets while positioning each head. But it can be done.
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post #7 of 12 (permalink) Old 11-11-2018, 09:32 AM
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I had to be incredibly careful not to damage the new gaskets while positioning each head. But it can be done
Too late now, but it's wise to use pilot studs. Pilot studs are bolts with the heads cut off, then the tops rounded slightly with a grinder, then slotted with a hacksaw. You screw two in a couple head bolt holes then you can lower the head down on the studs and don't have to worry about mis-alignment. Later you unscrew them with a screwdriver, draw them out with a magnet. I've used them for everything from slipping on a water pump to sliding in a 600 lb. heavy truck transmission.

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Last edited by LMJD; 11-11-2018 at 09:35 AM.
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post #8 of 12 (permalink) Old 11-11-2018, 11:36 AM Thread Starter
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Now that I’m pulling one drivetrain for another I’ll be able to remove those heads and possible overhaul the 6.9 on an engine stand, while running the 7.3 for the time being... I have used pilot studs for hanging a transmission on a Backhoe, which would work great for heads, too. Great tip!
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post #9 of 12 (permalink) Old 11-11-2018, 11:40 AM Thread Starter
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Still looking for the zf5 floor pan and transfer case cross member that will bolt in. Otherwise, I’m reading that both existing can be modified to accommodate this newer drivetrain... we’ll see
Additionally there are highbreed u-joints that are needed too
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post #10 of 12 (permalink) Old 12-03-2018, 11:53 PM Thread Starter
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Getting closer. Weather and a head cold have caused some delays, but I did get the trans, transfer and motor married back together. Trying to find a qualified Backhoe oporator is my next hurtle, with my hands being the guide back into the truck, I don’t trust just anyone... lol Aditionally, still looking for a rear transfer slip yolk and both shift levers w/ knobs 🙄
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post #11 of 12 (permalink) Old 12-07-2018, 11:46 AM Thread Starter
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I was able to put the entire assembled drive-train in by removing most of the front- end, including the bumper. I replaced the passenger side motor mount too. The transmission shift tower had to come off as well. The 86 crossmember from the t18/19 for the transmission support slid back a couple of inches to accommodate the zf5, lining up with pre-drilled holes in the lower frame just fine. However, the downward struts supports for the crossmember will need to have new holes drilled in the upper frame. Now it’s a matter of hanging all the accessories from the 6.9 on the 7.3 (alt, vac pump, pow steer, etc.)
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post #12 of 12 (permalink) Old 01-11-2019, 03:19 AM Thread Starter
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I’ve got her up and running now, hopefully reliably. There was I handful of issues but nothing that couldn’t be resolved. I wish I would’ve just change exhaust manifold gaskets while it was out.
- The rear driveline was exactly 5 inches too long, so machine shop and $170 bucks later (including a slip-yoke and hybrid U-join) and its good.
-The difference in glow plugs systems from the 86 to the 94 7.3 confused me a bit. I installed a controller-bypass push button kit for 32 bucks on eBay
-Another issue was the Temp-Gauge that would not register on my dash anymore.. I installed a Manual Temp Gage next to the glow plug dash button.
- Finally, I had to modify my floor pan to accommodate both shifters of the ZF5 transmission, reusing one boot and finding another, w/ shifter, I got it put back together.
Otherwise it’s a few little things here and there but it’s now drivable 👍
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