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Any 7.3 Ford experts?

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Old 04-30-2012, 03:16:40 AM
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vern0n vern0n is offline
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Default Any 7.3 Ford experts?

I have been working on this 1990 F350 7.3 for several months. I have replaced a lot of parts. It had been setting for 7 years. The main issue left is it leaks oil like crazy from the rear main area. I looked up top and it doesn't look like it is running down. I replaced the rear seal when I replaced the flywheel. It didn't look that bad. Leaks the worce when I am going down the highway. I checked the crankcase breather thing, seems ok, I could blow through it easy enough. I have sunk a lot of money and time into this truck and it seems the problems never end. I want to sell it cause I'm tired of working on it, but I wouldn't get half my money back. Anybody have any info on what or why it still leaks. It had the leak when I bought it, before replacing the seal. I have changed many an oil seal, but this is kicking my rear.
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Old 04-30-2012, 05:05:01 AM
Roland Hayes Roland Hayes is offline
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Default Re: Any 7.3 Ford experts?

Sounds like the rear main oil gallery plug is loose, spanner time!
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Old 04-30-2012, 07:07:06 AM
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Default Re: Any 7.3 Ford experts?

I'm sure you checked the crankshaft for wear at the seal area.
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Old 04-30-2012, 12:02:58 PM
Smokin Bob Smokin Bob is offline
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Default Re: Any 7.3 Ford experts?

I agree with what MoRo said. About 10 years ago, a friend of mine had the same problem. The crank was worn where the seal rides on it. He bought a seal kit from FelPro that had a spacer that you inserted into the seal boss before the seal itself so that the seal was effectively re-positioned on the crank. It worked for about 10,000 miles and then leaked again. Turned out, the main bearings were worn enough that the crank was no longer turning perfectly true and wallowed out the seal. How many miles are on that engine? The mains may be worn, especially if it was used for heavy work.

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Old 04-30-2012, 02:32:49 PM
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Default Re: Any 7.3 Ford experts?

Those 7.3's are a throwaway motor, 400,000 is about all they're good for.
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Old 04-30-2012, 09:45:53 PM
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Default Re: Any 7.3 Ford experts?

Couple of thoughts:

1. There is a seal between the CDR valve and the intake. Available through Ford, and it's cheap.
2. CDR drops down into the valley pan. Verify that connection is complete and the seal into the valley pan is good (if I remember right - the turbo'd ones are different).
3. While the CDR is off check to see if it's good. Should only be able to blow through it in one direction.
2. The rear valley pan is sealed with hylomar. Could be there If a valley pan was done before you got it. (once it seals with Hylomar it's sealed).
3. There is a drain in the valley pan that drains onto the starter. If you are getting oil on your starter it could be a fuel injection system related leak.
4. Valve covers are a leaking point
5. There are several small plugs tapped into the oil galley towards the back of the block. Verify those are sealed and tight.
6. There is a oil pressure switch back there that has been known to leak.
7. The advice here regarding the rear main seal is sound. Is it leaking from the flywheel inspection cover? That seal should always be replaced with the kit that comes with the seal wear ring. From everything I've ever seen, if it starts leaking from the rear main on the 6.9 7.3 you need to install a wear ring.

Do a search on your 6.9/7.3 related problems here:

Good luck and please post back on your progress,


---------- Post added at 08:45 PM ---------- Previous post was at 08:40 PM ----------

I have a recycled 6.9 in my pickup. Quite happy I didn't throw it away.

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Old 09-26-2012, 12:21:23 PM
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Default Re: Any 7.3 Ford experts?

In the eighties and nineties, I ran my own shop and rebuilt many 6.9 and 7.3 litre engines. Most of these were gutted by poor air cleaner design and jobber elements. The blocks are reboreable, a couple of oversizes of pistons are available. These engines are definitely not "throwaway"
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