Question on 94 3.9L Oil Pump rebuild - Defender Source
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  #1  
Old October 6th, 2011, 08:35 AM
flananuts
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Matthew
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Question on 94 3.9L Oil Pump rebuild

With the weather staying warm for the next week or so I'm going to pull the oil pump outer housing and gears out for a replacement/rebuild. The rebuild kits I have found include or suggest replacing the outer housing(where oil filter connects) as part of the kit, which is also the most expensive part.

My question is do I need to replace the outer housing or just the internals? I've read that it's common for the pressure relief valve/spring to stick which can cause the pressure to drop so I can see replacing that part makes sense. What should I look for when I pull the unit that gives reason to replace the outer unit?

Thanks

Matt
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  #2  
Old October 6th, 2011, 09:46 AM
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William Skidmore
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As I remember from putting in the new engine that where the two cogs sit in the surface has to be flat where it bolted flush (dont forget pack the cogs with vasiline) Take a straight edge and check to see if its still flat if not then replace. Think thats correct from memory
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Old October 6th, 2011, 03:33 PM
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Thanks, that makes sense. I'm thinking that it's the gears/cogs and bits inside that would be worn that would create lower pressure a idle right?
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Old October 6th, 2011, 03:58 PM
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The lower face of the oil pump 'may' have some scoring in it from the gears. If it is really bad - you may lose some oil pressure.

You can take that housing to a machine shop and have them flatten it. Or, you can do it yourself with a peice of glass and fine sandpaper. Both options are tons cheaper than a new unit.

If the damage runs deep then you may have to bite the bullet and go new. They are very spendy - but I may just have one in the garage.....
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Old October 6th, 2011, 05:12 PM
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Loic Fabro
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Pedro sanded the bottom portion with fine paper on a sanding machine. Engine was fine after that. I'd be surprised if the cog need replacing unless they ate something and can't contact right anymore between each other.
I'd say take it apart and find out what look out of place before buying anything!
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Old October 6th, 2011, 06:24 PM
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Quote:
Originally Posted by MonLand View Post
Pedro sanded the bottom portion with fine paper on a sanding machine. Engine was fine after that. I'd be surprised if the cog need replacing unless they ate something and can't contact right anymore between each other.
I'd say take it apart and find out what look out of place before buying anything!
Dude... You stole my thunder... I was going to post this morning and got caught in an unscheduled meeting.

Like Loic said... if you have scoring in the housing, get fine sand paper and sand it.

Here's how mine looked like.
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Old October 6th, 2011, 06:25 PM
flananuts
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Thanks for the pic.Thanks for the feedback. I'll do just that to get this gig rolling and post some pics of the innards. My very very pregnant wife will likely be looking at me strangely.
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Old October 6th, 2011, 10:15 PM
The Dro
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Originally Posted by flananuts View Post
Thanks for the pic.Thanks for the feedback. I'll do just that to get this gig rolling and post some pics of the innards. My very very pregnant wife will likely be looking at me strangely.
Be careful when sanding it. Get the super fine paper and work slow.
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