Front case oil leak

OK guys I'm out of ideas. Above the right hand silent shaft drive gear there is a threaded plug. The case has an o-ring grove to seal the plug. I cannot get that plug to stop leaking. I have tried everything I can think of to get it to seal. This is a new front case/oil pump assembly off of Amazon. I tried at first to use the o-ring in the gasket set with a little silicon. That is how the old case was done. After about 30 seconds it started leaking. Then I tried the o-ring with a lot of rtv silicon. I ran the plug in until I had a good squeeze out of rtv and let it dry overnight, then ran it tight. Same leak. I then tried a fatter o-ring. Same thing. I tried an o-ring that fit tightly around the plug to ride on the lip before the o-ring groove. Same leak. I went and got a fiber washer for an oil pan drain ,still drips. I have tried all of these with both silicon and permatex 1 and 2. I can now change a set of timing belts fast enough for NASCAR but I can't get that stupid plug to stop leaking.

How much pressure is on that plug? When I start the engine cold I have 75# of pressure. Has anyone had this problem? I ready to use the truck for a target.

There is a possibility that the pump housing assembly from Amazon is junk (sorry but you have to look at all the angles) All it takes is some dubious machining and it will haunt you into the afterlife. Now I know that this is not something to recommend but...thread tape maybe? If a strip of teflon tape goes adventuring into the oiling system it could easily cause a catastrophic failure (thus the reason why it is not done in the first place). Is there a torque specification on the plug? Can you try a different plug? :shrug:

I have already tried thread tape. I am going to pull the front end of the engine back off to check the lower cover. Like some other fools on this site I got this truck in "project" status. It had a cracked head along with some other issues. I replaced the head with a 4d56 head off of ebay. Had the injection pump rebuilt and installed new injectors. When I started it the oil pressure pinned at 100#. I have seen this before on other engines and felt it was the pressure valve in the oil pump. I went looking for parts and the only oil pump part seems to be a 'repair sleeve". I am not certain what the repair sleeve even does. My magic googling came up with this pump assembly from Amazon. I guess all I can do at this point is transfer the parts from the Amazon pump to the original housing. I have ordered a new lower gasket set which should be here Friday. That will teach me to get one of these new trucks. My 1973 Datsun 620 just keeps running:lmao:

I think the biggest problem is the trucks themselves. Things go wrong with them all the time, like bottom end bearings failing from lack of oil or timing belts blowing after only doing 195,000 miles. Nearly every truck has rats nest wiring in them because the factory wiring worked too well and was too simple to fix. The Datsun 620 is an amicable beast but you'll find out first hand what the little Mitsu hauler is all about once you've exorcised the ghosts of ghetto fixes gone by. Only beef with the 4D55 is the engine is crying out for a bigger turbo to get it breathing.

Well guys,
We have the answer. I tore the front end off the engine apart again. When I got the lower case under a 10x magnifier I found a small hole in the casting. More Chinese quality control. I am certain I could return it to Amazon but where does that leave me? My original problem was, in my opinion, a bad pressure relief valve. I cannot find the parts to fix. So I am going to clean up the original front case and put the parts from the new one to, I hope, fix my problem. And Mr. Geezer I have fixed the turbo problem. I have a Garret water cooled on this unit and some corresponding sized exhaust. My new lower gasket set has been shipped from RockAuto should be here soon. The adventure continues.

Hmm, drill and fill the hole with a swab of JB weld? (it's hell tricky but it could be TIG'd up - die cast metal is not easy to work on especially if it's already dicey...) It sucks that you got a bad part but it happens. I was expecting lousy machining but a bad casting? :shakehead: Should've seen the factory head from my G63B, you've never seen such a poor quality production head from Mitsubishi... Yay -Garrett! That will make sure it can get out of it's own way. Whatever you do, don't take out your frustrations on the truck. It's a victim as well and you're along for the ride. The oil pressure issue is but a small hurdle and even though the oil leak was caused by a bad part, you found the source.