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V6 Oil pump/timing cover issues

FinoCJ

1970 CJ5
Staff member
2026 Sponsor
Joined
Jul 18, 2013
I am reworking my oil pump....There is a long history of annoying little issues with my oil pump dating back 10 years ago when the engine was rebuilt (leaky, low pressure, distributor alignment/installation problems). A new, generic timing cover was installed at that point, and I didn't really realize all the little issues you get with that - unfortunately, I didn't begin to understand all those issues until recently (or maybe I forgot and am relearning), and so even when I redid the timing chain etc last fall, I re-used the generic timing cover. One issue was just finding the proper front main seal (its a bit different than most), another is the quality control seems to cause some slight misalignment between the distributor shaft and oil pump (makes installing the distributor a PITA), as well as what I think is a slightly too short distributor shaft accommodation such that when the shaft heats up and lengthens, it creates extra downward pressure on the oil pump thrust surface - which is probably not good for maximizing pump pressure/flow, generates extra heat, as well as it seems to want to push the oil pump cover/thrust plate down and off the timing cover, I think exacerbating leaking (as well as stripping the oil pump cover bolts out of the timing cover). I sort of went through this all a decade ago, but i guess I forgot and am learning it all again....I really wish last fall I would have bought a new, quality timing cover from TA or similar....but at the same time, it has worked for 10 years, so i think i can make it work again....so on to the oil pump...

Last fall, I swapped from the high volume, tall oil pump gears, to the OEM replacement Melling pump gears (short) and used the jim ruggles/kenne bell style booster plate from Vintage Jeeper. With that, you do a bit of grinding, need to use a special gasket (included from Sal), or available from TA, or modify (razor blade cut out) and standard fel pro gasket. I am not sure which gasket Sal includes with the kit, but this is the one from TA that I think is equally functional - it has the additional opening:

After installing the new booster, I have had a very slight improvement in idle oil pressure, and have revisited a lot of the same problems from 10 years ago. I had a lot of hassle getting the distributor to drop in, and it seems to want to sit a smidge too tall, and I am getting lots of leakage around the pump area (can't tell exactly where its coming from) - especially when its hot. Cold idle, no leaks. Park it in the garage after driving it around, puddle of oil. 10 years ago, I filed the slot on the oil pump gear shaft a bit deeper and wider to allow the distributor to fall in place, and eventually, I added a very thin washer/bushing between the distributor and timing cover to help it stay a bit higher and relieve downward pressure. I am wondering how much endplay is needed between the distributor shaft and the bottom of the oil pump slot to allow for thermal expansion?

At some point, I manage to get the oil pump leak essentially to a minor weap and ran it that way for years.....maybe my previous mods were truly a functional solution (and thus try them again), or time and wear on the gears and thrust plate self clearanced the needed play.......I probably should just consider a new timing cover.

FWIW...as part of my ongoing attempts to help oil pressure, I bought the shim kit from TA as well:

Installing these and checking for proper oil pump gear clearance would be much easier with the timing cover on the bench according to the instructions - wanted to include these from TA in case anyone really wants to go down the oil pump pressure rabbit hole (don't know if its worth it, but wondering if I should do a higher quality pdf scan or convert to text and post in our tech section?...assuming its not a legal issue with the site or TA?)
TA-oil-pump-instructions.jpg
 
Well....replacing the oil pump gaskets (for the 3rd time since re-installing the timing cover), as well as checking for proper clearance on the pump gears, along with new oil pan gasket hasn't stopped the oil leak - hitting the point of insanity. So a lot more inspection and risking of fingers, the best I can tell, the oil is actually coming from just above the oil pump - and it only leaks when the engine is running. So you give the area a good wipe down, remove all the oil, start the engine, and within 10 sec, there is a significant fresh oil in this area:
PXL_20260716_152520128.jpg


Its coming from above the gusset that supports the oil pump mount on the timing cover - and specifically from/or just below the shiny bolt head. I am not finding any oil coming from higher up, or from the front main seal. Within seconds of start up, oil starts filling that valley between the gusset and the cover....but where is it coming from. Wondering if that bolt is through going and I didn't get thread sealer on it - could it really leak that much oil around the threads? Or could there be a crack in the cover just above where the gusset joins - and of course where I can't get a decent picture or see?

I'd like to pull that bolt and redo it with thread sealant, but its essentially impossible to access to get a socket on it - maybe....I was able to get a socket on it enough to at least determine its plenty snug, but its another thing to actually get it out and back in. Otherwise I don't have much choice but to remove the fan and crank pulley for closer inspection....hoping not to have to remove the radiator to get the crank pulley off, but its starting to turn into a big job.....
 
I'm going with casting porosity.
Anything is possible, but this is the same cover that has been running for over 10 years. I wouldn't expect the porosity to increase that much in a short period of time, especially when that short period seems to overlap with when I replaced the timing chain. Seems more likely my work changed something. Also, I think of porosity as more of a slow seep. This is not a seep - 5 min of running and you've got a couple tablespoon puddle. The day I ran with John last month (obviously I thought had it figured out), it lost over half a quart.....either way, it's got to be solved - jeep is unusable as is. I really wish I would have bought a new TA cover last winter when it was apart.
 
Part of the reason I run stock pumps with low pressure springs. Stock housings. K201 pumps. Rarely have any issues. High volume, high pressure, extra plates ported reliefs and any other "enhancement " simply seem to cause issues. Buick v6s simply always had lower oil pressure. Nothing wrong with that. Fixing things that are not broken often results in more problems.
 
After a few 'maybe's,' definitively found the leak....its coming from around this bolt head that holds the timing cover to the block:
PXL_20260723_015511884.jpg


The question becomes how to stop the oil leak.....The bolt goes through the oil pump section of the timing cover, specifically through this boss and threads into the block. I don't remember if the block threads are a blind hole, but my gut feeling is the oil is coming from inside the oil pump/cover section (above the threads on the bolt), and thus thread sealer is not going to help (although i will definitely put some on).
PXL_20260723_021024391.jpg


Here is the bolt:
PXL_20260723_021241821.jpg


Anyone else have trouble with this bolt? My first thought is to try and put rtv along the upper smooth shoulder of the bolt. I also remember using a washer with an internal rubber gasket for one of the D18 holes that was open into the oil reservoir - I found them in my collection, but its too large - but maybe something like that? Or should this bolt not be experiencing oil and thus something else is wrong?
 
It has been a few years since I have seen it done, I was a young teenager. I witnessed using cord string with a coating of gasket sealant wrapped around the shank under the head to control leaks like this. The beauty of this was I remember the bolt was loosened, sprayed off with carb spray, string was coated then a few wraps around the bolt and tightened back up.
 
My favorite miracle cure is anaerobic flange sealant. I use it on threads and under flanges like that. It works where there are two machined metal surfaces and acts like a thread locker as well.

I am not a trained mechanic and it is a bit of an off-label use but it seems to work.
 
Glad you found it! Thread sealant and a sealing washer couldn't hurt and should help.

I suggest measuring and making sure the bolt is not bottoming out in the bottom of the hole (if blind) or where the thread shoulder is near the top of the tapped hole. It "could" feel tight, but in fact be a few thousandths loose.

Lastly - the pic "kinda" looks like a possible crack. May be an optical delusion.



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