Oil leak (Mystery)

[DeepC73]

UPDATE:
It’s the oil pump bolt that pushed through the oil pan. Nothing is loose that I can see. I’m going to weld up the hole on the outside to ensure I don’t make the clearance issue worse. I called Tom’s and asked if it was a common issue. They said it is. The oil pan will not accommodate an aftermarket oil pump. They said it is listed on their site. I didn’t know it was aftermarket. I guess I will buy a factory pump or shave the head on the bolt; which I prefer not to do. It never felt like it was hitting anything or bottoming out during installation. Lesson learned.

 

[ba123]

That sucks but great news on the other hand!

 

[DirtDonk]

They said it is listed on their site. I didn’t know it was aftermarket. I guess I will buy a factory pump or shave the head on the bolt; which I prefer not to do.

It might not be simply “aftermarket” versus “factory” but more likely to be standard volume versus high volume.
Since your pan is off, why not measure the depth of the pump body? Just to be sure.
It could very well be that they use higher profile bolts, where a correct pump would have low profile bolts. But I’ve run into this fairly often with, the Mustang pans and high volume pumps.
Could be a pan issue with new replacement pans, or could be a pump issue with new replacement pumps. But I have had to dimple more than one oil pan before to make clearance around the pump.

Is this the original oil pan, or a replacement? I think you said, but I don’t remember.
I know you said you thought the pump was not changed, but don’t remember what you said about the pan.

 

[ba123]

I believe the base of some aftermarket and yes, high volume, pumps are larger than the very small base of the stock.

Maybe someone can post a pic of what a stock one looks like? Here’s my milodon high volume:

@DeepC73 does yours look like that?

 

[DeepC73]

It might not be simply “aftermarket” versus “factory” but more likely to be standard volume versus high volume.
Since your pan is off, why not measure the depth of the pump body? Just to be sure.
It could very well be that they use higher profile bolts, where a correct pump would have low profile bolts. But I’ve run into this fairly often with, the Mustang pans and high volume pumps.
Could be a pan issue with new replacement pans, or could be a pump issue with new replacement pumps. But I have had to dimple more than one oil pan before to make clearance around the pump.

Is this the original oil pan, or a replacement? I think you said, but I don’t remember.
I know you said you thought the pump was not changed, but don’t remember what you said about the pan.

It is an aftermarket pan from Tom’s. I bought and installed it in July of 2022. I had no idea it was touching. I did end up measuring the pump. I ordered another “stock” pump from AutoZone to compare. It was a little shorter. The pump I had was 5 1/8” tall to the top and the Melling from AutoZone is 4 7/8”. The bolt heads add about 1/4”. The pump you want is the Melling M-68. That 1/4” or less makes all the difference. I found a second hole/tiny crack right where the other pump head bolt sits. Unfortunately, it was so small that I didn’t find it until after I had the original, larger hole welded up. I just smeared some JB Weld over it. I plan to make a post on the thread identifying the correct pump. The original pump that caused it was a Melling HV-68 high out pump and it was a little larger. I’ve only driven it about 10 miles to test it out. I did notice my oil pressure went from 40 to 50 psi at first. Now it’s about 45. I haven’t gotten around to changing out the fuel pump that was leaking oil from the weep hole yet. The increased oil pressure has caused the oil leak in the fuel pump to worsen, which makes sense. Also, a few of the bolts on the valve covers are leaking a little oil now, very minor and also likely from the increased pressure. What is the best way to solve that. They already have thread sealer on them.

 

[DeepC73]

I believe the base of some aftermarket and yes, high volume, pumps are larger than the very small base of the stock.

Maybe someone can post a pic of what a stock one looks like? Here’s my milodon high volume:
View attachment 915814

@DeepC73 does yours look like that?

Yes, mine looks just like that, except my pickup disk is flat and sits horizontal while yours is vertical.

 

[m_m70]

how's your pcv system?? crank case pressure can be an issue if your pcv valve or plumbing is off.

45/50 lbs of oil pressure isn't out of the ordinary. about mid range.

good luck with this!

 

[73azbronco]

engine assembly 101, always use playdough... or modeling clay

 

[DeepC73]

engine assembly 101, always use playdough... or modeling clay

What do you mean? Sorry, just wondering.

 

[Speedrdr]

I’m thinking it’s a reference to putting a layer of clay on a surface (oil pan, e.g.) and installing the pan and removing to see if anything marks the clay. Gives you a heads up as to a potential problem.

Randy

 

[DirtDonk]

I would think so too.
Clay under the pump body, and clay under the pickup to make sure it’s within the prescribed distance from the bottom surface of the pan.
But you can also trial fit any pan without the gasket first. That’s what I do just to make sure that a pan is not hitting a pump or pick up.
Without a gasket, if it doesn’t hit, then it certainly isn’t going to hit with a gasket. If it does hit though, you have to determine how much and whether or not the gasket will be thick enough to make up the difference.