Flat Jack Posted February 22 Report Posted February 22 Oh crap. Sitting here killing time reading posts on this and that and come across a August 2020 post from Bdblazer1978 about a brand new Mellen oil pump that came with his rebuild kit almost destroying his new engine. That's what came in my kit and is ( was ) about to go in my totally rebuilt 218. How disappointing. Put on my coat and hat and ran to grab my old oil pump for a quick look. After reading this post I plan on reusing it since it seems in good shape. Since that post was 4 years ago is this still a problem? I did notice two things on my old pump. 1) The gear has definite wear on the tips, and 2), The outer gear in the head has a 1/8" wide slot that runs against the housing that the Mellen does not have. Assuming the cam gear is worn the same as the pump gear could the nice new square tooth gear on the Mellen be trying to " climb" the worn gear on the cam? Could the slot have something to do with better oiling around the outer edge of the pump? What's your guys thoughts and how did Bdblazer solve his issue? . Is gray beard Dave Erb? If so I would like to thank him. I printed his article " Some thoughts on Mopar flatheads" several years ago and am putting all to work in my engine. Now please don't tell me he passed. Thanks Flat Jack Quote
wallytoo Posted February 22 Report Posted February 22 dave erb was graybeard, and he died many years ago. Quote
FarmerJon Posted February 22 Report Posted February 22 Have you looked at the Tony Smith guide to oil pumps? I belive there is a PDF in the tech archives here. He details what to check and modify on new and used pumps. Quote
Robert Harrison Posted February 22 Report Posted February 22 Eeee. I purchased a Melling pump in about 2006 for my 47 1/2 ton I just rebuilt. I was not aware of the be sure to fill the pump with oil or white grease. And some say not to do the higher pressure spring in these engines I was not sure why? I used the crank seal that does not bolt to the block as I fabbed bolts to be able to remove the flywheel more easily and thought the bolt on crank seal might be too close to the bolt heads. The engine is assembled but has not gone in the truck as of yet. I also installed the higher pressure relief spring I think it was green. If I remember correctly black was standard. I'm not adept at looking through this site can someone repost these two articles please? I would really like to get a look at them. I am a member of the 39-47 dodge truck group anyone with Job rated trucks should also check us out there is a lot of decent tech stuff there pics etc. 39-47dodgetruck@groups.io Nice to see someone else in the area as I live in Snohomish WA Bob Harrison Quote
John-T-53 Posted February 22 Report Posted February 22 (edited) I am not familiar with the referenced story mentioned in the first post, but how did a brand new oil pump destroy an engine? Was it missing the gears, did the gasket get installed backwards? I put a new Melling pump on mine and it worked fine. Just filled it with assembly lube and oil on first start up.... Edited February 22 by John-T-53 Quote
billrigsby Posted February 22 Report Posted February 22 Well you might count yourself lucky then, these are well-known for basically being trash, seizing taking out camshafts. The engine I'm currently building had that exact problem, the brand new pump that came with the rebuild kit seized fortunately only chipped one tooth on the cam. Then after that, winter came, car accident, hernia surgery, everything has been on hold ever since that episode. I've got three that I've pulled out of old engines and I'm going to go with one of those when I get back going on the project. I would (in my never to be humble opinion) never buy another Melling product in my life. Quote
Young Ed Posted February 22 Report Posted February 22 With it now a known issue couldn't someone give their new pump some test spins in a vice? You'd have to keep it oiled somehow Quote
JBNeal Posted February 23 Report Posted February 23 On 2/21/2024 at 9:18 PM, Flat Jack said: Oh crap. Sitting here killing time reading posts on this and that and come across a August 2020 post from Bdblazer1978 about a brand new Mellen oil pump that came with his rebuild kit almost destroying his new engine. That's what came in my kit and is ( was ) about to go in my totally rebuilt 218. How disappointing. Put on my coat and hat and ran to grab my old oil pump for a quick look. After reading this post I plan on reusing it since it seems in good shape. Since that post was 4 years ago is this still a problem? I did notice two things on my old pump. 1) The gear has definite wear on the tips, and 2), The outer gear in the head has a 1/8" wide slot that runs against the housing that the Mellen does not have. Assuming the cam gear is worn the same as the pump gear could the nice new square tooth gear on the Mellen be trying to " climb" the worn gear on the cam? Could the slot have something to do with better oiling around the outer edge of the pump? What's your guys thoughts and how did Bdblazer solve his issue? . Is gray beard Dave Erb? If so I would like to thank him. I printed his article " Some thoughts on Mopar flatheads" several years ago and am putting all to work in my engine. Now please don't tell me he passed. Thanks Flat Jack Tony Smith went into great detail about how to deal with flathead oil pump rebuilds on fb awhile back, it was referenced on this forum a few times so I took screenshots of his work and put his step-by-step instructions in the Technical Archives... Greybeard passed away a few years ago, but his wisdom lives on here with his technical expertise and stories... Quote
Matt Wilson Posted February 25 Report Posted February 25 (edited) I've read about this pump seizing issue for a couple of years now, or more. I've read about enough instances that I see it as an ongoing or recurring manufacturing problem. There are probably hundreds, or maybe even thousands of these pumps that get sold each year, and I suspect most of them don't have an issue (although I don't know this for sure), but there are enough that do have issues that the problem would seem to warrant more attention by Melling. But what I understand is that Melling almost invariably claims that it's caused by the installer failing to follow the directions that require submerging the pump in oil and spinning the shaft until all air bubbles are eliminated. The trouble with that argument is, there are a lot of folks who say they followed the procedure carefully and to a "T" and thoroughly removed all bubbles and the pump still seized. Upon disassembly, people are finding that the shaft has seized to the housing. The exact culprit is uncertain, but it thought to be either too little clearance between the shaft and housing or a shaft that is not as straight as it should be, or maybe there's still some remaining air pocket that's trapped around the shaft, or maybe a burr at the little oil hole in the housing that feeds the shaft. One guy on the Facebook Flathead 6 group, Ken Holmes, rebuilds these engines exclusively (for customers), and he employs a run-in procedure that involves submerging every pump in oil for 24 hours and then using his milling machine to spin the pump shaft for a period of time, with the pump still fully submerged. Most pumps have not been an issue for him, but even he has had one that seized up during this procedure. As a result of all this, I plan to do like a couple of you guys and reuse the pump out of my previous engine, which has only has around 7000 - 8000 miles, instead of the new Melling pump I bought. Edited February 25 by Matt Wilson 1 Quote
wallytoo Posted February 25 Report Posted February 25 (edited) when i first rebuilt the 237, circa 2009, i didn't touch the original oil pump. prior to the rebuild, running pressure was around 40 psi, and idle was around 15 psi. i was fine with those numbers. when the 237 threw a rod circa 2017, i pulled the pump and installed it on the "new" 251, although i did clean it and run oil through it prior to installing. pressure on the 251 is about 42 psi running, and 20 psi at idle. the original pumps are pretty solid, and work well enough. seems like a big risk to run a new pump if the original pump (or whatever pump came with a given engine) still works. in neither case did i submerge the pump in oil prior to installing, and it worked just fine (and pressure was indicated immediately during starting, prior to running). Edited February 25 by wallytoo 1 Quote
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