Melling High Volume Oil Pump for Type 4 Motor

[69BahamaYellow]

Anybody know where to find one of these gaskets for the Melling Type 4 oil pump? This is the .004" thick gasket that goes between the pump housing and the steel cover plate. The pump on the left is the Melling pump, vs OEM on the right.

Guess I could always make one, but if they can be bought, that would be easier....

[SGKent]

I think stock VW is .002" or .003". You might be able to combine a couple. Otherwise clean and use some sealer other than RTV on it. Curil or maybe hylomar.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

I have used both .002" and .003" with the type 4 Melling pumps I had with no problems.....before I quit using them... when I figured out how much it was bypassing from high oil pressure (stock oil cooler set up).

Very well built pumps.

The type 4 Melling pump uses the same gasket as the M-79C type 1 pump.

You can very probably get away with modifying a type 1 gasket with an Exacto knife (if needed).

Of course with the modern thin synthetic oils....I have been thinking about trying one again when using 0-30.

Or...check NAPA. They list a HUGE range of Felpro gasket materials. You may be able to get something thin enough. That gasket would be easy to hand cut. Ray

[69BahamaYellow]

Thanks guys. Didn't know the Melling type 4 pump was nearly interchangeable with the type 1, which seem to be readily available on eBay. I pulled this type 4 pump from a Porsche 914 motor and measured the gasket to be .004", but I suppose it could be swelled. If the type 1 gaskets measure .002"-.003" thick, I'd bet the type 4 is the same, since both are 30mm gears. I thought about just using RTV on it, until I measured the pump housing to be just about the exact depth as the gear length; that has me thinking the gasket is critical for giving enough clearance for axial gear movement and lubrication. I notice the pump has a groove around the outer edge of the housing with a return cut to the low pressure side of the pump, so I bet the oil that leaks past the ends of the gears gets into that groove through those little holes and notches in the gasket.

I still can't find that gasket sold separately for a type 1 pump either, so if I'm missing something, I'd greatly appreciate the intel

My original type 4 pump is in good shape, but like Ray said, I too like running the thinner oils, and in particular the Shell Synthetic Rotella T6 5W-40. That stuff seems to really work well with hydraulic lifters and already has plenty of ZDDP, so a higher volume oil pump seems to make sense.

Another thing I like about the Melling pump is that it gives much more clearance between the bolt heads of my aftermarket Web Cam Gear than the OEM pump. The Melling gives me about .020" vs only .013" for the OEM pump (that is without the gasket between the case and the pump). Since I recently had a cam thrust bearing failure that made my cam axial clearance open up to .024", I got damn lucky I caught that before the cam started hitting the pump

Here's a couple pics of the OEM clearance. I think another advantage of the Melling is that with it's cast Iron construction, I can safely mill off a little of the idle shaft boss to give even more clearance, but I'm not sure it's necessary, now that I've upgraded to double thrust cam bearings.

[raygreenwood]

Thats too little clearance. That clearance does not take any potential expansion into account along with the loss of say the inner thrust flange.

As you note.....024" for the thrust flange. I would not trust anything under .040"....and its easy to get off the melling as you note.

There have been some issues with the melling. Case fit due to expansion issues and internal leakage. That is not many thousandths though and can be fixed with a judicious apppication of a thin o-ring..... ring.... area around the inlet and outlet holes. Maybe .003" to .005" thick. Fully dried before installing the pump.
Permatex ultra gray is best as its 40 durometer....very close to normal o-ring hardness.

I will see if I have a picture of that mod anywhere.

The other issue is that a 30mm...especially that 30mm pump puts out so much volume that it can bypass your oul pressure relief valve and run very hot oil temps.

Thin oil should help with that....but you need to check it. Look at some of piledrivers posts on the STF regarding this exact issue.

You can use RTV on the lid. I have done it numerous times.....but its applied carefully and must be dry FIRST.....do not apppy it wet and them clamp it together. That gets RTV inside of the pump and squeezes it all out. Same issue applies. You have to use a high dudometer RTV. It has to be firm. I only use for making the stock gasket oil tite on its outer surfaces.

Oh....wait. I have some oil pump gaskets. Let me see if they fit one of my melling pumps.


You can get a pack of 10 type 1 oil pump to plate gaskets for $7.95 at CIP1. Ray

[SGKent]

has that cam gear been milled for those bolts? Usually it is a lot more than .013" clearance.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

[williamM]

Yet to be installed, but quite easy with a Harbor Freight "O" ring assortment and a small dremel round bit it seems to fit well- may use Gel Seal when installing.



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_________________
some days I get up and just sit and think. Some days I just sit.

opinion untempered by fact is ignorance.

Don't step in any!

[69BahamaYellow]

Yes, those are milled bolt heads. When I purchased the cam and gear from Webcam, they assured me the bolts and cut washers would give adequate clearance for the oil pump, without milling down the gear. So long as your cam thrust bearing is in good shape, I'd say that's true, but I'm still going to take a little metal off the oil pump for some extra piece of mind.

When my cam started making a knocking noise at idle, I only ran that way about a week before pulling the motor. More clearance between the cam bolts and pump may allow you to run longer, but for me, the lesson learned is that failure will be catastrophic if you ignore that little knocking noise in a type 4 motor....

[69BahamaYellow]

That O-ring solution by WilliamM seems to be a great idea to fix the leakage issue that others have talked about.

[Wildthings]

I have run lots of miles with a stock pump and 5w40 oil with zero problems so long as the ambient was below 115°F.

[Hoody]

There have been been lengthy discussions on type 1 pumps on the type4rum. In short the cam gear needs to be modified. Cam bolts need to be clearanced. From your pics yours look too thick at the head, no washers, red loctite, protruding threads on the back of the cam gear bolts removed and the bolts center punched. Minimum clearance is .040 as noted by Ray. That is the absolute minimum. Personally I would just use your type 4 pump if there is no wear and have the idler shaft pinned. The o-ring mod on a type 1 pump is useless because the type 4 case is too thin where the pump mounts and the o-ring just hangs out in the case and seals nothing. If you have a correctly modified type 1 pump and cam gear for a type 4 engine then if you are not happy with the results from your pinned type 4 pump you can switch back to a type 1 pump without tearing the engine back apart.

[williamM]

[quote="Hoody"]There have been been lengthy discussions

The o-ring mod on a type 1 pump is useless because the type 4 case is too thin where the pump mounts and the o-ring just hangs out in the case and seals nothing. (quote]


I don't under stand your thought here. The "O" ring is only filling in a .003 gap from the T-1 pump- and it is applying a vacuum to that "O" ring, not a pressure. This would tend to suck the "O" ring further into the pump, not "Hang out in the case."- Please share your experiences with this problem you are encountering with your installation of this mod. Thanks Bill.
_________________
some days I get up and just sit and think. Some days I just sit.

opinion untempered by fact is ignorance.

Don't step in any!

[Hoody]

I would not use a Melling pump. But to each his own. So I have no personal experience with this mod on a Melling pump. I am simply passing on information from others that have. If it works for you that’s great!

[SGKent]

There are differences in plumbing in the late cases where the excess oil dumps. In earlier cases it dumps back into the sump. In later cases it recirculates back to the pump. Make sure that one has the correct relief valve for the type of case they have, and that it is new. A little wear or crowning will allow leak down too. I am with Bob on this but he and I use only pumps blueprinted by Phil or NOS. I sold my last blueprinted pump that was also like new so I have none left. Haven't heard from Phil in awhile so I don't know how he is doing. He had a jig made to machine oil pumps.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

[raygreenwood]

Not to get off the topic of the original poster....but the stock type 4 pump is really an elegant little pump for a stock or even larger than stock engine without external oil coolers.

The construction means no outer plate to seal up, the o-ring seal on the inside means pretty damn good pressure with low risk of internal leakage....a very well made, low profile pump. I go to pretty good lengths to try to use, save or repair a stock pump....rebuilding, swapping gears, swapping body, swapping inner parts, lapping, pinning the shaft etc.
It think its worth it.

That being said...I am always torn on the Melling pump. It is a DAMN fine pump. Very high quality build....excellent gears and shaft quality. It could use a little flatter outer plate but that can usually be corrected with a little work.

The basic Melling pump listed for type 4...for the life of me I cannot find the part # for....and there is not one listed in the parts finder on Melling's site.

It is actually slightly different than the type 1 pump...so slight that it really does not matter for interchangability...but at one time there was a part number for it. The outer plate was a little thinner and the inner boss was slightly lower.

It may be that it was actually one of the other versions....there are typically M79-A, M79-B and M79-C variants that range from four bolt to three bolt and dished to not dished cams and late type 1.

Also I 'thought" that at one point in time (I may be imagining it)...that they made a 24mm and 26mm version of the cast iron pump as well.

I have thought about drilling a relief hole in the large outer boss...with either a check valve or bleed orifice....and bleeding volume back to the case...could "normalize" the basic 30mm cast iron Melling to not screw with the stock pressure system.
If that worked....it would be worthwhile as now type 4 people would have a non-nonsense drop in alternative to the rarity of the stock pump.

At some point in time when my 412 gets back on teh road I will make my Melling pump into a mule and test this and figure it out.

For now....the issue of expansion (or lack thereof) for the Melling and compared to the aluminum case...and internal leakage....and I can factually tell you there is leakage internally....because I sealed one of these pumps up for an engine I build back in the early 00's...to cut down on suspected leakage...and the oil pressure went through the roof...and bypassed the oil cooler with 10-30 oil.

...so...one may argue that point by saying..."hey...it makes so much over pressure/excessive volume...that it was ....working"...so who cares about internal leakage.
Well...you should care....because its not that we were not getting good oil pressure...we were getting highly ERRATIC oil pressure. Down at lower rpms...from idle to about 2500.....pressure was fine...maybe a tad high....but fine. However...you rev it or accelerate....and just below 3k....you get a "dump" or spike...as volume/pressure overcame the gap between pump and case.

It catches up as rpm continues to rise.....but you see spikiness to the oil pressure in the 3000 to 3500.
So...we thought this was just oil pressure relief valve modulation....after all...the gears are 38% larger than stock with the the Melling.

So...after reading about pressure issues on the STF in the early 00's...and after having some of my own issues with the Melling between 98 and 2000 on my own car....we pulled the pump on the engine I was working on and did some sealing around the inlet and outlet port....as an experiment.

Pressure went up about 10 psi across the board below 2500 rpm and about 15-18 psi at 2500 and above....
The oil pressure spikiness went away totally though

The o-ring mod......I agree with all parties on this one. O-ringing will work fine....but making it clean and making it work...I understand what Hoody is getting at.

There is just not enough room between the flange and the inner edge of the pump body around the inlet and outlet ports to make it really clean...well...unless you use a narrower o-ring cross section and CNC mill it.

But...this mod works REALLY well. The RTV spot gasket

You can put on a .002" to .005" (almost any thickness really)....gasket...around the inlet and outlet ports. I thought I had pictures from the last one I did...but remembered that it was pre 2004 for me so I had no "digital pictures ...so I did one this morning for the pictures.

This was about 25 minutes start to finish.

Materials:

Piece of glass
Sharp Exacto knife
Scotch tape (real Scotch tape and not that crappy Office Depot "Highland tape)
Permatex Ultra Gray...because its 40-45 durometer/hardness...about like an 0-ring
A spreader squeegee like you use for bondo...preferably a #m PA-1. Cut one side so it has a sharp edge

So how do we know how thick we are applying the RTV?

Because.....

The miracle of Scotch Tape is that it is one of THE MOST uniform roll products made on the planet. It is advertised at .0012" thick. That is .001" film thickness and .0002" adhesive thickness...which is 30.48 microns.

This roll measured out at 31.3 microns...so pretty damn close!

First..clean the pump port areas with MEK or acetone...or even soap and water. Must be CLEAN!

1. Measure the pump and bore and figure out how thick you want the RTV. Remember you have a port on each side and 45 durometer RTV will crush down about 40%. So if you have .005" of RTV it will crush down and compression lock into a solid...just like a gasket...right at .003" thick.

2. Figuring about .0012" per layer of Scotch tape...stack up several layers on the sheet of glass. In my case I was making it .005" thick....so 4 layers of tape worked out to .0049"

3. With a straight edge and Exacto knife...cut a straight strip about .080" wide to go between the outer flange and the port. This one is important because the edge of the acpplicator squeegee needs to ride on it like a rail so the thickness of RTV will be even and flat.

4. Cut a strip of the tape stack for the inner edge. Apply both of these and then lap a strip over each end and trim it cleanly so the whole tape mask is EQUAL thickness with no gaps.

This is what the tape mask should look like when applied. The red arrow is pointing to that thin strip of about .080" wide that is there to keep the squeegee level.

This is what the mask is supposed to be doing. The thin strip next to the outer flange...and the strip on the inner edge..combined act like rails for the spreader squeegee to ride on so the thickness of the RTV will be equal.

Make sure the squeegee card you use is new and clean with now nicks in the edge. You will need to make several passes with RTV to get it level and even.

Here is what it looks like after pass #2. I made three passes altogether.

Do not worry about the excess in the port or on the sides that the red arrows are pointing at...TRUST me..... ...if if you get in a hurry before it dries....you will bung it up!
It is really easy to trim off and clean up with an Exacto knife and Dremel with wire brushwheel later.

I got in a hurry for these pictures and you can see how I buggered it up a little around the port hole (red arrow) because I should have let it dry...and yes that small mark in the corner (yellow arrow) is where I dropped the tape .

But you get the gist.

So...why not just apply RTV all the way around?...because its harder to do than you think....and...then it would all be the same thickness with equal pressure all the way around....and that means there would be no high spot or ring around the port...so it would actually not crush down as far and not seal as well.

This works VERY well....and is very easy to make very precise to almost any thickness you need.

Ray

[williamM]

elegant- will have to try that on the next one- I take it this would be for the original assembly.

Also likr the "almost in the pump" pressure relief- might make it spray on the cam gear or bearing - maybe a ball point pin spring and BB?? Or are we getting to complicated now?
_________________
some days I get up and just sit and think. Some days I just sit.

opinion untempered by fact is ignorance.

Don't step in any!

[raygreenwood]

[SGKent]

very good Ray. Never saw that simple solution coming. Have to remember that trick. RTV acts weird with oil sometimes as it ages on surfaces that have been exposed to oil before - is there anything else that might be a better candidate or is cured RTV the best? I've seen some rubbers/vinyls/whatever on some later factory parts that hold up really well like it is vulcanized on - but the way it was applied is clearly as a flow of something. Valve covers, pans etc have that stuff on them sometimes these days and it is so durable it can be reused - one doesn't have to scrape it off and start over when a trans pan is pulled to change the ATF.

Also - I had a conversation with Phil tonight, He is blueprinting pumps again now and then. and also making a few of his famous aluminum VDO sender finned taco plates for any who want to travel down that route. (you provide your own oil-temp sender).

_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin