How to get a leak-free oil pump?

[jenkinso]

I've a 2165cc Type 4 motor with a cast iron oil pump. Not sure of the pump's spec or origins but it looks identical to the Melling pump on the left of the photo in the URL blow, so guess its the 30mm one.

http://www.volksbolts.com/faq/OilPump.htm

Anyway, no matter what I try, the damned thing leaks. I've run it with and without the paper gasket between the body and cover, with and without RTV silicone sealant between every possible mating surface, with and without the nuts that have the in-built silicone washers on the back, etc etc. I've never managed to cure the leak which ends up with oil being sucked into the 911 fan and making a dusty oily mess everywhere.

I've read that the biggest problem is the different expansion rates of the cast iron pump body to the Type 4 aluminium case. Not much I can do about that unless there's a swap for a good aluminium bodied pump?

Also, I also wondered if the 30mm gears are creating excessive oil pressure when cold or at motorway driving and causing the leaks (although I don't recall the pressures it runs at unfortunately as I've not driven it in a while and my memory).

Otherwise, I've an oil leak-free motor so this one leak is a little frustrating.

Anyone got any tricks, tips or ideas on how to get a leak free oil pump as I'm fed up with this problem and would love to cure it?

[Clatter]

This is a tough one...

Mellings iron pumps leak, it's just how it goes.

Some are using a modified type 1 Schadek, and o-ringing/anodizing them to solve their problems with a small OD.
You can buy these from Gene Berg, and modify for type 4 use pretty easily - My vote goes here.

Others are searching out good used type 4 factory pumps.

Some are re-machining/re-building them.

Good luck!
Let us know what you ended up doing, and how it worked.

[patto]

Ive just bought the CB Performance Maxi pump 914/T-4 and it measures in at 69.88mm vs the original at 69.92 mm, so there is only 4/100th of a millimetre difference, maybe this is the new go to pump for the type 4? not sure how the modified pumps spec out?

[wreck]

the stock type 4 pump measures around 70.07 mm , so that is almost .3mm or .012' under size . I think as Clatter mentioned the Berg O ringed pumps are the best answer . I shimmed a Shadek pump and fitted it in place with the case split. so far so good .

[GARRICK.CLARK]

As Clatter points out. Melling pumps leak. get rid of it and fit a standard type 4 one.

[patto]

Wreck, I re checked again in the morning after some much needed coffee it specced at 70.05 original pump just removed vs 70.03 new pump!
I thought that was in spec? O ringed pump does sound very attractive though.

[dunegoon]

After fussing around with O-rings and all sorts of bandaid solutions, I finally turned down a Shadeck pump, shrank an aluminum ring around it, turned it to the correct size, and then went full-flow. Awesome! The problem with O rings are many, including that they must be installed before bolting the case halves together, and the trapped oil squirts out the pump gasket.

[twodollardoug]

I wasn't aware that the type 4 pump was a different size than the type 1. With my 914 I went with a dry sump system and used the cb performance dry sump pump with a 36 horse cover. I didn't use any gaskets at all. I used yamabond 4 for the case to pump seal and curil for the pump to cover seal. And it doesn't leak a drop. I do this with all of my engines whether they are type 1 or type 4.

[twodollardoug]

In fact I quit buying gasket sets and just use yamabond 4 for nearly everything.

[jenkinso]

Thanks all for the great advice. I really appreciate people taking the time to offer me some suggestions. I think I'll have another go at sealing it with products before changing the pump, just purely due to cost and time. I'll check out the products you've mentioned twodollardoug

[jenkinso]

Btw, do you use the hardening or non-hardening type of Curil? I see Curil (hardening, good to 180 deg C), Curil K2 (non-hardening, good to 200 deg C) and Curil T (non-hardening, good to 250 deg C).

[twodollardoug]

I take back what I said. Now I remember having to shave the cam gear bolt heads to clear the pump. And seams like I had to reshape the pumps drive gear to fit in the cam. I use curil T. It's green and smells like mint. I use the curil t on everything that has very tight tolerances like the pump cover because it goes on thin.

[dunegoon]

Here is a simple tool I made to clean up the oil pump mounting surface. Pictures (if I do it right):

PICT1240.jpg

PICT1235.jpg

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[dunegoon]

Here are pictures showing the difference in the oil pump OD and the case bore for the pump, plus one of my many attempts to get it right. My problem with the loose pump was terrible hot idle oil pressure. At idle RPM, the oil found the easy path: right back to the sump. So, an O-ring was installed -- with disastrous results. So now the idle pressure was much better, but at speed the oil was hot and under pressure -- out the case gasket it went! And, you have to split the case to install the pump. I don't have a photo for it, but I tried a second O-ring right behind the flange. It sort of helped.

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PICT1195.jpg

[dunegoon]

So one day, I noticed that a #3 main bearing OD was the perfect press fit for the oil pump bore.

Let's fix this once and for all. Make the pump fit snugly, go full flow out the pump cover ( off road, I'm not running the OEM fan), and eliminate the chance of sucking air into the pump inlet with the loose fit. With a tight fit in the bore, the gaskets have it easy - no leakage pressure.

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Not shown is turning the pump body down to the ring ID.

20180219_095933.jpg

OK, I found that I had to buff out the OD because the ring expanded a bit when it was pressed on. Result is about 20psi at 1,000 RPM and 180 degrees oil temperature. Running Valvoline VR-1 30wt.