Oil Pump: The Whole Story

The VW water boxer was the final iteration of the original VW bug engine. It is in fact dimensionally identical in many ways, including where the oil pump fits. As a matter of fact, the oil pump itself is the exact same oil pump that VW used on the latest version of the 1600cc VW bug engine with “dished cam,” and had 24mm long gears.

The size of the gears in an oil pump determines how much volume of oil it can move at a given speed, which translates to how much pressure it can maintain at a given engine speed and at a given temperatures. As the oil warms up and gets thinner, a higher volume pump can keep up the pressure by moving more oil.

VW got a little lazy when it came to choosing this pump for this engine. They could have, and should have employed another commonly available pump with 30mm gears that VW bug enthusiasts had been upgrading to for many years. But in order to fit that larger pump, it would have required VW to come up with a different pump cover—to clear the coolant X-pipe that runs right past the oil pump cover. But they did not, and thus one reason the Waterboxer has always suffered from chronically low oil pressure.

We figured out how to modify the cover in order to fit the larger 30mm gear pump long ago, and have fitted one to every engine we have ever built. Replacing the original 24mm oil pump with one of our larger 30mm oil pumps provides two main benefits:

1) It helps solve the notoriously-low oil pressure issue that is typical of the water boxer engine design and the accompanying low oil pressure warning buzzer issue. If you've read our article on the subject—you know that our high-volume pump kit can help quiet that buzzer for good! We install this larger-volume oil pump on every rebuilt GoWesty engine.

2) Solves once and for all the oil common oil leak issue between the oil pump cover and oil pump. We achieve this by procuring the absolute best quality pump available, and then machining the pump housing to accept an O-ring. No more wish-I-could-get-this-silly-paper-gasket-to-stop-leaking gasket!

Our 30mm oil pump is not just an oil pump, it is a comprehensive kit that includes:

• 30mm high-volume pump w/GoWesty O-ring modification and tested gear
• Cover-to-pump & pump-to-block gaskets that come with the original pump
• Cover-to-pump O-ring
• Custom-machined OEM pump cover—lower profile to clear coolant X-pipe
• Bolts and sealing washers to replace the leak-prone stud/sealing nut combination

You say, “What the! I can buy a 30mm oil pump at other online retailers for half this price! What’s up, GoWesty?!"

First of all, make sure you are comparing apples to apples. For half this price elsewhere you do not get the needed modified cover, or the O-ring modification, or the superior hardware solution. Then there is the matter of guaranteed quality, every time. Unfortunately, simply switching to a 30mm pump was not the end-all to oil pump related problems!

We have found over the years (the hard way) that not all pumps are created equal. And not just that the quality varies from one brand to the next, but it is also possible that the quality of any give brand can vary from one shipment to the next!  

We use about 15 oil pumps per month on our rebuilt engines, and every single one not only gets the aforementioned modifications and hardware, each one also gets thoroughly checked out and fixed as needed, as follows:

  1. Each pump is remove from the box and visually inspected for obvious flaws
  2. The face of the pump gears where at the pump cover are lightly sanded to insure it is perfectly flat.
  3. The clearance between the gears and cover is measured. If too great, oil pressure suffers. If too tight, binding can occur. We have found not all the housings are machined exactly the same, and neither are the gears. Getting the clearance just right is a matter of shuffler gears around between housings, and sometimes cutting the gears or the housing, or giving up and returning the damn pump!
  4. The press-fit between the driven pump gear and the shaft that drives is tested.  The press fit can vary to the point where the gear can literally spin on the shaft causing all sorts of hard to diagnose oil pressure issues, and even engine seizure. We developed a special tool to test each and every driven gear/shaft fit by applying a torque to the gear. We have flunked as many as 50% on some of the shipments of pumps we have received in the past because the gear press fit does not pass our test.
  5. And finally, all rough edges are deburred, all parts are cleaned, and repackaged.

All this adds some cost, naturally. But compared to what all the individual parts would cost elsewhere—it is not a whole lot, whereas the value to you can be enormous. Do it right, cry once!

We are always striving to find the best pump-one that is perfect right out of the box. If we ever find one: We can finally stop checking them! But, don’t hold your breath…

Pro tip: On our rebuilds, we ditch the gasket and use Reinzosil sealant between the pump and the engine block.