30mm oil pumps - how to use

[Bruce2]

I haven't changed the oil yet as this engine has ran with 20/60 with no issues.

At the top of this topic you said you used 15W-40. Which is it?

[Dean...]

I'm using 15w40. People had said that it was this oil that was causing my issue. Because I've ran 20w60 at one time in the past with no issues, I haven't changed out the 15w40

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[Dean...]

I'm planning to buy a new line tomorrow to replace the one that I kinked. Fingers crossed it will resolve my issue..

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[Bruce2]

I'm using 15w40. People had said that it was this oil that was causing my issue. Because I've ran 20w60 at one time in the past with no issues,

Up until now.

[Dean...]

I found the issue!

When I did all the work on the motor, I ordered new stock oil pressure relief valves and springs. What they supplied me with were actually booster springs.

After finding a set of stock ones and throwing them in, I have no more issues.

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[FJCamper]

Hi Dean,

Yes, the stock springs are the best. We made a similar discovery a few years back and now we only run stock springs and solid pistons.

The grooved pistons that come with most oil pressure booster kits are actually old VW Type 3 pistons that improved oil cooling in those engines. We've used both the grooved and solid pistons in our racing engines and haven't seen any difference, good or bad, in cooling.

FJC

[Bruce2]

I've seen a service bulletin from VW that recommended using the grooved piston in tropical climates to help lower oil temps. I've tried it during a couple of trips around Mexico and haven't seen any improvement.

[Dean...]

There are 2 brothers who have a VW workshop who are in their 60's are were taught by their father who was Dutch, and all they have ever done is worked on VW. I bought the standard springs from them and they reckon that here in Australia at least, they have never noticed a difference between using the standard valve or the slotted one, so I decided to stick with what was in the motor before I worked on it, and not install the slotted valve.

I took it for a drive yesterday for the first time and the first thing I noticed compared to before I rebuilt the top end was I had good oil pressure. The valves must be doing their job, because what I found was when it was cold the pressure would rise and fall very quickly, but it never went above about 55 psi. Three pressure would shoot right up to 55 and then even though the revs either stayed the same or kept going up, the pressure would drop to 50 and stay there. When the engine is warm the pressure stays around 7-10 psi per 1000 revs.

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[FJCamper]

The slotted piston, when fully depressed by cold oil pressure, acts like a solid piston and allows cold oil to flow directly to the bearings.

But as the oil heats up and the piston rises, the slot is engaged and cold and hot oil are now able to flow to the bearings and to the oil cooler. This allows the cooler to get oil earlier, hence the premise the slotted piston promotes better oil cooling.

Once the oil is fully hot, and the spring has the piston pushed all the way to the top, only hot oil (above 180 degrees F.) is diverted to the oil cooler.

Knowing this, the slotted piston seems to have an affect only at the transition from cold to hot oil. If the engine ran in this mid-range at least half of the time (shorts trips?) the slotted piston makes sense. But that's not usually the case. And if it really helped, why not use in in all engine types? It was designed and put in service by VW engineers, so we have to take it seriously. They don't spend a Mark or invest an hour for nothing.

If anybody has any better understanding of this little piece of VW history, I'd love to hear it.

FJC

[Bruce2]

Do you think it acts like a mixing valve, mixing cold and hot oil? If so, that's not the way I see it.

The purpose of the groove is to allow pressurized oil to get to the groove. When this happens, the net area of the piston is reduced to the area of the small diameter at the bottom of the groove. This means the piston will ride higher in the bore at any pressure. This forces the oil to go through the cooler even if the pressure is really high.

[Marc]

The slotted "1500S" plunger was used in small-passage/single-relief cases and has no business in a large-passage/dual-relief case.
Unfortunately the late "orange" Beetle Bentley manual includes one old, recycled photo from days gone by which shows a slotted plunger. You'll find the identical picture in the "brown" `68-`73 Type III Bentley. That little editing error has caused mass confusion.
If you'll closely examine that picture, disregarding that it's labelled with a 1974 VWoA copyright, you'll see that it portrays an early small-passage/single-relief case's small-diameter pump pickup, NOT that of a large-passage/dual-relief case as all (`70-up) vehicles covered by that manual were equipped with.


The slotted plunger which comes in the ubiquitous "booster kits" is not identical to the OEM 1500s item, their slot has an angled lower edge which is an aberration unique to the aftermarket kits. It too is neither required or desired in a dual-relief case, the added length of either slotted plunger only confuses the "temperature" control system by increasing the spring tension.