Type 4 oil pump refurbishment (one method)

[raygreenwood]

Basic type 4 oil pump refurbishment:

This was part of a long engine build thread…but many may not want to go all the way through that. Having a heading for it may make it easier to find in a search.

The first question you should ask yourself is WHY you would want to rebuild a type 4 oil pump instead of just buying a new aftermarket type 1 pump and modifying it to fit and work.

There are a couple of schools of thought on this. Bear in mind….rebuilding ANY oil pump is NOT an exercise in saving money or time. You would be rebuilding this pump because you need or want to use it…not because there are not cheaper and (somewhat) easier options.

The Pros of rebuilding/using a stock type 4 pump:

1. If you are doing a restoration and want a factory pump in the car. 411/412/914…more common. A daily driver bus with lots of mods…probably not.

2. Along with the above reason….If your lifter bores are in spec, bearing clearances are in spec and your oil pressure relief and control valves are stock and in spec….and you want the pump and oil pressure relief system to work exactly like factory with no tinkering….rebuilding a stock type 4 pump is a good choice.

The Cons of rebuilding/using a stock type 4 pump:

1. It takes a lot of work and a good amount of time. Probably about 10 hours or more if everything is at hand. The work is not hard at all. Just meticulous and tedious.
So…..and this is not meant as an insult to anyone….it’s just reality… if you are the type that is not mechanically inclined, detail oriented or have a reasonable tool set or you consider your time more valuable….this refurbishment/rebuild is not for you.

2. It will not save you any money. It’s not expensive either…..but again…if you do not have cleaning solvents, fine and coarse abrasives, lapping compounds or the tools at hand….you can buy a type 1 pump cheaper.

There is nothing wrong with using the RIGHT type 1 pump. It can save time….but it will have issues that in some engines may take almost as much modification work.....as rebuilding a type 4 pump.

The Pros of using a new type 1 oil pump:

1. Its new, it’s clean, it has tight gears and it’s inexpensive.

2. You should not need anything bigger than the stock 24mm pump for ANY type 4 engine…unless you have really big oil clearances or a larger external cooler with hoses and thermostats. In that case…the ability to put in a pump with larger gears is great.

The Cons of using a new type 1 oil pump:

1. Depending on whose pump you buy it may have case to pump fit issues. The only fix for that is an O-ring or gasket modification at the inlet and outlet ports. That can add machine work and pitting effort.

2. You will have to do a little clearancing at the inlet and outlet ports of either pump or case or both. Not really a con actually but in needs to be done.

3. Unless you find the exact gear set size, you will generally end up with 26mm or larger gears. While the difference between 24mm and 26mm is only about 8%....its not always linear.
One could say with some truth that the oil pressure relief system in a type 4 should easily be able to handle an extra 8% of flow volume….that is not assured at all temps and with all oil weights. Your results may vary and you may need to tune for that.

4. there are some 24mm type 1 pumps…but they are made for beetles and will need to have the shaft boss clearanced to clear the cam bolts with aftermarket cams. Be sure the pump can handle that.

5. Unlike the type 4 pump…you have a cover plate on the outside. Make sure the plate your pump comes with is “quality”. It should be cast iron or steel preferably. And make sure that the plate has enough clearance between the pump and the fan housing. This is a problem on some.

So…..there are excellent Pros for using a type 1 pump, not the least of which is new tight gears. However hardly any of them are work or effort free.

NOTE: I am calling this a pump “refurbishment” really…because we are just tightening up its specs. We are not replacing gears or shafts or any parts. If you have other gear sets that have tighter specs….by all means swap them in!
But as long as the gears are within the spec range for lash and the pump body has not has the walls worn away by pumping grit in dirty oil…this pump should pump nearly as well as the day it left the factory.

The pump in this refurbishment:

As type 4 pumps go…..this one is in excellent shape as far as the main case goes. One of the best I have seen in years. The gears have a little wear but are not outside of tolerance. I would call them at about 75%.

If this pump is used in an engine with good oil filters and air cleaners and on time oil changes and an in tune engine….it should last another 125-150k miles after it gets tightened up a bit.

Note the 2 scratches. I think from what the owner told me that this engine died semi-violently. These two marks come from a couple of pieces of grit/metal being laying right in the port when the pump was pulled. No problem at all….just something I have seen before.

Moderate but common wear to the drive tang. Nothing to worry about yet. I will check the fit in the cam.
The idler shaft position is normal depth.

I opened this just in time. The oil had a very slight rusty tinge from absorbing moisture over the years.

The area in the circle is very faint/thin surface rust. Not an issue but if I had waited say another year to open this pump or clean it out it may have been toast.

This is the driven gear side. VERY clean and smooth pump cavity walls. Not a lot of grit or metal went through this pump. GREAT pump core!

The idler gear side looked just as good.

The pump plate had standard smooth wear rings. N big deal. I can lap that out.

You can see the gear edge is VERY smooth. Little or no grooving from pumping crap through the pump.

The plate side of the gear

The pump bidy side of the gear

It looks like the pump was surfaced slightly to put clearance into it.

OK…now for the measuring. A couple of important items when measuring gear backlash:

1. Check several gear teeth. It can make a difference. If the surface of one tooth had a little rust or is rougher…it can make a difference of about .0005” easily. If that goes into your decision not to use a pump or gear….it may only be that one tooth or the location on that tooth if you are close to the limit.

2. You do not need a jig as elaborate as mine…I mainly made it to practice my welding a few years back….but take a little time to make sure that the plate is supported and that the driven gear is rock solid locked so it cannot move.


NOTE: Do not say this is overkill...or costs too much to go through this much stuff on a type 4 oil pump.

As noted earlier if you are rebuilding or refurbishing a stock type 4 pump…you are NOT doing it to save money, time or effort.

The only reasons to work this hard on a type 4 pump is because it fits very well, gives proper relief valve operation without tinkering…is an elegant pump design (no pesky outside plate leakage or finding odd gaskets thicknesses)…and you are keeping it simply for originality, preservation and restoration purposes.

So here is the pump late locked to a small jig and the drive tang is locked tight and the dial gauge 0’d.
And……

This is the wrong way to move the gear…pushing from one side. Note that the dial gauge says this gear set lash is basically worn out….at the extreme of its tolerance at 0.008” of lash. And that is wrong. Note the yellow arrow I drew across the gear.

What happens is that the shaft diameter is 0.550”. The gear bore is 0.552”. It has 0.002” of tolerance. Just pushing at the top edge of the gear causes the gear to TILT against the shaft…giving you quite a bit of skewed tolerance.
When the gear set is full of oil and rolling/pumping...it has pressure all the way across the gear and shaft and loads it evenly with no tilt. If it did…you would see a slanted wear pattern in both the plate and body.

When you load the gear evenly in the center…..not the yellow arrows on my fingers and note that the reading changes to a dead stable 0.0064”….much better. Its at about 75% of its wear but still just fine.

You get this same mistake when using just a feeler gauge jammed in between gears from the top. It wedges the gear against the shaft at a slant giving you a higher level of wear reading.

Since we are going to be lapping the inside deck of the pump body to reduce plate to gear clearance, before you start measuring the depth so you can know how much you have lapped away as you proceed….lap the outer edge of the pump body just a little bit to make sure there are no ugly dips that will throw your measurements off greatly

The dial depth gauge is 0’d on the inner deck.

Now its on the gear showing 0.004” of depth difference. It is said…at least in type 1 pump building that 0.004” is the maximum tolerance. I think its way big. I will lap it down in the next episode.

NOTE: I agree with the Wilson book (How to Rebuild Your Volkswagen Engine)….really… the gear to plate tolerance should be close to “0”. Not dead 0.000” like he notes…but just close enough to 0 to allow clean smooth movement at freezing temps.
The pump expands as it heats up. You will get about .0015” to .002” from a dry room temp tolerance of about 0.0005”. It just needs enough clearance to force an oil film under it.

My funky back lash measuring plate:

Its made out of a piece of 2” wide X 0.125” thick mild steel strip and a couple of pieces of 1” side x 0.125” thick strip….a little grinding and drilling, some tack welding practice and cheap black paint.
I spent about 3 hours on it a few years back. Partly because I wanted to go through a pile of oil pumps….and I found the issue with reading lash accurately…and also…it was an excuse to play with the mig welder I just bought at that time….and you can see I needed the practice.

Removing the idler shaft and locator bushing from the plate:

So I made a wooden jig from a 2” x 4” and clamped it in the vise….

So the plate sits flat

I used a brass drift and a hammer to drive out the idler shaft

NOTE:

1. Mark the end that is in. The outer shaft section is polished smooth

2. Mark the depth that the shaft is pushed in from the outside. This one was 0.040”

3. VERY IMPORTANT: This shaft had to be POUNDED OUT. It was very tight and probably did not need to be pinned but I like to do this anyway on all of my pumps for long term safety.

BUT….if your idler shaft is very loose and can be easily pushed out or wiggles in the bore….your pump plate is scrap and should not be used, A loose shaft will allow the pressure between the gears to drive the gear apart making the shaft more loose.

Shaft is out

Using a sharp, clean edged, flat face punch…you will find that the locating bushing has a very slight ledge from the outside and can be tapped out easily with a few taps.
Alternate to each side. Clean up any burrs you make later with a needle file or sandpaper.

Locating bushing is out

Get a quick measurement of the plate thickness just for information. You are going to lap until the marks in the plate are gone anyway but this is a good insurance to make sure you lap evenly.
The machine work around each bolt hole on the outside is a little crude so you will get four slightly different measurements by each hole. Just number the plate with a sharpy and write them down. Its just insurance.

I used machinist layout dye. I always do this just for the start of lapping to get an idea if I am keeping things straight.

I am using valve grinding compound on glass to do the rough/large/fast removal

For the final polish I am using this. These are really nice. You can buy them at most good hobby shops. They are polyester film based wet/dry abrasive. Very uniform and tough.

http://www.ksmetals.com/19.html

For some reason the sanding films do not appear on their website but you can order them on ebay and in other places and most serious hobby shops sell them in varieties that range from 0.5 microns up to 150 grit.
By the way…0.5 micron is 60,000 grit and 1.5 micron is 13,000 grit. Serious sanding and polishing films.

So apply some lapping compound evenly to the face of the plate and some on the glass.

IMPORTANT: When lapping….DO not move a circular flat object like this plate around in circles.
Move in in straight lines like the red arrow in the pictures for whatever number of strokes you want. Then turn the part a measured increment and repeat the same number of strokes. Work all the way around full circle.
I did 10 strokes on each hash mark.

Why is this important?

Because the inner area of any surface being turned in a circle is smaller in diameter (red circle and lines)…than the outside perimeter.
So with each revolution the outer areas pass over a much greater distance of abrasive paper…wearing MUCH faster than the inner area…which will wear the part into a “cone” shape.

I did this on purpose for an example shown above. Notice the marks are worn away faster where the red arrow is. This was not a problem for this. It was less than .0002” so I just re-coated it and lapped it correctly to straighten it out.

After the first revolution…which was 16 angle changes as shown in that lapping diagram with 15 strokes on each axis. 240 strokes total.

You can just barely see a little bit of gear marks left. This took maybe 10-15 minutes. I stopped at the halfway point and added more lapping compound.

I finished it off with 10 strokes on each axis…160 strokes total, on 600 grit sanding film on glass

The finished plate.

NOTE: you MUST wash these parts with hot soapy water at least twice and then rinse wit ha hot solvent like carb cleaner.

The gears:

NOTE: We already noted the swirl marks in the gears. By the way…these marks are NOT caused by debris. These are machine marks in the original gears.
Any really heavy grooves caused by debris in these end face areas almost always show a ding or chip in the edge of the gear where a piece of metal or grit was jammed between the gear face and the plate or pump body.

I measure the gears first. The driven gear in this pump was 0.0004” shorter. Not enough to worry about.

The same lapping method. Note that I marked the starting gear tooth with a Sharpy marker.
These gears have 9 teeth so I used 9 axis changes and 20 strokes each (steel is harder than aluminum and takes more work)…180 strokes on each face.

Same on the 600 grit on glass

Lapping the area noted by the red arrow takes another lapping plate

I used another scrap of Mic-6 plate with a slightly oversized hole drill in it for the shaft to go through.
Though I do not recommend lapping seriously in a circular fashion because of the risk of making a surface conical….just lapping to smooth is not a big deal. Maybe 30 revolutions in a minute is all this took

And I finished it up with some 600 grit sanding film spray glued to the disc

The inner pump body deck:

This is my lapping plate. I was hoping my machinist buddy would have made me a tool steel one by now…but this works just fine. You can probably do about five pumps with this before its shot.

This is made from a 6” x 6” x 0.250” thick piece of Mic-6 aluminum jig and tool plate. You can get a 6” x 6” plate from McMaster Carr for about $17.
The inner bore of the pump body is about 2.6”. I clamped this piece of metal down and used a cheap 2.75” bi-metal hole saw to cut out a clean, oversized circle.

I then tapped the guide hole with an 8mm x 1.25 tap and installed a bolt. Put the plate in the drill press.

You really need a drill press for this..but you can do it wit ha drill motor locked in a vise…be careful. Turn the speed up to high and take an angle grinder with a 50-60 grit flap wheel and run it against the edge.

About every 2 minutes….pull the plate and mandrel out with a pair of pliers and cool it off in cold water. It easily gets to 300°-400°F. Measure it.
When you get to within about .005” to .008” of the plate fitting in the oil pump body….you MUST cool it all the way down to get an accurate measurement.
When you get within about .002”…stop using the angle grinder and use a fine file tilted back toward the mandrel side a few degrees. This angles the edge of the plate away from the pump body so you do not lap where you do not need to. Stop when it just fits with about .002” to .004” clearance…into the pump body.

IMPORTANT NOTE: unlike the flat plate and the gears….the distance between the outside edge diameter compared to the farthest point inward….of the inner ledge of the pump body….is not far enough apart to make a big difference in sanding/grinding speed.

SO…when lapping this part…to keep the lapping plate flat and wearing evenly…ONLY turn it around in complete revolutions…not in short back and forth strokes.

Apply lapping compound to plate bottom and a small amount to the ledges inside the pump with a Q-tip. Wipe off the edges of the lapping plate.

You can use a ratchet. It will take you about 20-30 minutes. Stop and add a little more water or lapping compound about every 5 minutes.

You can use a cordless drill at low speed…about 125-150 rpm. I used a drill and finished in about 8 minutes worth of work.

Note how the lapping compound dries out fast

BUT with a drill you must stop every 1-2 minutes and add lapping compound. I stopped after two sessions of 4 minutes with two applications of lapping compound and washed the pump body and measured the depth.

And here it is done. Both sides showed the depth of the inner deck is now .004” lower to match the gear height.

You can buy finer valve grinding compound than this. The plate is still quite uniform in flatness so I can do about two more pumps hopefully.

Smooth and flat with a few grooves. I will give those a polish with 600 grit

You can see a fine band where the pushed out lapping compound just “kissed” the outer wall. The depth of wear there is not measurable.

How the gears meet up with the deck now.

I flipped the plate over to the clean side, used 3M repositionable adhesive to glue some 600 grit sanding film onto the face and trimmed it closely. I spent maybe a minute polishing the inside of the body ledge.

Pinning the idler shaft:

IMPORTANT NOTE: As I noted earlier…if your shaft is loose in the plate…get another pump or plate.

There are probably several ways to do this but here are three:

1. The first one….my normal method can be done on a drill press. In fact it almost MUST be done on a drill press. The shaft is TOO HARD to drill accurately and safely through both pump body and shaft in one shot without a milling machine.

But on a drill press…first with a file, a square tipped carbide burr or an end-mill…put a flat spot on the outside boss of the idler shaft. It only needs to be about 1/4' in diamater. Just a flat spot for the drill.
Center punch it. Use the correct drill for a either a 5/64” or 3/32” spring roll pin. USE A COBALT BIT.

Since these pins are just to keep the shaft from turning or moving…you do not need a solid pin or a big diameter pin. You can use a solid dowel pin if you want….but it is harder to remove if you ever need to. The spring roll pin stays in under spring tension and if you want you can distort both ends for extra safety.

The object is NOT to try to drill a hole in the aluminun shaft boss.....and the shaft....at one time. The shaft is just too hard. The drill bit will slip sideways and ruin the hole in the aluminum boas.
You drill a small clean hole through the aluminum and make the barest mark on the shaft itself. Them press or hammer the shaft out.

Once the shaft is out…complete the hole through the other side of the housing. Then…file a small flat spot on the shaft. Center punch it. Carefully drill through it with a cobalt bit. It is VERY hard.

Then draw a line on the end so you can align it with the hole and watch as you press it back in. When you get it close….tap with a mallet and brass drift until the hole lines up for the spring pin.

The nice thing about the spring pin is you can be out of alignment by a few thousandth and it will still go in and work.

2. the absolute easiest and best way is on a milling machine. You can drill through the center/side of the plate through the shaft at one time…and install a pin or a set screw.

3. The one I did on this one is somewhere in between. I ground a flat spot on the shaft, deburred, marked the shaft. Then I drilled a set screw hole in the side of the plate and pressed the shaft back in and installed the set screw with loctite.

This is the notch in the idler shaft for the set screw to lock into. I made it with a dremel tool on high speed-30k rpm and a green silicon carbide wheel. It tool about 2 minutes. Then I dressed it with a diamond needle file.

Use the green silicon carbide wheels. This shaft is hard emough that the pink grinding wheels will not touch it and the brown aluminum oxide wheels get too cut and cut too slow.

This is the set screw sitting in the notch. Do not make a common mistake. You need to drill the initial hole through the side of the plate down to the shaft…just enough to mark the shaft. Tap the shaft out. Then drill the hole through into the shaft bore.

The mistake that is commonly made is leaving a little ring of un-drilled metal from the conical point at the bottom of the set screw bore.

Then tap the hole while the shaft is out. Use one of the gray dremel 426 wheels or points to deburr the hole exit inside of the shaft bore after tapping.

IMPORTANT NOTE: as in the picture above, make sure the notch is slightly wider than the set screw so that the shoulders of the notch do not contact the thread of the set screw keeping it from making full contact with the shaft.

Why did I use an 8mm X 1.25 set screw instead of 6mm? Because there is plenty of room and the 8mm has more thread area and more contact point area to lock with.
This means that I can make the set screw tighter to bute into the shaft without over-stressing the threads in the aluminum. Yes…its overkill..

This last part is optional but it helps to keep scoring down and oil the pump better. I have seen it done on other types of pumps.

So..find out which direction the pump turns…..and mark the leading edge of each gear for the direction it turns.
Use a Dremel # 425 rubberized 360 grit emery wheel to LIGHTLY polish a slight bevel only on the leading edges of each gear tooth. Do not go crazy here. It just forces a pressurized film of oil around to the face of the gear as it turns.

You can see where the yellow arrows are pointing that I have polished and beveled the leading edges in the direction the gear turns to scoop an oil film between the face and the plate and bore. The gritty look is just lapping compound.

IMPORTANT NOTE:
Some of these next notes are very important.

So after cleaning its time for partial assembly and mock up to see what else may need clearance. The first thing to do is to re-install the 6mm studs.

VERY IMPORTANT:

You will screw this up slightly if you do not make make some preperations. Make a check list. It will save you from pulling these studs in and out.
1. MOST IMPORTANT: at a “glance” all four of the oil pump studs look to be the same length. THEY ARE NOT!

The stud that goes into the hole where the plate alignment bushing is ….is about 2.5mm longer.
It is longer because the threaded hole is deeper to compensate for the thread loss due to the counter bore. So…sort out your studs, find the long one for the counter-bored hole and do that one first.

NOTE: I am using Loctite on these studs. Locktite dries fast. Even though it dries...in air…drying in air does not CURE it and cause it to have useful strength…so have your ducks in a row to get thes parts together quickly. So……..

2. As you work in order….BEFORE applying Loctite to the threads in the bore (not to the stud)…go ahead and tightly “double nut” the stud you are about to install FIRST.

3. Then with a wooden or plastic pic or rod…..put a small amount of Locktite in the threads DOWN in the bore about 2-3 threads away from the outside of the thread bore. We are trying to keep Loctite off of the inner deck mating surfaces.

4. IMPORTANT NOTE: When you install each stud…it will bottom out. When it does…back it out ONE complete turn. Mark the outer tip of the 6mm stud with a Sharpy marker so you can see it turn. Let the loctite cure for a minute or two and remove the two nuts.

Assemble the pump without the gears and tighten the nuts. Then look carefully at the inlet and outlet ports.

Because you lapped the inner deck….the plate will sit slightly farther down. Lapping out .004” is not much…but it actually makes quite a difference on a curved orifice. You can see the overhang at the yellow arrow above. Clearance this away with an abrasive polishing tip.

Also you need to clearance the outer housing…sorry its out of the picture…but the arrow at 6:00 is pointing to it.

Here you can see what needs to be removed.

This is the best tool I have found. This is a rubber polishing point impregnated with 600-ish grit abrasive.

This polishing point is Dremel part # 462. Its so soft that about 1 minute of polishing (about all this takes) will literally destroy the point.

You can also get them in pointed cones and square cones. These are the blue ones. They make them in several abrasive grits that are color coded.

IMPORTANT NOTE/QUESTION: Why would clearancing this small amount of “flashing” make a difference.

ANSWER: It does not really make much of a difference at all…in FLOW VOLUME…however it makes BIG difference in TURBULENCE at the port.
THAT can make a big difference in flow.

The whole point of this is to tighten the pump back up for efficiency.

The next thing I will do to update this oil pump thread….for posterity/knowledge…is that since I am taking the gear to pump housing down to between 0.00” and about .0002”…I will test the the turning effort while at freezing by putting it in the freezer. I will also heat it up to about 200° to see what the end play has expanded to. It should not be a problem either way as the gears will make clearance.

This is just about it for the oil pump except for oiling, assembly and turning to pre-clearance the inner plate…remember that this is set for near “0” internal clearance right now.

Also I will not be doing final assembly with o-ring until I can put it in each case half and check its alignment to the port in the engine case. I will be clearancing that area as well. I will add that to this thread when it happens
Ray

[Lars S]

Ray, once again a fantastic thread!
You are on your way to write the complete and detailed Type4 rebuild manual - I give it 6 points out of 5!

Many thanks!

/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[raygreenwood]

[tedco]

what/where is torque specific for m6 nut?

[raygreenwood]