Oil Cooler Structural Failure

[NWade]

My VW repair book (Bentley publications) recommends a 10mm tap into the plunger to remove them.

FWIW, a 10mm tap is too small for the pistons/plungers used on the AeroVee. A 1/2" tap is also just slightly too small. I believe a 17/32" or 14mm tap will be the appropriate size; but I'll have to buy one to find out...

--Noel

[Sonex422]

I used a pipe tap because it is tapered. As I recall it was 1/4" (at worst it is 3/8"). That way exact dimension is not critical.

[pfhoeycfi]

The manual I have is the "Volkswagen official service manual". It covers the Beetle, Super Beetle, and Karmann Ghia from 1970-1979. It shows a Bentley stock number of V179 and a manufacturing code of V179-25.

Excellent...

thanks,

peter

[NWade]

The saga continues: I have successfully threaded a 14mm tap up into the bottom of the oil control piston. Sadly, however, I still cannot get it to budge more than about 2 mm up or down. I have tried using vice-grips to pull on the square end of the tap (both straight down and while rocking the tap in various directions), to no avail. I've also turned the tap until it is fully threaded into the piston and cannot turn anymore. Then I can use a lever and vice-grips to continue spinning the tap - spinning the piston with it. Unfortunately the piston will spin (with some resistance), but pulling downward on the vice-grip handle while doing so does not result in any progress beyond the ~2mm of travel.

Open to any and all bright ideas!

--Noel
P.S. Do other Aerovee owners notice what looks like a "sleeve" inside of the tube/galley that the oil control piston slides in? Here's a photo - you can see the "sleeve" above the oil return hole.

[lutorm]

Hm, that sucks. If you thread it in too far, you might be expanding the piston and jamming it into the bore. I'd tap it as little as possible, just enough to grip. I assume the area is already plenty oiled? If not, turn the engine over a little.

Maybe you can now thread in a long 14mm bolt into the piston and tighten a nut against some sort of washer sitting on the seat where the spring holder washer sits? That's probably the best way to be able to apply significant pulling force straight out. (This is the method I used to get the oil passage plugs out to clean the case.)

[Area 51%]

I have both an aluminum and an Aerovee case, and they both have that "step/sleeve-looking" aspect. I'm sure the step was induced during the threading operation for the plug.

Wanna buy the mag case?

[NWade]

Update: SUCCESS!

I was finally able to rig up a tool and forcibly pull the oil plunger out of the crankcase.

For posterity, here's how I did it:

1. With the oil plunger nearly immobile at the top of its travel, I used a 14mm tap [CAUTION: this would bite me in the butt later, be sure to read on] to carefully cut threads into the bottom of the oil plunger.
2. I attempted to use the tap and a pair of vise-grips to twist and pull the plunger out, to no avail.
3. I belatedly realized that the tap I used is 14mm x 1.25 - do not use that thread pitch! That is mostly used for spark plugs and it is nearly impossible to find bolts and nuts with that thread pitch. If you ever have to do this operation yourself, I recommend a 14mm x 2 or 14mm x 1.5 tap.
4. Since a normal bolt was out of the question, I had to do a lot more purchasing and fabrication. I sourced some specialty nuts, a 14mm x 1.25 die, and a 9/16" aluminum rod.
5. I carefully cut threads into the rod with the die, cut it to length (about 5"), chamfered both ends of the rod, and thoroughly cleaned it.
6. I used a double-nut at one end of the rod, to give me something to clamp vise-grips onto - so that I could stop the rod from turning.
7. I threaded another nut onto the rod, about 1" above the double-nut. I stacked 3 thick washers on top of the nut, as a bearing surface against the bottom of the crankcase. The shape of the case means you have to choose your washer size carefully; I believe I used 3/4" or 7/8" OD washers with a 9/16" ID.
8. I used a small squirt of denatured alcohol up into the bore to wash out any metal particles and the remnants of my earlier attempts. I then applied a little bit of oil in the bore to lubricate the plunger as it was (hopefully) pulled down and out.
9. I carefully inserted the rod up into the oil control bore and twisted it to thread the rod into the base of the oil plunger (which had previously been threaded with the tap). I threaded the rod as far as it would go, and then backed it off about 1/2 turn.
10. I used my fingers to snug the washers and nut up against the bottom of the crankcase, then used an open-end wrench to "tighten" the nut while holding the rod from turning down at the double-nutted end. Since the nut & washers can't move upwards against the crankcase, this has the effect of pulling the rod downwards - and the oil plunger with it.
11. Because of the crankcase shape and the exhaust pipes, this was a very tedious process - I could only rotate the nut by 1 flat before removing and reseting the wrench. Slowly, however, the plunger began to move. Over 5-10 minutes I was able to pull the piston out completely with only minor scoring in the walls of the crankcase bore. [NOTE: the vertical scrapes you see in that last photo are from my earlier attempts to remove the plunger. The horizontal/circumferential grooves and ridges further up inside the bore are what appear to have been preventing the plunger from moving normally]
12. I then used very fine-grit sandpaper on a dowel to smooth the inside of the bore. This was followed by careful squiring of denatured alcohol up into the bore to rinse things out (being careful to not wash too much of it back into the sump through the holes in the side of the bore). Thin clean rag material was used with a dowel to aid in removing any grit and metal particles. This cleaning process was a few times. In the end the bore isn't perfect, but its a lot smoother and there are no raised ridges I can see.
13. I took a fresh replacement oil plunger and used fine-grit sandpaper to smooth the chamfers around the circumference of both the top and bottom of the plunger. I used 1000-grit sandpaper to polish the outside wall of the plunger as well. Then it was thoroughly rinsed with thinner / denatured alcohol and dried.
14. Although I had tried to clean up the ends of the oil control spring when I first assembled the engine, I doubled-down and did it again - using a small file to smooth the corners and ends of the spring. My concern here is that any sharp edges on the end of the spring could cause it to score the walls of the bore that the plunger slides in - and that could cause a bur or ridge that would jam the plunger. I ensured that both ends of the spring were filed in such a way as to prevent this scoring from happening (I did both ends so it wouldn't matter which way the spring was inserted into the engine).
15. Oil was coated onto the plunger and it was test-fit into the crankcase. First I put it in with my pinkie finger, slid it up as far as I could get it, then removed my finger and watched for it to fall out under gravity - which it did. Then I cleaned and re-oiled it, put it up inside the crankcase and used the oil control spring to push it to the top of its travel, and watched for it to fall out under gravity. It stuck momentarily, due to the surface tension of the oil, but then fell out. I then cleaned, oiled, and inserted the assembly with the plug screwed in to ensure spring tension pushed the plunger up to the top of its travel with some force. I then removed the plug and watched for the assembly to drop out due to gravity (I wasn't taking any chances)... Again it stuck momentarily due to the oil; then fell freely out of the engine.
16. Finally, I inserted the assembly, tightened the plug, refilled the engine oil, and let it settle into the sump for a few minutes.

After all of that, I cranked the starter (with all fuel & ignition modules off) while watching my oil pressure reading. After a few seconds of cranking, the oil pressure came up to ~30psi and stayed there. Huzzah! Ever since my early engine runs, I would see nearly 80 psi of oil when performing this check. At the time I blamed the 20W-50 oil and the fact that my hangar was only 40 degrees fahrenheit; but now I know it was due to the oil control plunger sticking.
I pulled out the fuselage, tied it down & chocked it, and started up the engine while my lovely wife watched for leaks and kept a fire-extinguisher handy. The engine started up easily and over ~60 seconds of idling between 800 and 1200 rpm the oil pressure remained between 35 and 58 psi (on a cold rainy evening).

Now its time to build the turbo cooling system, finish the canopy, the leg & tail fairings, and get this bird in the air!

--Noel

[Bryan Cotton]

As we used to say at Sikorsky- it's almost too easy! Congrats and good luck!

[kevinh]

congrats. nice write up!

[Area 51%]

Congratulations on your success. Your situation rings mildly of the Apollo 13 fiasco. A $3 part nearly mucking up the whole show.