Everyone has a recipe for how they seal up engines. Because the VW (and also Subaru) designs have a 'crank-case' which is split up the middle, they often leak more than the 'bored block' designs which is just a block of iron with large and small holes drilled in either end and a cylinder head and oil pan clamped onto opposite ends. Remember the oil-dripper's manta and keep it wholly: "Oil under pressure within an engine will find any unsealed avenue to escape." In other words, if you're building an engine, you'd better know what gap to seal, where in the gap to seal it, and what type of sealant to use.
The toothpick wielding backwoods airhead sez, "They all leak a little."
Bollocks. I've seen well built engines which do not leak a drop. If it is leaking, that means there is something WRONG. Fix it, before it becomes a bigger issue than it is now.
Based on my research, along with talking to the big dawgs who built these dry engines, the following are the generally agreed upon, idiot proof recipe for a dry engine:
Prep: A common caution is that " X is 90% preparation." It doesn't matter what the X is. It could be painting, or relationships or engineering or (think about it) sex. This is true of engine building, too. If you're mating two parts that are covered with oil, old bits of sealer and with pits and gouges that make the Pan-American Highway look like a glass surface, why would you expect any sealant to work miracles and form a 'dry' seal? Before you stick two pieces together with any expectation that they will stay together, ensure that they are oil free, flat, and un-gouged.
Sidebar:
Oil free includes the oil from your own patty-paws. I learned such things the hard way when re-lamping theatrical lights in my youth. Dangling 25 feet off of the floor, I'd disassemble an 'instrument' (what we called a theatrical light fixture, unless we were referring to a specific design: Leiko, Fresnel, PAR, etc.) The 'lamp' to be replaced would be removed, and then latch in a new one into the bayonet fitting. Reassemble the instrument (because if the glass envelope of the lamp blew when you lit it up, these high powered items tended to explode like a grenade) and yell to my assistant to power up a certain circuit.
BLAM!
Several times. I was going to pull the instrument out of service when the technical director (the only one who had a degree at this point and got paid to do this) came in, heard the tale of repeated blow bulbs, then asked me to show him exactly what I was doing. I dug out a new bulb from its cardboard, package, unwound the padding and tossed it in the trash, and went to pull the slip of plastic off of the glass envelope and discard it as well.
"STOP," my boss said with a gong-like bark. "The reason that slip of plastic is there is so that you can mount the lamp without getting your greasy fingers on it."
I started to object, but he pulled me over to a nearby window behind the upstage curtain. He took my hand and carefully wiped my fingertips on the glass. A very slight smear.
"That," he said with patience, "Is why you just blew through this year's budget for lamps in a single morning." When the oil from your skin gets on the glass envelope, and then the envelope is suddenly heated to 600°F, the glass envelope expands unevenly and explodes.
I'm embarrassed to admit that I am inclined to forget this quite often, even when I have my hands inside of a computer, which is my day job now.
If I start with a compulsively clean crankcase, taking care of any surface problems before I begin the build, I only have to keep NEW stuff from settling on or otherwise damaging mating surfaces. My final wipe down is brake cleaner and lint free towels. As clean and flat as possible before I add sealant to the mating surfaces. Also check your sealant's instructions: you may have 30 minutes or 3 seconds to get the parts joined. Or you may need to dress only one half of the joint and leave the other bare, or dress both. It depends on the product, so read first before you proceed. Also make the assumption that you will not be taking the engine apart again after you do get out the sealant. It could be an frustrating day if you damage your glued together engine case trying to get it apart again because you forgot to install the cam.
Products:
The following are the most commonly recommended products for assembling a Type4 engine to go "200k miles or until it breaks." You can often do with less high-born brand names, but if you want to do the job ONCE and not wonder, the following products are the best choices going:
- General Assembly Lube: Brad Penn Engine Assembly Lubricant 7105
- Thread Lock: Loctite Blue 242
- Thread Sealant: Loctite White 565 (Industrial)
- Case Sealant: Curil K2 (125g)
- Cylinder Base Sealant: Elring Dirko RTV Sealant 100g 036.161
- Fan Hub to Crank Nut: Molybdenum disulfide lube, no thread locker (Moly B)
- Case halves: Curil K2 (125g)
- Bearings: Brad Penn Break In Oil (7120)
- Lifters: Torco MPZ Engine Assembly Lube HP
- Case studs: Curil T (100g)
- Head studs: Curil T (100g)
- Valve Cover Gasket (Seal to Cover): Permatex Aviation Form-a-Gasket #3 pn 80018
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