TECH TIP Technical Index

Oil Leaks

By Mike C.

"VWs Never Leak OilÖ"

ÖThey just mark their spot! Or so, youíve been told. Yes, most people think that VW air-cooled engines are nothing but sources of leakage, and that there are two kinds of these Ė engines that do leak and the ones that will. While I can honestly say that this is pretty much true, after having owned an air-cooled VW in the past, there are many things you can do to prevent leaks or at least minimize them. You donít have to drive a VW that leaks enough oil to make the Valdez look like a drip. This article will deal with the how-to on finding leaks and fixing the problem.

Let me start by talking a bit about heat transfer 101. For an air-cooled engine, there is no radiator full of water or water jackets in the heads and engine block. Water is a very efficient means of cooling. Oil, however, is not very efficient at keeping things cool (compared to water, that is). It makes you wonder sometimes how air-cooled engines get by like they do, but there are millions out there that still rely on oil and air as their only "coolants" and do so in the most adverse conditions. Hereís the pointÖthe oil inside the crankcase is responsible for transferring heat away from the crankshaft, connecting rods, pistons, and heads & head components. Thatís it! Thatís all the internal components have to cool them. If you boiled the oil, youíve just boiled the engine. On the flip side, all the oil that leaked over the outside and covered everything is actually hurting the ability of the engine to keep cool, plus you donít have a full 2.5 quarts to transfer heat. Bare metal is a lot better at transferring heat to the outside air than metal with the oil coating. The point Ė keep the outside of your engine as clean as you can to aid in keeping the engine cool. Thatís where I come in with the oil leaks.

Begin your leak detection by thoroughly degreasing the engine on top and underneath. Get two or three cans of degreaser and take your VW to the nearest quarter-operated car wash. Be sure to take a bottle of rubbing alcohol (to dry the distributor in case you get water in it), something to cover the distributor with, and wear old clothes. Soak all engine surfaces with degreaser and wait a few minutes. Now blast it all off with the pressure hose. This may take a couple of times if your engine is really caked. Remember to do the underneath, too, including the transaxle. Now drive it home, park it, and let it cool. If you had to drive a little distance to the car wash and back or had a bad leak to start with, you should notice what is leaking by now. Is it coming from the hole between the transaxle and engine mating surfaces (transaxle seal or rear main engine seal). How about from the top, apparently from under the cooling shroud (oil cooler grommets). Or, around the oil filler neck area (breather deflector installed incorrectly or breather-to-filler neck seal is defective). If oil is covering just the bottom of the finned oil sump, it could be pushrod tube and/or seals, valve cover gaskets, piston jug-to-crankcase not sealing, or the oil sump cover is warped or is otherwise not sealing properly. Remember, the air blowing across all the engine surfaces will also blow the oil everywhere, so if you drive for too long, you may not be able to pinpoint the leak.

Letís take a systematic approach to stopping the leaks. Iím going to assume here that you havenít had the engine out of the vehicle for years. Chances are that everything is leaking enough to warrant pulling the engine out and sealing it up. Given this, go ahead and pull the engine. Even if youíve never done it before, itís not a difficult job, and might take a first-timer about two or three hours. After it is out, go ahead and replace the transaxle input shaft seal. Even though this does not have anything to do with the engine, it can still make a big mess of things and make any more leak tracking very difficult. Once you have done that, remove the flywheel and replace the rear main crankshaft seal. Next, pull the heads off just far enough to replace the pushrod tubes and seals. Do yourself a favor and buy new pushrod tubes. They are cheap and old ones may be cracked around the bellows at each end. Be careful when pulling the heads that you do not pull the piston jugs out with them unless you suspect that leaks are coming from around the jug-to-crankcase areas. After you button all that up, replace the oil cooler seals. This is usually a cause of a very big leak, since oil is under pressure when coming out of the old cracked seals. Make sure your valve covers are not warped and that you put new gaskets in these as well. I will tell you that I have had very good success with the stock steel valve covers and gaskets. If everything is straight and sealing surfaces are not gouged, the valve covers will seal with no sealants whatsoever, and no leaks. Oil pressure sending units love to leak when they are a bit old, so replace that $5 sender. This takes care of the really big stuff. While you have the engine out, everything is easier to get at, so letís wrap it up that way.

Now unbolt the oil filler/generator stand. There is a metal oil deflector with louvers between the stand and the case. The deflector louvers should be pointing down and the openings to the right. If this is not correct, the oil will be thrown all the way up the stand and out the cap. Use a little silicone sealant on both sides of this deflector and bolt the stand back on. Take off the oil breather. If the sealing surface of the breather is pretty flat, a thin o-ring the diameter of the upper part of the stand will seal very nicely, or use a small amount of silicone on it and bolt it back down. Make sure that the seal on the oil fill cap is in good shape as well. Pull the distributor out and replace the o-ring on it with a new one. I can almost say with confidence that everyone needs a new o-ring on their distributor, since this is an easily-forgotten piece. Now pull the fuel pump and spacer out. Check to see if the spacer has a crack in it. If so, replace it. Use one thin gasket on the bottom and one on the top of the spacer, and a small amount of silicone. This should take care of things on top.

Bolt the engine back in and proceed to change the oil. I bet your old sump cover is beat-up and worn, so get a new one. They are relatively inexpensive. If your engine doesnít have that many miles on it, you might could use 10W-40 oil. Why the thin oil? The thin oil will lubricate and flow much better on cold startup, and will transfer heat slightly better than the heavier straight-weight oils. The downside is that it will tend to "seep" through joints and around seals more so than the thick oils. Also, the higher mileage or harder-driven engine will need the 30W or 20W-50 oil. What about synthetics? I wouldnít recommend full-synthetic oil. It flows so well, it will cause leaks that were never there before, especially on the air-cooled VW engine. Use one of the synthetic/mineral oil blends and you can have your cake and eat it too. Ask Herschel Dalton about this one, as he has had good experience with the blends.

As you can see, there are many areas to look for when eliminating oil leaks on a VW engine. After you do this, however, keeping the engine clean and staying on top of the leak situation will be much easier, and you will be rewarded with a cooler running engine that you wonít have to add a quart to once a week. It will also make other engine repairs much more enjoyable without all that crud all over everything.

Make sure you read up in your shop manual on performing the repairs I have mentioned above, as there obviously would not be room for detailing every step in this article. See you at Fox Ridge on December 12th for a bratwurst pizza!

Your VW maniac and Tech Specialist,
-Mike C.