The Nut Behind the Wheel: Spring 1998

Last time I covered a few of the major sources of oil leaks coming from a four-cylinder Austin-Healey engine. This time we’ll continue with some other potential leakers, like the rocker cover, the oil filter assembly, the engine front cover, and the head itself.

When fitting the stock steel rocker cover to the engine, be sure the flanges are straight and the cork gasket fits the rocker cover. If the gasket has shrunk, then here’s another potential source of oil leaks. I glue the gasket to the rocker cover, not to the cylinder head. That way, when positioned on the two studs and “located” by the two special attaching bolts, the rocker cover can center itself without distorting the gasket. Now these special attaching bolts hove a cupped washer under their heads and a neoprene washer/bush under that. The washer/bush must seal around the bolt and seal the rocker cover at the same time. Here, the right stuff is needed. The correct cupped washer squeezes the neoprene seal both around the bolt and mashes the seal into contact with the rocker cover. If your rocker cover is dented inward due to too much tightening, you will need to press it back out, or possibly add another washer under the bolt head. Oh yeah, did I mention that the threads on the studs and attaching bolts are Whitworth? You got it. Here’s another source for mismatched parts or damaged threads over the years. Of course, they will all need to be cleaned out, the right fasteners on the right stud threads and the right distance between the rocker cover and the engine block to keep oil from leaking from the top of your engine.

It’s easier to change the oil filter off the car and a whole lot less messy. Simply place a rag under the filter head and separate it, complete with the filter canister, from the adapter plate attached to the block. Then carry the filter to your work bench and undo the filter head from the canister. Clean out the canister, being sure you captured all the internal parts, and re-assemble them correctly, noting the orientation of all internal parts. Then, insert the filter. A check of the correct parts list for your style of filler is really important. There are three different stock filter assemblies used for these cars, and each has a different number of internal parts and a different assembly sequence. It’s not uncommon to find mixed and mismatched ports from one unit in another. It’s also not uncommon to find absolutely nothing but old oil inside some of the filter canisters, as the internal parts have long since disappeared down the drain! Obviously, if you haven’t got the right stuff inside your filler housing, your engine isn’t being protected like it should.

To replace the O-ring in the filter head, you may have to pry out the old one if it is too dried out. Be sure not to damage the O-ring seating in the filter head. A very small screwdriver or an ice pick works well to remove this O-ring. Be sure there is no debris left from an old O-ring, and be sure not to stack O-ring on top of O-ring, or the second one is guaranteed to leak once oil pressure builds up.

Now a word of caution. The O-ring dimensions are specific to the kind of filter. The Purelator unit takes one size O-ring, the Tecalemit takes another, and of course, the Vokes takes yet a different one. You can’t (easily) substitute one style of O-ring for another without experiencing massive oil leaks! Be sure to order the correct O-ring for your style oil filter assembly when you order your replacement filter, as not all replacement fillers come with all three different sizes of O-rings!

With the correct O-ring in place, now fill the canister with engine oil. Making sure the canister seats on the filter head O-ring, re-attach the filter head. Now re-attach the entire unit to the engine block adapter with a new gasket, and you are ready to start the engine and check for leaks.

The engine front cover has a felt seal that keeps oil in the timing chain area from leaking out around the front of the crankshaft. Actually, this felt seal works pretty well if the oil slinging washer is also both fitted and filled the correct way around. Later Austin-Healey six-cylinder engines have a modern spring-loaded neoprene seal in their front covers. The later seal is much more effective. Why not fit one to the four-cylinder front cover? Because the cover wasn’t designed to receive it and retain it, that’s why! If you are really serious about oil leaks, then here’s an area where a little creativity will pay off. Even if you do manage to fabricate a holder for the seal, you will need to make sure it’s really in alignment with the crankshaft when fitted. Other concerns are that the crankshaft surface is smooth and round on which the seal lip is going to ride, and that you remember to fit that oil slinging washer, and that it’s fitted the correct way around! I’ve had no serious leaks with the stock setup, but do get a buildup of oil and dust around the front of the engine that needs to be cleaned away before each major event where someone may be looking inside my engine bay!

One other source of oil leaks can be from the joint between the engine block and the head. If either one of them is not perfectly square to the other, the joint gasket can fall in the middle of the block near the edge, and the joint will seep oil onto the engine. Serious leaks in this area are a candidate for a rebuild, especially if coolant is mixing with the oil. Minor ones can probably be tolerated. But it will always take both block deck and head resurfacing and a new head gasket to correct all of the leaks coming from this area. Only the most carefully assembled engines seem to not leak in this area.

Now, about that oil pressure gauge flex line. You’ve seen this lip before, but it’s still pertinent, as this line is notorious for leaking at the wrong time, and they are almost impossible to get to without getting under the car. So, to prevent laying down an oil slick to rival the Exxon Valdez spill and then wallowing in it, make sure an old line is replaced with a new one before you set out to claim the Long Distance Driving Award in your freshly restored Healey! The best way I know to make sure that the engine block end of the flex line mates properly to the adapter fitting on the block is to mate these two off the car. This way you can be sure that they are square to each other and tight in order to form a good seal. Then reattach the adapter flex line to the block from under the car. Finally, attach the other end of the flex line to the oil pressure gauge metal line that runs between the flex line and the gauge. Slick, huh?

So there you have it. The Nut’s take on oil leaks. I know my four-banger engine is alive and well because it does leak. But not very much!