Engine Oil Leaks

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Original submission by T Feb 23 2007:

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Oil Leaks as a result of using a flat Oil Filler Cap with a 2 hole Rocker Cover. The yellow lines mark the locations. The Engine should have the EH Type Cap. Photo by Dewso19. Click to Enlargen.

Engine Oil Leaks:

Old Holdens are not the only vehicles in the Universe to generate Oil Leaks so don't be disheartened if you encounter one or even a persistent one. The Romans used to say ....Those who endure conquer and President Calvin Coolidge said ....Nothing succeeds like persistence. If your Old Holden is anything like my two, it's asking for help. All those times it brought everyone home without drama, and now it's asking for a little TLC. The purpose of this page is to make the troubleshooting of Old Holden Oil Leaks easier.

Cutaway of a 179 showing the Rocker Cover Side Covers and Sump. The Fuel Pump retainer bolt holes are open to the crankcase. Photo by Jacks.

Causes of Engine Oil Leaks on High Time Engines:

Engine Oil Leaks on Old Holdens can appear after the engine has performed a period of service.

1. Gaskets Get Hard With Age and Don't Seal Properly:

The Cork Gaskets used for the Rocker Cover and Side Covers become hard with age and can no longer keep Oil in or Air out depending on whether the Engine has PCV or not.

Either way a hard Gasket will soon develop a weep that will eventually turn into a drip.

2. Piston Ring Grooves Gum Up and No Longer Gas Pressurise the Piston Rings:

Check out PCV and watch the animation to see what is happening.

3. The PVC System No Longer Generates Vacuum or has Been Disconnected:

Keeping the PVC System intact pays huge dividends in the oil leak stakes, even stopping the notorious Rear Oil Seal leak. It can be worth fitting PCV to an engine just to stop this leak alone.

4. The PVC System Has the Incorrect Filler Cap:

The PVC System needs to release Blow-By Gases when the Engine is at high power. A path must be provided for gases under these conditions. 3 Hole Rocker Cover must have a blocking Filler Cap and a connection into the Air Filter and the PCV Valve must connect into a centre tap in the Inlet Manifold so that all Cylinders will get an equal amount of PCV gas. 2 Hole Rocker Cover must have a Filter Type Filler Cap and the PCV Valve must connect into a centre tap in the Inlet Manifold so that all Cylinders will get an equal amount of PCV gas.

5. Overall Neglect:

If an Engine has been run for a long time in a poor state of tune with dirty Engine Oil the Piston Ring Grooves will become blocked up. See point 2 for more detail.

6. The Wrong Type of Running:

Engines that do lots of short runs and get "warmed up" very soon suffer gummed up Piston Ring grooves. The proper use of an engine involves getting it hot and making it work, i.e climbing grades in top gear with a high power setting.

Distributor Gasket. Photo by BIJ. Click to Enlargen.

7. Blocked PCV Connection at the Inlet Manifold:

wombat on Tue, 24/03/2009 - 13:16.

DO you have any suction at pcv as sometimes where the pcv hose connects on the manifold gets blocked with carbon and there no suction so the pcv is not working .. so check to make sure you have suction at the pcv.. wombat.

Causes of Engine Oil Leaks on New Engines:

Oil Leaks can appear soon after an Engine has been powered up for the first time.

Gasket Shrinkage:

The most common cause of new Engine Oil Leaks is Gasket shrinkage.
As soon as hot Oil (or hot Coolant for that matter) comes in contact with a Gasket, the Gasket begins to shrink. For this reason Gaskets will need re-torqueing soon after the first run of the Engine.
Many Head Gaskets need re-torquing soon after the Car's first run.
Try not to panic if Oil appears to be weeping from the Rear Seal. More than one conscientious Car owner has been deluded into thinking they have a disaster on their hands when the leak actually stems from an easy to fix source in an accessible place.
On my EFI VK Engine, the Fuel Pump Blanking Plate only needed re-torquing, but the Oil Stream ran all the way along the Sump Seam and back to the Rear Main Bearing area where the drop appeared. It only took a moment to retorque the cover and the drip stopped.

Seals Wearing In:

See Harmonic Balancer and Front Seal for more detail.

Un-Blinded Holes:

Forgive the term. It's my way of saying that a hole that was once blanked off with solid cast iron has been drilled right through into an Oil Gallery, the Sump or even a Water Jacket by the Engine Reconditioner. Gluing the stud or Bolt with Holden Cylinder Head Bolt Glue can help here, so can the use of Thread Tape which is made of white plastic and is taped to the Thread of a Bolt to prevent Oil climbing along the space between the Thread and the Nut.

Missing Oil Gallery Plugs:

At the Front and Rear of the Engine there are access plugs that are there for inspection and cleaning of the Oil Gallery. It's wise to check that these are in place before installing the Engine.

The PVC System Has the Incorrect Filler Cap:

The PVC System needs to release Blow-By Gases when the Engine is at high power. A path must be provided for gases under these conditions. A 3 Hole Rocker Cover must have a blocking Filler Cap and a connection into the Air Filter and the PCV Valve must connect into a centre tap in the Inlet Manifold so that all Cylinders
will get an equal amount of PCV gas. A 2 Hole Rocker Cover must have a Filter Type Filler Cap and the PCV Valve must connect into a centre tap in the Inlet Manifold so that all Cylinders will get an equal amount of PCV gas.

Identifying Engine Oil Leaks:

Be aware that oil leaks can appear to be from one location when they are actually occuring
in another. It's best to take a little time to investigate them rather than to needlessly pull an Engine apart when a mere dab of sealant will fix the problem for you. Often a well meaning person will needlessly disemble an engine only to discover
that the leak was caused by a very simple and easily fixed leak in a very easy to acccess
location involving only minutes of work.

Common Red/Blue/Black 6 Cylinder Oil Leaks:

Some items on these Holden Engines must be glued.
These include the Cylinder Head Bolts, the Fuel Pump Bolts and the Rear Main Bearing Cap.
The bolts mentioned here must be glued because they screw into open ended holes. In the case of the Fuel Pump Bolts, their ends face the Camshaft which throws hot oil on them. The hot oil works its way up the bolts and becomes a drip from under the Fuel Pump.
Submitted by Arsewipe on Thu, 28/06/2007 - 21:17.
Also try a little number 3 sealant on the threads of the (distributor) adjuster bolt, as it just threads into the crank case,
End of submission by John (Arswewipe).
It's easy to be deluded into replacing the Fuel Pump Gasket when in actual fact the leak is
coming through the bolts.

Rocker Cover:

A leak from the Rocker Cover is often caused by a gasket that has become hard and lost its seal.
Replacing the gasket is the best cure. Also refer to PCV
for more details.

Side Covers:

Like the Rocker Cover Gasket, these gaskets become hardened by temperature over time and no longer seal.
Side Cover leaks can effect PCV operation.

Leaks From the Rear of the Engine:

The Rear Main Bearing Cap must be glued with Holden Cylinder Head Bolt Glue otherwise oil under pressure will make its way between the Bearing Cap and the Crankcase and leak into the Bellhousing.
The Bearing Cap can be removed from the Engine and reglued in the car after the sump has been removed.

Rear Oil Seal:

Converting to full PCV can control real Oil Seal leaks because a constant vacuum is kept in the Crankcase while the Engine is running. On Old Holdens this is a Rope Seal which can be repacked while the Engine is still in the Car if the Sump and Rear Bearing Cap are removed. Many times owners are convinced that the Rear Oil Seal is leaking when the leak is actually
coming from elsewhere. Common errors are the Oil Filter being loose or still having the old rubber seal in place. The Rocker Cover can leak at the rear and drip oil onto the Rear Oil Seal area. The Fuel Pump can leak and cause oil to stream back along the line of the sump
and appear around the Rear Oil Seal. Further Rear Oil Seal info.


Replacing the Sump Gasket involves raising the Engine or removing the Engine from the Car.
Full PCV will reduce the likelyhood of Sump Gasket leaks. Retorque all the Sump Bolts then repair any remaining leaks with a Cotton Bud and Holden Cylinder Head Bolt Glue.

Front Cover Bolts:

The lowest 2 Bolts that hold the Sump and Front Cover together can show an Oil Leak. The Bolt Holes are blind and are not the direct cause of the Leak. The Leak is caused by the Gasket shrinking around the Bolts allowing Oil to weep though the Threads.  Remove both Bolts, wipe the area and the inside of the Bolt Holes clean, then dip each Bolt in Holden Sealant. Refit and tighten each Bolt to prevent Oil from running through the Bolt's Threads.

Front Oil Seal:

See the section on Front Oil Seal leaks.
Harmonic Balancer and Front Seal

Fuel Pump Oil Leak:

The Spindle Seal inside the Carter Fuel Pump wears out and allows Oil to spray rearwards and onto the Offside Engine Mount on red/blue/black six cylinder Engines.

Note the Thread Tape on the Mounting Bolts. Click to Enlargen. Photo by T.
Note the Roll of Thread Tape in the Foreground. Click to Enlargen. Photo by T.
Oil leaking from the hole in the centre of the image indicates that the Spindle Seal is worn out. There will also be Oil thrown all over the offside Engine Mount. Click to Enlargen. Photo by T.

Sump Plug:

An Old Holden Sump Plug is a 1/2" Bolt that uses an aluminium Washer. Fibre and Plastic Washers are not successful. Fibre bends out of shape and plastic never stops shrinking resulting in an annoying drip that can only be properly fixed by draining the Sump and fitting the proper aluminium Washer. If you're reviewing a Car to buy, check the Sump Plug. If it has Sealant around the Sump Plug, the Thread may be stripped meaning a lot of needless hassle for you.

Dipstick Tube Leak:

In both straight 6 Commodores and Kingswoods, a Leak can occur from the base of the Dipstick Tube. VB - VK, unbolt the Dipstick Tube, remove it, clean the Sump end, cover the end with Holden Sealant and refit the Dipstick Tube. Pre VB, mark a scribe line where the Dipstick Tube meets the Block, place a Phiillips Head Screwdriver in the Dipstick Tube large enough to prevent the Tube from being crushed,  pull the Tube out with Pliers, clean the Dipstick Tube, cover the end with Sealant and refit it to the depth of the Scribeline.

Timing Cover Leaks:

The Timing Cover Bolts can work loose and need retorquing. 

Oil Pump Leaks:

When these appear on red, blue and black sixes, it's best to remove the Oil Pump, fit new Gaskets and replace the unit. Over time the gaskets can shrink. Tightening the Bolts will close up the clearances and cause the Gears to sieze on the faceplate. See the Oil Pump page for further info. 

Oil Leak Types:

Types of Oil Leaks range from weeps through drips to sprays. The type of leak will indicate the type of problem and the degree of difficulty in repairing it. An Engine Oil Leak that is coming out under pressure is likely to involve more effort than one that is a mere weep. It's important to differentiate the type since excessive Blow-By gases are a big cause of pressure leaks it's best to address the Blow-By issue first otherwise any gaskets you replace before then will likely blow again. Professional mechanics seal off the Engine and inject smoke into the Crankcase to identify the real source of an oil leak. Wiping the area clean one day and inspecting it after the next drive can also give a true account of the source of the leak if you can't afford the smoke bomb method.


If this leak is coming from under a gasket it can often be fixed with a cotton bud and some Holden Cylinder Head Bolt glue. Check if the associated cover is loose, it may only need tightening.


More persistent. This indicates a larger hole. If the cotton bud method and retightening the associated gasket doesn't work
then a new gasket is the likely cure.


These are coming out under pressure. This problem is bigger than both the other two types and will need additional investigation. As well as Blow-by gases this could be caused by excessive Oil Pressure. The excessive Oil Pressure may be caused by a stuck Oil Pressure Relief Valve. It's always best to investigate this type of problem further before spending valuable time and money on gaskets that will only blow again.

Holden Sealing Compound:


its holden sealing compound ( cylinder head stud sealer . )
comes in 250 ml tin part number 3835215. get from your holden dealer. wombat. End of Wombat's submission.

VB - VK Commodores can develop Oil Leaks at the Dipstick Tube Joints. The lower Section is Welded to the Sump. The Middle Section is an Adaptor and the Top Section secures the Dipstick in place. Use Holden Sealer at each Joint to prevent Leaks. Photo  by Thunderbolt. Click to Enlargen.
Holden L6 Oil Pump. Scoring on the faceplate related to the failure of this Oil Pump. Photo by HQ_SS. Click to Enlargen.
Holden Sealant. Photo by snowdownunder. Click to Enlargen.


Oil Pump

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