Rear Oil Seal

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Submission by T Feb 12 2007:

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202 with 3 Casting Ribs at Lower Left Hand Side of Photo. This implies a Rope Rear Seal. See Ben Simpson's Comment this Page. Photo by Jacks.Click to Enlargen.

Rear Oil Seal:


Submitted by T on Mon, 12/02/2007 - 09:44. Make sure that the leak is really from there and not from somewhere like the rocker cover (higher up) or the fuel pump (oil tracking along the sump line) or a loose Oil Filter.

V8 Rear Oil Seals. Neo crank (right) and rope on left. Rope seal is also Harrop crank. Neo seal area is also smaller than rope. Click to enlargen. Photo by Nobody123.

You don't want to perform a lot of hard work over a misdiagnosis. Run a finger under the Oil Filter and see if there is a smear of oil there. Recently we had a post from a guy who had 2 gaskets under his Oil Filter that made him think he had a Rear Oil Seal Leak. Overfilling can cause the rear seal to leak. Check the amount of oil in the car against the dipstick because the dipstick tube may not be pressed in far enough. Converting to PCV can place control over the rear seal by putting a vacuum on it. Incorrect Crankcase ventilation can cause pressure to build up which will force Oil out of the Rear Seal. Make sure your PCV is set up correctly and has provision for reverse flow at high RPM. PCV

202 Crankshaft Rear Oil Seal. The Oil Slinger is in place positioned in its Groove. Refer to Ben Simpson's post. Click to enlargen. Photo by SickHG.

thats a neo block there. i think youll find the sealing surface of the crank is bigger in diameter on a rope crank than the neo ones. <p class="content">End of Ben Simpson's submission. <p class="content">  <p class="content">

186 Rear Oil Seal for use on a crank without the knearling.  See Thread 2. Click to enlargen. Photo and info by  kelvin01au.

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Red 6 Cyl Rear Oil Seals. Upper Neoprene, Middle Rope, Lower believed to be early 179 type. Click to enlargen. Photo by HQ_SS.

If there are 3 vertical ribs running externally between the cam tunnel and the sump rail at the drivers rear of the block then there is every chance its a rope seal. i have never seen a neoprene seal with these 3 ribs.

<p class="content">End of submission by Ben Simpson.

Gluing the Rear Main Bearing Cap:

On 6 Cylinder Holden Engines, the Rear Main Bearing Cap must be glued to the Crankcase.

This is because Oil under pressure enters the Upper Bearing Half via the Crankcase and is forced all around the Bearing and into the Crankshaft so that it can lubricate the Rear Main Bearing and the Big End Bearings. This pressurised Oil finds its way between the 2 halves of the Bearing and can weep out into the Bellhousing area. Using Holden Cylinder Head Bolt Glue prevents the Oil from leaking out from between the Rean Main Bearing Halves. Note * The other 5 Main Bearing Caps do not need to be glued since they will weep Oil into the Sump. The Oil loss from this weep is not enough to affect the Oil Pressure. Note * This is not a problem on V8's because there is a Groove ground into the Rear Main Bearing Cap that makes leaking Oil drip into the Sump.

Do Not Overtighten the Sump Gasket:

Cork Gaskets, such as that used on the Sump, are dependent on having some crush left in them to work properly. Overtightening flattens them excessively and weakens the Gaskets ability to seal.  End of submission by T

Seal Types:

Seals Submitted by WBJailwagon on Tue, 26/06/2007 - 11:04. Holden Red sixes actually had three types of rear main seals. The very early engines had a moulded rubber seal that fitted into a groove in the block (same as rope seal). Aftermarket gasket sets for these engines contained a rope type seal and were called "conversion" sets (converting the rubber seal to rope type). Early 70's engines used a neoprene seal that fitted over a raised lip on the block. Engines from late HQ on (IIRC) had rope type rear main seals. The seal area on all 202 crankshafts (neoprene or rope) is the same diameter. The seal area on 149/186 crankshafts has a smaller diameter. The diagonal notches on a rope seal crank are to lubricate the seal and make it swell, so enabling a better seal. Don't use a rope seal crank with a neoprene seal, or vice versa. A neoprene type crank with a rope seal will make the seal run dry and cause it to spin in its groove. The grooves in a rope type crank will obviously damage a neoprene seal, however, a neoprene seal with an offset lip was once available (and may still be) for use with a rope type crank. Cheers, Jeff. End of submission by Jeff  

t, you might like to know that the rear main seal area on a 202 crank is definitely different between a rope and a neo crank. the rope is 2.6" diameter, and the neo is 2.43" diameter. so jeffs post is incorrect stating that both are the same diameter.
regards ben


Blue and Black Six Cylinder Rear Seals:

All blue and black 6 cylinder engines have a rope seal and the later red motors had the same. It was only the early red 6 cylinder engines that had the neoprene rear main seals! Check the engine number not the colour of the paint on the block!  

Rope Rear Oil Seal Upper. Photo by Droobs. Click to Enlargen.
Rope Rear Oil Seal Lower. Photo by Droobs. Click to Enlargen.
The Photo shows the pressure fed Oil Supply Hole in the Rear bearing. Oil pours from both sides of the Bearing as a part of normal Lubrication. Oil pouring from the left side must travel down the Groove in the Bearing Cap. The Oil Slinger is machined into the Crankshaft. It uses Centrifugal Force to keep Oil away from the Seal. Photo by Droobs. Click to Enlargen.
Neoprene Seal in a Rope Bearing Cap. Exhaust Seal lower. Photo by Besty123. Click to Enlargen.
Rope type Rear Oil Seal. Click to enlargen. Photo by Perth Mick.

Blocked Drainage:

The Rear Main Bearing Cap has Oil continuously forced inside it from the pressure fed Bearing. This Oil needs to be able to drain out of the Groove in the bottom of the Bearing Cap. The Groove is between the Bearing and the Oil Slinger. In a neglected Engine, the Groove can become blocked, forcing Oil out of the Rear Oil Seal. Clearing the blockage will allow the Oil to drain properly. As a cure or prevention, proper use of the Engine coupled with clean recommended Oil may cause the blockages to clear and save the expense and downtime involved in Sump removal and Oil Seal repacking. Another trick is to temporarily block the Intake to the Rocker Cover which will force PCV Vacuum onto the Groove and maybe help loosen any Sludge.

V8 Rear Engine Seals:

Submitted by v8slrtorana on Tue, 26/06/2007 - 12:54. Also going on the holden fans advise with a v8, a neroprene crank will not fit into a rope block. Ive tried. End of submission by V8SlrTorana. V8 Rear Engine Oil Seal Info Nobody123's Shed

The yellow Arrow shows the Groove that can block up and prevent Oil from draining properly. The result is Oil streaming from the Rear Oil Seal. Photo by Besty123. Click to Enlargen.


By Another_HQSS 09/10/15@20:26

My 73 block 253 is neo, I think HQ 173/202 were as well the HQ engine manual certainly shows neoprene seal replacement not rope seals.
Every 75 block/crank I have is rope. (I do remember reading somewhere that it came in with HJ.)

Anthony - Lettuce Alone SS


Wrong Seal

Rope Type Rear Oil Seal Installation

In Car Neoprene Type Rear Oil Seal Installation

Rear Oil Seal Problem

Thread 1

Droob's Shed

Thread 2

Thread 1



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