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Sudden massive oil leak - 996 mk2 gt3


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I recently returned to the UK after 6 months away, I started my 996 and drove it out of the garage to let it idle and warm up, having run for less than 5 minutes the car developed a massive oil leak dropping nearly all of its oil from the rear of the engine (furthest towards the front of the car) Luckily I noticed the oil leak and managed to turn the car off before hearing any nasty noises, I have jacked the car up and had a look underneath however the oil is eveywhere so I cannot see where the oil has come from. There is not a spot of oil on my garage floor so the vehice was not leaking oil before I started it. Has anyone ever experienced anything like this before? or does anyone have any idea what may have gone wrong? it has been suggested that the rear main may have failed suddenly, im guessing this may be the case as the oil looked black on the ground, im guessing with the RMS failing oil would have picked up all of the clutch dust from the bell housing before leaking out. I would be greatful for any input from the experienced 911 owners.

Thanks in advance


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With that much oil leaking, I would suspect it to be one of the oil lines to the dry sump. There are 3 oil hoses going from the base of the oil filter housing if one of these came off it would leak oil from the top of the engine and cover everything below. So you might look on top for a problem with some of the oil lines. Was any work done to the car prior to storage?

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Thanks for the reply

There was no work done on it prior to parking it up, I too had thought it would have been an oil line due to the amount of oil that leaked out, I then spoke with a Porsche mechanic that said it would be the RMS. I live on a farm an had thought it might have been possible for a mouse to have taken a nibble at a hose but I can see no obvious sign of this either. Do you think that it is very unlikely for the RMS to cause this amount of oil loss bearing in mind that it dropped it all within a couple of minutes?

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I have seen a few RMS leaks but never seen one leak that much. If you are going to trouble shoot it yourself, you can refill the oil and add florescent dye. Have someone else start the car for just a moment and look for where the dye shows up using an ultraviolet flash light and UV glasses. If you do not catch it the first time you will need the clean the dye off with dye cleaner and try again. You would think with that much oil it would be pretty easy to spot. Another idea is the oil cooler that is behind the oil filter housing. These have developed leaks before but again never at this magnitude.

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I will be trouble shooting and repairing it myself and I had considered filling it again and looking for where it had come from but I was worried that the oil may be getting lost before it gets to where it needs to go, I may be being too cautious but it's an expensive engine to risk running without oil.

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I don't think you could be too cautious with the motor. Probably best to first check each hose that supplies the engine to make sure that oil is indeed getting to the engine. You could even pull the case plug to see if there is oil in the case and sufficient oil to supply the oil pump. I would probably try to clean it up as best you can and look closely where it may be coming from. Then if you cannot find any suspect places fill it with oil ( you can use cheap dino oil) since it is just going to be lost anyway. Have someone else start it while you watch for the leak using the ultraviolet light. Try to run it for the just a few seconds if you can. On the other hand if it looks like there is no oil in the case I do not think I would start it at all.

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With a leak that large, I find it difficult to accept that you cannot see the source you should be able to see where it is coming from with the car up in the air. You could also make sure the car is full and start it while it is up to look for it.

Edited by JFP in PA
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  • 2 weeks later...
  • 2 years later...

Apologies guys, fixed the car many months ago but forgot to update you. 


The cause of the leak turned out to be a corroded core plug in an oil gallery, the core plug sits horizontally on top of the engine, I presume it had been filling with water being kicked up from the wheels and had corroded over the years. I had to remove the engine in order to access the plug, I was surprised how easy this was to do with the use of a friends 2 post ramp.


I went to my local OPC to purchase the part only to be told that they have had issues with this core plug in the past and that Porsche had now modified the part, I was pretty shocked when they told me the modification meant that the core plug had been replaced by a much thicker screw in plug which also required me to purchase a new engine casing, I cant remember the price they quoted me but I would not have had much change out of £10000, I politely told them where to put there modified plug and retreated back to my garage to have a cry/think.


Once I had got over my shock I decided to remove the corroded plug to measure it with my plan being that I would have a new plug manufactured somewhere, on removing the plug I thought it looked remarkably similar in size to one I used to see regularly in my old workplace so off I went with my sample in hand, I was delighted to find that it was identical and I was given 2 for free. The car has been back on the road for months and hasn't missed a beat since.


Nearly forgot, the new core plug came from a pretty unlikely source...............a Massey Ferguson 135 tractor :)


I have some photos somewhere that I will upload as soon as I find them.


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