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Old 03-30-2013, 11:36 AM   #1
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Blown AOS & Oil leaks - Look what I found........

Hi all,

I thought I would share my findings after investigating another oil leak on my old Boxster....
In the last few months, we had 2 failed AOS units, I also decided to fit a catch tank and filter rather than running back into the intake. This seemed to sort things then recently we noticed an oil leak on the RHS side of the engine. On closer inspection, the catch tank was overflowing (1 litre!) so there was obviously another issue so.......

Up on the ramps, there was oil pooling under the AOS, pretty messy. I had read on another Porsche forum about the scavenger pumps, if they are fitted the wrong way round, they will not push the oil back into the sump so this could explain the false levels on the dipstick of late. So I removed the rear pump (RHS bank)....
Here is the (back of the) pump, plus the sheared off peg on the right. The unit appeared to be seized, hence the pin shearing off, so apart it came...


In dis-assembly, this is what I found. The remains of a m6 bolt that was wedged in the gear. At least this explains the broken pin and lack of oil being pumped back into the sump. This in turn was not allowing the oil to flow back into the head from the AOS directly above it....hence ending up in the catch tank....


Looking closely, the bolt as you can see was jammed in place and I had to remove with pliers! The pump is scrap now, fortunately the front pump was good..


Here is the complete assembly, generally robust as long as stray bolts don't find their way in!


I need to find a replacement pump asap.
No idea where the bolt came from but I will filter the drained oil tomorrow too, maybe drop the sump while I am under the car to have a look too....

Fingers crossed, I can get it all back together on Monday. I need to degrease and power wash the engine and gearbox as the catch tank overflow made a hell of a mess!

Happy Easter all!
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Old 03-30-2013, 01:10 PM   #2
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You need to know where the bolt came from. What is the length of the piece you have? You may need to replace the pump drive flange/gear also if worn.
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Old 03-30-2013, 01:26 PM   #3
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I plan to replace the whole pump assembly.
The remainder of the bolt is 1.5cm long, hopefully I can find the rest in the sump/filter. Its too small to be a load bearing bolt, similar to a sump bolt etc but without stripping the engine, not much hope.
I am planning to fit a magnetic sump plug too so any debris may be picked up here. I still have the drained out to filter too - can't wait!
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Old 03-30-2013, 03:18 PM   #4
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Quote:
Originally Posted by srad34 View Post
I plan to replace the whole pump assembly.
The remainder of the bolt is 1.5cm long, hopefully I can find the rest in the sump/filter. Its too small to be a load bearing bolt, similar to a sump bolt etc but without stripping the engine, not much hope.
I am planning to fit a magnetic sump plug too so any debris may be picked up here. I still have the drained out to filter too - can't wait!
I know you have to buy a new pump, I'm talking about the part that bolts to the cam & drives the pump by twisting the part that broke on the pump. Maybe the bolt was from the lifter guide that has about 20 bolts to fasten it to the head.
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Old 03-30-2013, 03:29 PM   #5
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I am off to see a breaker tomorrow. The part fitted to the cam chain gear is in tact, no damage, I think the shock was taken by the tab but I will grab a spare one just in case!
Cheers
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Old 03-30-2013, 06:49 PM   #6
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Expect the exhaust cam timing to be retarded on the bank that scavenge pump came from... And maybe bent exhaust valves. Approach with care.
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Old 03-30-2013, 08:46 PM   #7
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I have come across something very similar in my engine. I found metal in the oil filter so looked at the sump and found more metal. I had a leaking 4-6 valve cover so pulled that and found a bolt wedged very close to a exhaust cam lobe. Turns out it was a lifter carrier bolt being slowly machined by the cam! No damage to the cam or lifter. Another bolt next to where it came from was finger tight if that. When I removed the scavenge pump I noticed a roughness so took it apart to find a small piece of the bolt had gotten in there, dinged the drive gear and grooved the housing slightly. I pulled the 1-3 pump to look and it also had the same small damage. Not enough in either pump to jam it.
I replaced the lifter bolt and checked torque on all of them. I cleaned up the pumps and they are smooth running now. The car was running fine with all of this before! I have 90+% of the bolt intact so I'm hoping I have gotten the metal out of the engine and everything will be okay.
You need to find where that bolt came from! Good luck.
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Old 03-31-2013, 12:47 AM   #8
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srad....
You also need to locate the head of the bolt too - goodness knows where that will be but it's a fair sized chunk of metal to be floating around in an engine.....
Something snapped the head off the bolt which would take an awfull amount of force - something like a rotating camshaft or timing chain.
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Old 03-31-2013, 09:51 AM   #9
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Update - I have sourced a replacement pump from a breaker friend of mine. Sadly the engine was a later spec 200-> with the locating pin as part of the cam sprocket, rather than mine with it being a plate bolting to the sprocket.
Looking at the Porsche diagrams, this is only on early 96-99 cars. As its not available separately from Porsche, finding another broken Porsche engine is my only hope!
Oh well, it could have been a lot worse....
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Old 04-15-2013, 10:21 AM   #10
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An update....

So I managed to locate the timing plate that bolts on the end of the early 986 camshaft, from the USA, this took 10 days first class thanks to good old UK customs!



Armed with the new pump, plate I got cracking. ....

First job: Remove the cam cover on bank one to find the head from the bolt that broke my pump. Its odd as the bolt pitch/size of it is smaller than the ones used on the cam cover and timing chain mounts so with everything re-torqued, I moved to the sump; No debris found at all, filter clean (last oil change was 3k previously). Nothing else appeared loose of missing so resealed and refitted.



Second job: With the green cam plugs removed when I took off the cam cover, I wanted to check the timing too as it could have slipped fractionally due to the pump snapping. Its a pretty easy DIY job tbh,. Mine was slightly out so adjusted and checked bank 2 was still good - it was! Note: always use new green cam plugs - 6.00 form Porsche, often held on stock too.

I Removed and inspected the second pump too, fortunately all was in good order.



Third job: Completed a compression test on all cylinders to ensure no valve damage and while all plugs/coil-packs were out, it made sense. Again consistent values so happy days. Refit AOS, catch tank, air intake and lower cross member (moved back to ease access rear pump housing) etc



Fourth job: Temporarily refill engine with used/filtered oil to start, ensure timing is good and it doesn't leak oil. All appears good, so dropped the oil after cooling, replaced filter and filled with fully synth 5w40. Test drove it for 15 miles with no engine cover of cabin engine cover to ensure no leaks, bloody noisy, but better than having to strip everything off again!

The result is that no oil blew into the catch tank, ran smoother and no (touch wood) leaks noted. Result and happy wife.



Conclusion: Unable to identify the source of the bolt, I can't rule out that it has not previously been removed during oil & filter changes as I have not previously filtered the old oil. Other than stripping the engine, not sure if I will ever find the sourcce.

My learning is that If you have a repeat issue in a short space of time, such as AOS failing, its worth taking a look deeper into the engine as something else could be the route cause of the issue.

The key thing is that its running really smooth now and I know a lot more about the insides of my Porsche just that little bit better now.....
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