De Jeeper

Not with loose bearings and high g turns. Airation w pressure drop is real and proven so if the motor is not in good shape it will pop.

Icelia

Will do on that one. Looks like a great solution.

Icelia

OK, so building up my list of things to do to the engine.

I feel I must change out the primary chain tensioner (crank to IMS), and as I can't do that without splitting the case, it puts me in a quandry.

Is it possible to disassemble and replace while leaving the pistons in the sleeves? they are mated to the bores over 200k, so I would prefer not to remove if possible.

I have great compression (tested a year ago, but all in the 170s) So I would prefer not to do liners and pistons if possible.

Otherwise, maybe I will just keep dropping the pan and inspecting the tensioner pad every other oil change.

hkovalcik

you gotta leave this thing alone man. Normal maintenance will take you much further here. PM'd.

hkovalcik

uaos great product but nothing necessarily wrong with genuine porsche aos. Can be changed in under 2 hours. don't need to touch exp tank, manifold, alternator or engine mounts. if DIY guy i can explain how u do it and will save u $. pm me

GC996

No question. Probably the most durable part Porsche has. Almost as durable as the water pump blades, IMSB and lukasil coating. I put them on everything i own.

TexSquirrel

No need to worry about removing the pistons if you have the right tools and the skill to do it.
But, no, you can't split the case and leave the pistons in place.
You will need to pull and reinstall them.

TexSquirrel

Haha, quality IMSB, waterpump, Lokasil, and sunvisors.
Not to mention the lifetime transmission fluid.

I'm a former european mechanic.
It took me several hours to replace my AOS with the UAOS.
If you're very experienced like PorscheTech3, you can maybe do it in 2 hours, but a DIYer, or even an experienced mechanic it will take longer.
When my UAOS diaphragm failed recently, it took me 5 minutes to replace it.

Unless you have several years experience working a a water cooled Porsche indy, or a dealer several years ago, I really doubt 2 (or 4) hours is possible.
I'd love to watch a video proving me wrong though.

Porschetech3

When the Genuine Porsche AOS failed with a huge big cloud of smoke under the 50k mile Factory warranty or the 100k mile CPO warranty, Porsche insisted on replacing the engine due to the possibility of a slightly bent connecting rod that would show no apparent symptoms for several thousand miles like this car...This cars engine was torn down last week and posted on FB about the scoring on the pin side of the cylinder ( not the usual skirt side of the cylinder)The previous owner had an AOS failure , then replaced the AOS and a few other things then sold the car and the new owner found this...


#6 cylinder scored on pin side of cylinder

#6 rod slightly bent only about 20 thousandths

I'm not saying that EVERY AOS failure will cause a bent rod or cracked cylinder, but I am saying that thousands of bent rods and cracked cylinders have been caused by AOS failures, it is just a crappy part, and is inefficient to boot...This example was just found last week..

BTW :: The new owner now has a UAOS System to be installed on his new engine..the way it should have came from the factory...

hkovalcik

Tex biggest thing to note is you want to just break the coolant tabs off and deal with the existing hose clamps out of the car. Your view is under bank 1's intake manifold after you unclip the solenoid that rests atop the alternator. Reach around with right arm undo vac hose and break coolant port #1, reach around with left arm atop manifold and break coolant port #2. Get under car, undo 10mm variocam bracket and get lower hose off with pull&pinch. Once off remove bolts that bolt AOS to block. Feed AOS out from the top of car behind bank 1 intake manifold. Obviously this is with everything from intake to frontmost plenum removed. Getting frontmost plenum back in with manifold still mounted is hardest part of the job, but there's a special way to do it and I'm keeping that a secret.

uaos no question easier to replace.

I'm a european mechanic in my head. I'm 29 but have been working on cars since I was ~12.

"who's the better wrench?" - Top gun hk vs tex

Edit - because you doubted me - these are from my OP where I eventually did my own aos.

you need to remove coolant hose that goes to bleeder valve to give left arm room like so:




Right arm fed between plenums - this is where you look just above alternator and below manifold while your arm is back there. No view unless solenoid is unclipped and moved from atop the alternator.

hkovalcik

delete - yes uaos is great product but rod bend doesn't happen unless owner keeps driving the car. pooled oil in cylinders from failed aos is reason for rod bend and owner should replace aos/tow car immediately. there is a thread where people argue whether or not u can bend a rod just by starting the car with oil pooled in cylinders but general consensus was "unlikely"

Haalex

I'd second the if it ain't broke, don't fix it suggestion.
Maybe have it dynoed to see if it lost anything, but unless it burns oil or lost 50hp, I'd leave that car alone and keep driving it. Better spend 25 grand five years down the road than tomorrow.

GC996

Yep. Nothing better than being on the road or track in your 20+ year old 996 with old brittle parts that are known to fail as they age. Same can be said for the joys of being down 50 hp. Who in their right mind wouldn't embrace the joys of waiting for AAA on the side of the road.

allcool

Just to be clear, all it takes is 1 teaspoon of oil in 1 cylinder to do a total hydrolock that shatters pistons, breaks/bends rods, cracks cylinders, d-chunk cylinder.

Yes, just turning over engine with starter, with enough oil in cylinder, can cause damage that might not be apparent immediately but thousands of miles later will show up all to well.... Can't compress oil, so something (rods, cyl, piston, flattened/hammered rod bearing, etc,) has got to give....

jmo

allcool

As others have said, no. You must disassemble the pistons/cyl to get engine cases apart.

At 200k miles, your bores are way out of round/taper all the 996 experts say. The rings have now seated into OOR bores. Its not uncommon for out of round cylinders to seal and run well, as rings have worn/seated into their location. The problem comes from trying to seat new rings in old oor/tapered bores. The majority of these re-ring attempts result in wiping out the rings in a few thousand miles...

IMO, do a detailed cam dev check and a detailed leak down test and a new compression check. Also try and do a detailed inspection of all chains for broken/missing cracked rollers/pieces that can jam up the pumps. Use this new information to decide what you'll do...