Removing rear plenum

[Citgot]

 

Was this photo taken from under the car?  The AOS looks' like it is hitting the case to the left of the tube....

No that photo is from above with the bolts all the way in. I can tell that the AOS is not completely straight when looking from under the car. As far as I can tell nothing is in the way, but it feels like the tube bottoms out before the whole seal is in. Or maybe the seal gets a bit crooked and stops the tube from going any further. In the photo from under the car the seal looks a bit loose and jammed between the edges of the hole and the AOS.

 

The AOS is ordered from Porsche Center and should be the right one for my car according to part number

[JFP in PA]

OK, let's start with the basics: What year and model is your car?  What is the part number of the AOS you are trying to install?

[Citgot]

The car is a 996 3.4 2000 manual. Part number on the AOS is 99610702354.

Maybe I should invest in a boroscope so I can see better around the AOS so nothing is obstructing it.

[Loren]

996 107 023 54 or 996 107 023 55 - either should work for your car.

Though 996 107 023 54 is a discontinued part.

[JFP in PA]

3 minutes ago, Loren said:

996 107 023 54 or 996 107 023 55 - either should work for your car.

Though 996 107 023 54 is a discontinued part.

 

That was what I was just looking at.

[JFP in PA]

OK, something interesting:

 

Here is the part ending in 54:

And here is the one ending 55:

 

 

Notice the difference in the length of the tube that inserts into the block?

[Citgot]

OK, something interesting:
 
Here is the part ending in 54:

And here is the one ending 55:
 

 
Notice the difference in the length of the tube that inserts into the block?

That is strange. My AOS is certainly the one below with the longer tube which should end in 55.

[JFP in PA]

Something is not right here.  I would pull the unit and either use a borescope of a small mirror to see if something is still in the block. 

 

Did you say that you had the bolt in and the unit was flush with the engine case when the tube was not all the way in?  If that is correct, there is something wrong with that AOS unit.  Did you compare it to the unit you pulled out?

[Citgot]

I think I’ll invest in a boroscope to look into the hole in the engine case. Maybe the answer is there.

It is not completely flush when the bolts are turned all the way in, but pretty close. It looks like the tube wants to go a few mm further in for the AOS to be completely flush with the case.

[JFP in PA]

1 minute ago, Citgot said:

I think I’ll invest in a boroscope to look into the hole in the engine case. Maybe the answer is there.

It is not completely flush when the bolts are turned all the way in, but pretty close. It looks like the tube wants to go a few mm further in for the AOS to be completely flush with the case.

 

While you have the AOS out, physically compare it to the unit you removed to see if there are any obvious differences.

[Citgot]

Yeah, will do that tomorrow. Thanks for all your help. Midnight here so good night.

[JFP in PA]

4 minutes ago, Citgot said:

Yeah, will do that tomorrow. Thanks for all your help. Midnight here so good night.

 

Good night.  Leave you with a thought: Try a lighted mechanics mirror before jumping for a borescope:

 

It has two LED's to illuminate and is a great time saver.  I have both this and a borescope in the shop and reach for this way more than the borescope.

[Citgot]

Good morning. I compared the old and the new AOS. The old one’s part no ends with 53 and the new with 55 (the bag said 54 but on the AOS it said 55). The tubes are the same length but the seal is different.

 

I’ve looked and there is nothing in the hole in the engine case. My conclusion is that it is the seal that stops the tube from going in. I’ve tried both silicon lube and engine oil but no luck.

 

When I try to pry the tube inwards I can see the seal flex a bit and the tube moves in the hole. So I guess the seal is the problem. I’ll see if I can ice it a bit and make it shrink before I try again.

 

Edit: Maybe ice isn’t the beat way to shrink the seal. Heatgun could maybe work better.

 

[JTT]

Maybe it’s an optical illusion, but it looks like the length of the section before the seal is different between the two.

[JFP in PA]

3 hours ago, JTT said:

Maybe it’s an optical illusion, but it looks like the length of the section before the seal is different between the two.

 

Older AOS units had a single o-ring seal, later units have multiple seals.

[Citgot]

This is the best I can do. Freezing it didn’t help. Heat gun maybe a little but the seal started to harden so I couldn’t apply any more heat. I guess I will have to try to drive like this and see if the seal is good enough.

Clearly the seal is the problem. In the photo it is obvious that the last bit of the seal has been squeezed to a bulge at the end. That bulge stops the tube from moving that last mm. At least 3/4 of the seal is where it should be.

[Citgot]

This is the best I can do. Freezing it didn’t help. Heat gun maybe a little but the seal started to harden so I couldn’t apply any more heat. I guess I will have to try to drive like this and see if the seal is good enough.

Clearly the seal is the problem. In the photo it is obvious that the last bit of the seal has been squeezed to a bulge at the end. That bulge stops the tube from moving that last mm. At least 3/4 of the seal is where it should be.

[dporto]

Use some degreaser to clean up that area good before you start to run/drive it - otherwise it'll make it difficult to see a weep/leak (unless the oil is dripping out).

[Citgot]

Use some degreaser to clean up that area good before you start to run/drive it - otherwise it'll make it difficult to see a weep/leak (unless the oil is dripping out).

Yes, I thought of that. I cross my fingers for it not to leak.

[DBJoe996]

Please come back and let us know how it worked out.  Sorry for your pain and agony on this one.  Replacing the AOS  is a major PITA job even if everything goes right.  It is an extremely difficult job.  I still question that AOS but time will tell whether it is right or not.  If it does leak or show signs of a massive vacuum leak, then you will know.  I took a flashlight and tried to see if I could get a picture of my replacement AOS from underneath to see how my seal seated  but no go on that one.  Best of luck and hope it works out.

[Citgot]

Yes I will let you know when I have done some driving. It could be useful for others to know if they come across the same problem. Thanks for all your input and help.