Big Coolant Leak

Hi Guys, New owner again, 2003 996 4S I have attached photos I have a massive coolant leak. It seems to be coming from the back of the engine just before the transmission driver-side. I don't know what this part is. Any ideas? Thanks in advance.

I am guessing this a UK car with right hand steering if your saying driver side leak, the last picture is showing a leak at the engine oil cooler,

Right hand drive I guess UK version but picked up from the factory in Stuttgart and driven.

sure looks like the oil/coolant heat exchanger is leaking. This could be past the o rings, or because the part itself is leaking. Best to pull/inspect it and get it pressure tested. If it passes, install new o rings (perhaps with a smear of hylomar. It's a bit of a fiddly job, but can be performed with the engine in the car.

I just watched a YouTube and it looks like you have to dismantle half the engine

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I guess 'half' is a matter of opinion, yes, some things have to be disassembled (from memory: alternator belt, airco compressor, intake manifold, drain a bit of the coolant), but it's doable in an hour or 2 to 3.

There is a video on the FCP Euro Youtube channel Battery Disconnect & Airbox Removal- M96 Coolant Drain Procedure- M96 Engine Oil Drain Procedure - Drive Belt Removal- Supporting the Engine With a Jack - Throttle Body Removal- Air Oil Separator Removal - Plenum Removal- Hydraulic Fluid Extraction & Reservoir Removal- A/C Compressor Removal - Right Side Manifold Removal - Old Oil Cooler Removal - New Oil Cooler Instal- Intake Manifold Install- A/C Compressor Install - Plenum Reinstall - Hydraulic Fluid Reservoir Install- Throttle Body Install- Drive Belt Install- Airbox Install I think it's a bit much for me but their oil cooler kit is great value

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You can buy the kit and take it to your Indy. That's what I did. Cost me a couple hours of labor, but wasn't worth my taking two days to do it. I did watch though and they dropped the engine down enough to make it easier to get in there.

I think that's what I'm gonna do I'm not sure if they'll let me buy the part they make a bit of profit on that.

Has anyone upgraded to the 997.1 3.8S oil cooler? allegedly straight swap - has bigger capacity.

Some sort of mixup with my Indy so it looks like I'm doing the job myself. Apparently it's fun.

Hi guys, so I've started with removing parts to get to the oil cooler and I found this sensor I think just lying between 1st and 2nd manifold on the right. It looks like it should plug into something, but I did not unplug it. Anybody know anything about it?

Engine bay temperature sensor. It is what the ECU/DME reads to control the engine bay fan.

Porsche 911 Carrera Engine Sensor Replacement - 996 (1998-2005) - 997 (2005-2012) - Pelican Parts Technical Article This will show you where it belongs.

Thank you guys

Another problem guys, removing the right-hand manifold to get to the leaking oil cooler. I noticed a corrugated tube running through the manifold and then through the other manifold and then down and round the back of the engine. It actually goes through the manifold, so I'm not gonna be able to take them off to get to the oil cooler on the AOS. It looks like it is held in place through the manifold with a cable tie. Any ideas?

Weird. This does not look original. Do you know where the end of the tube goes?

That corrugated tube connects bank 2 (at top of cilinder head, cilinder 4) to thr AOS, I would say.

I don�t think it�s original I haven�t seen anything like it in any videos or drawings

Don't recognize it either, but could've been used to plumb the aos (the oem pipe often cracks) Key thing is to figure out where both ends go.

Yes if it does go to the AOS a strange modification

I found the breather hose on fCP euro so it�s not a modification. I just haven�t seen it on any videos or diagrams before

This is the breather hose I found

Looks like it comes apart in the middle

If it's the aos breather hose, it's wrongly routed, but can simply be clipped loose from the breather part that comes out of the right cilinder head towards the rear of the car.

Is it this hose that connects to the bottom of the AOS?

Yea thats it mine was through the intake on my 3.4l. It can be removed from the bank 2 head and the intake can be removed. U may want to replace it because they always crack. Also @Porschetech3 was making a replacement that was much easier to rought across the engine but not sure if it was for your motor.

I can't really see where it connects to the right cylinder head. The photo with the engine removed is not my 996.

Is it in 2 pieces could I pull it apart?

https://i.imgur.com/440azBF.jpeg That's where it should attach to the head. I would not try to separate it, as it could break.

Thank you for the photo unfortunately it's just confused me can't see where it attaches to the head my 3.6 doesn't look anything like that.

So, after further investigation, I have discovered that this fully corrugated pipe is in the correct place routed between the manifold and under the plenum. People also say that on the 03 the AOS cannot be replaced without dropping the engine. The fully corrugated hose has a joint in it, if I could pull that apart I would be able to get the manifold off and replace the oil cooler, which is how this all started. I cannot pull the hose apart maybe I could cut the hose and join it with something any ideas?

If this is a replacement for the aos hose, it connects the right cilinder head to the aos, and can be unclipped at either end. You should thus be able to unclip it at the right cylinder head.

Thanks, I know I should be able to get to it, but if you look at my previous photos I can't even see it.

Undo that plastic corner thingy that holds the wiring hardness (there's a m6 bolt in there). It's about underneath there.

Yes, that is the AOS cross-over breather pipe from bank 2 .. Yes I was making an upgraded pipe that went around the back of the intake and up the back 2 side ( instead of going "through" the intake)) ... It was made from 19mm 5052 Aluminum Tube bent and formed to around the outer perimeter of the Intake with 10" of flexible Tube on the ends with the V2Quick Connectors...It didn't sell well because it cost more and people still complained of difficulty, so it was discontinued... BTW: The AOS "can" be replaced without dropping the motor completely out or removing the Intake...I had an Indy in Arizona install the UAOS System in about 3 hours by removing the left rear wheel, lowering the engine a few inches. and taking the two AOS retaining bolts out ...