If you have a 957 MY08-10 Cayenne, then you should be aware that it looks like I "may" be seeing the tip of the iceberg in terms of an emerging coolant pipe issue for the 957 V8 4.8 DFI, not to dissimilar from the well known issue in the 955 Cayenne.

Apparently, this is making the rounds on other boards and I do not think it was brought up here yet. So I am deliberately airing on the side of caution and opening a thread with what I know so far for the sake of the community. Hopefully, this turns out to be a little over zealous.

Note: All included images in this post were pulled from Google Images in the public domain. These images were not taken by myself.

Background

I have only been able to confirm a handful of cases, but given the circumstances it is fair to say that others will be affected as these engines age. First check out the open complaints on the official government NHTSA site.

This is the part in question that is failing:

http://www.design911.co.uk/uploads/i...4810606104.jpg

To be more specific, it is the hose barb to the left of the number 3 on this image that is slipping out and causing massive coolant leaks:



This what is looks like when the epoxy fails and the barb becomes unglued from the rest of the water distributor housing:







Considering that coolant barb epoxy failure is common on the 997.7 Metzer engines, it is reasonable to assume this will happen more frequently on the CTT engines.

Here are a couple of threads from our 911 brethren with similar issues:

https://www.6speedonline.com/forums/...e-failure.html

https://www.6speedonline.com/forums/...s-repairs.html

Here is a video showing the issue on the 911 from Sharkwerks:


Solution / Repair


Unfortunately, the official Porsche repair calls for dropping the engine! This is mainly due to the placement of where this part is - squeezed behind the back of the engine and the firewall.

If we take a look at how the 911 guys are resolving this, many of them are drilling a small hole in the barb and main casting, tapping it, and inserting a set screw to mechanically bond both pieces; thus stopping the barb from backing out and avoiding a catastrophic coolant failure:





Another enterprising individual, actually welded his barb to the main casting:




Any of these solutions are much better than just buying a factory replacement coolant distributor since it looks like they have not changed the design to remove the two piece epoxy solution.

 

Notes

Interestingly enough, I was also able to confirm that there is an upgraded aluminum coolant pipe upgrade under the intake manifold for the Cayenne 957 (similar to the 955):

http://www.ecstuning.com/Search/Site...910/ES1907250/

Replacement Part Numbers

Water Distributor (without screw plug - Turbo only) - Qty. 1 - 94810606106

Water Distributor (with screw plug) - Qty. 1 - 94810606104

Water Distributor Gaskets- Qty. 2 - 94810615401

Upgraded Coolant Pipe - Qty. 1 - 94810606910

Coolant Vent Line (optional) - Qty. 1 - 94810602604


Affected Models

Right now, I have only been able to confirm that Cayenne Turbo and Turbo S with the 4.8 DFI will be affected. Not sure about the NA 4.8 DFI.

EDIT: Confirmed. This affects all variants of the 957 V8 4.8L DFI engines. This includes the the NA V8 DFI in the Cayenne S, Cayenne GTS, Cayenne Turbo, and Cayenne Turbo S. See attachment for vehicles that cross-reference with upgraded coolant pipe and water distributor.

 

Personally, I will be proactively addressing this concern on my own CTTS in the next week since a replacement engine is cost prohibitive at this point.

 

Great post, I was wondering when this issue would come up on this forum. I am also going to be proactively fixing this issue in the next few weeks.

I am curious if it is possible to get to the fitting with the engine in place? Also wonder if the fitting should be removed and re-glued (JB welded) before pinning is done?

 

I know that you can reach the fitting if you have small hands. I hear if you remove the high pressure fuel pump on the driver side, you will have a little more room to work.

If yours has not failed yet and you are trying to reseat it with a better epoxy, then you might have an issue working the current one loose in such a confined area.

In a perfect world, I was going to either:

A) remove my barb, thread the hole, and insert a threaded barb fitting with epoxy or thread sealant.

B) weld the barb and the casting together

C) remove the barb, rough up the inside of the casting, clean with acetone, JB weld (epoxy), and use a set screw

In the end, I think all of these solutions are slightly over engineered (not a bad thing). Just not sure if it is worth the pain of completely removing the water distributor, modifying, and reinstalling in such a tight area.

I am now leaning towards taking advantage of the fact that my transmission is out and just drilling, tapping, and installing a set screw (like the 911 guys) while the water distributor is still installed on the engine.

This is the easiest solution and should prove adequate in the long run.

 

Thank you for making this a sticky. I believe this may be the source of my slow coolant leak. I guess I will find out when I do preventative t-stat and coolant pipe replacement, etc.

Good find on the metal coolant pipe you listed. I also found this when looking a while ago, though I'm not sure exactly whether the 957s need it... I'm assuming they came with plastic. If so, that'd be good preventative maintenance.

http://www.ecstuning.com/Search/Site...907/ES1441597/

There is also a lower cost option of that piece made by Hamburg-Technic

http://www.ecstuning.com/Search/Site...907/ES2771199/

What are the chances this will be an official recall? This kind of issue is unacceptable on a vehicle of this caliber... no, any vehicle for that matter. If this happened at Toyota, I'd bed they'd be recalling every one. Can't loose that reputation for reliability! God knows there is no other reason to buy a Toyota

 

No worries - anything that can potentially be a recall and cost us an engine, necessitates a sticky.

If so, be glad you caught it before it failed completely.

I was able to cross-reference the part you provided "94810604907" and it explicitly states for 2003-2006 (955) Cayennes. So the 957 Cayenne does not have this part. As a matter of fact, I believe the upgraded coolant pipe I listed is the equivalent to this part on the 4.8 DFI.

Unfortunately, I was also able to cross reference the upgraded coolant pipe I listed and it includes all variants of the 4.8 DFI, including Cayenne S and GTS

Updating the original post now to reflect this...

Not sure - However, I do not think the 955 coolant pipe issue and the 911 coolant pipe epoxy issue necessitated a recall. Perhaps it has something to do with the low volume in which these cars are sold.

 

Update:

Just completed drilling and tapping my hose fitting with a set screw. I used a automatic center punch, M4-0.70 stainless steel socket cap screw (8mm length), a #30 drill bit and a M4-0.70 tap.

Here are the pics:

This is the area that I will be working in (transmission fully removed).. you can fully see the water distributor from the back:



Here is a close up showing the problematic barb that may come out with time (circled in red):



This is where I will be drilling a hole to install the set screw (red dot):




I used a centering punch so the drill bit will not walk:



Hole drilled. In hindsight, I wish I fully drained all of the coolant first. About a gallon came out:






This is my M4 thread tap and adapter. I will be using a hand tool to create the tapped threads since space is limited and the aluminum is soft to cut:








I used JB Weld (Marine) on the screw threads to permanently bond the inside fitting and the outside casting of the water distributor together:




This is the finished results; a permanent solution. Now I will pressure test the coolant system (after epoxy cures) to make sure this hole will not weep

Note: I abandoned an attempt to smooth out the casting around the hole after realizing that it wasn't worth the effort:

 

Also, for those following along, you can see the back of the original plastic composite coolant pipe that runs under the intake manifold and splits into two lines. Note the orientation of the spring clamps..

Will change this out next to the upgraded aluminum version received for the 957...



If you look closely, you can see the OEM plastic coolant pipe here under the fuel system:



Also, here is the upgraded aluminum coolant pipe for the 957:

 

Update:



Just finished changing out to the aluminum coolant pipe, new coolant vent tube, and engine coolant temp sensor.

This was not easy since the plastic coolant tube was fused to the aluminum inside the water pump housing and had to be chiseled out. In hindsight, it may be easier to just cut the pipe in the middle and remove the entire water pump housing assembly. At least it will be easier to remove the plastic pipe on the work bench.

Coolant system was pressure tested to 25 psi with no signs of leaking.

Here is a clear pic of the OEM plastic coolant pipe (without fuel rail):




Here is a final pic of the new aluminum coolant pipe (without fuel rail):



Final pic with fuel rail reinstalled:



Just have to reinstall intake manifold and refill coolant.

 

Thanks for the great pictures and info. I have determined for sure that my t-stat is stuck open on my Turbo S, so I will be doing that part of the job at least. Now I'm trying to decide if I should try to tackle the coolant pipe and also the JB-Weld job. Is that coolant pipe able to be removed from the top? It looks fairly easy to get the Y-section off with the trans removed, but I'm NOT doing that! If not, I'll just let it go for now as this was just preventative maintenance.

Can you confirm that to do the t-stat on a 4.8l 957 V8, the parts needed are the thermostat itself with o-ring 94810612501, water pump with o-ring (might as well replace it at the same time in my opinion) 94810603301, thermostat intake socket 94810610103, and this special grease for the intake socket 00004320593?

I'm also going to replace the water pump pulley 94810609100 and serpentine belt 7PP903137 while I'm in there for that job.

Then if time permits, I will do the upgraded coolant pipe 94810606910 and replace the coolant vent line 94810602604, and expansion tank 95510614723 as preventative maintenance.

Sound good? I may buy a remote spring clamp tool to make the job easier (especially for those rear clamps on the upgraded coolant pipe) and a coolant evacuation tool (is this necessary?) It's time to put 957 coolant issues to bed!

 

(Catching up on 6speed reading and reminded I need to fill out my 955 coolant lawsuit paperwork (coolant leak + transmission issue = $12KFn repair) when I read this about our 957 CTT may also spontaneously explode = crushed.)

Ken - you rock once again! Great write-up and follow-up.

 

Need to cross-referencing part numbers..will have to get back to you in a little bit

Thanks man! Good to see you around the boards!

 

One more failure to add to the list;
Cayenne S 2008
Pipe blew right out during a downshift, causing sudden coolant loss.

I've been told there is a newly designed water distributor with Part Number 94810606107. Apparently this time the outlet is threaded into the water distributor housing instead of just bonded in place. The way it should have been done initially.

Of course it seems the only way to get that part installed safely is by dropping the engine...

Thank you to the bean counters who decided to save $1 in this area despite knowing that it would compromise safety, brand integrity and customer satisfaction.

Has anyone had any luck yet tapping the thread from the top of the engine?

 

For reference