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I love following Porsche/Audi’s approach to engineering and i figure id post some things i learned about this motor that i haven't seen too much of.
As some of you are aware, there is a vacuum line connected to the water pump, and there is an issue where the water pump will leak coolant into the vacuum line, contaminating everything in the vacuum circuit. The coolant regulator/switch over valve also leaks coolant and is connected to the vacuum circuit.
This contamination goes as far as the vacuum switch over valves, boost controller valve, vacuum pump, brake booster, intake system and everything else that uses vacuum.
The theory behind the design from my understanding is that the vacuum changes how the water pump operates in terms of speed or velocity, and the vacuum/coolant switch over valve can warm up the cylinder heads and block independently. The priority is to warm up the engine as fast as possible as this will cause the emissions to be cleaner faster. The only way they figured to accomplish this is to add the water pump and switch over valve to the vacuum circuit.
I did a repair on this today and thought i shared some of this info to 3.0L Cayenne owners. Also this issue has been common on the 2.9L TT, and the 4.0L V8’s.
Usually the water pump, coolant pipe o-rings, coolant switch over valve, Intake pipe gasket, boost controller with all associated vacuum lines and electric switch over valves, vacuum pump and a new brake booster lines get replaced to resolve a contaminated vacuum system.
Hope you guys find this interesting and let me know if you have any questions.
Pics for pleasure:
Faulty water pump, you can see traces of coolant on vacuum nipple
Vacuum pump/Brake booster/Intake pipe junction also contaminated with coolant.
Pic of semi-completed repair (water pump left, coolant switch over valve right)
Appreciate you sharing and posting. Going to check mine this weekend.
My thoughts are bringing back the nightmares associated with the plastic coolant pipes that failed on first gen cayennes. Once failed, coolant would destroy to starter, torque converter seal, etc. every generation seams to have some coolant issue that leads to very expensive repairs.
How many miles did you have on your cayenne.... Or it doesn't really matter because it could happen at any time
This was like at ~60K miles and the vehicle (2019) was out of new vehicle warranty, but we were able to take care of it under the emissions warranty.
Ive seen this happen as early as 45K, but it may happen earlier or later based on peoples different driving habits.
This issue will usually throw a check engine light once it contaminates the vacuum circuit, usually an underboost code relating to the turbo. If a check engine light comes up it will usually fall under the emissions warranty especially with boost codes and the emissions warranty is like 7 years/70K and is only in CA, CT, DE, MA, MD, ME, NJ, NY, OR, PA, RI, VT, & WA. CELs, The coolant switching valves and boost pressure regulators are just some of the list of items covered under emissions warranty.
I might be missing something let me know if you have any other questions!
What is the specific mechanism of failure which allows coolant into the vacuum system? Is it a seal that fails? A valve?
Seems like preemptively replacing the water pump and changeover valve would help avoid the collateral damage to the vacuum system. But what an expensive and time consuming preemptive maintenance task.
What is the specific mechanism of failure which allows coolant into the vacuum system? Is it a seal that fails? A valve?
Seems like preemptively replacing the water pump and changeover valve would help avoid the collateral damage to the vacuum system. But what an expensive and time consuming preemptive maintenance task.
Yes it seems some kind of seal internally in the water pump fails and allows coolant to enter the vacuum system.
Agreed, it is costly and timely to preemptively replace. If i were under 70k miles/7 years i would just let the dealer handle it, take note of how many miles it failed at and preemptively replace the waterpump again before it fails, again.
Thanks again. Also of note - V8 water pump is shaft-gear-driven and V6 water pump is belt-driven. Both V8 and V6 water pumps appear to be failing so the pump drive mechanism appears not to be the issue but rather the vacuum-actuated shroud over the impeller, to control flow.
This was like at ~60K miles and the vehicle (2019) was out of new vehicle warranty, but we were able to take care of it under the emissions warranty.
Ive seen this happen as early as 45K, but it may happen earlier or later based on peoples different driving habits.
This issue will usually throw a check engine light once it contaminates the vacuum circuit, usually an underboost code relating to the turbo. If a check engine light comes up it will usually fall under the emissions warranty especially with boost codes and the emissions warranty is like 7 years/70K and is only in CA, CT, DE, MA, MD, ME, NJ, NY, OR, PA, RI, VT, & WA. CELs, The coolant switching valves and boost pressure regulators are just some of the list of items covered under emissions warranty.
I might be missing something let me know if you have any other questions!
SUPER helpful. This is what Rennlist is about. Thanks for taking the time to share.
Fuel economy and emissions requirements strike again! Prior to these requirements, the mechanical pump simply pumped coolant. Now, the pump is a fancy “active pump” designed to shut off coolant flow in order to heat the engine faster.
The coolant flow is shut off by sliding a vacuum controlled orifice plate over the impeller. (The plate is illustrated in red on the diagram below and further demonstrated in the video.) Vacuum shuts off the flow. It is fail-safed so that the spring-loaded orifice plate retracts and provides full flow in case of vacuum failure. (The only good design element of this system).
The orifice plate slides on rods connected to a vacuum diaphragm. It uses seals that separate the coolant from the vacuum system. When the 50 cent seal leaks — BAM — you pay $9,000 to replace not only the pump, but the contaminated vacuum system as well.
Fuel economy and emissions requirements strike again! Prior to these requirements, the mechanical pump simply pumped coolant. Now, the pump is a fancy “active pump” designed to shut off coolant flow in order to heat the engine faster.
The coolant flow is shut off by sliding a vacuum controlled orifice plate over the impeller. (The plate is illustrated in red on the diagram below and further demonstrated in the video.) Vacuum shuts off the flow. It is fail-safed so that the spring-loaded orifice plate retracts and provides full flow in case of vacuum failure. (The only good design element of this system).
The orifice plate slides on rods connected to a vacuum diaphragm. It uses seals that separate the coolant from the vacuum system. When the 50 cent seal leaks — BAM — you pay $9,000 to replace not only the pump, but the contaminated vacuum system as well.
This is awesome information thank you for expanding on the waterpump itself. So crazy but its like you said, all in the name of fuel economy and emissions.
This is awesome information thank you for expanding on the waterpump itself. So crazy but it's ctualllike you said, all in the name of fuel economy and emissions.
Actually - all in the name placating government regulators.
Thanks @Schnave . So the failure is the rod seal. Shame that it leaks internally, in other words not visible. If the seal failed gradually and with external leaking or weeping, it could possibly be caught before causing collateral damage to the vacuum system.
What is everyone's guess on the production price (price that VAG pays the production supplier) for the rod seals which fail and cause the collateral damage?
03-28-2024, 12:41 AM
9YA/9Y0 Cayenne Cooling Issues
