Reposting. My thread was deleted (admins complained about my username/email address) it seems and I can't access the information anymore:

Not sure if this is a common issue on the Continental GT.
The code returns after some driving.
From experience on other cars, I suspect failing N75 valve (anybody know how to get to them, assuming there is one per bank/turbo), leaking hose to N75 and/or from N75 to turbo wastegate, leaking wastegate.

000564 - Boost Pressure Regulation P0234 - 001 - Limit Exceeded (Overboost Condition) - MIL ON

To test for leaks, I would like to "smoke" the engine (leak test with pressure tester using smoke). Any practical suggestions where to insert the 'smoke'?

 

Your back! We discussed spraying starting fluid here and there to see if there was any engine RPM drop. Were you able to do this? Should RPM changes occur with the starting fluid trick then the smoke test is good for pinpointing.

Under the left side US. wheel well plastic liner is a blue vacuum pump with a line running back towards the rack and pinion steering. Disconnect that 8MM line from the top of the vacuum pump system and smoke test from there. Then under the small middle plastic Bentley heat shield on top of the engine, there are two 13 mm lines that run down behind the steering rack. With extreme care disconnect them from the back of the intake manifold. Smoke test down each of these as well. The unit on the left side US driver side will double check the vacuum lines to the brake system. The 13 mm line to the right passenger US will verify if the EVAP system is leaking.

These are not just vacuum lines they are also charge lines. Depending if the engine is producing vacuum or boost determines the pressure or negative pressure in the lines.

Determining if n 75 is failed is not straightforward. Volkswagen and Audi owners are able to change n75 and n249, the location on these cars is easier ( the W12 Audi and Volkswagen are not turbocharged and do not have these solenoids).


The other test is to remove the engine undershield. Locate the small vacuum line at the base of each wastegate diaphragm. Disconnect the line and apply a small amount of vacuum to the silver diaphragm vacuum port. See if the wastegate activation rod moves inward. Should the rod not respond to vacuum there's a possibility the wastegate is stuck in the casting and needs to be lubricated. Lubricating the pivot point of the wastegate is not easy due to accessibility. Do not do anything to the silver diaphragm casing. Inserting lubrication into this will only ruin it.

Would also make sense to disconnect the rubber turbo intercooler tubes at the bottom of the intercoolers and check for metal filings or excessive oil. Use an inspection camera to check inside. Also remove the air cleaner units and look with the inspection camera down the charge tubes to make sure the impellers are in good shape.

A 2006 Bentley would require engine out for changing n75. There are other causes of overboost. There can be an ECU malfunction. The pivot of the wastegate can get stuck closed etc.

 

Here are a couple of views of the above the transmission solenoids.


For the record n75 rarely fails. Overboost can be very high boost pressure or the boost at a specific RPM exceeds what the PCM expects.

 

@1eapplebaum seem like the Pre facelift one has different design than the new one... mine doens't has the Vacuum line on top of the transmission

 

The Silver Spur never had the vacuum lines above the transmission. Sometimes having four doors has other advantages.😉

There has been discussion that the GT mid year 2007 was the transition from the above the transmission solenoids.

By the way glad you sorted out your Spur! Welcome to the club of been there done that.👍

 

How's the smoke test coming? Noticed that the problem on the car has been posted on different forms. This has been a long road?

Any new discoveries?