Engine Mechanical

Vehicle Details: 2006 BMW 330xi.  121000 miles

Technician: Todd

Client Concern:

Client noticed thumping or banging noise when in sharper turns like when navigating a driveway.  Also noticeable but not as pronounced when doing faster turns at speed (merging off a freeway).

Diagnostic Process:

Initially the client took his car back to his tire shop since this problem seemed to occur shortly after having tires replaced.  The tire shop could find nothing wrong with the basic suspension and drive train components (eg:  ball joints, axles and CV joints, struts, etc) and thus they advising seeing a BMW specialist.

Upon arrival Todd performed the same inspection as the tire shop but when that proved to be fruitless he checked the engine mounts – knowing the pattern failure of engine mount to cylinder block bolts.  Sure enough the bolts were broken (engine mount bracket removed in this picture):

BMW N52 engine – broken engine mount bolts

Repair Process:

The repair requires extraction of the bolts and replacing them with new.

N52 engine mount bolts

N52 right side engine mount bracket

Once re-secured the vehicle is test drive to ensure the client’s concern has been resolved.  We have NOT seen this escalate into bigger problems yet but we suspect that driving one of these cars with a broken / detached engine mount will eventually cause other problems.

Technical Discussion:

The reason BMW use this fastener (bolt) style is the N52 engine has a magnesium block.  A steel fastener, in this application, would cease in the block thus aluminum fasteners are employed.  Unfortunately they aren’t as strong as steel and can break.  On a positive note we have only seen this problem with the all-wheel-drive (xi) vehicles / we suspect this is due to additional rotational forces from the front axles.

Vehicle Details: 2004 Porsche Cayenne S. –  75,000 miles

Technician: Brad

Initial Condition:

• Overheating
• Coolant Leakage – Down the back of the engine
• Towed in

Diagnostic Process:

Performed pressure cooling system tests – confirmed coolant leakage down the back of the engine.

Double-checked other cooling system components to make sure this was the correct repair.

NOTE:  This is a common / known problem on the first generation (9PA) Cayenne.  It only affected the V8 engines.  When the problem first came to light the repair was much worse:  to replace the coolant pipes required removal of the engine to get the rear cross-over coolant flange/pipe out.  This made the repair very costly in labor.  Porsche later updated the parts so that the pipes could be replaced with the engine in-chassis.  The materials were updated as well – from plastic to aluminum.

Repair Process:

Generally the work is straight forward:

Start with removal of the airbox and air snorkel tubing.

Cayenne V8 intake

Remove intake manifold:

Cayenne V8 intake removed

Remove coolant pipes, note  that there is a grouping of three on the top and a lager single pipe underneath.

Cayenne – old plastic coolant pipe under intake

To remove the lower pipe you will have to cut it.  This is why, when repairing this the old way, the engine had to be removed – there is no ‘collapsing’ of the pipe so they can fit with the engine in-chassis.

NOTE – we stuff shop rags into the intake ports of the engine to ensure nothing accidentally falls into the engine!

Cayenne V8 with under intake coolant pipes removed.

Here’s a close-up of the back

coolant cross over pipe and hoses – rear of engine

Here was the actually leak – hard to see but if you look at the mirror in the middle of the picture you can see the coolant

Lower pipe leak

Here is the leak in the lower pipe (pipe removed).  NOTE this leak / crack in the pipe is much (much!) smaller than they typically are when we do this repair

Lower coolant pipe – crack in plastic

Here’s the new / updated parts.  NOTE how the larger pipe is now shorter and Porsche have provided a short rubber hose.  This change in design is what allows the repair to be done in-chassis (saving very large amounts of labor).

updated coolant pipes (aluminum)

This is a little closer look at the lower three-piece pipe

updated lower pipe design

Going back together – here’s the pipes installed.

new coolant pipes intalled

close up of collapsible / three-piece lower pipe installed.

Conclusion:

After re-assembly we pressure test the system and get the engine up to temps / ensure there are no other leaks and the repair should out-last the rest of the vehicle.  NOTE sometimes this coolant leak can also damage the torque converter seal (!) – this is usually the case when a LOT of coolant has washed down the back of the engine.  BUT if the vehicle develops a transmission leak shortly after this ‘event’ that is likely what happened.  This leak or defect has given the Cayenne a bit of a bad reputation but we advise to consider it in context:  the is a top-end performance SUV that is otherwise a blast to own and drive.  We see this repair occasionally but it’s not an epidemic.  Let other people think it’s a huge problem and then buy yourself a cool V8 Cayenne for a good price – reduced because of everyone’s fear of this problem!

Vehicle Details: 2005 Porsche Boxster S.  65,000 miles

Technician: Brad

Initial Condition:

• Loud Engine Noise (sudden)
• ALL Dash Warnings on
• Towed in

Diagnostic Process:

Physically inspected engine – found broken-off water pump pulley:

Boxster broken water pump pulley

Upon closer inspection it was clear this was NOT the vehicle’s original pump but it WAS a Porsche-OEM replacement.

Brad, as a Gold-Meister Porsche tech with over 15 years experience had never seen this before.

Boxster water pump shaft sheered-off

The pump’s impeller was NOT ceased.  Pump had been seeping from the bearing (see yellowish material on pump).

Conclusion:

Boxster new water pump installed

This story ends well:  a new pump and belt and then a good road test demonstrated a successful repair.  No other cooling system or engine damage occurred.  This success was due to a diligent client that pulled over immediately and called in to the shop to arrange a tow-in.  AMAZING to see a problem like this but it goes to show anything can happen.

This failure could have been avoided:  the oil pickup tube was clogged from a previous repair.  The timing guides were starting to fail and thus were replaced / the shop didn’t sell the additional work of removing the oil pan to clean the pickup tube.  As a result pieces from the timing guides made their way to the pickup tube and restricted oil flow.  This lead to oil pressure loss and catastrophic failure of the main bearings.  Net Result?:  Whole engine replacement for this otherwise perfect X5.