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: 2011 Land Rover LR4 5.0L. Approx 80,000 miles.
Technician: Tyler
Client Concern:
- Sudden loss of braking power!
- Engine runs/idles fine. No Warning lights.
- Towed in
Diagnostic Process:
Pretty simple: brake inspection showed all four brakes good (brake pads / rotors / calipers). Brake master cylinder full of brake fluid and not brake fluid leaks in brake hydraulic system. Brake pedal very firm with very little pedal-travel. Test-drive (CAUTIOUSLY) demonstrated basic brakes working but NO power assist to brakes. Note that this vehicle uses a brake VACUUM power assist booster – a very traditional and wide-spread power brake system. Tracing the vacuum source line revealed a broken plastic fitting on the vacuum pump:
LR4 broken brake booster vacuum pump fitting – in engine bay
Further inspection showed that one of the engine drive belts had frayed and a sliver of it had broken off and (presumably) hit this plastic fitting and broken it – causing the vehicle to have a sudden loss of brake power assist.
LR4 – Jaguar AJ V8 broken brake vacuum pump
Land Rover broken vacuum pump output fitting – plastic fitting
NOTE – KEY to the problem is the location of the water pump belt in relationship to this vacuum pump’s fitting:
Land Rover V8 5.0L vacuum pump fitting near belt
The drive belt that you see in the picture is the water pump and cooling fan belt. It is of more modern design in that it is a ‘stretch to fit’ belt – it has no tensioner assembly – it is self tensioning. Our opinion is that this belt failed and hit the vacuum pump fitting and broke it – causing sudden braking power loss.
Repair Process:
The repair was straight-forward: replace the belt and the vacuum pump (the fitting is NOT available as a separate service part from Land Rover). Interestingly the vacuum pump was on national back-order through Land Rover USA and not available through aftermarket suppliers. Land Rover updated the vacuum pump part number (this usually means an update to the design) however when we received the replacement pump we were disappointed to see it still has a plastic fitting for the vacuum output.
LR4 new vacuum pump
LR4 new vacuum pump – front view
Land Rover V8 updated vacuum pump – plastic output fitting
Here’s the special tool used to help install the stretch belt. We suspect that the installation process can create abnormal strain and possibly premature wear/failure of the belt. This tool makes the job easier and reduces that risk.
Land Rover V8 5.0 stretch belt installation
Here’s the new pump installed – NOTICE the proximity to the water pump belt:
New Vacuum Pump Installed
Technical Discussion:
Traditionally a brake vacuum booster is provided its vacuum by a large vacuum hose attached to the engine intake with a one-way check valve to preserve the vacuum. Some engines – notably Diesels – don’t produce vacuum and thus the design has to change to either an alternative vacuum boost or other power source. Some manufacturers have elected to use hydraulic pressures for this type of system with the most common being General Motor’s Hydraboost system – which taps power from the power steering pump. Other manufactures continue to use vacuum as the brake booster power source and add an auxiliary pump to produce the needed vacuum. As brake vacuum pumps were introduced the typical setup was to provide the brake vacuum boost system with two vacuum sources: a pump like this on AND engine vacuum. This Land Rover setup uses a vacuum pump exclusively and, unfortunately, the physical location and the decision to use plastics makes this engine and its vehicles susceptible to loss of brake power assist. Our advice to vehicle owners: be sure to service your belts before they fail. Our advice to the vehicle engineers out there: if you MUST use a design like this have a belt guard or more substantial materials to ensure a belt failure cannot cause braking power loss.
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: 2002 Land Rover Discovery II. Approx 165,000 miles.
Technician: Tyler
Initial Condition:
- Drivetrain and vehicle vibrations – more with speed
- Loud Undercarriage Noises – increasing with speed
- Loud snapping noise and vehicle stops
- Engine runs/idles fine. No Warning lights.
- Towed in
Diagnostic Process:
Pretty simple: a physical look undercarriage showed a broken front driveline. The picture below is with the transmission already out of the truck. The U-Joint on the left side is the guilty party. This U-Joint started to fail and, because the symptom of more drivetrain vibration and noise wasn’t addressed, the joint eventually failed. This caused the driveline to spin out of control and smash a huge hole in the transmission case.
Land Rover Discovery broken drive shaft and transmission
Here is a view further back of the damage.
Discovery transmission case broken from bad front drive line.
Conclusion:
Land Rover Discovery transmission removal
The solution is simple / although painful: the truck needs a new transmission and drive line. The tragedy here is that this is completely preventable: had this come in for service when the drive train started getting loud the repair would have only been to replace or rebuild the drive line. Any Land Rover specialist like us would proactively inspect this drive line whenever such a vehicle was in for service. Additionally, despite having a less-than-perfect reputation in other areas, the Discovery’s transmission has actually a good reputation for reliability and longevity.
Tyler fixed it.
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.
Vehicle Details: 2000 BMW Z3 2.5L, Automatic Transmission, M54 Engine, 35465 Miles
Technician: Tyler
Initial Condition:
- Check engine light on
- Engine is running rough
- **had recent oil change
Diagnostic Process:
Scanned vehicle and found the following faults In the Engine control module (DME):
- P1522 control VANOS position inlet camshaft
- P1520 control VANOS end position fault, exhaust camshaft.
- Ran test plan for the VANOS control on both the intake and exhaust and discovered that the VANOS degree angles were not changing.
- Removed oil filter cap and inspected oil filter, looked newer and was not plugged.
- Removed the filter and found that the oil filter housing had been broken from someone doing an oil change.
Broken oil Filter Housing
- Removed all of the remaining pieces of metal that were in the oil filter housing and replaced the broken oil filter housing unit.
- Started the car and re-Ran VANOS tests and again found that The VANOS degree angles were not changing.
- Removed the VANOS and disassembled and found that there was a piece of metal inside the unit that was causing the exhaust VANOS valve to hang up in its bore and not allow oil pressure to the VANOS gear/Timing actuator causing the angles not to change.
Vanos disassembled
Replaced the VANOS Unit with a rebuilt one and test drove the car and reran the VANOS tests and the car is performing well now.
Conclusion:
The client confessed to doing his own oil change and not being able to remove the oil filter cap. As a result excessive force was used on the filler cap causing the internal metal flange to break. Had he then replaced the oil filter stand before proceeding further the vanos would probably not have been damaged. This is one of those tougher lessons to learn about not ignoring something that is broken. End result was good: the car runs well now. Had more metal circulated through the lubrication system there could have been much more extensive engine damage. Great work Tyler on figuring this one out!
Vehicle details: 2007 Cadillac DTS 4/Automatic transmission/ Cadillac Northstar V8 engine 124,820 miles
Technician: Todd Hansen
Initial condition:
- Stabilitrac light on
- Loss of engine power
- Rough running
Out of State Cadillac dealership attempted ABS repairs / no luck. Recommended engine tear-down and partial (or possibly complete) engine rebuild. Client came in looking for an alternative solution.
Diagnostic Process:
- Monitored engine data with scanner and verified misfire on #6 cylinder as well #8 cylinder.
- Removed #6 and #8 spark plugs, performed simple/basic compression test on those 2 cylinders, results:
- #6: 0 psi
- #8: 175 psi
- Tested Cylinder #6 further: leak-down test and wet cylinder compression test – still: ZERO compression. So far – dealership recommendations are correct: The engine clearly has a mechanical problem.
- Valves, or their ability to seal compression into a cylinder, usually fail for one of three reasons: They overheat and their sealing surfaces pit – causing poor sealing (this is condition is called a BURNT valve).
- We ruled this out because burnt valve conditions will cause low compression that will increase during a wet-cylinder test.
- Knowing the client was looking for the possibility of an alternate solution we got out the borescope camera to get pictures of the inside of cylinder #6.
- The borescope found one of the intake valves stuck open in cylinder #6 – creating a no-compression condition.
- We now know: the engine has a possible bent valve or broken valve spring.
- We also know: a BENT valve was not very likely because this problem was only in ONE cylinder. Bent valves are caused by out-of-synch timing components and thus almost-always involve more than one.
- Removed valve cover
- Removed intake camshaft for that cylinder bank and confirmed that the valve was stuck open due to a broken valve spring:
Northstar broken valve spring.
- Replaced the valve spring, valve seal and keepers – a job that can be done with the engine in-chassis and without engine disassembly if other tricks are used.
- Re-assembled engine and retested: Smooth running engine / no more misfire codes!
Conclusion:
Often dealerships will take the less risky road with repairs. This is common with franchises since they are required to perform their services and their service recommendations within standards agreed upon that allowed them to become a franchised representative of the manufacturer. Our alternate repair required buy-in from the vehicle owner and more risk since the possibility existed that time taken to diagnose and perform this alternate repair could have proven unsuccessful and thus resources would have been wasted. The tipping point came from the use of the bore-scope – a tool that is simple in concept but very powerful. End result: better information lead to a better solution. The client’s out-of-pocket expense was less than 25% of the dealership’s proposed repairs.