We had another annual tech session at our shop on Saturday, March 28, 2015. (click on the picture to see larger versions)
First up was a quick lesson on fasteners, their materials, the advances BMW have made, and the importance of torque specs.
Our second topic was all about BMW’s cooling systems. Including water pumps, system bleeding, electric water pumps, and why thermostats can set check engine / service engine soon codes in the engine computer (DME).
Our last topic focused on BMW’s V8 engines (did you know BMW used to make pushrod V8-engines? – don’t worry we didn’t either)… We covered the strengths and weaknesses of the M62 series V8s including a dead 4.4L and a dead 4.6L
A special thank you to the Utah BMWCCA chapter and to Michael Bontoft for the photography. See you next year!
Vehicle details: 2007 Cadillac DTS 4/Automatic transmission/ Cadillac Northstar V8 engine 124,820 miles
Technician: Todd Hansen
- 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.
- 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:
- 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!
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.
Vehicle details: 2009 Mini Cooper S / N14 Engine / 66,xxx miles
6 speed manual transmission
Technician: Tyler Seawright (Master ASE Certified)
- check engine light on, hard starting condition and noisy engine.
- Dealership diagnosed as valve timing problems: Broken timing guides, bad VANOS pulley, and possible other repairs needed
- Client came in looking for a second opinion
- Verified with computer diagnostics: misfire codes for all of the cylinders
- Visual inspection of ignition components (spark plugs and coils) suggested they were ok
- Tested basic engine datastream – found all parameter data with the engine off was correct, IE Coolant temp, Oil Temp, Battery voltage, Etc.
- Monitored low side fuel pressure (the N14 is equipped with direct fuel injection system so it has 2 different fuel supply systems): Low side fuel pressure system was good.
- Attempted to start the vehicle and it started.
- Ran running fuel pressure tests. Fuel pressure within specs
- When running the DME (engine computer) set a code “2B64 Intake manifold, unmetered air“.
- Per MINI’s technical service bulletins, removed the valve cover to physically check the valve timing. With the camshaft alignment tools in
place we found that the valve timing was correct.
- Also inspected timing chains, guides, and tensioners: all ok.
- Further running tests found that the variable Valve timing( VANOS) degree measurements would not deviate from 36degrees.
- Monitored the Duty Cycle command to the VANOS Solenoid actuator and noticed that the Duty Cycle was changing when being commanded from the DMEto change but the actual valve timing was not changing.
- This lead us to a physical fault with the VANOS system that cannot truly be measure electrically by the DME.
We removed the VANOS Solenoid and found that it was physically broken and was not able to supply engine oil to the VANOS gear and therefore would not change the valve timing. (pictured below – broken solenoid in front / new (good) solenoid behind)
This is a classic case of a physical inspection trumping what a diagnostic tree / computer diagnostic process suggests. The dealership followed all MINI protocols and formal test procedures to conclude, consistently but incorrectly, that the problem was with the physical valve timing components. Knowing that as a weak-spot in this engine design, MINI’s repair suggestions weren’t a bad thing for the vehicle but would not have fixed the client’s concerns.
In the end, we saved our client over $1300 of misdiagnosed repairs. A big win!
This engine is not equipped with a oil level warning system to alert the driver that the engine oil is getting low. We Suggest that every other time you fill your car with gasoline, Check the engine oil.