Tuesday, July 26, 2011

Sludge


Three months ago, a 2006 Audi came in for an oil change.  We’d never worked on it before.  We did an oil service and some other routine work.  The car left, and we didn’t hear from its owner until today.

After lunch, I got a call from a garage in Colorado who had the car in for service.  The mechanic told me the car had 54,000 miles on its odometer – 4,000 more than when we had it here.  He said the car came in with a cam adjuster fault code, and the engine oil was very dirty.  In response to that, he drained the oil, ran BG engine flush through the motor, and changed the oil again.

The mechanic said that the oil was very black, which caused him to think we must not have changed it.  He alleged this supposedly overlooked oil change caused the customer’s present problem, which he believed to be sludge buildup causing the cam adjuster to act up.

In response to his allegation I reviewed the internal shop ticket for the car.  The ticket showed the technician worked on the car a total of 5.1 hours on March 22, and the materials charged on the final bill were pulled from stock.  An oil change was indeed on the list of tasks.  There was absolutely no reason to doubt the oil was changed from the records I saw.

However, it raises a good question.  When someone comes in for a service like an oil change, and then says “you charged me for it and never did it,” what do you say?  When you put a new tires or wiper blades on a car, they are plain to see.  However, new oil looks pretty much the same as old oil, much of the time.  

You can recognize new oil right after it's installed, but in some engines it will be black the very next day.  Unfortunately, those tend to be the engines whose owners generate complaints.  To answer, I first say we are presumed to have done what we say we did, in the absence of evidence to the contrary.  When a bill says "change oil" most people accept that the service was provided as described.

The “black looking oil” cited by the Colorado mechanic is not evidence that we hadn't changed it.  It was just black oil.  No more, no less.  Since visiting our shop, the car was driven cross-country, from Massachusetts to Colorado.  If the car had sludge in the engine before we saw it, the detergents in the Mobil 1 would flush it and as a consequence the oil would be black, after 4,000 miles of cross-country driving. 

All the oil companies stress that point - you cannot judge the suitability or age of modern engine oil by looking at the dipstick.  Analysis is needed.

I’ve seen Mobil 1 oil turn black quite rapidly in other sludged motors, during my twenty-five years in this business.  For all I know, this engine is no different.   Black oil after driving to Colorado is not evidence of anything but a dirty motor. 

The only way to know what happened inside that particular engine would have been to sample the oil and send it to Mobil or another lab for analysis.  That’s not possible in this case because the shop owner drained it and flushed the engine.  For other people who have the same question in their own cars, oil analysis provides valuable insight.  If you were charged for a certain oil and you doubt you received it, analysis of a sample is the only way to resolve the question. “Looking dirty” is not the basis of an informed decision.

More important, analysis will tell how often the oil should be changed based on wear in your motor, and how it's holding up. 

Sludge buildup is a big problem in some of today’s cars; one that is widely known as the result of extended neglect, or repeated use of oil with the wrong rating for the car.  It’s not a problem that crops up all of a sudden, if the car was driven a few thousand miles past the target oil change interval.   Sludge buildup happens as a result of short duty cycle driving patterns combined with too-infrequent service intervals over a long period of time.

Mercedes, BMW, and Audi all specifiy oil change interval of 10,000 miles or more, which many mechanics feel is too long.   The only way those intervals can be met without sludge buildup is by the use of special long-life synthetic oils.  Use of inexpensive conventional oil is a recipe for disaster when change intervals get long.  Even with good oil, many prefer to change more frequently, using intervals of 7,500 miles instead. 


Many people encounter sludge when they buy a used car, only to discover it had poor care or no care earlier in its life, and they are now the recipient of whatever problems will ensue.  If you suspect your engine has sludge buildup, I encourage you to use an oil with strong cleaning properties, like Mobil 1 0-40, and change it every 4-5,000 miles until an analysis shows the engine to be cleaner.  In some cases, engine disassembly is needed to resolve the problem.

If the sludge stays in place in a motor it many not do any harm.  The risk is that a sludge clump will break loose, clog a vital oil passage, and precipitate the failure of the engine.  It's the automotive equivalent of a stroke.

The whole issue of sludge damage can be prevented with more frequent service.  Take better care of your car, and this won't happen to you.

Sunday, July 17, 2011

Rover V8 head gaskets

With all the talk of Land Rover liner failures in the pushrod V8's you might think head gaskets are no longer a problem.  Not so!  Here is what happens when head gaskets fail slowly . . .

This photo shows a failed gasket.  There is a split in the material right next to my finger







The area at the top is the part that surrounds the water jacket, visible on the left  side of the frame below. These V8 motors have coolant flowing into the head at the front and rear of the block, through the tall narrow passages.  There is no from from block to head for the middle cylinders; hence you can only have a head gasket coolant failure on an end cylinder.

The picture below shows how the coolant turned to steam and scoured the interior of the cylinder.  That steam cleaning is visible using a borescope; it's a positive means of identifying internal failure through the spark plug holes.  If you see that telltale on an end cylinder it may be a head gasket or a block failure.  In a middle cylinder, it's block failure for sure.

One other thing this image shows is how the block became slightly eroded in the area of the leak.  If this engine were fixed by simply slapping on a gasket it would probably fail again.  The cure would be to deck the block, or fit a top hat liner.  Both those options involve total overhaul, though, so some would go for a used motor instead.


This photo shows a middle cylinder for comparison.  The effect of coolant scouring is obvious now.

Range Rover Sport front differential failures

When differentials fail in Range Rovers, they tend to fail in front.  Over the years we have changed 3-4 times as many front as rear differentials.  I'm not sure why that is, as the same part is used front and rear.  Some say it's because of the traction control.  Others suggest the front does more work because those are the steered wheels.

We recently had a 2006 Sport differential fail, at 75,000 miles.  The truck had Mobil 1 gear lub all its life, changed at 15 and 45k miles, yet the bearings came apart as you can see.


I wish I knew what we might do to avoid repeat failures, but I don't.  For now, we fit the factory replacements and hope for a preventative answer

Friday, July 1, 2011

Putting a new interior in a vintage Lincoln

This is a 1963 Continental Convertible project that we just delivered.  The task was to replace the old off-white vinyl interior with leather and wool a la Rolls Royce/Bentley.  This is the starting point:

















Here's the finished interior:





This is the whole car, headed home:


You could buy a car like this for ten grand a few years ago, but now good examples routinely sell for over $100K.  With that kind of value, owners are expecting a substantially different level of quality when it comes to workmanship.


This is a very nice example









We used Wilton wools under the floor, with heavy padding.  The feel is a lot softer than original.  The carpet edges are bound in matched green leather.  The same carpet is used for floormats, but the mats are edged in the same tan leather we used for the seats.





We covered the door panels in leather, and did contrast beading like the seats



The interior is totally transformed.  We dyed most of the original plastic.





Even when they have "leather interiors," many cars just have leather on the seat faces.  On this car, everything on the seats is leather.  In addition, it's Rolls Royce grade Connolly, not the vinyl covered stuff on most cars.  You can smell and feel the difference.  The piping makes for an interesting contrast.






Some areas that were originally plastic looked better in leather



This is the process of dyeing the dash:



We were able to get a near-perfect match between the leather and the dyed plastic.


Here are the newly remade seats.  As you can see, we made new springs and pads in addition to new covers.  That means the car "sits" like a new vehicle.  All too often restorers will only restore the parts you can see, leaving the innards tired and worn.




We made a rough template for the carpet, laid it in the car, marked, cut and stitched/bound it as you can see:



Quite a change from where we began: