Thursday, October 30, 2014

Blown Head Gaskets in Bentley Turbo R and Azure

“My Bentley overheated, and now the engine is smoking.” As the cars age, I hear that more and more from Turbo R and Azure owners.  As the story unfolds, the narrative often runs something like this:

“I pulled out of my driveway and went down to the ramp for I-95.  I gunned it to move up the ramp, and accelerated to 80 in the left lane.  I looked down a moment later and the temperature gauge was all the way to the right.  I started to pull over, and the engine stalled.  When I started it back up, smoke came pouring out from under the hood.  You’ll have to send a wrecker for it.”

Steam comes out of the head bolt holes on a Turbo R with blown gaskets
Coolant leaking from head bolts is a sure sign of head gasket failure, and maybe more damage

People describe the problem as head gasket failure, but it’s often quite a bit more involved.  And it’s happening more and more as these fine cars age.

When you look at the motor on one of these cars you may actually see coolant coming out around the head studs as shown in the photos above.  Most times, though, you don't see anything but steam from the radiator and bubbles in the expansion tank. What’s that tell us? It means the head gasket has blown out, and the motor has to come apart.

A Bentley engine with heads removed (c) J E Robison Service
An assembled Bentley Turbo motor, vintage 1996 (c) J E Robison Service
How far apart, you ask?  It depends on how much damage the engine has sustained.  It's hard to know that until it's taken apart, and even then you may not be able to tell. The only sure cure for overheating damage if a full rebuild, which few people want to do.  So we take apart the top and see what we can see . . . 

Rolls-Royce Bentley V8 with 20 head studs on each side (c) J E Robison Service

To begin, all the turbo and intake piping comes off, and the valve covers are exposed.  The covers come off, as do the rocker shafts and exhaust manifolds.  The head bolts are now exposed, 20 of them on each side.  The first clue to the extent of damage is how tight those bolts are.  If they are still torqued that’s a good sign.  If they are loose you should expect some trouble and possibly a number of pulled studs.

Once the head is off you can often see the blowout.  In my experience the cylinders that are physically closest to the turbocharger are the most likely to fail.  The next photo shows a blown head gasket.

Bentley Turbo motor with head removed - front two cylinders have blown out
When the fire ring fails (that’s the part of the head gasket that seals the combustion chamber) the combustion gases burn through the inner gasket material and pour into the cooling passages.  Check out the closeups in the photos below.  The hot combustion gas fills the cooling system with bubbles, which reduces the efficiency of the coolant.  It also pushes coolant out the radiator overflow as the system is over pressurized.

Bentley Turbo - head gasket blown at the bottom on both cylinders (c) J E Robison Service

That is the means by which head gasket blowout translates into an overheating failure.  But that’s just the first step . . .

Closeup of burnt Bentley head gasket - blown into water jacket. The red band is part of the head gasket - it's extra sealing around a cooling water jacket area. As you see, the gasket is burned through from there into the combustion chamber seal (c) 2014 J E Robison Service

When the engine overheats the metals expand.  The aluminum block expands more than the steel studs, so the tension on the studs rises as the motor heats up.  That’s good to a point, because it makes the head gasket clamp tighter at normal temperatures.  But when the motor overheats – particularly when an area near a stud gets really hot – problems develop.

When the aluminum expands the stud stretches, and the gasket compresses . . . to a point.  Beyond that point, the studs pull out of the block, taking the threads with them.

Here’s a pulled stud, with strands of aluminum block clinging to it.

Bentley head stud with threads pulled (c) 2014 J E Robison Service

I used to think these Bentley head gasket jobs were simple.  Not anymore!  It seems like every one we've seen in the past few years has had more complications than the one before.  Most of these engines have one or more pulled studs and some have other damage.

Head stud and insert (c) J E Robison Service

A repaired head stud (c) 2014 J E Robison Service

The most common stud failures are on the top and bottom rows.  That's lucky, because the center rows studs can't be fixed without stripping the block.  If you fix studs, it's absolutely critical that you drill the repair holes straight.  If the studs are even a little bit crooked the head won't go on!  The photo below shows the alignment fixture we use to drill straight holes.

One engine this summer got hot enough in the front cylinder to melt the injector tip.  What do you do then?  A wise person would change all 8 injectors on a 20-year-old car, but that is several thousand dollars of parts.  When the fuel rail is apart don't forget the other o-rings that you can't get at when the motor is together.  Repair of these motors can get expensive fast.  You don't want to ask how bad it can get because the answer is over $50,000 as of 2014.

Before you dismiss that number as crazy, consider these costs if you drive your Turbo Bentley until the engine overheats and seizes

  • Rebuild long block engine after major failure - $35,000
  • Replace melted injectors and rail parts - $3,000
  • Replace water pump, radiator, coolant hoses and thermostat - $3,000
  • Replace other heat-damaged parts - turbo, pipes, possibly catalyst - $3-6,000
  • Labor for all this work - $10,000+
All you can do is shut the motor off the moment you see it's overheated, and hope your case is not the worst case.

When an engine has gotten hot enough to pull studs you have to look for other issues.  The first is warpage.  The heads are almost certainly going to be warped, and we would surface them as a matter of course.  The mating surface on the block – called the deck – may also be warped, but it’s not so easy to fix that.  The only way to true a warped deck is to remove the motor, strip it completely – including stud removal - and then machine it flat. It's very common for people to skip this step - "just throw some new gaskets in and per er together" - but that really just sets you up for later failures, often worse than the first one.

Here’s a cylinder head after it’s been surfaced.  The surface is uniform and smooth but we had to shave off .008 to achieve that.  If we had skipped that step the head gasket would have been overstressed in the high spots and under stressed in the low ones.  That's why surfacing is important.  

We also do a full valve job, to ensure the car runs as smooth as possible.  I often see shops skip this step too, but why?  If you can spend a few more hours here and get a smoother car, why would you not do that?

Bentley cylinder head ready to install (c) J E Robison Service
When studs pull out of the block you have two choices.  Mild damage can be fixed with a Heli-coil insert.  More major damage calls for a solid insert.  In both cases the fitment of larger inserts between the stud and the block makes for a stronger joint than original. That means we can assemble with 110% of the original torque, which reduces odds of failure even more.  Strong studs - strong engines.

What's the typical repair consist of now?
  • Remove heads, clean all parts, and check for damage. Always pull both heads, even if only one is blown.  If you don't, the other side will fail soon after.  We have learned that the hard way.
  • Check the heads for cracks and warping, and do a full valve job with guides and seals.
  • Check all the injectors and replace all fuel injection o rings.
  • Replace the thermostat, belts, and other consumable parts.
  • Use a fixture to test torque the head studs 20% tighter than stock and ensure they do not begin to give way when left overnight.  Repair any that are marginal.
  • Use a gauge to check block flatness and consider full overhaul if the warpage is more than .004
  • Replace all the hard rubber hoses in the center engine area - this is your time to get at them easily.
When you do all this work, you always wonder . . . is this as deep as the damage goes?  Unfortunately, there is no way to know, short of total engine disassembly.  It’s possible the pistons have seize damage, and it’s possible the liner seals are damaged.  There are other possibilities too, but they are less likely.  You can look for evidence, but if there's nothing to see you have to put it together and hope for the best.  

What can you do to check for other damage?
  •        Look at the cylinder walls for signs of scraping.  That could be evidence of piston damage.  If you see this, the engine should be removed and the pistons pulled.
  •        Look at the oil, and sniff it. Is it burnt?  Burnt oil is a very bad sign because it means the core of the motor got very hot.
  •        Look at the amount of warpage in the deck.  If you have .003-.005 of warping (measured with a good straight edge) that’s probably ok.  .010 of warping and you may have bigger problems that will necessitate engine removal.  When the metal is warped at the top it may be warped at the bottom, and if the crank journals are out of true the engine will eventually fail.

 Why do these engines fail?

That's an excellent question.  Here's my theory.  When the car is new the head bolts are torqued to around 50 foot-pounds.  With 20 bolts per side, this adds up to many tons of clamping force on the gasket surface. This force is increased every time the engine gets hot, and it's relaxed when the motor cools down. When the motor is overheated the pressures skyrocket.

After a few such cycles the gasket gets squeezed a tiny bit thinner, and the torque on the bolts starts to drop.  The result - lower clamping force on a cold engine.   When the motor heats up, all is still well because the thermal expansion tightens everything up.  But on a cold engine we have an incipient disaster.  When the low clamping forces of a cold engine with relaxed torque come up against the high cylinder pressures of a turbo engine under throttle the result may be a blowout.

That is why Bentley Turbo head gaskets blow out on cold engines.  Hot motors are much less at risk. It's one more good reason to warm your Turbo up thoroughly before you get into the throttle.

Bentley engine - always check the desk surface for warpage (c) J E Robison Service
We use Copper-Cote to help seal the head gasket after a blowout.  Reassembly of a Turbo R (c) Robison Service
Applicability of this article:

The information in this article applies to all Bentley Turbo R, Continental R, Continental T, and Azure cars, from the late 1980s to the early 2000s.  It's also mostly applicable to newer Bentley cars (Arnage, etc) with the 6.75L twin-turbo motor, though the teardown and reassembly of those engines may be more complicated and they are likely to have additional damage.

Bentley Continental T (c) J E Robison Service

Bentley Azure (c) J E Robison Service

Bentley Turbo R (c) J E Robison Service, Springfield, MA, USA
Give us a call at 413-785-1665 if you'd like to talk about a Rolls Royce or Bentley engine repair.  We handle all aspects of engine service and rebuilding.

Robison Service has provided independent service, repair, and restoration for Rolls Royce and Bentley owners all over New England for over 25 years. Our company is an authorized Bosch Car Service Center. We also service Mercedes, Jaguar, Land Rover, Porsche, and MINI motorcars. We have flatbed transport throughout the region. We also offer pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.

Monday, September 15, 2014

Is a Software Bug Setting MINI Coopers on Fire?

In the summer of 2013, we got a call from the owner of a 2008 MINI Cooper S, an R56 model. She’d gotten in her car to go to work, and her power steering wasn’t working.  We got the car in, and found a burnt steering motor (EPS) and a damaged high power electrical connector.  We replaced the parts, checked the coding, verified that the steering worked, and sent her on her way.  We’ve replaced quite a few steering motors so this one didn’t raise any eyebrows.

A year later the pump failed again.  This time the connector actually melted enough to separate from the steering motor.  When the owner tried to plug it back in the sparks told him to back off.  MINI supplied a new motor and connector under parts warranty, and we changed them.  Once again the steering worked.  We thought it strange that the motor we changed a year ago would fail.

A month later the owner drove the car to dinner and parked it for the night at 8PM.  Twelve hours later – at 8 on a Sunday morning – a neighbor spotted smoke coming from the MINI’s cowl.  The owner opened the hood to find a fire above the new EPS steering motor.  It seemed like it had gotten hot enough to start a fire.  What was going on?

The car was examined by two forensic investigators, each representing insurance companies that might be involved in settling the claim.  The first investigator’s job was to learn whether the EPS started the fire, and if so, if there was a workmanship error in its fitment. There was no error found.  Installation of the motor is simple and straightforward.  

The second investigator built on the first investigator’s findings, in an effort to further understand the cause of the fire.  Both investigators agreed that the fire was started by an overheated EPS unit.  The question was, why would the EPS overheat and start a fire after sitting overnight?  There is no circumstance where the power steering motor should activate in a parked and locked car, 11 hours after it was parked for the night.

The EPS just sits there when the car is parked.  It draws no power at rest, and should have been at ambient temperature by late that night.

A conversation with the owner revealed that this was a pattern of failure.  The steering never failed when the car was in use.  Instead, the motors burned out while the car was parked.  The complaint was, “no steering when I got in the car,” as opposed to, “the power steering quit while I was driving.”

We began to wonder how many other MINI owners had experienced similar failures.  We searched our own service database and realized most MINI power steering failures we’d seen were “in the morning” as opposed to “while driving.” An Internet search raised quite a few more possibilities.  And we read of some troubling and unexplained fires in parked cars.

The investigation has ended – for now at least – with no definite answer.  The car’s insurance will pay off, and the owner will get a new car.  We were never able to determine what woke the car’s electronics up and caused it to start steering till it caught fire.

We were able to determine that the car slept most of the night undisturbed.  An analysis of the charge in the battery told us how much energy the steering motor had absorbed.  A calculation told us how rapidly that had to occur, to build enough heat to start a fire.  Another calculation told us how fast the steering could heat up, given the limitations of fuses and wiring.  We determined that it woke up and started trying to steer 30 minutes to an hour before catching fire.

That raised an interesting possibility.  Could the car have been woken up by radio signals, and come to life in an unexpected and destructive way?  We know the pushbutton entry system can do more than unlock the car.  So can the radio link that the BMW/MINI service and concierge people use.  Might something have come into the car through those channels?  We don’t know.  It’s an idea, but without more evidence we are stumped.

What’s your experience?  Do you know of a MINI that caught fire while parked, with no good explanation?

Robison Service has provided independent service, repair, and restoration for BMW and MINI owners all over New England for over 25 years. Our company is an authorized Bosch Car Service Center. We also service Mercedes, Jaguar, Land Rover, Porsche, and Rolls Royce and Bentley motorcars. We have flatbed transport throughout the region. We also offer pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.

Monday, September 8, 2014

Fixing Grinding Noises in Mercedes Transmisisons

Do you have a grinding noise in your 2007-2013 Mercedes 4Matic gearbox? Do you hear a grind that starts at low speed and increases as the car speeds up until it’s so loud you’re afraid to drive it? Many people confuse the noise with wheel bearing failure, but it’s not. The 2008 and new C-Class 4Matics are prone to this same failure. S550 and C300 4Matics are the most problematic. If you’ve got either of those models, read on.

We’ve seen several W221 S-Class Mercedes 4Matics with noisy transmission / transfer case assemblies, and we’re thinking this may become more common as the vehicles age.  The cars we’re seeing have 60-90,000 miles on their odometers when they start grinding.

Our most recent client came to us after the local Benz dealer told him he needed a new transmission, because Mercedes didn’t want them making internal repairs.  He thought $6,000-some was a lot of money for a bad bearing and he asked if we could help.

Of course we said yes.  Lead tech Danny Ferrari in our Mercedes shop removed the transmission and tore it down, whereupon the failure was obvious.  The bearings had failed. The ones that carry the transfer case shafts and take the load from the driveshaft had totally come apart.  It seemed like an easy fix, but Mercedes does not sell internal parts and they build this gearbox in-house.

We have spent the time to locate sources of original quality repair parts overseas, and we’re now able to fix these formerly unserviceable units. We can generally save you a few thousand dollars over the cost of a dealer exchange part.

Our shop can perform any service or repair on these fine cars, including transmission services. However, there’s no preventative maintenance we know of that will head off this bearing failure. It may be that the load on these bearings is just too much for their size, or there may be another cause.

If you've got an older Benz, look to us for transmission fluid flushes, filters, repairs to the sensor plate, and repair of leaking electrical feed-through connectors.  The older Mercedes transmissions are showing more problems because the years and miles are piling up, but we can fix anything that happens to them.

From what we can see the repaired transmissions will last as long as the originals, and repair takes less than a week, start to finish, for most units.  J E Robison Service is a Bosch Car Service specialist in Springfield, MA.  Find us at 347 Page Boulevard, in the Springfield Auto Complex, in Springfield, MA 01104.

Robison Service has provided independent service, repair, and restoration for Mercedes Benz owners all over New England for over 25 years. We also service BMW, MINI, Jaguar, Land Rover, Porsche, and Rolls Royce and Bentley motorcars. We have flatbed transport all over the region. We also offer pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.

Visit us online at or call 413-785-1665.

(c) 2014 John Elder Robison

Friday, August 29, 2014

The Commodore's Jeepster

When you’re the Commodore and you can buy any new car you want, what do you choose?  It’s a weighty decision.  After all, as Commodore, you set the standard.  That means you can’t just buy a mass-produced idea of style and form.  You must create your own; an expression of automotive craftsmanship fine enough to park beside the finest hand built yachts. You commission a motorcar as others commission a new kitchen.

It’s a hard choice, but someone has to make it.  American or foreign?  You’ve got both, and for this car, it’s going to be American.  They build some beautiful yachts in Europe but our native craftsmen are very fine too.

Sedan or utility?  That’s an easy question.  This vehicle’s job is to travel to the waterfront, and there may be a need to carry rigging, guests, live bait or giant fish.  An open utility is the only answer.

Open car or closed?  It’s summer on the oceanfront, folks! The only way to ride is under and open top.  How else will you move the fishing poles, and how will parade guests stand and wave? Open tourer it is.

Now we’re getting down to it.  Who makes such a vehicle?  Not Cadillac.  Not Lincoln. Not Chrysler. International Scout?  Too boxy.  One of the best loved open top sport utilities in the postwar period is the Willys Jeepster.  That, folks, is the Commodore’s Choice.  Isn’t this a magnificent example?

The common Jeepster had an economy level of finish, with inexpensive vinyl seats and basic, simple trim.  But even simple can be interpreted with beauty.  Basic lacquer can be replaced with the finest Glausurit urethane finishes.  Basic vinyl seating can be replaced with the finest leathers.  Wilton wool can pad the floor better than tar paper.

It didn't start out that way.  This is what we began with. And it was described as "restored!"

What did we do instead? Try powder coated seat frames, new marine plywood bases and cushions, Connolly leather upholstery and top-grade Wilton carpet. Which seats would you prefer?

Some people would change the engine for a new hot-rodded piece of iron.  But why? This engine was good enough to take American solders to victory all around the world.  Surely a rebuilt version can take a few modern day connoisseurs to the club and back!

This is the famous Go-Devil motor, the engine that earned a reputation as “the motor that won World War II” in the original Jeep.

Here's how it began . . .

And he she is today . . .
1948 Jeepster engine bay with Go Devil engine

You won’t win any drag races in this old Jeepster, and you won’t be running the fast lane on the Interstate, but in a car like this you will have something truly unique.  Like a fine wooden boat, this is a car to treasure for a lifetime.

There’s restoration, and then there’s Restoration.

We started with what was optimistically called "a well restored example."

In the image above expert body man Al Keinath looks at what we're facing.  Three different shades of burgundy on the nose alone. A full quarter-inch of plastic filler in some spots. Rust holes covered in household caulk. A cardboard firewall that's painted car color to hide the crumbling. Chips, bangs, and nothing fits. It takes two hands to shut the door, and a good kick to get it open.  The bottom of the hood has a layer of black goo to hide the imperfections.  And the condition of the undercarriage . . .

But we will make it new again! Better than new, in fact. We'll be finishing this with the level of  craftsmanship you find in a fine wood boat. No corners cut in this job . . 

Reshaping the rear contours

The body work is done on a stand

A thousand little parts to refinish or rebuild

Almost ready for paint

Lots of metal work

The burgundy paint is on!

Painting the gloss black two-tone

Some final welding on the body

The convertible top attachments are handmade wood

Inner panels get painted first, in Glausurit

Fitting the frame for the convertible top

Fitting up the interior

The finished body

Rebuilt engine and transmission ready to install.

The Go-Devil engine goes back in place

Installing new vintage wiring

Summer has arrived, and this 1948 Jeepster is once again . . King of the road . . .

At Robison Service, we started out restoring European classics, many years ago. We were lucky to find patrons who appreciated our work and commissioned more and more. As we grew, people asked for higher and higher standards of workmanship.  I wasn't surprised - after all, we worked on some of the finest cars in the world.  Mercedes-Benz, Bentley, and Rolls Royce. Then people said, "Can you do that level of work on my father's old Willys?" And of course we can.  And we did.  These are the cars America grew up with and loved, interpreted in a whole new way.  You may have seen Jeepsters, but I guarantee you've never seen one like this!

The greatest thing about these projects is that each one is totally unique. I'm proud to call them expressions of the auto restorer's art; translating our client's visions into drivable pieces of sculpture..

John Elder Robison is the general manager of J E Robison Service Company, independent restoration and Bosch Authorized Car Service specialists in Springfield, Massachusetts.  John is a longtime technical consultant to the Land Rover, Porsche, and Rolls Royce Owner's Clubs, and he’s owned and restored many of these fine vehicles.  Find him online at or in the real world at 413-785-1665