Monday, December 22, 2014

When Heat Fails Us

This is the time of year when we depend on heat in our cars.  For most of us, the heat delivers on its design promise.  For a few unfortunates, though, it doesn’t.  The mechanic checks the coolant level, and makes sure the thermostat is working as it should.  If the engine is up to temperature the next place to look is the heater control circuitry.  When all else fails we are left with the possibility that the heater core itself has failed.

Heater core replacement is the automotive equivalent of a root canal.  It's ugly, painful, and costly but sometimes it has to be done.

Heater cores are like small radiators that shed some of the engine’s heat into the passenger compartment.  There are two ways a heater core can fail – by leaking or by clogging.  Leaks are obvious because you’ve got coolant all over the floor.  Clogged cores are more subtle.

Take a look at this core from a 2006 Land Rover LR3.  There’s nothing obviously wrong from outside, but when we cut the core open we saw a different story.  The whole far side of the core is clogged.  Only the left side of the core remains open.

You might think that would cause weak heat, but it actually created a different problem. This Land Rover – like many other late model cars – has separate temperature controls for the driver and passenger.  The air that blows through the core is sent to the left and right sides respectively, so with one side clogged we had normal heat on the passenger side, and virtually no heat for the driver.

This seemed like a control problem but it wasn’t.  When heater cores clog the repair is often a big deal.  In this Land Rover the whole dash had to come out for repair, as you see.  Jobs like this can run into multiple days of labor, and cost thousands of dollars.  And this is no place to cut corners looking for a low bid – this is detailed work.  Every fastener left loose, and every broken bracket is a potential rattle.  There are a hundred electrical connections, and any that come loose are problems for tomorrow.  This is work for someone who knows Rovers and specializes in large interior repairs.

When a job like this is done there will be faults in the airbag system and many other dash electronic systems.  The person who does the work will need to have a factory-level test system to clear those faults and ensure everything is working as it should.

 At Robison Service we are proud to be known as experts in repairs like this.  Author John Robison is a long time Land Rover service manager, and a technical advisor to many Rover clubs.  He’s written many articles on Land Rover service – indexed here.

No Land Rovers were harmed in the writing of this story, and environmentally friendly repair methods were used throughout.  We are located in Springfield, Massachusetts, where we stand ready to provide top-quality service and repair to owners of BMW, Jaguar, Land Rover, Mercedes-Benz, Porsche, and Rolls-Royce and Bentley motorcars.

© J E Robison Service

Wednesday, December 3, 2014

An Index to John Robison's Land Rover Service Thoughts

The Supercharged Range Rover (c) J E Robison Service

The ex-Buick V8 that Land Rover sold in America from 1987-2004 was never known for its reliability.  However, things took a sharp turn for the worse in 2002, and the last Discovery engines appear to have been doomed from the start.  Here are three articles about internal problems in the V8s:

V8 engine failures - slipped liners and more - from 2009

Should you rebuild a failed Land Rover motor? I have an article about that situation here that covers the decision process

What's the latest on top hat or flanged liners? This article tells all you want to know about the flanged liner overhaul

Discovery II models also have a problem with frame rust.  We first began to see this in the spring of 2014, when we saw several trucks whose rear frames rusted right through over the winter.  These vehicles seemed more vulnerable to rust than the earlier models.  Read this article to find out why, and what you can do about it.

Are you thinking of restoring a Land Rover?  This article shows some of what's involved.  This article explains the difference between repair and restoration, two very different processes.

If you drive a Range Rover Sport or LR3, read this story on differential failures

And if your supercharged Rover is losing power - read this

Programming keys for your Land Rover is here

(c) J E Robison Service

John Elder Robison is the founder of J E Robison Service, independent Land Rover specialists in Springfield, MA.  John's shop has supported Land Rover owners since 1987. They are experienced at all aspects of service, repair, overhaul and restoration.  Find Robison Service online at or on the phone at 413-785-1665.

Friday, November 28, 2014

Index to Rolls Royce and Bentley tech tips

Bentley Arnage - (c) J E Robison Service

A rare Rolls Royce Corniche S - (c) J E Robison Service

I've written quite a few articles on Rolls Royce and Bentley, and I have begun gathering them together here.  One day I'll probably turn them into a book.  Till then . . . Feel free to comment or offer corrections.

Thoughts on buying a used Rolls Royce or Bentley - applies to Silver Cloud and newer series cars

More thoughts on Spur - Spirit - Turbo era car buying

Thoughts on restoration - applies to all cars

Evolution of the RR/B models - Silver Shadow through Arnage/Seraph - original article from the Robison Service website

Inspecting a Rolls Royce or Bentley - Applies to Corniche, Continental, Azure, Turbo R, Mulsanne, Eight, Turbo R, Silver Spur, Silver Dawn, Silver Spirit

More Things to Look For in a 1981-2000 Rolls Royce or Bentley - this is the original article from the Robison Service website

The last Crewe built Rolls Royce convertibles - applies to 2000-2002 final Series Corniche

Repairing convertible top hydraulics - Applies to 1996-2004 Rolls Royce and Bentley Corniche and Azure cars

Head gasket failures in Bentley Turbo cars - applies to Turbo R, Continental R and T, Azure, Arnage

Checking engines after head gasket failure - Applies to all cars

Checking and inspecting Rolls Royce hydraulic systems - all cars after Silver Cloud and print to Silver Seraph. Applies to all Shadow/Spur era vehicles

Case Study - brake failure in a Shadow - Silver Shadow era cars with RR363

Rear suspension gas springs - Applies to all 1981 - 1999 cars prior to Silver Seraph

Changing batteries in seat and ECUs, Applies to 1980s-1990s Silver Spirit / Silver Spur / Mulsanne /Eight / Turbo R

Changing alarm ECU batteries,  Applies to 1980s-1990s Silver Spirit / Silver Spur / Mulsanne /Eight / Turbo R

Servicing Shadow and Spur series brakes - applies to 1966 - 1999 cars after Silver Cloud and prior to Silver Seraph

Alcon racing brakes for Continental and Azure - Applies to all 1990s cars but most particularly to the final series Azure, which had these brakes fitted at the factory - a unique variant

Fixing Power Steering Leaks - applies to 90s cars with the reservoir above the alternator

Questions and answers on collector car storage - Applies to all cars

Evaluating paint - Applies to all cars

I hope you find these suggestions useful, and I wish you luck and success, keeping your Rolls Royce or Bentley motorcar on the road!

Best wishes

John Elder Robison

John Elder Robison is the general manager of J E Robison Service Company, independent restoration and repair specialists in Springfield, Massachusetts.  John is a longtime technical consultant to the RROC and other car clubs, and he’s owned and restored many fine vehicles.  Find him online at or in the real world at 413-785-1665

Wednesday, November 26, 2014

Convertible Top Repair in Bentley Azure / Rolls Royce Corniche

Convertible top hydraulics are shaping up as a major weakness in the Bentley Azure and Final Series Corniche from Rolls Royce.  These cars were built from 1996-2004 (a newer Bentley variant remains in production today) and all are vulnerable to this issue.

The Bentley Azure and RR Cornice are fine cars but the tops are a weakness (c) J E Robison
Here’s the problem, in a nutshell.

The engineers at Crewe wanted to design a fully automatic convertible top for the new Azure series.  But they did not have the resources to do a new design; they had to adapt something else that was already out there.  The Mercedes SL500-type design was well regarded, and they chose to adapt it to the Azure body.

Unfortunately, the design didn’t work as well on the RR/B.  It’s remarkably reliable on the Mercedes, and astonishingly flimsy and incredibly costly to fix on the Azure.  What went wrong?

There are a few essential problems.  First, the systems use very high hydraulic pressures.  Older automatic tops used big cylinders and rams.  With several square inches of ram, you don’t need very high hydraulic pressures to generate the force to move the top.  However, the newer cars use tiny actuators hidden in the top. They are smaller, so the hydraulic pressure needed for a given actuation force rises.  Because the hydraulics are hidden, they are often at a mechanical disadvantage (leverage in reverse) and need to push harder to move the top.

The result:  hydraulic pressures on a 2001 Bentley convertible top can run almost 10 times as high as the pressures on a 1987 Bentley convertible top.  With that factoid in mind, it should not surprise you that the newer tops are not as reliable.

In addition, the newer tops use automatic latches instead of human power to pull it shut and locked.  Those latches are not as rugged as they should be.  Why, you ask?  Look at a Bentley Azure and then look at an SL500.  What do you see?  The Bentley top is significantly larger.  That multiplies the forces on every component and it’s one more reason a reliable Mercedes design didn’t work out the same on the RR/B.

The next problem probably started in Crewe’s engineering department, though I doubt they would admit it.  Mercedes uses plastic lines that are impervious to hydraulic fluid, but that material selection did not translate to RR/B. Someone there chose a hose material that deteriorated with contact with hydraulic fluid.  The result – when they get to be ten years old you see the black rubber casings falling off the hoses, and blowouts inevitably follow. 

How do you check your convertible top hoses?  Look at the hoses in the main hinge area when the top is partly lowered.  Here are examples of hoses that are coming apart.

The upper photo is a closeup of jacketing peeling from a hydraulic hose.  Failure is imminent (c) J E Robison Service
If this problem is ignored you will see leakage, as evidenced by the leaked oil in these photos.

Leaked hydraulic oil in the convertible top well (c) J E Robison Service
Oil seeping from the convertible top hydraulic line bundle 
If you ignore it even longer, you will eventually be showered with oil when a line blows under pressure and the interior of the car is sprayed and damaged.

Header bar line with deterioration.  These are the worst if they blow
"Green showers" most often come from the header bar, when the lines above the rear view mirror blow out.  The reason those lines are the first to blow is that area takes the most beating from the sun. In a hot climate that area can be over 200 degrees all day, and the oil they originally used breaks down into a green jelly that won't pump, and causes pressure surge and blowouts.  Jaguar is known for having this problem too.

The new hydraulic oils are synthetic and they resist this, but the moral there is - change your top hydraulic fluid every few years, or else.

When the top is partly folded there is another thing you want to check – the cables.  These new automatic tops need to fold into a tight space to be hidden under the rear deck.  To do that they rely on cables sewn into the top lining.  Loops of wire around those cables pull the top fabric against the bows and fold everything properly.  If the cables break the top will jam in the bows, and if the bows bend as a result – you have big trouble.

Broken stay cable on Bentley convertible top
In most of these cars you will see leakage from the hydraulic actuators in addition to problems with the lines.  Here is a set of actuators removed for service.  We rebuild these units rather than replace them.

So how do you fix this?  You remove the trunk lining, and the pump and lines.  Open the convertible top boot and remove the top as an assembly. Remove the cover in the convertible top well, and unthread the lines there.  Remove the rear seat, both side panels, the right side floor covering, and the right side dash and windshield pillar trim.  Remove the windshield header bar covers.  Remove the lines and remaining actuators.  Replace and reassemble.

Sounds easy?  Look for a job time of 60-90 hours, more if you are not experienced or run into trouble.

In the next convertible top installment I will begin to cover the actual repair process.

This article is about the automatic convertible top system used in Rolls Royce and Bentley Azure and Corniche from 1996-2005.  Check out this article for thoughts on the newer Bentley GTC convertible top and its problems

And here's an article on 1997-2005 Jaguar XK8 and XKR convertible tops - they have some of the same issues but are simpler to fix

Good luck
John Elder Robison

Robison Service has provided independent service, repair, and restoration for Rolls Royce -Bentley owners all over New England for over 25 years. Founder John Robison is a long time technical consultant for the Rolls Royce and Bentley Owners Club. 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 northeast region, and we work with Intercity and other transporters for greater distances. We also offer pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.  Our drivers are available to pick up cars in Boston, Hartford, Greenwich/southern CT, New York, Rhode Island, Vermont and New Hampshire.

Checking an engine after head gasket failure

Engines can have head gasket failure in two ways:
  • They can leak oil or coolant onto the ground, with no internal failure
  • The fire ring seal can fail, allowing combustion gases to pressurize the cooling system

Of those two failures the second is by far the worst because it’s usually associated with overheating and sometimes catastrophic engine failure.  The common dealership repair is usually to slap a new head gasket in place and send it down the road.  That works for some engines.  But on others, the result is a repeat failure – a month, a year, or three years later. 

A blown head gasket. Area in the red box is the coolant passage.  The half circle is the combustion seal 
Most of the cars we see are in this latter category.  For example, we get quite a few Land Rover engines that have a “history of head gasket replacements.”  No engine should have repeat head gasket failures.  When that happens, some repair step is being skipped, or there’s another root cause. 

Almost every engine we see needs some additional machine work when the heads come off.  That makes me wonder if the shops who are just slapping in a new gasket are ignoring that and trusting luck, or if we just see the “repeat offenders” because we are more a shop of last resort when the local mechanic could not fix the car.

How can you tell if a gasket alone will fix your problem?  You measure.  Read on, and I’ll show you how we check for problems and what we do when we find them. 

The first things we do are tank clean the head, and then blast it with walnut shell grit to get it as clean as new. Next we measure the head for flatness with a straight edge.  When aluminum heads are removed from an engine, they are usually slightly out of flat.  In addition, they can be corroded.  Sometimes we see damage from coolant gone bad, and we occasionally have to weld that up.  We also see cracks on some engines.  Cracks are typically repaired by welding too.  When all that is done, the surface of the head is machined flat.  If the engine is a V6, V8, or V12 we surface both left and right heads equally so as not to cause a compression imbalance.

Repaired cylinder heads for a Bentley (c) J E Robison Service

If an engine has more than 75,000 miles the heads will always benefit from freshening up.  In that, we reseat the valves, check the guides and fit new seals, and clean the ports. We check for valve seat damage, which will lead to burnt valves.

A burnt valve as seen in the head (c) J E Robison Service
Burnt valve removed from the head (c) J E Robison Service
If the owner wants his engine blueprinted we will also measure each combustion chamber’s volume and increase the size of small chambers to match the volume of the largest chamber.  This is typically done by grinding material away and by recessing the valves deeper into the seats.

The heads are the easy part.  Now we check the block.  We use a straightedge to measure the deck surface for flatness.  Sometimes we find broad warping, while other times we find depressions or valleys.  The head gasket can take up a few thousandths of warp, but a block with 5 or 10 thousandths has to be taken apart and repaired.  The reason:  major warpage of the deck often means the bearing journals are warped too, and if that is ignored the engine will have a lower end failure at some point.

Significant deck warping is a sign of major overheating. 

Illustration of a low spot in an aluminum block deck (c) J E Robison Service
The next thing we look for is out-of-round in the cylinders.  We measure the cylinder bore front to back, and inside to outside.  The difference between those measurements is called “egging.”  We don’t want to see more than .002 inch.  More than that and the piston rings won’t seal well, and the engine will use oil and possibly lose compression.  Egging is another sign of overheating.

We also make those measurements at the top and bottom of the cylinder.  Again we don’t want to see more than .002 difference.  Top to bottom difference is called “taper.”  When a motor has too much taper it may know, and that’s a sign it’s worn out.

Measuring cylinders for taper and egging, BMW V8 shown (c) J E Robison Service
Finally, we test the studs or the head bolt threads, particularly on aluminum engines.  We look for evidence of stripped or pulled threads, and we repair any damaged ones with inserts. An insert repair will be stronger than the original in most cases.

Repairing damaged head studs with oversize inserts Bentley V8 shown (c) J E Robison Service
If the block is out of spec in those areas it should be removed and overhauled.  We can fix dimensional errors like that in most cases.  The other thing we look for is corrosion damage.

If you think this sounds like a lot of work compared to slapping in head gaskets, you are right.  The gasket slap is a strategy for dealerships working on factory warranty (where it just has to last to the end of warranty . . .) and new cars (where corrosion and wear are seldom issues)  If you work on older vehicles, or if you want your repairs to be at least as good as original (as opposed to almost as good as original) this is the only path to take.

Quality engine work takes time, and costs money.  Jobs done correctly last, and the price is soon forgotten while poor quality never goes away.  

If you're wondering what's below the heads, read this story about liner failures in Land Rover V8's and how we fix them.

Good luck
John Elder Robison

Robison Service has provided independent service, repair, and restoration for BMW, Land Rover, Jaguar, Mercedes and Rolls Royce -Bentley owners all over New England for over 25 years. Founder John Robison is a long time technical consultant for the Rolls Royce and Bentley Owners Club. 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 northeast region, and we work with Intercity and other transporters for greater distances. We also offer pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.