Tuesday, April 21, 2015

When starters go to die

We’ve all heard the noise – a horrid metallic grinding as the car’s starter tries to engage a running engine.  What’s it mean when you hear that noise and the motor isn’t running?

It could mean the starter is going bad.  More often, it means there is a damaged spot on the ring gear, the big gear on the motor that the starter engages to turn over the engine.

In extreme cases, the starter can totally destroy itself and the ring gear. 


Sometimes you can make the symptom go away by fitting a new starter.  But the permanent fix is to change the starter and ring gear, which requires removal of the transmission for access.  Here are some examples from a Porsche 911 in our shop today . . .





For comparison, here is an undamaged starter gear . . . check out the difference



John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent restoration and repair specialists in Springfield, Massachusetts.  John is a longtime technical consultant to the Porsche, Mercedes, BMW, RROC and other car clubs, and he’s owned and restored many fine vehicles.  Find him online at www.robisonservice.com or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.



Thursday, April 16, 2015

Fixing oil leaks on British Motorcars

Rolls-Royce and Bentley motorcars are renowned for their ability to leak oil.  They do so from orifices, joints, and sometimes through seemingly solid metal.  Today I’d like to show you how we address crankshaft oil leaks at the front of the engine. 

A Rolls-Royce V8 being assembled after overhaul at Robison Service (c) JE Robison
The early V8 motors used a loop of rope to seal the hole where the crankshaft emerges from the timing cover.  Behind the rope they had a large washer – an oil slinger – whose job it was to “sling away” most of the oil on the end of the crank, so it didn’t reach the seal.

Rope seals had their origins on steam engines, where they could be wrapped round a shaft and held tight by a large covering washer and nut.  “Tightening the seals” was a regular activity on those old engines.

Inboard power boaters know those rope seals as the gland nuts and packing that seals the propeller shaft where it passes through the hull.  Rope works well there, too, as long as you keep it lubed and tight.

The rope seal doesn’t work so well in a car.  When rope is packed into a groove in the timing cover it seals for a while.  The oil behind it ensures it stays lubricated.  But at some point the rope will wear, and with no way to tighten it up, it will begin to leak.  Collector cars are particularly problematic in this way, because they sit a long time, and the seals dry out.  Then when they are started the dry seals wear quickly until they are wetted by fresh oil. That leakage produces the characteristic drip spots under the front of these motors. 

Traditional Englishmen took those drips in stride, but they prove vexing to many Americans, who are accustomed to leak-free vehicles.  Fix it, they say!  But that’s easier said than done.  When it comes to the free expression of lubricants, British cars are most easily treated with acceptance.  Fixing a front seal leak on a V8 Rolls requires extensive disassembly of the front end, to allow removal of the crank pulley.  Only then – after a couple days of hard work – can you see the seal.  But even now it’s not accessible for change.  No.  The front cover must be removed and once it’s off, you can refit the same piece of nineteenth-century sealing technology, and hope it holds a few more years.

We have a better answer here at Robison Service.  100-some years after the rope seal was invented the idea of using rubber seals came along.  Rubber seals backed by springs are much more durable, and more effective.  State of the art seals that use modern synthetic rubber (pioneered by the Germans in WWII) are even better. They are one of the developments that made the modern leak free car possible.  We can install those seals in your vintage car, and together, one by one, we can stop its ugly drips.

Removing parts to access the front seal - engine removed for ease of service
Here’s a series of photos showing the front of a Rolls-Royce V8, the covers removed, and the new metal and rubber seal.  Through hard work and diligence, we have brought the sealing technology of 1965 to this 1972 Rolls – a feat the original carmakers could never quite accomplish.  It took BMW ownership – and a multi-billion dollar investment – for Rolls-Royce Motors to do this on a production scale.  We can do this on your car for a tiny fraction of what BMW paid.

If you have a leaky old engine, and you want the bleeding stopped on a more permanent basis, this is the way to do it.  Just remember though – this article addresses ONE leak spot.  The typical British motor has over 117 points of potential leakage, all of which must be addressed to eliminate drips.   Many mechanics say that’s simply not possible.  We just say it’s difficult.


But we love challenges, and we are British car fixers through and through.



We remove the front cover, and machine the cover to accept a modern seal, which is pressed into place.  Once done, the seal can be serviced without removal of the front cover.  



Here is the new seal, set in place, prior to refitting the cover.


John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Rolls-Royce and Bentley 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 www.robisonservice.com or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.

Friday, April 10, 2015

Suction Throttle Valves and other vintage Rolls-Royce AC troubles

If you have a 1965-1976 Rolls-Royce or Bentley, and you have weak air conditioning the problem may be in your suction throttling valve.  If your air conditioning can’t be adjusted – whether it’s on weak or full blast – the suction throttle valve is likely at fault.  If your AC system won’t make normal pressures, and it’s full with a good compressor, the suction throttle valve or expansion valve are almost certainly stuck.

Both valves are located under the brake reservoir.  The suction throttle valve’s job is to regulate the amount of refrigerant delivered to the expansion valve. By doing so it regulates the capacity of the refrigeration system.

Look for the suction throttle and expansion valves on the left fender well, under the brake reservoir 
All the valves in the Shadow climate control system are operated by servo motors.  This one is no exception.  The servo pulls the valve open, and springs on the body of the valve pull it closed.  You can see those pieces in the photo of the valve, removed from the car.

Suction throttling valve with the operating servo attached, removed from car

Several things go wrong with the suction throttle valves.  All the problems are illustrated in this series of images, of a valve from a 1972 car.

Deformation of the valve body is obvious in this top view of the suction throttle valve
The first problem comes from the heavy springs used to pull the valve back to its resting position.  Over time, the strain from those springs warps the housing and when it warps enough, it jams.  That is a recipe for failure on most of these.  Albers sells a machined aluminum replacement that is less likely to deform in that manner, as shown in the photos.


A new machined housing next to the old suction throttle valve
When the housing warps the piston can't move in the housing.  If this state of affairs is sustained over several years or decades (as is often the case) the valve may be held quite tightly by corrosion.  We soak then in penetrant and knock them free.  The diaphragm on the other side is replaceable.






The next thing that happens is that the valves clog with debris.  The desiccant leaks from the receiver drier and small particles clog the screens on this valve and the expansion valve.  When the screens clog the air conditioner quits working, but not before the compressor has been ruined by trying to pull a vacuum too long (in most cases.)
Sediment from a clogged throttle valve
Clogging is a problem in every vintage Rolls.  In my opinion, the screens don't serve much purpose and you're better off taking them out.  If the screens are in place, the clog and the system fails.  The clogged part has to be found, removed, and cleaned or rebuilt.  Without screens, the valves might eventually clog, but it would take longer and it might never happen.  

Rebuilt Rolls-Royce suction throttling valve with attached servo
Suction throttle valves have not been used in cars for 40 years, and they are unknown to younger technicians.  But they are essential to the good functioning of your car's AC system.

Till next time
John Elder Robison


John Elder Robison is the general manager of J E Robison Service Company, independent Rolls-Royce and Bentley 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 www.robisonservice.com or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.