LEYLAND 680s AND HERITAGE DMUs

Response to Railtrack's "urgent safety related defect report No. NIR623 dated 9/10/98" relating to a Scottish Class 101 DMU. Comments added by M.G. Owen of Class 107 Limited.

Introduction
The report concerning a Leyland power unit model no. 680/1 series informs us that a connecting rod burst through the engine block. It does not inform us of the reason[s] nor of Scotrail's reaction to the incident. I would like to take the opportunity to record my experience of a "near miss" with a Leyland 680/3 series which I encountered on our power car SC52006, which hopefully will assist private preserved DMU owners, avoiding the possibility of losing their power units in a similar manner.

Brief History of the 680 Series

The majority of private owners have little or no knowledge of the origin of their main power units, except the withdrawal date of the particular DMU set. Leyland diesels or Leyland built many hundreds of Leyland Series 2 and 3 power units, the original Leyland Series RE680/1 were first supplied to BR in 1959. The three types are:

Series 3 is a hybrid 680 called a Leyland L11, or a TL11 cylinder head mounted onto a 680 block and sumps, but with an Austrian Friedman fuel pump in lieu of the typical Lucas CAV system. This Leyland modification was introduced during 1987. Six hundred were built specifically for railway use.

The 680 diesel power units have given many years of service by being systematically overhauled at the old BR works Derby/Doncaster, latterly at Crewe. Consequently their life expectancy has been stretched over the past 25 years. It was envisaged by BR during the late eighties that the disastrous TL11 model would replace the 680s on the remaining Heritage Class DMUs.

All model/variants of the Leyland 680 have an anticipated design mileage of 500,000 and is regularly achieved when applied to road coaches, Leyland Tiger and Olympian Buses and Aveling Barford heavy dump trucks but is rarely achieved in its DMU role (the same phenomenon applies to the Wilson self-changing gear boxes).

In Service Problems
A consistent inherent cause of premature failure of any diesel engine is excessive periods of idling - this in turn causes carbon build-up to form as the engine running temperatures are well below the design values, i.e.

If allowed to continue over lengthy periods interrupted by periods out of use, carbon deposits will adhere to the piston crown and exhaust valve areas. The oil scraper rings become gummed up - ceasing to become effective and causing lubricating oil to pass into the exhaust system, thus accelerating the degenerative process.

Privately owned preserved DMUs are usually stored for weekly-monthly periods of time. During these periods it has been proved that the main crankshaft oil seals dry out and in some cases harden up, causing lubricating oil leaks. Many Heritage DMUs suffer to some degree as oily deposits are evident around the flywheel areas.

A further common defect is cylinder head gaskets tending to leak internally. Evidence of this has been discovered in our vehicle SC52031 whereby water was discovered in one cylinder bore, making starting difficult. The long aluminium cooling manifold can corrode, especially on the cylinder head adjacent to the injectors. The power unit may sound healthy, i.e. it fires regularly and evenly, emitting a brownish exhaust under full power when up to full working temperature as no temperature gauge is fitted to most units, this is difficult as it takes up to 5 miles to bring a typical power unit up to speed.

The usual signs of heavy breathing through the rocker cover vents - oil - steam - are the normal signs of wear and tear. Water lubricating oil contamination is serious, the power unit should be "stopped" immediately. Regular oil filter/oil changes are recommended, i.e. every 12 months. Sump oil samples can be analysed at most ex-BR depots and a small charge may be levied for this, but it is worth considering. It in doubt - get it out. Before the power unit self-destructs!

Removal of Leyland 680 Series Power Unit
A 3tonne forklift truck complete with fork extensions is a must, as the power unit weighs in at 900kg, i.e. 1 ton.

After removing all the connections, i.e.:
Fan shaft
Water outlet
Water inlet
Saloon water heater connections
Compressed air
Starter motor
Fuel connections

A detailed engine removal and installation guide is available from Class 107 Ltd., taken off the Regional Railways Job Sheet No. MP1/06 dated August 1996 Revision B. (This is available to all DMU owners for £1.00 including postage and photocopying).

An inspection pit is also desirable for this operation. After careful removal the unit should then be taken to a suitable workshop either within their premises, or more usually a diesel engine specialist.

Preventive Action
We selected A.B.E. Diesels of St. Helens, who we considered more than capable of fixing our Series 3 680.

It was collected, steam cleaned - stripped right down into its component parts, assessed, discussed and repair agreed with us at the factory. The prescription needed to complete and return our power unit to "as new" condition.

Two pistons were well on their way out. The cylinder heads leaked across internally. The saloon water heater return connection on the cylinder head a large hole was revealed in the casting. As previously mentioned the long water jacket cooling casting had failed electrolysis and antifreeze, but was easily replaced from their vast store of stored TL11s.

The Cure
The power unit was rebuilt using genuine Leyland components, i.e. piston rings, valves, springs etc. The fuel p/p was calibrated and tested. The fuel p/p drive (very often fails in service) was checked and found to be satisfactory.

Upon completion the power unit was bench tested to the appropriate BR WOSS specification and then repainted and matched up to its original Leyland beige.

Conclusion
There are numerous genuine diesel engine specialists, but few have railway DE knowledge, but most can bench test your spare power units for a small (£150) consideration.