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Welcome to the official Dorman Diesels website

Welcome to the official Dorman Diesels website

1869 – 2023

Dorman Diesels

We provide spares, servicing and support for all Dorman engines, old or new. We also supply parts for the Perkins 4000 range of engines.

When an engine does breakdown, Dorman Diesels is committed to ensuring an engine is operational with minimum delay, achieving the urgent despatch of replacement parts by the fastest means possible.

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Ongoing reliability ensured

Our warehouse facility in Lincoln stocks thousands of line items and holds over half a million individual components.

Our workshop facilities are available to enable us to undertake a full overhaul of customers’ engines and major components. This support is extended worldwide through our contract maintenance and servicing schemes.

All service work is carried out to the same high standards by factory trained engineers who have an extensive knowledge of our products, gained both through specialist training and practical experience. Our engineers are specially trained in diagnostic techniques and to undertake preventative maintenance.

Frequently Asked Questions

The History of Dorman Diesels

Founded by William Henry Dorman in 1869 on Foregate Street, Stafford, W.H.Dorman began by manufacturing cutting tools for the footwear industry, but soon began to produce more specialised machinery such as printing, sewing and grinding machines.

A selection of historic Dorman literature taken from Grace’s Guide to British Industrial History. Copyright © Grace’s Guide to British Industrial History.

Design department at Dorman Diesels factory on Tixall Road, Stafford, photo taken around 1985. Copyright © Staffordshire Museum Service and the Staffordshire Past Track website: www.staffspasttrack.org.uk

In 1903 W.H.Dorman produced its first internal combustion engine for the emerging motor car industry; this became the main activity of the company.

During the First World War the company was made a Controlled Establishment under the Conditions of War Act and made a notable contribution to the war effort, especially in the development of aerial warfare.

In 1929 Dorman began to move part of the plant to a new 20-acre site on Tixall Road, Stafford. By 1939 the manufacture of engines for road use had ceased and the company began to concentrate on the production of industrial and marine engines.

In 1939 the Ministry of Labour requisitioned the Foregate works for use as a training centre for engineers. The remainder of the plant transferred from Foregate Street to Tixall Road and concentrated on the production of industrial and marine engines.

In 1959 W.H.Dorman bought the old established Stafford engineering firm of W.H.Bagnall’s Ltd.

W.H.Dorman was taken over by the English Electric Company in 1961 and by 1979 Dorman Diesels Ltd. was a subsidiary of GEC producing Dorman Diesel engines at Stafford and at the old Ruston & Hornsby factory in Lincoln.

The Dorman diesel engine business was bought in 1987 by Broadcrown and was later purchased by the Perkins Engines Company of Peterborough in 1993. The last Dorman-branded engine was produced in 1995, however the DNA of the Dorman engines lives on to this day in the form of the Perkins 4000, which is a development of the Dorman SE.

In 1998 Perkins sold the Ruston & Hornsby range to RHL Spares Ltd following the closure of the Dorman Diesels Central Spares Division in Lincoln. Formed by a group of experienced former Dorman employees to support the Ruston & Hornsby and Dorman Diesel engine ranges; RHL purchased the stock and rights to exclusively support the old Ruston & Hornsby range of engines. The RHL Spares business was purchased in 2006.

In September 2010 Perkins Engines agreed to sell all of the Dorman Diesels non-SE related parts business including all of the technical records and intellectual property relating to the ST, DA,Q, J, L, LS, P, Y, Monair, F, and DWD engine ranges.

“It’s a joy to work with Simplex-Turbulo. Their customer service is fantastic: speedy and friendly. This is what all suppliers should aspire to.”

Robert Cooper
Managing Director
Lunar Marine Trading Ltd

SLX Group testimonial

“I must admit it has been a pleasure working with Simplex-Turbulo again. Your engineer has been very professional and meticulous in the way he has approached the challenges we have faced. He has tested the seal boxes at every step, in order to minimise the risks of leakage when we filled up.”

Alex Munro
Vessel Superintendent
DOF (UK) Limited

SLX Group testimonial

“Big thanks for fantastic cooperation we have had through entire project with your Simplex Engineers. Your lead engineer has presented himself as a professional individual providing us constant feed-back info on every single stage of project, he’s showed very good planning, communication, engineering, managerial skills and personality, big respect from rest of his Team and Borealis Technical Crew.
It has been a pleasure to have them on site and work together, looking forward to future operation.”

Tomasz Jaron
Dry Dock Superintendent
Fred. Olsen Cruise Technical

SLX Group testimonial

Contact us

Call us

+44 1522 781706

Email us

Find us

Dorman Diesels Limited
Great Northern Terrace
Lincolnshire LN5 8HJ

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Solid and reliable

  • A1 credit rating
  • ISO 9001 certified
  • £5m product liability insurance
  • Founded 1935

Solid and reliable

Latest News


Dear Dorman Diesels,

I have a Dorman 4LD engine powering a Newage 67kva Generator that has done less than 200 hours from new, and I need a new lift pump as the one currently installed does not work. I will use this unit to power a small coal recovery plant on my site.

The engine is a DORMAN 4LD – engine number: 04035 / 0972 / 121 – and this unit was originally installed as a back-up generator in an Aerospace Manufacturing Plant in London in the 1970’s or so I believe, and I have had it running. It runs very well, but now the lift pump is not providing any fuel to the twin fuel filters that are installed in-line, before fuel is supplied to the SIMMS Fuel Injector Pump.

The lift pump currently installed does not look quite right to me, though it has the original Dorman Green Paint on its body and it seems to have been removed and refitted, probably many years ago.

Anyway, can you supply me with a new lift pump and if so then please let me know the cost and how I can pay. I would like any parcel to be delivered – to the address below – by Royal Mail – as I find couriers unreliable, so please include for this in your charge.

Any hints or tips you can give me will be most welcome.

Could you advise oil capacity for the following please:
Eng No 082322/0590/001
Eng No 123392/0690/003
Dear sir,

We have a milk processing factory and it was established in 1956. We have a Dorman generator in our milk collecting centre at the moment, that generator is no longer in working condition due to under compression state. We couldn’t find any local agent that could repair it, so we disassembled the engine and we found the piston rings, scraper rings and cylinder liners should be basically replaced. So can I know about the possibility of getting spare parts and technical and operations manual of this generator engine? Details of the engine is given below. I decided to do that repair due to alternator side is in good condition. Thank you.

Engine type – 6LB
Make – W.H Dorman & co. ltd, British
Serial No – 71976
Spill – 26”
Hi all,

Would you be able to provide any details or information on the attached engine please, we have just taken into stock?

We believe this is a Dorman 6750 Diesel Engine complete with Clutch, 6-cylinder engine.
Hi there,

I am trying to track down a manual for a Dorman 6 Cylinder Diesel (Type – 6LB, No. 68068, Crompton Parkinson, 3 Phase 77.5 KVA).

Was hoping you may know how to get a PDF of the manual?
Hello, we have a Dorman Diesel Generator at one of our telephone exchanges, undergoing repairs at the moment.

I am hoping to get access to a schematic, of sorts, for the pulley wheel tensioner for the fan belts, as we have none of the original documentation on site.

The pulley tensioner had broken off so we’ve had a new pulley machined, but unsure on the order for the parts to go back together.

I have attached some pictures for reference, the generator details are as follows: Dorman 12QV 170kW Generator S/N 94282.
Dear sir,

We have faced with piston breakage on our generator.

Engine type: 8SETCA2
# 082323/9524/I56

Generator: Ser. Number: C060072/02

Please give us information about:
Causes of breakage
Spare parts offer for repair
Offer for repair and service
Other recommendations.
There are some pictures attached from broken parts.
Good morning,

We look after a 12 and 6 PTRC engine for a customer here in New Zealand and have a couple of questions regarding each engine.

The 12PTRC engine turbos were recently sent away for overhaul only to come back as possibly corroded together and unable to be disassembled, also the turbo charger repair company noted that these turbos are obsolete and have been since approx 1998.

The number on the one of the current turbo chargers is:
Make: Holset

Do you know of an equivalent turbo that will fit this engine for continued operation?

Also regarding the 6PTC (r) engine it currently has, I believe, the original oil filter arrangement with cartridge type filters, is there a kit available to modify this to spin on type oil filter?

Bit of a long shot, and probably not something you deal with.

A friend of mine has, what is believed to be, the last early Pagefield lorry left in existence.

He’s looking for a Dorman 4JO engine, or parts. Even a 2JO would be a start.

Would anyone know of any, or maybe contacts I could approach?
Kindly help me out with the above engine timing please for a Dorman 12QT.

I do appreciate your response.
One of my DORMAN diesel generator sets was out of work. Could you please notify us of the details of the gensets data, like engine flywheel dimension and others?

Can you please send me a wiring diagram to this ECU for a Dorman 12STCA?
Good morning,

Hope all is well your side. Is it possible to help with a engine spec sheet for a Dorman 80TK model? Looking for fuel consumption, kw of engine and info about the gas flow exhaust.
Hi Mate

Hope you blokes are well over in England….

I’m enquiring about an engine rebuild kit and workshop manual for a Dorman 4LDT.

Please reply when you have a chance.
I was wondering if you could help me out with obtaining the SAE sizing for my Dorman 12STCA R3?

I am trying to fit a new generator alternator to the engine.
Hello there,

We have been tasked by our customer to completely refurbish a fire pump that was purchased from us back in 1999.

This fire pump was fitted with a GEC Diesel Ltd, 12ST engine with the serial number 12131/0682/010.

If possible, please can you provide a list of the components (both electrical and mechanical) that will need to be replaced as part of the refurbishment?

I am considering buying a restored 1962 Dorman 3LB for a new narrowboat build and wanted to know what parts availability was like for this engine please? Also if you have any comments about the suitability of this engine for a narrowboat?

I’m in Western Australia and have a marine vessel fitted with a Dorman Diesel engine. The previous owner has no information on the engine. At this stage all I can find is 6L 750 stamped on the side of the engine. Is there a Dorman supplier in Australia that I can contact for information?
Good day,

I am operating “E range vertical diesel engine” as power supply for our milling machine. Engine number: 78ESL6B418 Works order: BE 13753.

So what happened is when we started the engine 4 days ago it worked just fine for about 2 hours and suddenly the water pump alarm goes on and the engine shut down. I had an engineer here looking at the water pump. He said that the water pump is working just fine. So he said that he needs the parameter sheet for this engine so he can diagnose the failure and the spare parts needed to fix it!

I’ve been looking through the web this morning and I found your website and see that you specialise in this engine. Can you supply me with the manual of parameters for this engine. And do you have spare parts for it available?
Good evening and thanks for the chat on the phone about these engines.

I think the head gaskets have gone as we have water in the pots. We have removed the injectors and swung it over and yes water was expelled.

What would you recommend? Also, what’s your approx. price to put right if it is head gaskets? Is there anything else we need to check?
Dear all,

We have a diesel engine DORMAN type 6QT.

What is the oil capacity for drain maintenance?
Hi, I have a Dorman 5 cylinder diesel engine, Type 5LD, engine no. 97241. Telex no. 36156.

I want to know what it is worth.

It is in mint condition, with only 828 hrs on the meter.

Please advise.
Good morning.

I am currently testing a Dorman SET 12 CA2 Engine. Could you tell me how many teeth the flywheel has please?
We have an 8QT 26L engine, what is the fuel burn per hour of this at 1500rpm with loads of 25% 50% 80% and 100% load?

What hp is this engine?
Hi Dorman Diesels,

We have a large engine (Dorman 6LDT) that you have manufactured and would like some info on it if that is possible?

It is in good working order and used as an emergency backup power generator, for our reheat furnace water cooled system.

The only info I have on it is on the name plate, as above – I can’t find any information on the model on-line, only info regarding the history of your company.

If you have a manual or any info on manufacture date, specification, parts / service info, it would be much appreciated.

At some point in the future I would like to get it serviced by a specialist, can you recommend anyone local, or if your team do onsite servicing?
Good morning

We have an air cooled Dorman Diesel six cylinder engine type 6DA no.91739. This motor was originally coupled to a generator approximately 100 kv.

We wish to couple a Warman pump. Serial no.S36960. 6” inlet 4” outlet to the motor. What hp rating is the motor? Can the injector pump be rated for greater hp if needed?
Hello, I am hoping to get some information pertaining to the engine above.

Can you tell me how much gear oil is required. Also, any information on its clutch would be fantastic.
I want to change the oils in a Dorman 6QTV. Could you please tell me what is the oil capacity for drain maintenance and also at what oil pressure should the engine be operating? Thank you in advance for your time.
We own a 6LDTCA II used as a power generator, but we don’t have any kind of manual for it. Do you have available, in a PDF file, a service , parts and owner manual for this engine?
I have been asked to remove a generator from a basement of a building and was hoping you might be able to provide me with the drawing or weight of the engine – the ID plate is for a Dorman 6SETCA(2).

© Copyright 2023 Dorman Diesels Limited, Great Northern Terrace, Lincoln, Lincolnshire LN5 8HJ, United Kingdom
Tel: +44 1522 781706.