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Engines

The following table provides a quick overlook of the main engine types used in BXs:

Date BX, BX 14 BX 16 BX 19 BX Diesel
BX E/RE
Leader
RS
TRS
RE TXi GT
TRS
TRI GTi GTi
16V
TZi 17 17 turbo 19
Oct 1982 150A 150C 171B                  
Sep 1983 162A
Oct 1984 171C 159A
Jul 1985 161A
Jul 1986 D2A DFZ
Aug 1986 D6A
Mar 1987 B1A/A D9B
Jul 1987 D6C
Dec 1987
Feb 1988 A8A
AJZ
May 1988
Aug 1988 K1G DDZ
Sep 1988 B2C B1E
Jan 1989 D2E DJZ
Mar 1990 DKZ
1991 BDY D2F D6D
1994

Engine variations

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All gasoline engines are four-cylinder, aluminum alloy, in-line, overhead camshaft, water cooled engines mounted transversely. The engine type can be found on the engine number and manufacturer's plates.

Engine oils

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The primary job of the oil you put into your engine is to stop the various metal surfaces from grinding together, causing rapid wear of the parts. At the same time it has to dissipate the heat generated from friction, to transfer part of the heat of combustion away, to hold the byproducts of the combustion in suspension, not allowing them to stick to the engine parts. The oil has to comply with all these requirements under significant pressure and a wide range of temperatures ranging from the chilled engine in a winter morning to the high temperatures in an operating engine. In addition, it has to retain its performance under these varying circumstances and to remain reasonably stable until the end of the recommended oil change period.

Oil Additives

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The advice is plain and simple: never use them! There are many oil additives and so called engine treatments (often sarcastically referred to as snake oils) available on the market but they all share one thing in common: none of them was ever proven to be advantageous, actual tests found quite the contrary more than once. Manufacturers routinely claim that independent laboratories tested their products scientifically but they don't rush to disclose the names of those laboratories or the circumstances under which the tests were conducted.

Air and oil filters

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Citroën specifies Purflux oil filters but there are other manufacturers producing similar units as well. For the air cleaner element, Citroën specifies Miofiltre, Lautrette and Quillery but only using its part number instead of some manufacturer code.

Washing the engine

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Steam and water cleaning older engines with fuel injection is always a little bit risky. Humidity getting into some parts can make re-starting a challenge. Note that we don't speak of permanent damage, only that you'll have to wait or dry those parts with compressed air. If you do this yourself, there's no problem, but at a garage, when other cars queue up behind you, it can be bothersome.

Diesel Basics

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Diesels are taken for granted in 99% of all cases--the truth is, most of them can take an incredible amount of "just driving", but the neglected maintenance results in slow decay. However, even engines treated extremely poorly can easily run 100k miles or more.

Diesel Combustion

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A lot of things happen at the moment the fuel is injected. If the fuel was somehow perfectly microscopically atomised on injection, it would not self-ignite at all. It would have trouble igniting even with a spark plug. Ignition needs a richer fuel-air mixture, and this is locally provided by the start of the injection being full of larger drops of fuel, because it occurs at a lower than maximum pump pressure (about 2-3 times lower). The evaporation of components from the fuel as it enters the hot compressed air is what makes it ignite. This is called creation of ignition precursors, and it is responsible for a delay between injection and ignition. Once this happens, the temperature rises sufficiently for the rest of the injected fuel to ignite. This is the principle behind pilot injection, a technique that makes things like the HDi common rail possible and quiet compared to old style direct injection engines.

Diesel Engine Care

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Most people are not aware that the main reason a diesel engine wears out is improper combustion, usually caused by worn out injectors, improper timing, or simply lack of air (influenced by several factors, one of which may simply be a dirty air filter). Anything which produces soot (eg. particulates), including the "black smoke" effect, results in particulates ending up in the engine oil. This soot then accumulates in areas where oil flow is low, like behind the piston rings. As the deposits grow, the ring is being forced outwards. The user knows nothing of this until the very end--the constant tension actually improves compression, but wears out the cylinder and the rings, reducing the life of the engine at least ten times.

Diesel CAV Troubles

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CAV fuel pumps give an endless amount of trouble. Problems with idle speed, speed oscillation, stalling are among these typical failures. In other cases, the engine might idle normally but it gets stuck at higher or lower idle revolutions when the accelerator is first pressed and released. Or it can get stuck at a certain speed over idle regardless of accelerator position.

Diesel Head Gasket

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A new type of head gasket was introduced in 1993. The older one was a mica press with metal inserts, the new variant a steel-aluminum-steel sandwich construction. The old one failed for me at 130,000 km: part of the gasket lining burned out, leaking gases into the coolant as well as the adjacent cylinder. Such failure is not possible with the newer gasket.

Changing Adjusters

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Some mechanics would tell you that the camshaft housing has to be removed (together with the camshaft and all that this implies, timing belt, etc.) to change the adjusters. This is not true, nothing more is needed than removing the camshaft cover and, naturally, knowing what to do.

Engine supports

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There were the wrong type of engine supports fitted to early diesel XMs, supposedly up to Q1 of 1992). The replacement top ones are softer and taller, and have a different shape. In fact, the original ones made the engine sit at an angle (the gearbox end was higher by about 1/3 of an inch). Post-1993 microfiches show this replacement, pre-1993 ones do not. If you buy replacements, check that the salesman is checking the right microfiche or you may get the wrong supports: those for a 2.0 liter gasoline engine. The new supports made such a difference I though I had a different car!

Fuel cut-off valve

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It usually dies either when you (try to) start the engine or when you stop it, rarely while it's running. The engine will not start because it will not be getting any fuel. The reason is usually overheating and deformations in the coil whichresult in the valve plunger getting stuck, or internal shorts or open circuits (due to heat) in the coil.

Timing Advance Solenoid

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This is a typical problem with CAV DPS/DPC fuel pumps. The fuel leaks along the edge of the solenoid housing (a round part with a huge nut on its housing, screwed into the side of the pump). Remove it by unscrewing it with the appropriate wrench, having unplugged the electrics first, of course. The leak develops where the back of the solenoid is joined with the rest of the body, and the replacement is very expensive (cca 160 Euros).

Turbo Diesel Failure

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Clean combustion resulting in clean oil (assuming it has the proper grade, not some cheap concoction) is essential not only for the engine but for the turbo as well. Most people are not aware that a turbo can be--and actually should be--cleaned every 150,000 km or so. This procedure will make it last forever. I can tell you that I looked at mine when I changed the head gasket, and even though the car has been tortured before I got to own it (I am not to certain it had its oil changed more than twice in 120,000 km, injectors were still the original ones, never touched), it was in excellent condition and could probably have gone at least that much longer without any problems even if I hadn't touched it.

2.5 turbo diesel aux belt tensioner

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The jockey arm type auxiliary belt tensioner is no longer available from Citroën. If yours starts to rattle, warning of an impending failure, you only have the option to modify it. There are two possible ways to do it: either fix it permanently or use a replacement tensioner with the necessary modifications to fit it.

The fixed solution is much simpler but it has the inherent problem of being fixed. Citroën changed from an earlier fixed arrangement to a spring damped one for a reason. If anything (road debris, pebble, any small object) gets behind the belt accidentally, the belt will snap immediately, rendering the car motionless and to be trailered (the auxiliary belt drives both the HP pump and the alternator). A spring loaded tensioner will yield in the same situation and the belt will survive.

If you decide for this second solution, here is a working example. The part we found as the appropriate candidate was the tensioner of Peugeot 206 1.4 HDI engines of around year 2004 (part number: 9638380780):