Citroën BX – XPO – Engine Installation – Eps41

6 min. read

After a long wait, the moment avid readers have all been waiting for is the engine installation. Remember, at this point, the engine has only been turned over manually. Manual rotations for some two years! The sense of trepidation is hard to put into words. Engine rotation is a long way off a running car. However, the only way to know that I have built it right is to complete the engine installation!

Engine Mount

Before I can install the engine, I need somewhere for it to sit. If the engine were mounted directly to the vehicle body, it would soon shake itself apart. Worse, the vibration would create stress fractures everywhere. The engine sits on rubber mounts to isolate the harsh engine vibrations from the vehicle body.

July 2023 - A template marks the position for a 5mm hole.
July 2023 – A template marks the position for a 5mm hole.

There are a number of mounts, upper and lower. Ultimately the engine and gearbox assembly is secured in three points. At the top, the upper engine mounts sits on top of a large rubber tower. Forward and rearward movement is restricted with side buffers.

Additional engine mount holes are drilled and sealed.
Additional engine mount holes are drilled and sealed.

While the main upper mount is readily available, the correct Citroen BX engine mount buffers are no longer available. The original Citroen type has been unavailable for many years. Fortunately, the mount for the Peugeot 205 will fit, with a small modification that requires drilling a 5mm hole.

Peugeot style engine mount buffers are installed.
Peugeot style engine mount buffers are installed.

With the hole drilled, the Peugeot-style buffers can be installed, ready to receive the left-hand engine mount. The buffers will probably need shimming once the engine is in, to get the buffers closer to the engine mount. A new rubber mount is also prepared for the gearbox upper mounting.

Engine Installation

There are a number of ways to get the installed on the Citroen BX. My preference is to drop the gearbox and engine assembled, from above. The load leveler on the engine crane makes this relatively straightforward. Although there is a good argument for loading the assembly from below, or even installing the engine and gearbox separately.

From experience, the XU9J4 engine likes to lean backwards on the crane. To aid installation, I use a plank against the firewall to guide the assembly in. At the engine mount end, I usually end up dragging something against the paintwork. A thin board here protects the bodywork. If you are installing a BX engine this way, I recommend removing the mounting stud from the gearbox. This innocuous post tends to catch on everything. While installing the engine is a one-man job, having a spotter/guide to swing the engine into its hole is recommended.

Engine Ancillaries

The case of the missing parts

Over the last few months of the build, I have been increasingly frustrated by the missing engine pieces. While I knew XPO wasn’t 100% complete, I was certain many missing pieces were in the car when it arrived. As I couldn’t find the missing bits, I spent many hours searching for parts in my stocks and on eBay.

The missing box of parts is finally found.
The missing box of parts is finally found.

Just as some of the parts where becoming critical, I solved the mystery of the missing parts. Discretely hidden under the parts washer, in an unmarked box, I found all the small missing pieces. Doh! Time to throw them at the car and start making some progress.

Engine Ancillaries

October 2023 - Engine installation continues with ancillaries.
October 2023 – Engine installation continues with ancillaries.

The engine installation continued with the installation of the air intake manifold, followed by the fuel, ignition, and electrical systems. The hydraulics are all installed with a new hand-made main feed pipe from FDV to the HP pump. A new belt is installed over the replated pulleys.

Throttle body is looking much happier after fettling.
Throttle body is looking much happier after fettling.

When the throttle body arrived, it was very roughly spray-painted black. Such a waste of a beautiful casting. Most of the paint was flaking off too. First, the throttle body was stripped and cleaned with a combination of ultrasonic cleaner and manual abrasion. After that, the throttle body flaps were reset, and linkages lubed, ready for reinstallation.

Buy cheap, buy twice with these ignition leads.
Buy cheap, buy twice with these ignition leads.

New NGK plugs are connected to a new distributor with some very cheap HT leads. These leads will come back to haunt me. Despite clearly being the wrong length, the seller wasn’t particularly helpful. On seeing the pictures, the seller told me he’d never had an issue with the many sets already sold. And that was that! This isn’t the only issue with the leads, as I will discover.

Air intake hose

This intake hose is not the solution.
This intake hose is not the solution.

One big problem I had with the engine installation was the air intake hose. Sitting between the airflow meter and the throttle body, the hose is critical to starting the engine. The engine did not come with one, and the only pipe I had failed on Jazz a long time ago. While I’d ordered a hose from BakerBM, Stuart was unable to find the last ever hose.

Toddman comes to the rescue with a NOS air intake hose!
Toddman comes to the rescue with a NOS air intake hose!

Fortunately, the BX community, globally but especially in the UK, is an amazing group. A few messages to some of the best BX parts finders and a large box arrives. It contains a brand-new air intake hose, CV boots, and other small parts that are missing. Thank you, Toddman! Engine installation can continue!

All belts are replaced with genuine Gates parts.
All belts are replaced with genuine Gates parts.

A key part of the installation is the auxiliary drive belt. As only the alternator and crank pulley are connected, the Citroen BX 16Valve takes a relatively short 5-peak belt. Like all the other belts, I’m installing genuine Gates belts.

Engine Fixings

Most parts of the Citroen BX are shown in the parts catalogue as ‘NFP’. Or ‘no longer available’ in English. However, there is a relativley easy solution for bolts. The part catalogue usually lists the dimensions of the bolts. Fortunately, overall lengths and threads are listed along side the length of unthreaded sections.

A very cheap shopping trip at Lloyds and Jones.
A very cheap shopping trip at Lloyds and Jones.

A quick trip to Lloyd and Jones with a shopping list, and many of the missing bolts are sourced. In most cases, I’m replacing mild steel bolts with A2 stainless where possible, simple for the longevity of the finish. Nobody likes rust nuts.

With the lower yoke installed, engine mounts are complete.
With the lower yoke installed, engine mounts are complete.

A significant step in the engine installation is getting the last of the engine mounts installed. The lower engine mount consists of a large rubber damper in the lower engine mount bracket, connected to the subframe by a yoke. Although the main rubber is easy enough to find, the yoke can be a little harder to source. What was eventually installed on XPO is actually the second purchased yoke. It will take several months until I find the first one. All are installed with shiny new bolts, and we are getting very close to starting the engine!

Coolant Hoses

Depending on the engine, I wont always do the first start with the coolant system connected. However, the MI16 engine gets very hot, very quickly. The risk of damage to the engine with no coolant is far higher than a diesel-engined BX, for example. So, the coolant system needs to be assembled.

BakerBM hose needs shortening when used with a plastic manifold.
BakerBM hose needs shortening when used with a plastic manifold.

About 15 years ago, I worked with BakerBM to remanufacture the Citroen BX 16V coolant hoses in silicon. At the time, we recognised that there were two bottom hoses. The dimensions depend on the manifold type at the back of the engine. This means that where the plastic manifold is used, the hoses need trimming. Without the adjustment, the bottom hose is overly long and would rub against the anti-roll bar if not trimmed.

Plastic coolant manifold is wider than the metal version.
Plastic coolant manifold is wider than the metal version.

The later manifold sits closer to the edge of the engine, and 10mm needs to be trimmed off the hose. I usually put a suitably large socket inside the end of the hose and then trim it with a new blade in a Stanley knife. The later plastic manifold is also a little bigger, so a small amount of lubricant is well worth applying.

Trimming the BakerBM bottom hose.

Trimmed 10mm, and the hose fits perfectly.
Trimmed 10mm, and the hose fits perfectly.

Trimmed back and reinstalled and the hose is clear of the anti roll bar and drop link.

The wheel arch liner will hold the hose in place.
The wheel arch liner will hold the hose in place.

The bottom hose sits perfectly against the underside of the chassis rail. Fortunately, the plastic wheel arch liner will hold the pipe up and out of harm’s way. Incidentally, the Peugeot solution is actually a shaped metal pipe in this area. This makes a lot of sense, as a solid pipe would definitely be out of reach of the wheel of the anti-roll bar end.

Let Her Rip

Engine installation complete, and ready for start up.
Engine installation complete, and ready for start up.

Everything is connected, and the engine installation can finally be declared finished. Although there is still some tidying to do, drive shafts to fit, etc., however, all the parts needed to turn over the engine are in place. Regardless of months of turning over by hand, this is the moment of truth for my engine-building skills!

XPO first start, November 2024

Well, it took some time, but the engine actually ran. Although the engine was previously turned over on the key and the fuel system manually primed, this was genuinely the first start and a successful one too! Oh, there’s no exhaust either 😀

XPO has left the building, but why, and how?
XPO has left the building, but why, and how?

And there we have it. Engine installation complete. XPO has left the building!

Stay tuned for the next article to see what happens next. But as a hint, there will be LHM, probably not where it should be.

M


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2 thoughts on “Citroën BX – XPO – Engine Installation – Eps41”

  1. At last, big smiles this end : )
    I need a 16v in my life – once the barn is built when my numbers come up

    1. Thanks Panky, your support means a lot. I was trying to get the car finished and down to Rustival2, but didn’t quite make it. Not long now though!

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