After many months of preparation, including the fuel pipes and engine bay, the time moment for refitting the engine was getting ever closer. If you have followed this write-up for the last three and half years, you might remember the engine rebuild. After a lot of work on the old G-SEG engine, it had been rebuilt to a short block level. That means the engine had been built to the point the belts were on, and the engine innards could be rotated. However, in May 2023, the time had come for finishing the engine for reinstallation.
The Build Book
Helping me through the engine rebuild, I have a build book and a parts book. As wonderful as these look, they are really just fancy covers on top of readily available information. The parts book is a copy of the Citroen parts catalogue microfiche from 1998. The build guide is a copy of the Citroen Workshop manual sections related to the MI16, as well as a few extra notes and images.
As simple as the documents may be, the real value is in the notes. The parts list has notes of torque settings or installation conditions for most of the major fixings. This is a work of love, with hours spent pouring through workshop manuals to find the torque settings. The build book notes all the work completed on the engine so far, with hints and tips from forums and Peugeot manuals.
Oil Temp Sensor
As you can see below, the oil temperature sensor on the G-SEG engine came to me completely destroyed. Being exposed on the very bottom of the engine it is not unusual for the oil temperature sensor to scrape the ground. However, there is normally enough left to get a good connection.
When I finished the engine, I couldn’t locate a replacement oil temperature sensor in the UK or at a reasonable price. Despite parts from Europe being reasonably cheap at the start of the project, by 2023, imports were expensive. An imported sensor would likely cost £50 to £70.
The alternative was to use an old but functional spare I had tucked away. It, too, had dragged the tarmac, and while there wasn’t enough thread to make a connection, I had an alternative plan. Carefully drilling through the copper screw connector and a wire was threaded through, and a permanent connection was made.
Engine Mounts
Rear Engine Mount
Next up for the refurbishment process was the lower engine mount. Cosmetically, the rubber motion damper didn’t look in too bad condition. However, by grabbing hold of the centre section, the inner bush could be rotated more than thirty degrees. This rubber’s service life had evidently been exceeded.
Fortunately, an earlier Christmas present to myself meant I could quickly change the bushing with hydraulic pressure. This Sealey YK10B bench press may look compact, but it packs a punch.
Opportunistic purchasing of many Citroen service tool kits over the years means I have the official tooling for changing the engine mount bushing. A few pumps and out she flew.
With a new rubber bushing installed, the refurbished rear engine mount was bolted back onto the engine. The fixings were torqued up and marked so that I know they have been correctly installed.
Front Engine Mount
As simple as it may look below, the front engine mount also needed a little TLC. The upper section is held to the lower with threaded studs. However, one of the studs came out of the lower mount. Buckets of thread lock, and a few days later, it was ready to reinstall.
And there it is, reinstalled onto the G-SEG engine, torqued up, marked up, and rolled out. Wait, that’s transformers. Either way, the process of finishing the engine was flying along.
P Seals
During the short block rebuild of the engine, oil was added to the sump. Since then, the engine has been periodically rotated manually. And that highlighted a small leak from the newly installed sump. I immediately had my suspicions about the P’seals, which fit either side of the crank plate.
The crank end plate seals half of the crank to the block. The plate is required to remove the crank from the block. When the plate is installed, two seals are slid down the side of the plate with tabs to keep them in place. The tabs make the seals look like the letter ‘p’ or a golf club.
Finding the leak
My suspicion is that the P-seals might be the issue, which was triggered during the plate’s installation. The legs of the seals are excessively long and have to be trimmed to length. One required much more trimming than the other, meaning one was not installed correctly. Sure enough, with the oil system sealed and pressurised, bubbles of leak detector appeared around the crank plate.
I dreaded having to take the engine apart. But after several months of mental block on taking the sump apart and a fear of what may lay inside, I couldn’t put it off any longer. Especially if I was ever going to finish the engine.
Resealing and closing up
With the sump off and the crank plate out, one seal slid out of place during the installation, causing the leak. To prevent the p-seals from escaping again, new seals were installed with a little sealant.
After hours of careful cleaning, the sump spacer was installed with new sealant.
Finally, a new gasket and the sump were reinstalled, torqued, and leak-free. I should add that the rebuild was over a year ago, and to date, no oil drip has come from the P-seal end. Whoop.
Exhaust Manifold
The next step in finishing the engine is to install the exhaust manifold. The lump of steel takes the exhaust output from the four cylinders through the eight separate valves and out to the exhaust. On the Mi16, the manifold is both complex and beautiful.
Unfortunately, the original exhaust manifold fixings were past their best. The studs sticking out of the engine were mostly destroyed, and then the exhaust manifold was removed. So, a whole new set of studs was installed into the head.
A new gasket and copper exhaust manifold nuts secure the exhaust manifold to the short-block engine. Slowly but carefully, I’m getting closer to finishing the engine.
Oil System
Before the inlet manifold goes on, all the major piping must be installed onto the engine. First up is the oil system.
Oil Breather
Most combustion engines leak some cylinder gasses past the piston seals once they are over 30 years old. Wear of the cylinder walls and piston rings lets just a little gas from the cylinder into the oil system. As this gas passes over the engine oil, it picks up some oil particles that we don’t want to get out into the air.
An oil breather lets some of the gas out of the oil circuit and tries to capture some oil particles by condensing on a metal surface. The original filter was a mild steel mesh, like chain mail. Unfortunately, the filter was long past best when the engine was taken apart. A trip through the ultrasonic cleaner resulted in the mash falling to bits. Some of the filter mesh was even found in the sump! The filter material was replaced with a stainless steel mesh in the form of a pan scourer. This is a very marmite solution, with a risk of getting harder stainless steel particles into the oil system. However, I’ve done this on a few older vehicles and had no issues.
Oil Pipes
With the oil breather refurbished, the oil system and pipes can be installed on the engine. I deliberated for a long time about what to do here. I have three sets of original oil hoses for the MI16 from scrap cars and my own BX 16V. Without a doubt, I have enough complete hoses to make a set.
However, despite having a full set, the main oil filling pipe always ends up soft and often collapses. All three spare pipes I have where showing signs of going soft. While an expense I don’t need at over £100 for three pipes, I ultimatley opted for new hoses. The BakerBM silicone oil breather kit has been about for more than 10 years now, and is really good value for money compared to a failed engine.
Ignition System
Next, I could focus on overhauling the ignition system with the oil circuit complete. While not strictly required to allow the engine to be installed into XPO, this felt like a good time to do some of the fiddly bits.
Spark plugs
To finish sealing up the engine cylinders, I needed to fit some new spark plugs. These go quite deep into the engine, so I find them easier to install when you do not have to reach over a lot of bodywork.
Choosing a spark plug can be a bit of a minefield. While I’m biased, I genuinely believe that the Denso Iridium range has the potential to generate a stronger spark and help even combustion. I ran Iridium plugs in my 16v for more than eight years and never had any issues. However, recently, I returned to the OEM spec NGK BCP7ET, and honestly, I can’t see any difference. So this is what my 16v engines will get in future, and I’m stocked up for the rest of my life!
Rotor Arm
While not strictly needed for the engine to be installed in the car, I’ve taken a moment to install a new rotor arm while the thermostat housing is out of the way.
While I’m a little nervous about FAC quality, I’ve really struggled to find a genuine 5940.41 Citroen rotor arm. In this case, the material quality and finish look okay, and it is all I have. Installing without the gearbox and thermostat in place helps with the screw alignment.
Coolant System
Next up in the process of finishing the engine for installation is the coolant system. Well, some small parts.
Thermostat Housing
Oversized steel bolts in an aluminium casting in the relative presence of water are stupid. I have no idea why manufacturers do this. Not surprisingly, one of the two M8 bolts in the thermostat housing was snapped during the disassembly of the G-SEG engine.
After days of lubrication with BDX, the bond between the steel bolt and the soft aluminium didn’t really want to give up. Experience has taught me that heating up alloy castings only makes them soft and results in threaded hole stripping. Heat is not the solution here.
However, respite being well stuck, I have a spare housing if it all goes wrong. Sanding the stud back flush and drilling the core, I managed to get the steel threads out using an extractor tool. I’ve never actually had these tools work before.
After a small mercy, I could reinstall the thermostat housing on the engine. I always struggle to get the alignment on the pipe retainer, and while not glamorous, this clamping arrangement did work. Really I should have put the clamp against the pipe, but didn’t want to mark the Santorini metallic black finish!
Finally, Finishing the Engine
A mere two months later, and by July 2023, the engine is just about ready to be installed into the engine bay of XPO. Getting over the hump of taking the sump off really spurred my excitement to get the car back together.
There is still a lot to do before I can drive off into the sunset, but having the plated parts finally go back onto the engine is a big emotional boost. Who knows, maybe one day, this three-month project will be complete, and XPO will have a new MOT!
M
All your articles are interesting but I do hanker after an XPO update – and it’s a good one. I cut the breather can on my Minor open to fit a similar pan scourer then clamped it back together with a Mikalor clamp, so far it hasn’t fallen to bits and yes the original filter inside was a rusty oily mush – probably wasn’t doing it’s job.
Thank you, as always, Panky. I need to increase the pace of the articles as the car is not far off ready for an MOT! Glad to hear I’m not the only one using the scouring pad filter approach. Seems to work fine on tractors, but I’ve seen scathing remarks on car places. More to come shortly!
and I thought that I had invented the pan scoured mod! Seems that everyone else was ahead of me.
I suspect neither of us was the first. I imagine it was common in the 60s and 70s, but I wouldn’t know.