1999 HDi (110) Running OK until recently, had 3.5mm high pressure lines burst and patched, then auxiliary belt shreded after only 3 years and 14K and now another Core Plug has corroded (looks like external corrosion) and leaked coolant so I believe this might have led to the engine cutting out a couple of times after squirting coolant onto the fuel pressure sensor, which has a dodgy connector plug
When I knocked the old Core Plug out that was roughly the coolant level so again I doubt any overheating has occured. So after changing the Core Plug in the cylinder head, I bled the fuel rail, topped up the coolant (2 litres), the engine started up OK and idled nicely but as it warmed up I noticed when reving engine it sounded a little more gruff than normal and didn't want to rev beyond 3K.
I disconnected the injector plugs in turn to check the effect on the engine running, the engine stalled on No.2 and had minimal effect on No.4
I then cracked off the injector fuel feed pipes carefully to eliminate any air locks, the engine stalled on No.2 and No.4
The engine check light was now on so stopped engine and disconnected the vehicle battery for 30 minutes to re-set.
Re-started the engine and continued to warm engine which was still running a bit gruff.
Coolant Temperature and level warning light was flashing STOP and O warning - I thought the cooling fans would have been operating at this stage (
Pin 1 5v
Pin 2 Neg
Pin 3 Neg
I shorted Pin 1 and 2 - no effect
I shorted Pin 1 and 3 - both cooling fans ran low speed
I reconnected the blue plug and the engine started running a lot poorer after about 5 seconds both fans slowed and stopped at the same rate.
So the fan motors do work, coming on around 95 degree C on the vehicle gauge (I'm still in the rabbit hole though).
Today I had a theory that the the coolant system had either an air lock (causing the coolant level warning light) or the level had dropped overnight so I made up a higher header (no coolant bleed nipples on HDi) and ran the engine, it took almost a further 1.5 Litres but no warning lights today. I think the coolant system is now full and free of air-locks.
The cooling fans came on after a very long warming time with heavy exhaust smoke due the engine running poorly, I think it's taking so long to warm up as it doesn't sound like it's firing on all cylinders.
I feel like after re-reading the Haynes manual I might have knackered the ECU by shorting the temperature sensor wiring.
My only other thought is that the timing belt (I changed in 2021 (edited) so covered 25k in just under 5 years) may have managed to jump a tooth or two with the current symptoms but it drove home fine ?
Any thoughts / suggestions from the forum ?