As above, good luck with the treatments for your son and that will be a great project to look forward to when he's back on his feet. My lad is only 5, but I hope one day, he'll want to do a project too!
Assuming you're in the UK, you won't have an O2 sensor. They only put them in some European model back then for emission control. The blue temp sender test does suggest it's feeding back a signal, whether it's the right signal, we can't be sure. If it's not too expensive, I'd swap it out, just in case.
No worries, unfortunately, I'm down south, so I don't know anyone up near you. Might be an idea to put a shout on the FB page, it's much busier, someone may know a garage.
Could be the blue temp sender. It lets the car know when it's cold, to enrich the fuel etc. Next time, try unplugging it when you're having issues. If it does turn out to be it, don't buy a cheap one, there's a lot of dodgy pattern ones floating about on ebay.
Ok, there are two things that I would check, first being the compression. I've had a mk2 16v before where it would start and run, but once up to temp, the compression dropped and had no real power. I'd also struggle to restart the car. Genuinely hope it's not that one, as there's no cheap fix for it.
Second (and more likely) thing is that metering head: The mk2 golf 16v runs on K-Jet, a mechanical form of fuel injection. Essentially, it relies on incoming air lifting a flap (under the big black boot, above the air filter) that increases the fuel pressure being supplied to the injectors. When it works, it works well, but it needs to be set up correctly and from the sounds of it, the car runs well when warming up, which is when the warm up regulator is pushing more fuel into the inlet, but when the car comes up to temp, it shuts off and drops the fuel, leaning out the mixture. You could detect this by going to a garage with an exhaust gas analyser (any MOT station) and asking them to measure what's going on when it's running rough, if it's lean, that's your problem.
Now the compression can be done quite easily by yourself, if you're happy tinkering and have a compression tester. The fuelling should really be done by someone who knows how to do it and has an exhaust gas analyser. You don't mention where abouts you are, if you let us know a location, someone nearby may know for a good garage.
I do really like those Chris Fix videos, shame he's slowed down producing them.
So how slow was the cranking getting? As oil pressure builds up, you will notice it slow a little, also, your battery is probably starting to get tired (unless you're charging it between fault finding sessions). One thing you didn't mention, did the oil light go out? If it goes out, you've got good oil pressure again and can attempt a start.
Another thing you could try is to take out all four spark plugs, this will remove the resistance caused by the engines compression, it should spin pretty quickly then and get oil everywhere it needs to go.
Good to hear the engine is still spinning, fingers crossed, you may get away with it. Must admit, I keep coming back every couple of days just to see how you're getting on!
Thinking about it, it might be that there was just an air lock around the oil pump and it didn't pick any up. I wouldn't try and overfill the engine, just fill it up to full, pull the king lead and then turn it over for a minute. The slower speed of the pump should pick the oil up and send it around everywhere, once you see the oil light go out, you know you have pressure. Give it a minute or two and look at the oil level again (you may need a small amount more), then replace the lead and attempt a restart.
Thanks both really appreciate the reply and the help. @Monkey the engine has been solid for the last 5 years but hardly gets used nowadays tbh. I'll go through the steps and update. In the meantime I've created a link to the pictures I took of the stuff in the Sump and from underneath which may give a bit more context.
Those red bits look like the dipstick tube red bit has broken before and gone into the sump, probably been replaced.
Agreed, I can't think of any other red plastic that gets anywhere near getting that close to the oil supply. Can't get my head around what that collet it though, was it in the sump? Looks like one of those collets that go around bolts in modern engine rocker gaskets.
Either way, that oil doesn't appear glittery, so that's a big positive. You could just have a dead oil pump.
Ok, few things could have set off the oil buzzer; You could have a blocked pickup, did you inspect it when the sump was off? You could have not put enough oil in/some has leaked back out, that will also set off the oil buzzer. You could have used the incorrect weight oil and put too thin in, again causing a drop in pressure. Unfortunately, the oil pickup could also have collapsed (the god knows what you described in your oil). When you reassembled the sump, did you inspect the crank? did you see a build up of any dust or debris where you'd left it open?
If I were you, I'd check the level of the oil, then see if you can turn the engine by hand. This will give you an idea of the condition of the engine and what has happened to it. If there's enough in there and the engine turns over by hand, you're safe to attempt a restart, Then pull off the dizzy king lead (so it won't start) and crank it till the oil pressure light goes out. This will ensure oil has gotten around the engine again and it'll be safe to attempt another start. Keep your eye on the oil pressure light and oil temp (if you can).
If you can't turn it over by hand, then unfortunately, something bad has happened and the engine has picked up. If the oil pressure light doesn't go out when cranking for 30-50 secs, you're not getting oil everywhere, stop cranking, drop the oil sump back off and inspect the oil that comes out and the oil pickup on the oil pump. You might get away with fitting a new pump and trying again.
If I've understood correctly, you want a head unit with a CD player, DAB and Bluetooth connectivity? If that's the case, there are plenty of options out there if you just want to buy one, just google something like "Car Stereo CD player DAB" and it'll come up with a selection. If you want it fitted too, you could go somewhere like Halfords and speak to them, I'm sure they do a fitting service on their kit.
As for the aerial, DAB is slightly different, you can get window mounted aerials that look quite subtle. You'd still need your wing mounted one if you want to listen to normal radio though.
Now one other thing to consider is how much it's going to cost. I've tried to do everything myself, but here's a breakdown of what it's cost me to get installed: Full mk3 AC setup (only really need the evaporator box, but I didn't know that then) £120 Mk2 Switch - £65 Crossmember Welding - £60 Full Lupo AC pipework - £110 Compression fitting - £7 Lupo AC Drier - £20 Lupo Condenser - £65 TT Compressor - £180 Mk3 Expansion Valve - £22 AC Regas Can - £30 Processional Regas - £46 Fusebox - £35 Consumables (welding/grinding/wiring/o-rings etc) - £40-£50 Pollen Filter Housing (3D Printed) £10/£15 Pollen Filter £15
So at just under £700, it's not a cheap undertaking, but if you to it like me over the course of a number of years, it's not too bad.
