Build Drivetrain & chassis
AAZ engine swap
The AAZ swap was a fairly spontaneous project, but in hindsight a necessary one: the "new" engine has far fewer kilometres on the clock than the old one. On top of that, the combination of the JX injection pump and the AAZ now gives the bus over 80 hp, which you really notice. I only sketch the conversion here, because the linked guide describes a lot of it very well.
This post is structured as follows:
- Preparation
- Donor car
- Work on the engine
Preparation
For preparation – and as a kind of bible for this conversion – I can only recommend Harro's guide (in German). It covers pretty much everything really well. Still, I had a few experiences of my own that I'd like to share. You should at least skim the guide to know what you're getting into.
https://www.t3-infos.de/images/PROJEKT_AAZ_detaillierte_Beschreibung.pdf
After reading the guide, you should be clear about the condition of your current engine and its ancillaries. For example, I decided to get a new or freshly rebuilt KKK turbocharger and to replace the clutch at the same time.
Fitting an oil cooler is really a must, because the AAZ runs even hotter than the JX. I've linked the 19-row oil cooler I chose below.
In general, I recommend searching the big parts dealers by OE number so you don't end up buying overpriced parts from specialist shops.
I bought the following new parts:
- 4 x glow plugs
- Gasket set without cylinder head gasket OEN 028198012B
- Oil filter housing gasket OEN 028 115 441 C
- Gear oil, 4 l
- Turbo return plug bolt M18x1.5
- JX oil sump gasket OEN 026103609D
- Pilot bearing OEN 056 105 313 C
- Special tool VW 2068A
- Clutch kit OEN 068 198 141 — VW
- Bosch JX injection pump seal kit BOSCH 1 467 010 467
- Oil cooler kit, 19 rows
- Timing belt kit AAZ OEN 028 198 119
- Oil filter that fits despite the oil cooler
- New turbocharger
- Turbo supply and return lines, if needed
- Engine oil, 6 l
Besides standard tools, you'll need external and internal multi-point (XZN) sockets, as the drive shaft, the turbocharger and the crankshaft may be fixed with those bolts.
To set the injection timing and the valve timing you'll also need the special tools VW 2065A and 2068A. If you replace the clutch, the flywheel has to be locked – there's a special holder for that, or you can solve it with an impact wrench.
Donor car
My donor was a 1998 Golf 3 estate. It had 177,000 km on it and the speedometer still worked, so I assume that figure is correct. The Golf had been sitting for two years because the clutch was broken. After selling the body on, I effectively paid only €500. Of course there's a risk that the engine is no good, since I don't know how it was looked after. But the risk was worth it to me. I've now driven a good 5,000 km with this engine and haven't found any faults so far.
Alternatively, you can buy a rebuilt engine for around €2,000, but it may not include certain parts such as the injection pump bracket, the oil filter flange, the timing belt cover, the valve cover or the dipstick – all of which you need.
We took the engine out of the Golf, which would have been difficult without a lift. Unlike later on the T3, we didn't remove the gearbox and engine together, just the engine. Removing the JX is also described very well in the guide. We used a pallet truck and a lift, which made the job fairly comfortable.
Work on the engine
Once both engines are out and roughly cleaned, it's basically like LEGO, just with bigger parts. The oil sump, oil pump, vacuum pump, heat exchanger, exhaust manifold, coolant pump and alternator bracket are taken over from the JX. For the power steering drive, the JX pump and bracket are used. Here the spacing has to be adjusted slightly with washers so that the belt lines up with the crankshaft pulley.
The needle bearing or pilot bearing has to be fitted; the clutch and flywheel are taken over from the JX. The hole below the exhaust manifold is closed with the M18x1.5 bolt. You need to make a small bracket for the turbo, the AAZ injection pump bracket may need to be filed or milled out a little, the dipstick has to be adapted and the boost compensator (LDA) has to be raised slightly. Those are really all the major changes.
Naturally, all gaskets and seals should be renewed while you're at it. Changing the timing belt makes sense too, as does renewing the glow plugs and checking the four injectors.
The whole conversion took me about 5 days. Including the turbo, clutch and oil cooler, it cost around €1,400.