Engine Bay basics


To the uninitiated, the engine bay of a Bus can be an alien environment, full of strange-looking oily bits, but it is really very simple, once you know your way around… 

The flat four VW engine is a pretty straightforward beast. After all, it did originate in the 1930s, and its design altered little during its extended lifetime. In general, it is also a very reliable unit, and it is a rare occurence that it will break to an extent that you cannot get home. A couple of members of staff here in the Camper&Bus offices have even managed to coax their sick Dubs home having dropped a valve! However, despite its inherent reliability, the trusty flat four still needs to be looked after, so neglect it at your peril! And always remember that, even if it’s new or reconditioned, the engine in your Bus is not a modern unit, with service intervals every 20,000 miles, that you can thrash from cold and never think twice about. To keep it happy, it needs regular maintenance and oil changes. Carry these out and hopefully you will not need most of the information in this section!

If there are only two things that you keep an eye on, ensure they are oil condition and engine temperature. VW did not see fit to bless its Buses with a great oil filtration system (except for late fuel injection ones) and the factory set up does a very good impression of a tea strainer but very little actual filtering. So change the oil every 3,000 miles with a good 30w mineral oil and keep on top of the other procedures we’ve listed in our tech guide section and you should experience many trouble-free miles, even if you experience some small hiccups along the way.

Below is a quick guide to what’s what in the engine bay of your Bus. (You can click on the image to see it larger).


  1. Carburettor – Most air-cooled engines came with just one of these. It can often be the source of idling issues.
  2. Distributor – This distributes the spark to each clinder. No spark means no running.
  3. Fuel pump – All air-cooled VW engines were equipped with a mechanical fuel pump. These can and do fail.
  4. Dynamo – This generates the electric power for the car and charges the battery when you’re on the move.
  5. Bottom pulley – This carries the fan belt. If it is loose, oil can leak from the engine.
  6. Fan belt – Runs the dynamo / alternator and keeps the cooling fan cooling.
  7. Coil – Stores electrical energy to provide a spark to the spark plugs.
  8. Inlet manifold – This channels the air / fuel mixture from the carburettor to the cylinder heads
  9. Spark plug leads – Four of these, they transmit the spark from the distributor to the plugs.
  10. Spark plugs – Create the spark that ignites the fuel in the cylinder.
  11. Heater hose – Directs air from the cooling fan to the heat exchangers.
  12. Air cleaner – Prevents wear-inducing dirt entering the engine.
  13. Oil breather – Allows excess crankcase pressure to escape.
  14. Oil filler – You need to be able to put oil in somewhere!
  15. Warm air control flap – Directs warm air into the carburettor to prevent it icing up on cold days. Allegedly.
  16. Warm air hose – Provides the supply of warm air to the aforementioned control flap.
  17. Dip stick – Shows engine oil level.
  18. Oil pressure switch – Triggers a dash warning light to alert you of low oil pressure.
  19. Fuel filter – Prevents the carburettor filling up with dirt.
  20. Tinware – Directs the vital cooling air around the engine.