In November 2025 I picked up a 1988 Golf GTi that I'd won in a prize draw (lucky so and so I hear you saying) and for the first 3 months or so drove it occasionally (including to work and back a couple of time when the modern cars lost arguments with potholes). However driving home one night I noticed the temperature gauge climbing quickly so pulled into a supermarket car park, turned the engine off and watched steam coming from the front of the car. I opened the bonnet and was greeted with this...
At first I assumed that the head gasket had gone, but before I'd managed to remove all the rusted bolts holding the exhaust pipe to the manifold someone suggested that it may be the oil cooler that's failed and not the head gasket after all. So as a check I removed the rocker cover and discovered that I did not have coolant in the oil, rather the mess all over the engine bay was caused by having oil in the coolant...
Cue putting everything back together again so that I could start cleaning all the mess out of the cooling system. First was to clear out as much as possible by flushing the system by blasting water through the hoses with a hose. Next, connect everything back up and bypass the oil cooler by removing the inlet and outlet hoses on the cooler and connecting them together using a piece of pipe. Finally, fill the cooing system with water and some laundry detergent or a dishwasher tablet, make sure there's enough oil in the car and then start the engine.
Squeeze as many coolant pipes as possible to bleed the system as it heats up and keep an eye on the level in the expansion bottle. Once the engine is warm and you're sure there's enough fluid in the system (it takes just over 5 litres from empty) put the expansion bottle cap on and wait until the engine gets hot enough for the radiator fan to kick in. Whilst the engine was warming up I noticed that oil was coming out of the oil cooler, indicating that it was indeed a failed cooler that caused the mess.
Switch the engine off and wait for everything to cool down. Repeat the procedure until the "chocolate milkshake" has been pretty much banished from the cooling system. Then a final flush using something like SpeedFlush. Now you can drain the cooling system and the oil from the car so that the oil cooler can be replaced and the coolant hoses reconnected to the cooler. Fill the fluids back up after replacing the cooler and putting a new oil filter on, fill the cooling system with coolant, bleeding the system as required and hey presto, a car that doesn't try and send the temperature gauge off the scale any more.
