1930s MG Aluminium Oil Cooler Sump Pan

Pre-repaired 1930s MG Aluminium Sump
Repaired 1930s MG Aluminium Sump Inside
Repaired 1930s MG Aluminium Sump

This sump was found by one of my customers amongst a ‘job lot’ of bits from an auction.  It is a sump that was used on a 1930s MG racing car.


Why does it look like this?

You will see from the photographs that the sump has fins cast into it.  Looking at the picture showing the ‘inside’ of the sump, you can see that it’s quite a bit wider than the area where the bolt holes come through to attach it to the underside of the engine block. 

When the engine is running oil runs down from the engine bearings and collects in the sump.  The fins and the extra volume in the sump allow it to carry more oil, with the fins cooling the oil down as they’re in the air that runs underneath the car.  It's important to cool oil down as when it's very hot it becomes less viscous (i.e. more runny) and is much less effective as a lubricant.  This is particularly important for a racing car where the oil temperatures can get very high.

These days you sometimes see the fins and the extra volume on motorbikes but the modern approach is to pump the oil through a separate small oil cooler radiator to reduce the amount of oil needed.

What is it made of?

The sump was so corroded and covered in grime that it wasn’t obvious at first what it was made of!  There was an initial suspicion that it was made of magnesium alloy, like some of these sump pans from this era.  I thought that this was a good candidate for repair with a low temperature solder which I’d had recent success with (see the Aluminium Bellhousing Case Study).  Investigation of magnesium alloys suggested that this solder technique would work just as well.

However, once the sump casting was cleaned up it was apparent that it was made of cast aluminium due to the way it reflected the light and the ‘colour’ of the metal.  Closer examination of the sump, now that it had been cleaned up, revealed that it had corrosion holes (rather like a net curtain!) so this was going to be a challenge.

Repairing the holes

I set to work and made up some scrapers to get inside the pits in the metal with angled ends.  Using the low-temperature type of solder system enabled me to heat up the casting to a temperature around about 240oC.  Other so-called low-temperature solder systems tend to work at about 400oC.  Due to the difficultly of controlling the temperature it’s very easy at 400oC to overdo it in a localised area, melting the base metal which can result in a real mess.  Working with this low-temperature solder I was able to slowly but surely fill up the corrosion holes.  To help me along I had to clamp inside the sump a stainless steel plate to stop the solder running out as I moved along the outside of the sump.  Eventually I was able to clean off the outside with the result that you can see in the photograph.  A water test showed that I’d been successful in stopping the sump leaking. 

This sump pan now has a new lease of life and is heading for a restored racing MG engine.