Mk1 EscortRace | Rally | Rebuild

· Build Videos, Mk1 Escort Videos

Pressure-Testing the DIY Sump – Dave's Garage Zetec RWD Mk1 Escort Ep 6

Dave's Garage UK Zetec RWD Mk1 Escort – Episode 6 title card: pressure-testing the DIY sump on an old block

A fabricated sump is only as good as its welds, and a pinhole you miss on the bench becomes an oil leak under the car. In the sixth video of the Zetec RWD playlist (the channel’s “Sump Part 4”), Dave’s Garage UK checks his home-made rear-drive Zetec sump for leaks before it’s painted and put away. Rather than build a dedicated jig, he turns a spare engine block into a pressure-test rig.

Video: Dave's Garage on YouTube · watch “Ford Escort MK1 MK2 DIY Zetec Sump Part 4 Testing Rig” on YouTube

What happens in Episode 6

Testing the smaller pieces first (0:00). One opening is capped off with rubber pipe and a clamp, and a blower nozzle wrapped in tape is jammed into another to push air in. He brushes washing-up liquid and water lightly over the welded faces. Bubbles show straight away along one edge and on the top, so those spots are ground back, re-welded and tested again until they’re clean. The elbow he made also passes with no bubbles. The bung he uses is a short length of rubber hose squeezed between washers on a bolt: tighten it and the rubber swells and seals, the same idea as the blanking plugs plumbers use.

Why use an old block (3:48). He considered making a flat plate with curved sections to match the sump flange, then realised the old engine block could be pressurised instead. The cylinder head can’t simply go back on to seal the top, because its valves are out. He doesn’t want a permanent seal either, because the block will later be used with the head on to mock up the engine mounts in the Escort.

Building the rig (4:50). A steel plate is cut to the size of the deck, held down with some of the head bolts and sealed with silicone. The water passages are separate from the oilways, so only the oil holes need blocking. The dipstick hole is blocked and tacked, and an oil gallery port takes a threaded fitting so the compressor can connect directly. Only low pressure is needed.

Sealing the sides (9:20). For a temporary seal he lays a 20 mm wide, 1 mm thick rubber strip along the flange and taps the bolt holes through with a ball-pein hammer, the way he made gaskets earlier. It doesn’t need to be airtight, just tight enough to hold most of the pressure while he checks the welds for porosity. The final fit will use a proper RTV silicone sealer made for sumps, which he has used on his daughter’s Fiat 500 and on earlier sumps.

Sealing the engine and testing (10:52). With air going in, the first leak shows quickly. It is cut out with a thin cutting disc, re-welded and tested again. In the end he finds only two pinholes, and the rest of the sump is sound.

Paint and storage (13:01). The sump is washed, primed and given a coat of gloss black acrylic left over from another project. The ST170 won’t be ready for it for a while, so he oils the inside and stores it somewhere dry.

Parts, tools and materials mentioned

  • Spare Zetec engine block used as the test rig, with a steel plate bolted to the deck using head bolts
  • Silicone sealant for the plate and a threaded compressor fitting in an oil gallery port
  • Home-made bung made from rubber hose, washers and a bolt
  • 20 mm x 1 mm rubber strip and a ball-pein hammer for the temporary flange seal
  • Washing-up liquid and water, a blower nozzle and a compressor
  • Thin cutting disc and welder for repairs, then primer and gloss black acrylic
  • RTV silicone sump sealer for the final fit on the engine

Lessons for your own Mk1

  • Test before you paint. Soapy water and a bit of air pressure find pinholes that look perfect to the eye.
  • Use what’s on the shelf. An old block gives you the exact flange and bolt pattern, so you don’t have to build a jig.
  • Keep it reversible. Sealing the deck with a bolted plate leaves the block free for mock-up work later.
  • Re-test after every repair. Each re-weld can open up a new pinhole next to it.

Mk1 context

Turning a Zetec north–south for a rear-drive Mk1 means its front-wheel-drive sump has to be replaced with a different shape, and a fabricated sump has a lot of weld. Pressure-testing it on a spare block is a cheap check before it goes anywhere near the car. The sump is fitted to the ST170 later in this series.

Mk1 EscortZetec