In addition to this article the Y Register have now acquired some original drawings of the Jackall System and these can be found on this separate page. Original Y Type Jackall System Drawings.
The built-in jacking system of the MG Y is a standard kit from Jackall, then owned by the Smiths people. Many cars of the era carried this system but most had the pump under the front passenger seat floor. On the Y it is bolted to the nearside dash, under the bonnet. The system requires normal single-grade SAE 20 mineral oil and is a very simple system, so good in fact that many still operate today having had little maintenance over the years. The first bit to leak is the flexible hose to the rear axle. This simply falls to bits after about 40 years but the MGCC Y Register sell a kit to fix the problem. The other common leak is inside the pump itself and again the Y Register can supply the three little seals that cure this problem. But eventually the rams themselves leak, usually caused by people not cleaning away crud from the leg before it retracts itself and the grit damages the seal.
Study the Jackall leg diagram and the leakage areas are H, F, D and G. We will deal with each as we go through the photograph sequence that follows. Note how the springs (there are two, one inside the other) are pinned to each end. This spring pulls the leg back in when you release the pump valve. Do NOT unscrew item ‘A’ as it is a real PIG to get back inside, leave it well alone. If you do unscrew it the spring pulls the threaded bit into the leg! If it does not leak, leave it alone. If it does leak, it will just require tightening up on its copper washer, item ‘H’. To release the pipe unscrew it at the olive union (the pipe that enters the joint). There are missing numbers in the sequence because the photos were rubbish.( Photo’s 3 & 18 not shown. )
Photo 1 above is the simplest method of stopping the oil escaping from the system, by simply sealing the reservoir’s cap with a sheet of polythene and the cap screwed up tight. This stops the air entering; but you can drain it all out if the oil is old by simply leaving the cap off and putting a container under the disconnected pipe at the jack end.
Photo 2 is the pump. If the red bit is awash with oil, you need new seals inside it. Remove the black valve by unscrewing it fully out, remove the red selector (two nuts) then unscrew the tube it sat on. Under this you will find a little round seal (the smallest one in the packet you got from the Y Register). Lift out the old one with a scriber, and fit the new one. With the red selector off unscrew both fwd and rear valves and remove the seals underneath them, WATCH OUT for the spring and do not lose it. Assembly is obvious and you will carry out this operation much quicker than you read it here. Assemble the red selector carefully as it runs on a cam device that hopefully you took note of on stripping down!
Photo 4 ( below left ) is of my leaking jack, you can see the oil drips on the foot.
Photo 5 is the jack in the vice having the foot undone where you will have to be brutal to undo threads that have not moved for 60 odd years. As I was to fit new legs I was not too bothered about damaging the old ones, but if you are to re-use your legs put some aluminium sheet between it and the mole-grips.
Photo 6 is the foot undone and the return spring’s locating pin (look at the diagram of the jack again).
Photo 7 A better view of the pin partly removed. Note the spring is very strong and you will need to thread strong wire through it so you can pull it out again on re-assembly.
Photo 8 is the seal holder on the end of the ram being undone. You will need vee-shaped vice jaws to grip the cylinder, or you will flatten it so the leg cannot move inside. It is not critical if you do as the leg is a loose fit; you can ‘unflatten’ the cylinder in the vice. The idea of a vee shape is to hold the ‘tube’ in four places.
Photo 9 is the copper washer inside the seal holder, item ‘F’ in the diagram. If someone left this out in a previous stripping, this may well be your leak and not the seal! Make sure you fit a new one, it can be copper or soft alloy.
Photo 10 is the seal holder’s other end with the soft rubber ‘U’ shaped inside (see last sketch for this seal).
Photo 11 This is the old rubber seal partly removed. Note how you have to feed it out and why you cannot refit a modern steel-backed seal.
Photo 12 The old and new leg with the old and new seals. The new leg is of stainless steel and the new seal is in two parts; a rubber outer ring with a plastic centre. These items were supplied by SVW Spares Ltd, 01964 671046 – www.svwspares.co.uk.
Photo 13 is my old leg with too much damage to be able to seal with the new type of seal. The older ‘U’ shaped rubber ones could cope with some damage as they sealed over a larger area. These new seals have a pin-point edge so require a good surface.
Photo 14 The new seal going into the holder AFTER it has had a good clean out. Corrosion can get behind the old rubber seal so clean this up well inside.
Photo 15 The new leg inserted and the holder screwed back on.
Photo 16 The foot also requires a copper or soft alloy washer (item ‘G’ on the diagram) or the oil under pressure can escape eventually. But just like item ‘F’ it too looks like the main seal is leaking.
Photo 17 Foot with the washer and a new rubber ‘O’ ring assembled ready to fit. The ‘O’ ring keeps the muck out when the leg is retracted. You can get these from any motor-factors in packets.
Photo 19 The return spring pulled out and gripped ready for reconnecting to the foot.
Photo 20 The pin refitted to hold the spring. Again take care as things can fly apart here if you are not careful.
Photo 21 The foot being screwed back on. Note the bit of soft alloy protecting the ram legs surface.
Photo 22 All assembled again.
Photo 23 And it works!!!
Last diagram is of the two different seals, old and new.
Refill using SAE 20 mineral oil. Keep the legs clean.