I see there’s been a fair bit of discussion about XK120 recirculating ball steering boxes leaking oil. Mine the same, cured now (I think),
Decades ago I flushed the innards of mine with solvent, checked and cleared all the components for wear, changed the seals and gaskets, reassembled the box and bolted it to the column, threw a coat semigloss black paint on the thing and set it aside dry. Before installing it a few years ago I filled the box with 80W140 gear oil, the only stuff available locally, and leaned it up against a wall. After a couple of days there was a puddle of oil on the floor. Figured the rocker shaft oil seal must have dried out over the years of storage so replaced it with a new one and installed the steering column. Still leaked. The garage floor below is well stained.
It was obvious the leak wasn’t through the oil seal but through the lower end. Disconnected the wiring harness and removed the four nuts securing the end plate to the housing - actually only one of the nuts came free, the other three came out still attached to their studs. First observation (and clue) was the tapped holes in the housing aren’t blind and when the studs came out the oil followed:
This pic depicts the parts breakdown. There’s
- the bracket that clips the wiring tube, two 1/4” studs that thread into the end plate w/ nuts and lock washers, pinch bolt/nut/lock washer and a dense felt seal.
- the four 3/8” studs/nuts/lock washers that secure the end plate to the housing, and
- the end plate, stack of shims, gaskets and packing washer that fixes the lower ball race in position.
I expected the lower ball race might want to drop out of the housing once the end plate was removed but it stayed in place.
There are apparently five avenues for oil leakage. The most obvious are the gaskets, but I’d replaced those years ago. Maybe through the shims? I’d applied sealant to them at the same time - maybe not so smart since there are eight of them, they’re only a couple of thou thick and the added sealant increased the bearing float - but the leak couldn’t be there. I’d also applied sealant to the felt tube seal so it shouldn’t have leaked either.
That leaves the two 1/4” studs securing the tube bracket and the four 3/8” end plate studs.
Cleaned everything up thoroughly, including the shims, applied thread sealant to the six studs, and reassembled with two new gaskets and Permatex #2. I did not reapply sealant to the shims. Refilled the box with the recommended straight SAE 140 gear oil and now after several days there is no evidence of a leak.
I’m reasonably certain the 80W140 oil was seeping past the threads in the studs and the thread sealant cured the leak. Also likely the thicker SAE 140 oil is less prone to seep through tight clearances, so a two-part solution.