Have to replace some (or possibly all) of my 4 front brake wheel cylinders Jaguar 4177 (Lockheed 30635). This is for a 1954 XK 120 and I know that the same system is used on the XK 140.
The early XK 120 had Lockheed front brakes without automatic compensation. It uses wheel cylinder Lockheed 25452 (Jaguar 2037). The availability (and price) of this earlier version is much better than the later one.
If we compare the two Lockheed cylinders, we see that the rubber cup, cup filler and spring are identical for the early and the later version. Obviously the piston is different as is the cylinder body. See data below.
The pistons of my “old” cylinders are still looking good (it’s the cylinder wall that is “beyond repair”) and the pistons also don’t play a role in sealing the cylinder.
Has anybody ever tried to make a conversion using the “old pistons” in the earlier Lockheed 25452 wheel cylinder? Or are the cylinder body dimensions so different that a conversion is impossible?
Since the cylinder wall is beyond repair, is it not possible to fit a fit a cylinder lining ( sleeve ) of some kind? Probably is must me hand made.
I have RVS sleeve’s is my rear wheel brake cylinders on my S-type, fitted 20 years ago.
Hard to say what is beyond repair in an aluminum cylinder.
I did a lot of stone honing, and then wrapped Scotchbrite around my hone and polished the bores for awhile with oil, and they all came out mirror finish. I made stainless steel pistons with copper hats.
Front cylinder, new and old pistons.
Hi Bob K
As you can see the cylinders are basically the same but the early ones do not have the hump to hold the rubber boot (dust cap). As you said, the piston is different but also the “bowler hat” behind the rubber cap and there is no spring fitted behind the “bowler hat” (see second picture).
The inside diameter (1 1/8") and the rubber caps plus all other measurements are exactly the same.
So basically its possible to pair an early cylinder with the later internals except the hump for the rubber boot (dust cap).
I had two wheel cylinders from the US with brass sleeves, but the seals kept on leaking. May be I should have (re)polished them like you proposed.
Lukas,
Very interesting! So the dimensions of the early and later body are the same. Only the extra rim for the
rubber (dust) cap is an addition to the later body.
The Lockheed parts list (see my earlier pictures) does list a spring for the early cylinder and I also think that the photo of the cross section of the early cylinder you refer to, does show the (compressed) spring within the cup filler (or “bowler hat” as you describe this part).
So I’m gonna further investigate this route and trying to find a way to keep this dust cover in place. The existing clamping wire on the later cylinder does provide already some force to hold the cap in place but don’t know whether that’s sufficient.
Glad you were able to make this picture of the two wheel cylinders for comparison!
You are very welcome, actually I work on the brakes anyway (transfer back to original) thus it was not a big deal to put the cylinders beside each other.
Yes, the front cylinder housings are exactly the same, except the “hump” to hold the dust cap. On a turning lathe it should be possible to make a slight recess at the end for the dust cover.
Interesting comment to the spring behind the “bowler hat” - on the sectional drawing there is distinctively a spring visible but I’'ve found no springs in our very early original brake cylinders and they slept untouched for at least 55 years… And the “bowler hat” has a different shape, compared to the picture out of the service manual… Strange, very strange but definitaly something I have to make sure before assembling the brakes further…
I’m back, after being off line for a week dealing with computer problems.
The stainless hats were made from tube caps bought from Truly Tubular. I cut down the length in my lathe, drilled and countersunk a hole in the center for a flat head screw, welded a pair of square keys for brake shoe guides, and drilled and tapped the piston for the screw.
