1989 vaccum assist conversion

My vaccum assist tank appears to be bad. I bought the kit and heard there is a double diaphragm that works well. Anyone have a part number or source?

David …

I believe the “go to” booster of choice for the brake conversion on our cars is from a series II XJ-6. Part number 53950, rebuilt by Cardone. It’s a dual diaphragm 8" unit which is as big as you’re going to be able to fit in the space available. I’m very pleased with mine.

Hey Gman, you sure about that part number? I can’t find it.

Should be 535950:

Thanks , I did find it at rock auto but they are out of stock. anyplace else I can look?

Try NAPA or Advance Auto Parts.

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Well I have been looking for 2 days and that part number isn’t available anymore, is there another booster that will work? Non Jag as they all seem to use the same part, even the cac1227 is out.

Well, I have done a ton of searching and I think I found a booster that will work. It is a duralast B 4224. Any input would be appreciated.

Well that wasn’t even close, any other alternatives?

How about this one?

Yes tried that one also, no longer available. I can get one but they run 700 to 1200 and I cannot justify that at this time.

Have you spoken to “Booster Dewey”?https://www.powerbrakebooster.com/

Although this Jaguar booster is listed for later models if the picture represents the true booster it certainly LOOKS exactly like what you need. May be worth looking into.

That one only has 3 studs, but I wonder if I could rebuild it myself with their parts?

OK, I will show my ignorance on this topic. Would something like this work?

David …

I would think that you could easily make an adapter plate to work with the 3 studs, or just modify the one you have. Actually if you rotated the booster 180 degrees (non return valve on the bottom) It looks like the 3 bolts would be more accessible and a lot easier to mount to your plate than the 4 bolt model. The only requirement is that when you install the booster the two bolts on the other side are perfectly horizontal. I’m assuming the new booster is the same size and those two bolts are the same distance apart as your booster.

Interesting if the only difference in part numbers is just the 3 vs 4 bolt pattern.

Although I have no experience assembling a booster I definitely would not break open a freshly rebuilt unit.

Actually that looks like it might.

David, check the archives for posts about vacuum brake conversion. Try this in the forum search box (omit the underscore between the ‘#’ and the ‘xj40’):

#_xj40 vacuum brake conversion

There are a lot of posts and some even refer to using a GM booster. A quick check of RockAuto.com turns up some 1980s GM models that use a booster with 4 mounting studs that look similar to the NLA Jaguar-specific unit.

Thanks, I had heard that but had no idea where to look, definitely going to try that.

Does anyone have a non jag brake booster on their xj40, and if so what did you use?