Lotus Elan

Alternate brake master

PostPost by: JerryBoone » Sun Jun 04, 2023 12:35 am

Let me begin by saying I am not trying to keep my Elan S4 (federalized version in the US) a concours winning car. My goal when I purchased it three years ago was to enjoy both driving and working on it, and making upgrades when and where I thought they were justified. To that end I've rewired it with a modern multi-fused harness, swapped the distributor for one with electronic ignition, changed both the starter and generator for modern pieces etc etc.

So when my brake pedal recently went all the way to the floor with no discernable decrease in momentum, I had to decide if I wanted to spend somewhere between $250 and $450 (depending upon where I decided to send it) to have the original dual circuit master cylinder rebuilt or look for a more modern replacement.

Dan Morrison recommended I look at the master cylinder from the Ford Courier pickup truck. He had done the conversion on a Lotus Europa, based on a posting on the Europa site by Joji Tokumoto, who began with information from Europa owner Doug Shepard.

The swap proved to be rather straightforward, tho, as is my habit, I took a bunch of missteps along the way to make it far more time consuming than it needed to be.

I began with a master cylinder from Rock Auto. It is '75 bore so the pedal travel is reduced, tho brake pressure is slightly more. The mounting holes are just a tad farther apart than on the original piece, but a 1/4 inch grinder bit in an electric drill and less than 10 minutes work had the holes lined up perfectly.

The major issue with the new MC is that the casting has the outlet ports extending much farther than the original, and as a result everything I tried fouled against the clutch master. I tried a variety of adapters, angle fittings etc but nothing did the job.

The solution I finally came up with is a 7/8-inch spacer between the MC and the firewall. That moves the MC out of the way of the clutch MC and allows for easy connections. Channeling the spirit of ACBC, I made the spacer out of a couple pieces of scrap plywood, glued together. I did paint them black, but you could leave them raw to save weight.

Ford uses a metric thread (10mm 1.25 thread) on the MC outlet ports. Adapters are readily available. I ended up taking off the original brake line and changing the flare on the MC end from a bubble flare to a more common inverted flare. Had I stumbled onto the spacer idea earlier in the changeover, I would have used the original banjo fitting and purchased a second one to make a cleaner looking job. To do the banjo fitting, you have to shorten the metric banjo bolt a bit, but that's an easy task.

The other challenge is fabricating a new pushrod. The rod in the new master cylinder goes about an inch into the plunger. I used a 5/16 grade 8 bolt, sawed off the head and smoothed the cut end. I placed the new and old master cylinders side by side and added in the length of the spacer to determine how much of the bolt I needed to cut off. I also had to get a new clevis to screw onto the pedal end of the rod, which allows for some adjustment once it is installed.

Lastly, it is imperative that the new MC be thoroughly bench bled before installation. When I first installed it, I assumed I could pressure bleed the air out and all would be well. I did, and it wasn't.

Once properly bled and then installed, the pedal came up to the top of its travel and remains firm under multiple stops. It works well enough that I was able to lock up the brakes on one panic-stop test application.

What did I save? The entire project cost under $100. It was about $70 for the MC, another $12 for the clevis, about $4 for the bolt and a few more dollars for the metric brake line ends. It took me weeks of trial and error to get it done. If I had to do it again, I think that once I had all the parts, I could accomplish the same thing in a long afternoon.
Attachments
New brake master.jpg and
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PostPost by: Frogelan » Sun Jun 04, 2023 7:20 am

Jerry,

Thank you for that post. It is a very neat solution and well explained.

It makes a great deal of sense as a transparent reservoir is a legal requirement for road (or sensor) in Europe.

If you happen to have the part number it would ber very useful (I presume that the Ford Transit Courier is the same world wide, but it would be useful to be able to double check).

Andrew
1965 Lotus Elan S2 26/4022 (originally Dutchess Lotus East, PA and NJ Area, USA)
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PostPost by: JerryBoone » Sun Jun 04, 2023 11:55 am

I do not have a Ford part number. The master cylinder comes from an early 1970s Ford Courier pickup truck, also sold in the US (and I think other places) as a Mazda B-series pickup. I bought mine from a company named Rock Auto in the US. They listed a number of manufacturers and rebuilders. The one I purchased was DYNAMIC FRICTION 35554004. I lean toward buying new vs rebuilt as I've had only about a 50 percent success rate with rebuilt units. I hope that helps.
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PostPost by: arcangel » Sun Jun 04, 2023 6:32 pm

Jerry, nice writeup and good looking job. I used the Courier MC with Cardone part number Cardone 13-1777. As you stated its from the first generation Ford mini pickup truck made for Ford by Toyo Kogyo (Mazda).back in the 70s One thing I was wondering was the retaining mechanism for the pushrod in the MC. How did you keep the pushrod from falling out of the MC. I no longer have Elan so can't check the pedal assembly to see if it has a pedal stop and the pushrod is not captured like the Girlings.

Secondly, for anyone considering using the Girling banjos, be aware that the 10 mm banjo bolt will be a sloppy fit with the Girling banjo. A safer method is to use 10 mm banjos which unfortunately will require using AN flares and fittings.

Joji Tokumoto
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PostPost by: JerryBoone » Sun Jun 04, 2023 8:56 pm

Joji:

Thanks for your comments.

Unlike in the complex brake mechanism in the Europa, the pushrod can't fall out in the Elan. It goes so far into the plunger in the master cylinder that there simply isn't enough room for it become disengaged when the brake pedal is fully retracted.

I think there is about 3/16 inch of freeplay vs the half inch the rod extends into the master cylinder.

On final assembly, I connected the pushrod and clevis to the brake pedal, then fed the rod into master cylinder as I placed it against the firewall/spacer. Once everything was bolted up tight, I was able to turn the rod into the clevis to create just a bit of freeplay.

I hope that explanation makes sense. If not, let me know and I'll try again.
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PostPost by: vstibbard » Fri Jun 09, 2023 9:42 am

Is your pushrod secured with retaining washer and circlip? Your description makes no reference to it!
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PostPost by: JerryBoone » Fri Jun 09, 2023 11:31 am

No. It is not retained with a circlip or a washer. There is no provision in the master cylinder casting for one. The rod extends a half-inch into a hole in the master cylinder piston. Once the clevis end is attached to the brake pedal arm and the clevis is adjusted for appropriate free play, there is no way for the pushrod to come out. The fit is so close that I had to mount the pushrod to the pedal and then feed the pushrod into the master cylinder as I mounted it to the firewall.
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