Lotus Elan

Scramblin On The Road

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Along with the surge of adrenaline came a gaggle of emotions that threatened to paralyze me in a cloud of fear, shame and self-incrimination. The suspicion that something was going on with the brakes had just turned into hard evidence as the pedal was getting closer to the floor with each application. Small amount of brake fluid had been mysteriously disappearing for some months but a check outside the hotel in Sonora this morning had shown a little more loss than usual. It was enough to notice but there seemed to be no immediate cause for alarm. Maybe I was lulled into stupidity by the success of the trip so far. We had driven from Redwood City to Sonora yesterday afternoon. It was an easy 2½ hour drive giving us time to scout around the area, walk through the old mining twon of Columbia and thoroughly enjoy our dinner at the restaurant in the City Hotel. Yakking with the locals in the quaint bar at the historic Sonora Inn, where we spent a restful night was an unexpected pleasure.

Now the mushy feeling under my right foot informed me that the loss of fluid had apparently accelerated drastically in the last hours with the result that we were to be completely without brakes very shortly. Of course brake loss can be frightening in any circumstances but our particular situation augmented my fear. We were on the second day of a weekend in the Sierras, going into the northern approach to Yosemite on Highway 120. We had just passed the place where a car full of federal security jocks were killed when they were hit by some speeding local yokel cops during the Queen's visit to Yosemite. It was all downhill now!

A combination of macho pride and hopeful optimism kept me from immediately telling Pat about our predicament. I gingerly applied the handbrake - THAT'S why it's called an emergency brake! To my amazement it held. In the year and a half I had spent messing with various parts of old Daisy, our Elan+2, I had never had occasion to perform even the most perfunctory inspection of the handbrake mechanism. Pat finally asked why I was using the handbrake. I told her that we were experiencing some brake problems and that careful use of the gearbox and handbrake would get us safely to the service station on the floor of the Valley. Pat trusted the explaination and seemed to expect only some momentary inconvenience. I was completely pissed at myself for getting us in this predicament and scrambling around in my head for a diagnosis of the problem and a solution that would keep us off the hook or worse, the bus.

As we worked our way carefully down into Yosemite Valley I began to speculate as to the exact nature of the malfunction and how to facilitate temporary repairs - I had to patch the damn thing up enough to get us home safely. The brake boosters had been on my list for some time but lack of an inexpensive solution ($400 apiece to replace the boosters) and relative ignorance of the details of the system had kept me from starting the project. I was still beating myself up about this now dangerously stupid procrastination when we pulled up in front of the auto service center across from the grocery store. Just in time too! The exhaust began spouting white smoke in alarming amounts.

A check under the hood confirmed that the brake fluid reservoir was empty. Using the small tool kit I take on trips, I disconnected the vacuum lines from the intake manifold to the twin brake boosters. The clear oil fluid with the distinctive aroma dripping out of the rubber lines confirmed what I had already deduced. My mysterious brake fluid disappearance was a leaking seal in one or both boosters that was sucking the fluid into the booster vacuum reservoirs. At least one of them had filled up, causing the fluid to be sucked into the engine via the vacuum hose and intake manifold. That was what was causing the white exhaust smoke!

The fix that would get us home was mercifully obvious. I would plug the vacuum hoses and we would use the brakes unboosted. The service center had brake fluid and I could bleed the system if I had to. We looked around on the ground for sticks of the correct diameter and after finding some likely candidates, I shoved two of the right sized into the booster ends of the vacuum hoses and retightened the clamps.

Firing up the engine verified that the hoses were tight - no vacuum leaks. The brake pedal felt hard - real hard, without the boosters, and so the system didn't need to be bled. The fluid reservoir was filled and a short test drive verified that the brakes worked but without the boosters in operation there was no hope of locking the brakes.

Even though the situation was no longer grave, I was in no mood to stroll around casually admiring the scenery. I wanted to get home as soon as possible and put this trip behind us. The fact that I was going to have to implement a permanent brake system fix before the car was driveable again didn't fire me up much.

To make a long story short, we made it home okay. When I removed the boosters, I found that they were both full of fluid due to leaking seals. The seals failed due to corrosion pitting of the aluminum bore in the booster. Moisture absorption to the fluid over time probably contributed to the corrosion. All of with cars we plan to keep a long time should completely replace the brake fluid every other year.

So much for the safety aspect of the tandem master cylinder and dual boosters. I decided to figure out a way to get rid of at least one booster. Money and engine compartment room would be saved if I could achieve this goal. I talked to several people and read what I could find, but there were some serious holes in the information available. I couldn't find a schematic of the booster internals or find out the line pressures it generated. As a start, I decided to try a boosterless system. Stan Murawski gave me (maybe it was a loan but it's going to stay in the car) a stock Elan master cylinder. In order to get it to work, the actuation road length had to be changed. This was due to the differences in the mounting flange to piston distance in the two master cylinders. A lot of measuring, some luck and careful heliarc welding resulted in a workable solution. The Elan master was necessary because it has a smaller bore than the +2 unit; a 0.75 versus 0.90 inch. The trade off is higher line pressure for the same pedal force but longer pedal travel. Its analogous to a lever system. The closer the fulcrum is to what you want to move, the more force you generated for the same push on the lever, but the shorter distance you move it per unit of movement of the lever. My goal was to be able to stop the car safely without having to use the boosters.

Turns out that it worked. I can lock up the brakes even though I have to push pretty hard on the pedal. I think I better control over brakes without the boosters since they're not so touchy. So why, you ask, does the car come with boosters? The plurality part of the question is answered by two words - FEDERAL REGULATIONS. I found out the reason why the boosters themselves are necessary when Pat was helping me bleed the system. She was sitting behind the wheel pushing on the pedal as I needed it. As I was bleeding the master cylinder, I noticed that force that Pat put on the pedal was significantly deforming the area around the pedal box. The pedal box, which holds the brake and clutch master cylinders as well as the pedals and pedal pivot was being pushed up as Pat's pressure on the brake pedal deformed the fiberglass structure that the pedal box bolts to. In order to minimize this deformation, the Lotus designers probably felt it necessary to include a vacuum booster in the system to lower pedal pressures. The original configuration for the Home Island was just find but I think the change to a tandem master cylinder and the addition of another booster to satisfy Federal Regulations needlessly complicated the system.

I'm pleased with the way the brakes work now. They drag me down in a hurry from 100 mph to about 30 mph at Sears Points' Turn 11. I can see no cracking of the structure around the pedal box and I know how I would beef up that area if it becomes necessary. I think that I can control the simultaneous application of brake and throttle (mis-named heel and toe) now. Since it takes more pedal pressure on the brakes, the foot rocking action that blips the throttle does not affect the brake action as much. It's just not a touchy as it was. And it's great having more room on the left side of the engine. I can actually get to the oil dipstick now.

Pat says I drive Daisy like a race car now even on the street. I don't seem to drive the Datsun any different. I think I have a lot more confidence in the +2 now that I've restored so much of mechanicals. I used to baby her thinking there was disaster imminent at any moment. Now that she's survived hours on the track, I driver harder on the street. Not necessarily faster, but harder. It's fun!


Original article located at <a href="http://www.gglotus.org/ggtech/e2brakeboo.htm">Golden Gate Lotus Club</a>