Friday, February 17, 2023

Boosting Brakes

I was winging my way home from work one fine February day, and life was grand.  That is, it was until I stepped on the brake pedal and didn't get the Whoa I was expecting.  The pedal was hard, and the car didn't stop well.  I got off the highway and found the engine running rough.

Hoo boy.

I made it home safely.  The brakes still worked, but it was not easy.  Alice wanted to stall at every light.  But when I got near the house, I noticed something.  The engine only ran roughly when I had my foot on the brake pedal.  If I just used the parking brake, she ran great.  I knew what this meant - the vacuum booster had failed.

These are the things that happen when you have a nearly 50 year old car and don't replace every single component.  The booster just aged out and lost its ability to hold a vacuum.

Ah well... I did a little looking around, and I found that I had the unobtainable unit fitted only to the 1975 MGB.  Which is Alice.  This was no longer a fine February day.

I did some more research and learned that the later units for a '76 - '80 would work.  Dimensions are almost the same with about a 1/4" difference in length.  I decided I'd take a chance and ordered one from Moss Europe.  Why the UK?  Because the unit was only $100 USD, and even with $60 shipping it was cheaper than the same unit from Moss USA ($220).  And, I got it in a week.

While I waited, I removed the old unit.  This is not an easy task in any case, and on the '75 it's even harder because the pedal box is just-ever-so-slightly different, which makes it almost impossible to get the retaining nuts off from the inside.

But I did it.

I ended up cheating a little.  I removed the cover from the pedal box to find four nuts holding the booster to the box.  The top two nuts came off straight away.  The bottom nut behind the clutch pedal was easily accessible from underneath.  That last nut, though... I couldn't get a socket on it from underneath (between the pedals), I couldn't get a ratchet and socket on it from above, and I couldn't get enough swing on a ratcheting box wrench.  So like I said, I cheated... and I cut a little notch in the box to give the ratcheting wrench enough swing to loosen the nut.  I was then able to spin it off with a finger from underneath.

Once those nuts were loose, I removed the pin that attaches the booster to the brake pedal.  It was a tight fit but a needle nose pliers did the trick.

Finally, I removed the brake master cylinder's two nuts... and then I loosened the clamp holding the rear brake line to the inner wing... then the one holding the lines to the firewall, at the bonnet hinge... then the air cleaner... and then with a deep breath and trepidation, I was able to move the master cylinder backward enough to let me swivel the booster out of the way.  And it came out.

Believe it or not, fitting the replacement is almost as easy.  The '76 unit does match up well, aside from being a bit shorter in length.  It slid into place with little effort, and three of the four nuts went on with little fuss.  That fourth nut, though... the one behind the brake pedal... is not so easy.  I have ordered a flexible extension to see if that will be sufficient to get that nut into place.  For now, there are only three.

Before the master cylinder can be refitted, the pushrod that links the booster to the master cylinder must be adjusted.  There are tools designed for this purpose, but I don't have one.  The intent is to get the pushrod when in place to exactly, barely touch the cup in the master cylinder so there is almost no play.  There is a multiplier in distance here - I don't exactly know what it is - but a little play makes a large difference in the feel at the pedal.  Too much play will result in a low pedal with a hard feel when it does engage.  Too little will cause the brakes to bind.  So I cheated again, and carefully measured the distance the old pushrod protruded from the old unit.  I adjusted the new unit's pushrod to match.

Then, I put it all back together.

When I started the car, the pedal sank a bit like it is supposed to.  Actually, it sank a bit too much.  I wanted a little bit higher pedal, so I unbolted the master from the power booster and adjusted the linkage to be a millimeter longer.  This time, I was satisfied with the feel and height of the pedal.

After reinstalling the air cleaner and refitting the retaining clamps for the brake lines, I went for a little jaunt.  The brakes felt solid and easy to modulate.  I was able to lock up the brakes with a hard stomp on the brake pedal.

Once I get that flexible extension, I'll get that last nut installed (I don't think it is wise to leave it as is).  Then, this job will be done!  It was not pleasant but very satisfying, and I can rest easy knowing the braking system is in safe and sound condition.

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Friday, February 3, 2023

Hood II

Alice has her hat on.

Installing the top was a lot less stressful than I thought it would be.  It helps that the top I bought from Prestige Auto Trim is a perfect fit and came with good instructions, though I modified them a touch.

First things first - raise the frame and lay the top on the car to see how close the fit is, attaching it to the fasteners.  It happens to be ideal.  In fact, Prestige even had a mark indicating roughly where the header rail would attach - and it happened to be spot on.  I left the protective paper in place until the end so I wouldn't screw it up and drip stuff on it.

Next, stretch the fabric to see how well it will line up with the header rail.  As I mentioned before, the top fit extremely well and matched the marks from Prestige.  The instructions say to mark the center of the material and the header rail so you can align those marks.  However, I skipped this as the top is not exactly large and it is pretty easy to see how it will fit by looking at the edges to ensure it covers the header rail.

The step beyond is the one that requires courage: attaching the top to the header rail with contact cement.  The instructions say to make a chalk line outlining where the header rail meets the fabric.  However, I already had it!  I used Weldwood contact cement, which comes in small bottles and are the perfect amount for this job.

I carefully applied contact cement to the header rail (which I cleaned well first) and the fabric up to the mark.  I let it dry for about 5 minutes, and then stretched the fabric and tacked it down in the center.  I then pulled fabric into alignment on each side.  You get a little working time and a couple of tries, but that's it.  I practiced this a half dozen times before applying the cement.

The result was nearly ideal!

Once dry, the next step is to attach the seal to the header rail.  The seal and its retainer come as a kit from Moss, which also includes the proper rivets to attach the retainer.  This also acts to hold the fabric in place to the header rail.  The seal fits into the retainer pretty easily as it is soft.

The top from Prestige also came with a nice extra strip of fabric on each side that helps relieve stress on the edges of the fabric.  I glued this fabric down with a little contact cement, then attached the seal retainer.  I had to punch holes with an awl through the fabric before attaching the retainer.  I used the rivets, and I modified my rivet gun to help it fit into the small gap available without bending the lip of the retaining rail (too much).  Lots of people use screws instead.

I then fitted the seal and attached the header rail to the windshield frame.  This is where your efforts really pay off - the top should be tight, but not drum-tight as it will shrink a bit in colder weather.

On my frame, there is a strip of fabric attached to the top around the back rail on the frame (the part that sticks up the most).  I applied contact cement and glued this together to encapsulate the rail.  This was not 100% successful, and I'll have to go back and use some thread to make it stronger.  But that's okay.

Finally, I attached the snaps to the fabric where it meets the windshield frame.  This is what provides teh seal against the window when it's up.

I am extremely pleased with the result!

The hood fits perfectly and the car is actually quite quiet when it's raised.  There is only a little wind noise even at highway speeds.  The rear window zips out as well.  I also bought a new boot cover for when the hood is lowered, and that also fits perfectly.

This was the last step to having a complete car.  Now, I can focus on improvements - and driving!

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