RE: IML: Brake Light Switch on '56

[Jeff Cantor <jcantor791@xxxxxxxxxxx>]

Paul,

Both the fluid incompatibility and the dirt issue make at least some  
sense to me however, there are two important points that I probably  
should have mentioned in my original post.  First, the entire  
hydraulic side of the brake system was replaced with new components  
two years ago with the exception of the two brass junction blocks  
which I cleaned very thoroughly with alcohol and compressed air.  I  
think this makes the dirt scenario rather unlikely.  Second, while I  
did upgrade from the "original" spec DOT 3 fluid, I did not go with  
the silicone DOT5.  Instead I used ATE's DOT4 fluid which seemed to  
me to be a nice compromise (it also has the advantage of being  
available in different colors to make flushing the system very easy).

Therefore the jury is still out as to exactly what might be causing  
the problem.  However, in the interest of protecting the car's very  
nice tail end while also avoiding the potential for whiplash, I'm  
going to install the "modern" pushbotton brake light switch that I've  
purchase at least as a temporary solution.  This will allow me to  
safely drive the car this season while still puzzling over what else  
might be going on.  In the fall when I'm planning to flush the brake  
fluid anyway, I'll probably take the switch off and see if I can  
determine what the issue is/was.

Thanks,
Jeff
'56 Sedan
Trenton, NJ

Subject: Re: IML: Brake Light Switch on '56
Date: Mon, 30 Apr 2007 23:41:57 -0400
From: randalpark@xxxxxxx
Reply-To: mailing-list@xxxxxxxxxxxxxxxx
It sounds to me like the switch is clogged with foreign material. I
would suggest replacing it again.

I saw the post about the hydraulic switches possibly not being
compatible with DOT 5. I haven't found that to be the case either. That
type of switch was used through 1961. I have that type of switch in my
1948 L.C., as well as my '55, '56, and both '60 Imperials. The switches
do go bad, and they don't always leak. I had the most trouble with the
one in my 1960 LeBaron, and that was before I changed everything over
to Dot 5. Apparently, there was some crude in the lines on that car.
Eventually, it worked its way into the switch. I was lucky that I
didn't lose my brakes. I didn't know then that a switch problem like
that could be a warning sign of a more serious problem.

Knowing what I do now about brakes, rotten Dot 3 fluid in old cars, and
changing to Dot 5, I would consider a light switch problem like you
describe, especially if it should continue after replacing the switch
the second time, to be a possible indication of dirt in the system. On
your car, it would likely be from it entering the reservoir during
removal of the lid to check the level. It would be very easy for that
to happen, and then work its way into the switch. If there is enough
dirt in the system, it will also eventually cause the brakes themselves
to not work either. A sign of this would be good brakes when the pedal
is depressed gradually, with a super hard and non-responsive pedal when
pushed suddenly for a panic type stop. It doesn't take very much dirt
or very big clog to effect brake action seriously.

I apologize for saying that I thought you should look elsewhere, and
then not suggesting what else to check. It has been that sort of a day.
I would replace the switch, and see if that fixed the problem. If it
happens again with the new switch, I would suspect foreign matter in
the lines. That would indicate the need for a complete flush, or
possibly replacement of all the lines, including the metal ones. The
junctions should all be cleaned and inspected as well.

If a car sits long enough, and heaven forbid that the brake system was
some how left open, such as if the master cylinder had been off for a
few years, the fluid will turn gloppy and finally solid in the lines.
Flushing them doesn't always get it all out.

I hope this helps.

Paul W.



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