Re: [A/S] Brake Problems

["overlander_64" <overlander64@xxxxxxxxxxxxxx>]

Greetings Lawrence!
I had a similar experience with one of my vehicles, and it was the 
result of something not mentioned in the earlier posts in this 
thread.  I don't know whether this would apply to your situation, 
particularly if you have diesel power.  On my big block gas fueled 
tow vehicle (the '75 Cadillac), the brake fluid was boiled producing 
the exact situation you describe when the exhaust heat riser valve 
froze in the closed position causing excessive heat transfer to the 
car's firewall and from there to the brake master cylinder. 

I haven't had it happen while towing, but have had it happen at 
least half a dozen times when traveling solo.  The usual scenario is 
heat in excess of 85 degrees, humidity in excess of 70%, stop-and-go 
city traffic (St. Louis, MO or Madison, WI), and air conditioner 
operating at full-maximum.  The solution was a new exhaust heat 
riser valve; and an added step in routine service -- my mechanic now 
services the exhaust heat riser valve at each oil change (haven't 
had a recurrence in more than six years).  I also had one other 
modification made that may have helped reduce the exhaust heat 
transfer to the car's firewall by having a custom fabricated less 
restrictive dual exhaust system installed with dual catalytic 
converters.

Good luck in solving the issues with your tow vehicle brakes!

Kevin D. Allen
WBCCI/VAC/Free Wheelers/Computer Club #6359
1964 Overlander International/1999 GMC K2500 Suburban (7400 
VORTEC/4.10 Differentials)
1978 Argosy Minuet 6.0 Metre/1975 Cadillac Eldorado Convertible (8.2 
Liter V8/2.70 Final Drive)