My coolant manifold developed an inch-long crack right in the center and
away from any hoses. It may have been due to extremely low coolant level
resulting in super-heated steam running around the pipes, but that incident
started a domino effect that included a cracked head among other things. As
I limped into the mechanics' driveway, he measured the temperature of the
heads and suggested that they may have warped. I had him change out the
coolant manifold and then he told me that the heads were leaking like a
sieve. I couldn't afford new heads at the time, so I started my own
troubleshooting. It turned out that one of the long nylon pipes that run up
to the radiator also had an inch-long crack right at the end. Two minutes
with a sawz-all and I was back on the road. Later I added some JB weld to
seal the crack in the head, and I have put about 40,000 miles on it since!
Note that the low coolant level LED on the water temp gauge NEVER came on
and still hasn't even when I know there were several occasions when it
should have...

On a related topic, I had the coolant system fully sealed just as winter
started this year, so I decided it was time to switch from 100% water to the
50/50 mix of water and coolant. I thought this would be a great opportunity
to flush the system, hopefully removing any crud that had built up. I used a
chemical flush (don't have the brand at the moment but I think it was
Prestone) and proceeded to fill the system with the coolant/water mixture.
It quickly became apparent that flushing with a chemical is a BAD IDEA.
There are now at least two or three points around the interface of heads to
block that are leaking (where did I put that darn JB weld?). Has anyone else
had a similar experience?

Mike Frost
'86 GL wasserleaker