[TR] cooling tr-3

[Randall]

---- Gary Nafziger <nafzigerg at yahoo.com> wrote: 
> My conclusion
> is that some time during a drive (approx 25 miles) the radiator is boiling and
> pushing out fluid........or can it push out fluid without boiling?  At any
> rate I'm assuming that when fluid is pushed out........it later should be
> sucked back into the radiator and thats not happening.  My overflow bottle was
> also almost full after the cool down after the last two drives .......when I
> think it should be at normal level.
> 
> Any thoughts or ideas?

Several possibilities.  The coolant does expand when it gets hot, so if you fill everything full, it will get pushed out while driving.

The original 4 psi caps were not designed to be used with a recovery bottle; they leak and allow air back into the radiator.  Especially with the bottle down low (about the only place to mount it on a TR3), the cap has to hold some vacuum to pull the water back up.  I tried adding a rubber gasket, and sealing the rivet with silicone sealer, but never could get it to suck water up.  For awhile I ran a modern cap that I modified to match the longer TR3 fill neck; but now I have the neck replaced so I can use most modern caps.  The cost was only $20 or so while the radiator was in for service anyway.

I've also had problems in the past with water pumps that would suck air.  If your bottle is mounted below the level of the water pump, that might be an issue.  Or the water pump might just be losing water slowly while driving, as my current pump seems to be doing.

Another possibility of course is a leaking head gasket.  I've spent literally years fighting with head gaskets that only leak a little bit, and only combustion gases into the water jacket while accelerating.  If the leak is small enough, the air works it's way into the top of the radiator and forces water out the cap, but doesn't interrupt the flow enough to cause a boil-over.  My 59 TR3A was actually more or less drivable that way, with the system low by a half gallon or so, as long as I didn't get into any big traffic jams or whatever.

Any radiator shop can test for this condition, with a tool that checks the CO2 concentration in the air in the radiator.  Although my shop charged less than $20, I went ahead and bought the "Block Tester" tool so I can do it myself.

Randall