Hi ArtQ,
Have you done the test I specified on the radiator building pressure?If you do the test correctly , it will identify a leaking head gasket. Let me know as I would like to help you with this problem.
Bobby R

Bobby R. Yes, I did the pressure test. Actually, the best AH mechanic in OC did it while I watched (cheap education). He also did the chemical test. Both tests showed no sign of a leaking head gasket or cracked block. I'll see what the water pump looks like on Monday. Hopefully, Bill S is wrong and the problem will be fixed.

Art

Hey Art,
I wouldn't think this is a cracked head.Usually,you would have the exhaust pouring out white smoke as soon as your engine gets to operating temp.I really don't think there is anything wrong with the water pump either.Like Dave said,this is a tricky one.Try to keep me up to date on this. If I can be of any help,let me know.I have one question though.How do you know that you lost a gallon + of anti-freeze the other day? Is it because you had to refill that much or did you see a large amount of coolant pouring out after your ride? Remember, A cracked head or head gasket that uses that much anti-freeze would be smoking out the exhaust pipe.Have a good day.
Bobby R

I always check the coolant level before I take a drive (along with all other important fluids. It was at the normal level when I left. When I returned, it took a gallon+ to bring the level back where it was. At the drive's end, the overflow tube was only spitting steam because the tank was empty and the body rails and cross members on that side of the engine were soaked in coolant.

Also,I have never had a smoking problem (either white or blue)

Friends:

A leak between the coolant and combustion chamber will not put dectable amounts of coolant into the cylinders -- but will instead leak combustion gases out into the cooling system. The reason it goes mostly one way is because the combustion pressure is so much higher than the cooling system pressure.

Coolant leaks that end up in the exhaust probably find their way there via the head intake passages where there is vacuum.

I suspect the leak you have is very small and does not do much until you are under sustained high load. This makes the combustion pressure very high.

I too hope I am wrong, I would first look at the water pump, thermostat, radiator, fan belt, engine timing, carb mixture, all the usual stuff that can cause overheating. Could be your engine is merely overheating and boiling, it wouldn't be the first Healey with this problem!

Bill S

Another possibility would be to do a leakage test on every cylinder and see if bubbles showed in the radiator.

The leakage testers at Harbor Freight are pretty inexpensive.

Really all you'd need to do is make a pressure hose with an air fitting at one end and a spark plug end on the other end--then pressurize each cylinder to, say 150 lbs at tdc, then observe whether there were bubbles in the rad.

Do the above test when the engine is stinking hot, so as to replicate the operatong conditions.

Make it a point to not burn yourself in the process (especially removing the radiator cap).

I used to have a similar probem with my BJ 8 and bot a coolant recovery bottle that I did not really expect to work but it did and have had no problems since (have owned the car for 24 years).

I also added a small coolant recovery bottle, that seems to work well. I placed mine under the right front fender sort of next to the heater blower.

Recovery tank is always a good idea.

At a recent British car show, I managed to get a NOS Spridget (brass) overflow/recovery tank. Now I need to get my priorities straight and blast/paint a well-used bracket so I can mount the thing.

I'm still unsure of what cap to put on the original radiator; what did you guys use? It has to allow siphoning the coolant back into the radiator during the cooling down process.

I used the 7 lb cap with the correct length that I had previous to installing the recovery tank (E4 printed on the top of the cap).

Okay, thanks!

Hi Randy,
The NAPA - Balkamp #703-1411 7 lb. cap works well. It is the correct long reach type, has a good top seal, a good bottom pressure seal, & a one way valve to permit coolant to be drawn back into the radiator. Some caps don't have a good top seal. The spring brass types come to mind.

The coolant recovery bottle must be freely vented to atmosphere.
D

Outstanding! Now I know it will work

The Spridget tank doesn't freely vent though, so I'll have to do some surgery on the cap for it. I like that tank because I can polish the brass, and it has a genuine siphon tube. Also, it won't look out of place in a fifty (50) year-old car.

Edit: Woo Hoo, local NAPA has two (2) in stock!

I finally found the correct thermostat from BCS a few years ago. It's not cheap, but it does work better than the aftermarkets.
Patrick