I have a 62 BT7 Tri Carb. The radiator was rebuilt about a year ago and two new rows added, it has a 165(or 160) thermostat installed, a flex fan(installed with the rebuilt radiator) and the engine lower end was rebuilt, new brass freeze plugs installed, etc. about 2 years ago. Since the radiator rebuild, the car does not get overly hot (233) except in extreme conditions (stop and go traffic @ 90) and even then the temp drops as it should when traffice clears, etc. I use 50-50 anti-freeze and have kept the coolant at about the same level adding when needed, since the rebuild.

About two weeks ago, I began to have major coolant loss problems only when I drive the car above 4000 - 4500 rpm (70 mph)or run up the revs in lower gears (I do not have overdrive). If I stay under 3500 rpm I do not lose any coolant. If driven at high rpm or speed the car will blow out the overflow tube a gallon or more of coolant. I have had the system checked (chemical and pressure) and I do not have a head gasket problem or cracked block. I assume the thermostat is working properly, because the engine temp reacts up and down as has been normal over the last two years.

The only potential villain that seems to be left is the water pump. Any other ideas????

I'd test or replace the cap before the waterpump; much easier and cheaper. It may not be able to handle the increased pressure.

For the conditions you describe, the w/p impellar would have to be quite eroded. Not that that couldn't happen...

My own car had been suffering cooling problems (no o/d on it either) but adding an engine driven fan (requiring me to remove my shock tower brace) seems to have cured that. At least for the time being...

I forgot to mention that I had replaced the cap. Cheap and easy is always the first choice for me. I have had the car for over three years and have not inspected or replaced the wp----no thought about it until now.

Hey ArtQ,

How much is 'major'?

The reason I ask is that my car also does quite well at low revs only loosing a small amount of coolant < half pint. At higher reves, cruising at 4,000 for example, it looses about one and a half pints, but it doesn't loose any more and it stays cool.

So I have put this loss down to the system needing expansion space in the header tank and the higher the revs and pressure, the more space it needs.

Is your loss more than one and a half pints?

Good luck

Maccers

This is a strange one. It's almost certain that air is being introduced into the system or the pressure cap is not holding. The most likely cause of air would be the water pump seals or combustion pressure leaking into the coolant.

A radiator shop can do a quick chemical test on the coolant to determine if combustion byproducts are present in the coolant. From your above statement, I assume this has been done.

Healeys require a longer pressure cap than standard, are you sure you have the correct cap?

Sorry, no good ideas.
D

Art,
If you used an after market thermostat instead of the original
skirted type of thermostat, it would be possible to install it upside down in the opening.
I think there would be a problem with the full flow of hot water like is needed under high RPMs if it were accidentally installed upside down.
In a low flow situation, enough coolant may pass through to keep it from boiling over as soon as the engine got to operating temp. Also, it is possible that the gasket is interfering with the full opening of the thermostat for some reason. If any formagasket was used to seal it up, a glob of it could be preventing the thermostat from opening all the way.
Since you have checked that there are no combustion byproducts in the coolant, I would suspect;
.. Upside down thermostat
.. gasket interfering with the full opening of the thermostat
.. bad water pump.
.. loose, slipping fan belt at high rpms.
.. a foreign object loose in the water passage of the head, at full flow, it moves up and blocks the water flow. When you let off, it returns to the bottom of the water passage and doesn't interfear anymore.
Good luck in your search for the gremlin,
Ed

Hi Art,
I used to have the same problem with my BJ8. I stopped topping off the radiator and the problem stopped. I have never flushed my system, stock old radiator and one of those terribly noisy stainless flex fans. I don't know what level one gallon short puts your fluid at but mine is 2 3/4" below the top rim of the filler and no problem on 100 deg. plus days.

Good luck,
Walter

HI Art,
First of all,What pound cap did you buy ? Second,Did you test the new cap with a pressure tester ? Seeing how a Healey has no recovery tank for expansion, the top tank will need an amount of space for the coolant to expand. Cooling systems seek their own level.As long as the coolant level always stays above the cores of the radiator ,you're ok. Losing a gallon of coolant is excessive.I'd be looking for pressure building up in this cooling system. Get the engine to operating temp. Without burning yourself,take off the rad cap and put on a pressure tester.Pump the tester to about 5 to 7 psi as starting pressure.Start the engine and watch the pressure gauge.If the pressure exceeds 16 psi I would think you do have a compression leak into the cooling system.If you have the tools to do this test , I think you should try it.Let me know the results.I will watch for your post. Good Luck.
Bobby R

After a successful chemical and pressure test, replacing the rad. cap with exactly the same type as had worked for two years and still having the problem, my next step will be to replace the water pump. The part is ordered and and will be installed on Monday. Also, since I live in southern CA and don't really need the function of a thermostat, I'm going to leave it out.

Thanks for all the ideas. Hopefully, the new water pump does the trick and I can get back on the road.

Everything I've read says you need a thermostat to restrict circulation so that the coolant stays in the radiator long enough to transfer heat. You should leave the thermostat in.

Agreed.

You also want the thermostat functioning so the engine reaches operating temperature as quickly as possible.

I don't completely agree. This is a commonly quoted misconception. Removing the thermostat can decrease cooling but NOT for the reason stated.

The rate of flow through the radiator cannot be too fast for the coolant to be able to give up it's heat. With more flow, the heat loss per pass through the radiator is reduced but offset by more water passing through, so the two balance out. Flow tests have actually shown that higher flow through the radiator can create turbulant flow in the radiator tubes which results in more "hot" water being in contact with the tube surfaces. Slower, laminar flow, results in the outer surface of the water column being cooled, but the inner part of the column never contacts the tubes. So turbulent flow can increase cooling.

The thermostat/restrictor raises the local pressures in the water jackets, especially around the exhaust valves, combustion chambers & reduces the tendency for localized hot spots to vaporize the coolant (spot flashing). With the restrictor, the localized (water jacket) pressures can be much higher than the actual pressure cap setting.

The second benefit is that by raising the head pressure on the pump, with the restrictor/thermostat, the pump inlet pressure is also raised (suction reduced) which helps prevent cavitation of the pump. Cavitation is basically when the pump creates so much suction that the fluid vaporizes in the pump internals, which reduces pumping capability.

Ref. "The Engine Cooling System" by "Technology Transfer Systems, Inc", Livonia, Michigan.
D

Had the same problem with a Healey years ago...it was the thermostat..cheap to pop in a new one..... had a "mechanic" put one upside down in my 62 Vettte years ago....sheesh!


Pete

An MGB in Louisiana will overheat when you remove the thermostat.

I stand by that statement.

I think you have a bad head gasket or cracked head, leaking combustion gases into the coolant.

This sort of leak cannot be detected by a simple pressure test because the combustion pressure is so much higher than the pressure you apply in a pressure test. But the combustion gases displace coolant and blow it out the overflow tube.

I have had this problem with modern cars, and your car's behavior is similiar my Subaru. This Subaru cooled perfectly until it was under strong load -- high RPM and high throttle settings, like climbing a hill at high speed. Then it would blow out coolant profusely. I did a lot of fruitless work on the cooling system before replacing the head gaskets -- that finally fixed it.

You can sniff the radiator gases for exhaust but at slow speed, you may not leak enough to be detectable. You need to sniff when the engine is under load, not easy to do.

Sorry for the bad news, but that's what I think is probably wrong with your car.

Good luck!

Bill S
Albuquerque.

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

For those of you still following my sad story----water pump replaced and I still have exactly the same problem. So after all of the actions taken so far, which I won't repeat (they're in the posts above) the next step is inspection and correcting anything wrong with the head and changing the head gasket.

Any suggestions about what else I might want to do or have done while the head is off?

Art,
Did you try running it with the thermostat removed to eliminate any possible problem with it ?
( not all the time, just for a test for all of you that will jump in and say that you should use a thermostat ).
..... If it turns out to be a head gasket, you should ask for a full refund and explanation from the person who checked your coolant for combustion byproducts and found nothing.
Ed

Art

You need something in the thermostat housing, I had the same problem when I first bought mine - losing coolant but not to the same extent, and found the thermostat to be missing. I put one in and no problems since, coolant level about half inch above the core.

The race guys do leave them out but substitute the thermostat with a disc with a hole in it to restrict the flow.

Are the airways through the core clear of dead flies, cats stray dogs and people? How is your temperature ?

For a quick check on the thermostat, open up the radiator cap and view the flow in the head of the radiator at 4000 revs If you have the equivelant of white water rafting flows then this could be an indicator that all is not well with the stat.

Bob

Art,
In spite of your earlier statement:
"I have had the system checked (chemical and pressure) and I do not have a head gasket problem or cracked block."

You do have all the signs of combustion pressure leaking into the cooling system.

While the head is removed, check both head & block surfaces for flat within 0.002" & correct if needed. A perfect time to also have head & block checked for cracks.

Replace head studs & nuts with new. Clean all stud holes in the block with a tap & chamfer the tops of the holes. Use sealer as needed on any tapped block holes that extend into the water jackets. Actually sealer on the blind holes also, won't hurt anything, just make sure that the sealer doesn't create a hydraulic lock as the studs are screwed in.
D

here's a exert from a earlier post
in 1972 the head of vehicle maintenance for the silicon valley taught a class.
a 1/2 inch of coolant in the tank, just enough to cover the tubes. when the coolant heats it will have room to expand. if you are spitting out coolant the pressure can far exceed the cooling system's rating. the tank is for expansion. air can escape from the tank much faster than liquid. the more coolant in the system the longer it takes to cool down. When i bought HER XKE it ran 240 normal driving the last owner used all antifreeze, no water. antifreeze is not a good coolant, water it a good coolant. the first equipment sent to the Alaskan pipe line over heated in sub zero weather, they had been filled with pure antifreeze. he also said not to use flex-fans at higher rpm the fan flattens to reduce drag if you pulling a hill at slow speed the fan is now blocking the needed air flow

before you get all greasy,
to check to see if the thermostat is closed and then opening at the right temp. and see if the pump is pumping. start it cold with the water level at the top of the tubes, look in the radiator tank when it gets warm you should see the water pumping out the upper hose inlet. i use a meat thermometer to check it. if it's too hot the thermostat might be in upside down. if that all looks good and it still over heats get the good block sealer about $7 the instructions will tell you how to put it in,,,, after you run it for ?? minuets, let it cool, then drain the system and let it dry over night. if it stops over heating the block sealer sealed a bad head gasket or a cracked head. all head gaskets leak !
I was a mild mannered bodyman until i started driving vegi oil burning VW diesels now I'm a head gasket ex-spurt ....hope I've helped you i know how frustrating it can be to work on your own car.

The car is reportedly losing more than a gallon at a time. The coolant expansion on a typical Big Healey is a little less than one quart under 7 psi pressure. Normal expansion no where near accounts for this large coolant loss.

the lost coolant has to be replaced or displaced by "something" - either air, combustion gasses, or?

The end result of "block sealers" is to coat the entire inside of the cooling system with a heat insulator & partially plug the water passages. Not a good long term solution.
D

I agree with you Dave, "not a good long term solution" on a car engine, but when I owned a V12 XJS several years ago and it called out for a couple of packets of "Bars Leak" on coolant changes. Semi trucks use the sealers quite often.
Patrick

K&W Nanotechnology is new since May of 2006, I’m not talking about the old block sealer.
the radiator tank has 3 qt's of expansion room and on top of that it spits out 1 gallon that's nearly 2 gallons that isn't in the engine and it tests ok for combustion gases. That's a big problem for a engine that tests OK.
This is EZ. take the thermostat out. put just enough water in it to cover the tops of the tubes start it and look for the water pump circulating the water in the radiator tank, if everything looks good take it for a drive and see if you duplicate the symptom. if it's OK jump for joy. If it over heats, you can pull one spark plug wire off and drive it do this 6 times see if witch one stops the over heating. if you chose to use the block sealer you will be leaving that plug wire off during the treatment. Or you can pull the head and take a good look at the head gasket around that hole. it should be a uniform color, no darker spots. if it looks good to you, get a second opinion,. if it still looks good, strip the head and take to a machine shop and cry on there shoulder.
It's very hard to work on your own car, you/I start to imagine all kinds of problems. it's best to keep testing. When realize I've hire a Ouija board mechanics i fire them ....jim

Just got car back from shop, head had some minor rough spots and was corrected at machine shop, new head gasket was installed, block was checked and is within spec. Engine temp was correct on drive home and coolant loss was small and typical of amount spit out before big problem appeared. I'll take it out for a full run this weekend and if it performs as it did on the way home, I may have the "mystery" solved.

Thanks for all the ideas, most of which I would up trying (wish the cheaper versions would have fixed the problem).

Art