Overheating Problems
 

The last two times I have taken the Roadster out, I have had blow back from the quail with over heating. The first time it happened, I thought that the antifreeze that was in the car originally was the problem. So I drained the radiator which had some chunks in it and flushed some water down into. I refilled it with prestone 50/50 (plenty of it too and ran it in the garage with no problems. I thought I was in the clear (which was foolish because it was just running in neutral so it never got a chance to heat up as in a driving situation). Took it out today with problems again, maybe worse. Got to 200 degrees right after I turned the car off and 210 after 5 minutes. What should I do?

My wife saw something that Les Andrews wrote about distilled water and some additive that I can't remember that made the car run better because antifreeze decreases the freezing point.

Re: Overheating Problems
 

There are many reasons for overheating, but the most common is the radiator is plugged up with rust or hard water scale.

Re: Overheating Problems
 

Quails are pretty, but they usually leak. Cap should seal and the pressure should escape out the over flow. I know this isn’t your Problem but I’ve been down this road.

Re: Overheating Problems
 

To run a good test on your core, drive 45 mph for ten straight minutes. It should be able to do this. I’m sure it can’t. In the long run, you will end up buying a new radiator. Buy it now. Good luck.

Re: Overheating Problems
 

After I bought my A about 14 years ago, it occasionally overheated, so I removed the radiator and took it to someone who knew how to rod it out. He found something like 23 tubes were totally clogged, and was able to carefully rod out all but a couple. Car has never overheated since.

Re: Overheating Problems
 

You might check that there are no bubbles in the radiator, a blown head gasket can eject water from the radiator and cause overheating. NAPA sells a combustion gas test kit that you can use to test for a head gasket leak
Good luck

Re: Overheating Problems
 

Terry, how in the world did you find someone who could rod out an A core? Not many around. It would be worth the shipping. Jack

Re: Overheating Problems
 

No bubbles, I do not think it is the head gasket but I could be wrong (but no other signs). Runs fine (transmission will eventually need an overhaul but that is another story).

Re: Overheating Problems
 

Not sure if my radiator is original or not. I think it is but I could be wrong. Either way, it could not have been overhauled long ago along with the engine but I know how quickly blocks can rust.

Re: Overheating Problems
 

It might be. My cap never would fully go down onto the neck. Figured out from people on here that the repros aren't threaded as long as the originals, which obstructs it from getting all the way down. The quail likes to wobble to, so that isn't helping either. I also can't remember if I put a gasket in under the cap...

Re: Overheating Problems
 

A poor sealing quail is a source of angst for many drivers. The sure do look pretty but require a good job of fitting and adjusting to make them seal properly.
You should not get water out of the cap with the temperatures you are stating. It should be pushing out the overflow tube.
How full are you filling the radiator? If you are adding coolant and filling to the bottom of the neck you are probably filling to far and it will push excess coolant out due to expansion as it warms up. A poor fitting quail will spit coolant in a hurry.
Don't add coolant unless it no longer covers the tubes. As long as they are covered all is good.
I'm glad your using a 50/50 mix of antifreeze and distilled water. It will help it run cooler, prevent rust and protect against freeze damage.

How are you measuring the temperature of the coolant?
I use a cheap dial meat thermometer placed directly into the coolant in the radiator. The quails get you "close" but the thermometer puts you spot on.
Get one of the meat thermometers and you will know for sure.

Re: Overheating Problems
 

I usually fill it just above the tubes. After I did this, it just spit out what it didn't want into the oil pan under the car. I used a brand new heat gun to grab the temperature. I don't know if this is unusual, but it seemed to be the hottest towards the top.

Re: Overheating Problems
 

Has anyone used a NAPA combustion gas detector to check for leaking head gasket? Do I plug the overflow tube??

Re: Overheating Problems
 

I bought a quail cap from Macs about 8 years ago. Fits great, has never leaked. Make sure you're advancing the timing properly, advance it until it just starts to ping, then back off a click. Improper timing can definitely cause overheating. Call around to the very rural farming towns, you can still find radiator shops there that'll know how to rod out an old radiator. There are solvents you can run through the radiator too, make sure you install a coolant filter as lots of stuff will come loose and start floating around in there. Then you'll really have a plugged up mess.

Re: Overheating Problems
 

I had the same problem when I first got my Model A, spraying out from the Quail radiator cap. I was quite concerned, spoke to some of the older experienced guys in the club, they felt I was over filling it. That is why the water kept dripping out of the over flow tube as well. One of the gentlemen, bless his heart rebuilt my quail radiator cap so it fit properly.
Next thing I know I was not adding water, none coming from the radiator spraying onto my windshield. After every the end of each day I put a meat thermometer in the radiator check the temperature, never above 170 degrees.
As a new owner, I think 100% of my so called over heating problem was inexperience with a Model A and not looking at the obvious.

Re: Overheating Problems
 

I've used the Napa Block Test Kit. Easy to use, Just follow the supplied instructions. Fill the syringe with the supplied liquid to a fill line on the syringe. Place the syringe over the radiator fill opening , and use the supplied rubber bulb on top of the syringe to draw air (not coolant) from the radiator through the syringe liquid. If it turns color it has detected exhaust gasses in the radiator.. Casts about $50 for the kit, and there is enough test liquid to do a lot of tests/radiators.


No you do not plug the overflow hose.

Re: Overheating Problems
 

Hello CHRS,


I had the same problem by fast running. I solved that by inserting a slightly thicker gasket under the quail lid. Then the closure sits tighter.

That the temperature rises after switching off the hot engine is normal. The hot engine block heats the water a little longer up and it goes on the top of the radiator.

Radiator-antifreeze hampers a bit the heat emission. When it is very hot weather, it is advantageous to reduce the amount of antifreeze to 20%.

Re: Overheating Problems
 

The following is what I learned from 6 years of dealing with overheating in my truck that was revived from a 50 year nap in unheated farm buildings, and was not prepped properly for that type of storage. I've highlight key info.


Anti freeze can raise the boiling point slightly in an unpressurized cooling system. In a pressurized cooling system like modern cars, it raises the boiling point substantially. Modern cars have been designed and have the cooling systems/materials to run at hotter temps.


The A was not designed to run at the those higher temps. If an A runs at those higher temps it will cause motor damage, some damage due to what is called oil flashover at the piston rings, where the pistons can lose lubrication. Oil at the rings get so hot it burns away instead of lubing the rings/piston.


I consider Boil Over an early warn sign to slow down in hopes the motor temps cool down, or to pull over and let things cool off.


If you do not have one, I highly recommend installation of a Coolant temp gauge in you upper coolant neck or hose. It allows you to catch the issue before it boils over.


In the vast majority of As, antifreeze is an excellent option, once you have a clean system, it prevents formation of scale rust.


Water actually has better characteristics for cooling than antifreeze. It is better at absorbing heat from the motor, and dissipating the heat into air in the radiator. Some As in mountainous areas where the altitude causes a reduction in the boiling point use water, and in some high heat area like desserts use water. If using water use distilled water with a rust inhibitor like NAPA 1300 Rust Inhibitor, in a clean system Red Line Water Wetter can also increase the efficiency of the dissipation of absorption of heat in the motor and dissipation of heat in the radiator. This combination inhibits the formation of rust/scale, but not as well as antifreeze.


Another key is that you cooling system needs to be in great shape. If your radiator is a 2 row core, (unless Brassworks - is OK), replace your radiator with a good 3 row or 4 row core radiator. Insure your system is clean. 1st run some detergent (like Dawn) in the radiator water, and then back flush. It will foam. This cleans out any oil/grease that may have gotten into the cooling system. Typically caused by over greasing the water pump. The water pump only rarely requires a small partial pump of grease. Run treatments of Thermocure or Rust 911, and backflush, once back flushed and cleaned out, install an upper hose coolant filter to keep rust/scale/contamination from plugging up your radiator.


So to summarize

A model a cooling system in tip top shape runs cool enough to not overheat in typical summer heat. It can actually run without the fan, except at very low speeds and idle.


Do your trouble shooting with Distilled Water and rust inhibitor. Once issue is resolved try going back to antifreeze. Less damage to paint with water, and easier to clean off.


Insure your system is in tip top shape - backflush as outlined above.


Make sure your radiator is a good model - Brassworks or a good 3 or 4 row tube core.


Install a coolant temp gauge.


Install an upper hose coolant filter.


Antifreeze is good, if you still have problems try distilled
water/rust inhibitor/water wetter.


Hope this is helpful.