Thermostat

[Donny_L]

I thought it would be a good idea to replace the old thermostat. Since I live in Vegas and it's soon going to be over a hundred degrees daily,I bought a 160 summertime unit. To my surprise there wasn't any thermostat there to be replaced. So what kind of damage might of been done as a result of having no thermostat at all? Is there something I should be checking?

 

[elrey]

Having a lower temp thermo. just means it opens sooner. It does not have any effect on the maximum temp. attained, which is the important part. Your cooling system may be compromised or the previous thermostat may have failed leading to it's removal. The engine is designed to work within a certain range of temperature. The thermostat moderates the rate of flow through the radiator in order to maintain this optimum temperature. Check the temperature gauge frequently, always. Of course you might flush the radiator, check condition of hoses, flow rate, and check the belt tension. Renew the belt if you have not already. There are threads in the archives here that you can search that have information on engine cooling, aftermarket fans, etc. Many are using a fan called the Texas Cooler with success. There are many other offerings. If you still have the stock 4 blade you may wish to upgrade at one point. You shall soon find out! --elrey

 

[Cottontop]

Addmitedly, I have a SBF-V8 in my Healey, but I have not run with a thermostat since my rebuild 15 years ago.

Back in the 50s & 60s when I/we were hotrodding, I/we NEVER ran with thermostats.

In the late 50's I worked in a radiator repair shop and learned that the reason for a thermostat was ONLY to get the heater to warm up faster.

Now-a-days, since we now have emmision standards and know that a warmer engine burns fuel more efficiently and cleanly.

Back when gas was .25 - .35 cents a gallon, nobody cared.

Tim

 

[bob hughes]

When I bought my BJ7, water could be seen dribbling out of the over flow from the rad. I kept topping it up now and then and eventually found out that the thermostat was not in. I nipped over to my local specialist to get one and discussed the issue with him. Apparently, the racers leave them out but insert a disc with a hole in it to cut down the amount of splashing caused by the pump. It was this splashing that caused the dribble.

 

[Superwrench]

You should always run a thermostat. A 180 or a 190 are better. They alow the block to warm up and expand. The aluminum pistons expand at a much larger rate than the block. They are getting the heat from the combustion. If you do not allow the block to warm up by running the proper thermostat, you are causing unwanted wear on the pistons and rings ! I can always tell if a guy ran a thermostat or not when tearing down an engine. Put one in ! :hammer:

 

[Cottontop]

the racers...insert a disc with a hole in it to cut down the amount of splashing caused by the pump.

Right... Restrictor discs/plates are sometimes used to prevent a high volume water pump at high RPMs from overcoming the relatively low pressure of the pressure cap at the top of the radiator.

Many of the new crop of radiators used by racers and other car builders are a cross-flow design with the radiator cap on the LOW pressure, or cold, end.

Because the cap and overflow are on the low pressure/sucking side of the radiator, over pressure and puking of water caused by the water pump at high RPMs does not exist.

Tim

 

[RAC68]

Hi Donny,

There are two things that the original sleeve thermostat addresses. First, as many have mentioned, the thermostat slows the coolant flow to allow time for the air stream passing through the radiator to cool the fluid. Second, there is a passage cast into the head that allows approximately 25% of the coolant to bypass the radiator for quicker warm-ups. When at temperature, the thermostat sleeve closes off this bypass passage to direct full flow through the radiator.

Without the thermostat, your warm-ups are slower and you potentially loose a quarter of your cooling capacity. Other factors such as loss of cooling as a result of overflow, fan inefficiency from air leaking of the ends of the blades (no shroud), and high-pressure blockage from air passing around and under the radiator, will greatly diminish your Healey’s cooling.

I would suggest you look at the replacement of a sleeve thermostat as one step on the path towards cooling your Healey.

Good luck,
Ray (64BJ8P1)

 

[Keoke]

I would suggest you look at the replacement of a sleeve thermostat as one step on the path towards cooling your Healey.---Keoke

 

[elrey]

How do the cognocenti feel about those fail-safe thermostats? You know, the type that fail open instead of closing upon failure. --elrey

 

[Cottontop]

You should always run a thermostat.

Super,

As I stated above, I have not run the thermostat for 15 years. I initially put a 180 in, but in playing with air dams & splitters, a second onboard radiator, fans, shrouds, and a few other tricks, I wanted to see just how each modification (experiment) affected the radiator's ability to cool.

I removed the thermostat and instrumented the radiator INPUT and OUTPUT, enabling me to know how much the radiator was cooling and how much the engine was heating.

The end result was that just in putting around town, the radiator input temperature was 180F-185F and on the highway, the radiator input temp. rose to 190F-195F.

Since that was just where the thermostat would hold the temp., it was just easier to leave it alone than it was to disassemble to install a thermostat.

I agree that everybody should run the thermostat recommended by the manufacturer.

For MY SBF in a Healey... I was the manufacturer.

I have now installed a 24" wide, copper/brass, downflow, radiator in my Healey and have again thermocoupled the top and bottom of the radiator.

As soon as I get a baseline, I will undoubtedly add a thermostat, and/or maybe one at the bottom of the radiator if the coolant is "TOO cool" coming out.

Tim

 

[Cottontop]

as many have mentioned, the thermostat slows the coolant flow to allow time for the air stream passing through the radiator to cool the fluid.

Ray,

I don’t disagree with anything you said except your statement above.

The job of the thermostat is indeed to moderate (throttle) the flow
of coolant through the radiator, but in order for the engine to be
maintained at a specific MINIMUM temperature.

The thermostat is NOT there to have any effect on cooling, especially
not for slowing the coolant for efficiency.

Tim

 

[Keoke]

How do the cognocenti feel about those fail-safe thermostats? You know, the type that fail open instead of closing upon failure. --elrey

Rolls Royce just loves them. course now they don't want you to ruin a very expensive engine if they can help it.---Keoke

 

[elrey]

They cost twice as much but in the scheme of things I feel they are cheap insurance. I don't know if they last as long or what, but my vehicles are wearing them. I figure i will know if they fail by either the temp gauge reading or the heater not working. Nice thing about this generally blissful climate is you won't freeze to death if the heater stops working. --elrey

 

[elrey]

ention the sun sets INTO the ocean here! Freakish and disquieting, --elrey

 

[Superwrench]

Tim, You still want the block and pistons to warm up at the same time. If cold water is circulating through the block that isn't going to happen. You have a awesome car and a very good installation. Put that thermo. in there or some other means to cut water flow until things warm up. take care, Bob :hammer:

 

[Cottontop]

10-4, Bob.

Tim

 

[Johnny]

You should always run a thermostat. A 180 or a 190 are better. They alow the block to warm up and expand. The aluminum pistons expand at a much larger rate than the block. They are getting the heat from the combustion. If you do not allow the block to warm up by running the proper thermostat, you are causing unwanted wear on the pistons and rings ! I can always tell if a guy ran a thermostat or not when tearing down an engine. Put one in ! :hammer:

Running without a thermostat allows the water to circulate constantly, thus the water will never stay in the radiator long enough to cool.

 

[Cottontop]

Running without a thermostat allows the water to circulate constantly, thus the water will never stay in the radiator long enough to cool.

John,

I hear that a lot, but I have yet to find someone in the cooling business to agree with that.

I urge everybody to read these cooling Tech Tips <span style="font-weight: bold">(especially Tip #3)</span> and FAQ’s on the Stewart Components web site. Stewart makes cooling equipment.

https://www.stewartcomponents.com/tech_tips/Tech_Tips_1.htm

https://www.stewartcomponents.com/Stewart_faq.htm


Water is a fluid. Air is a fluid. Using the logic that engine heat can be removed more efficiently from slow moving water also says that we should get smaller, slower, fans as slower moving air can remove radiator heat more efficiently than fast moving air.

People who design cooling systems and equipment (OEM and aftermarket) agree that moving coolant faster (and/or in greater volume) will result in a greater heat transfer to moving air. That is why companies make high volume water pumps and low restriction thermostats. The faster the coolant moves through the engine, the more heat will be removed from the engine.

It is the radiator’s job to provide an efficient transfer of heat from the coolant to the moving airflow and again, the faster/higher volume the airflow, the more the cooling will take place.

There is no device to moderate/throttle/control the temperature of the coolant OUT of the radiator. It is what it is.

If the coolant moves through the engine such that the engine temperature drops below the thermostat set minimum temperature, the thermostat will indeed close as much as is necessary to keep the engine warm.

<span style="font-weight: bold">The thermostat is there to keep the engine warm, not to help the the radiator cool.</span>

Tim

 

[RAC68]

Hi Tim,

Yes, the thermostat is their to achieve a minimum temperature as quickly as possible, however, in the case of a Healey 6 the sleeved thermostat also helps cooling by blocking the by-pass.

I think most Healey owners have noticed that when driving at high speed the temperature move higher rather then lower. With all the air passing through the radiator, you would think the engine would run cooler than at idle or slower speeds. This seems to be a common observation by most LBCs of the era and a group of Morgan owners seem to have extended, what I have experienced is, a good solution. The problem is created when air passing around and under the radiator creates a high pressure block within the engine compartment. This air block slows free air flow through the radiator and, as a result, impedes radiator cooling. Many have inadvertently eliminated this air block when they installing hood louvers or fender vents, however, the solution proposed by the Morgan owners (who work as engineers for a large truck manufacturer that design alterations to improve over-road performance) requires only simple add-ons that are almost totally invisible on our Healeys and can easily be reversed. Although these modifications were design and wind-tunnel tested for Morgans, I have installed them on my Healey and found them to be effective.

Mod 1: Vertical 4”x length of radiator Fan Shrouds. These are flat pieces of metal installed on both sides of the radiator and attached using the radiator mounting bolts that assist in directing the air flow and diminishing air bleed from the end of the fan blades.

Mod 2: A rigid panel attached to the bottom of the frame covering the front 1/3rd of the engine compartment (from front cross member to approximately 6” forward of the pan). This panel, along with a soft covering of the lower 1/3rd of the lower radiator tank that extends to the panel, eliminates engine compartment pressurization by moving the under-car air stream back for better directional air passage through the radiator (especially at speed).

All the best,
Ray (64BJ8P1)

 

[Cottontop]

Hi Ray,

We agree!

In general, Healeys do not have good airflow for removing heated air from the engine compartment.

I maintain that is why Geoff added a louvered hood in the 100Ms (to get the hot air out) and a hood scoop on the 6 cylinder cars. Introducing dense ambient air into the top of the engine bay helps the fan push the less dense radiator air out under the car.

I also maintain that is why he also added wing vents, not larger radiators, to his racers.

In my experience (of more than 50 cars), nearly ALL V8 Healeys run hot (=200+). Before my current series of mods, I had a 3" tall air dam from side to side, under the front crossmember. I also had a 9" X 14" motorcycle radiator (plumbed to the heater hoses) mounted immediately behind the 100-6 grille. These add on's almost always kept the temperatures below 190.

I have recently added A/C which would normally bump the engine temperature by 10o-15o.

My "new" cooling system has a 24" radiator (pictured above) with dual 12" electric fans on the backside. The radiator is slanted, bottom forward, at a 30o angle.

On the front side, the radiator is totally shrouded on the sides and top so that NO grille air will be allowed to flow around it.

On the back side, the fans are shrouded to flow the radiator air down and under the car. Not yet installed is a belly pan from the front crossmember back to the trunk floor and between the frame rails. This pan is intended to smooth the airflow (=less swirling) towards the rear of the car.

I am evaluating 2"-3", downward hanging, 45 degree angled, "vanes" under the transmission/driveshaft area to start moving airflow out from under the car forward of the rear wheels.

By measuring the radiator input and output temperatures, I will be able to evaluate what works and what doesn't.

Now... We need to work on your incorrect notion that slow moving coolant is more efficient than fast moving coolant.

Tim