running without thermostat

[geoff]

I have had so many problems with hot running, I am thinking of taking out the thermostat and running without one. I was planning to take out all of the inside components of the thermostat and then replace it using it just as a "T" piece.
I only use the car in nice weather so I don't think having no thermostat will be a problem.
Is anyone else running without a stat?

[SteinOnkel]

Bad idea for two reasons.

1) The engine will take aaaaaaaages to reach operating temperature. That means excessive wear on everything lubricated by oil, so virtually the entire engine.
2) The thermostat also "holds" the coolant in the radiator for a time. If the coolant just blows right through the radiator unhindered, it doesn't have enough time for meaningful heat exchange with the ambient air to occur.

Not even on our racecars do we run without thermostats. It's all around a terrible idea.

Fix your coolant system. The main culprit is trapped air. These cars are a nightmare to bleed, but here's a bulletproof method I've found:

- go to your local Autozone and borrow the radiator leak kit. It's just a pump to pressurize the coolant system with, really.
- fill er up
- put the pump on, pressurize the system to what your cap is rated for (side note: you can also test the cap with this tool)
- System should hold pressure indefinitely
- If the needle moves on the tool, something is leaking. Look for the hole somewhere on the coolant system
-If the system holds pressure though:

Here's the kicker

- Remove the tool from the radiator without depressurizing it. You wlll hear lots of gurgling and hissing.
- Top off the radiator
- Pressurize the system again

Do this 3-4 times and you will have all the air out of the system. Easy peasy.

Cheers
Steiny

[rridge]

I think the notion of coolant moving through the radiator "too quickly to cool" without the resistance of the thermostat in the circuit is an old mechanics tale. Think about it. The cooling system is a close circuit. The coolant that spent less time in the radiator releasing its heat also spent less time in the engine absorbing it.

What the tale is getting at though is that removing the thermostat is sometimes associated with a decline in coolant system performance. One reason is that the water pump is designed to work against back pressure and removing the thermostat body from the flow stream reduces that back pressure and can lead to pump cavitation and the erosion and eventual the destruction of the pump impeller.

Maintaining back pressure is the reason the recirculation side of the cooling outlet tee has a reduced outlet hole on the pump side. Without the radiator in the flow circuit the pump would be working against too little pressure.

When the external thermostat is constantly acting up there is usually an underlying reason that needs fixing. A common reason is an air leak, which if left uncorrected will cause corrosion of the cooling passages in the head. At a minimum try squeezing the one of upper hoses and listening for the whistling sound that often reveals the location of that leak. The minor hoses that supply coolant to warm carbs and manifolds are a common source. So are the coolant tees that many of us add to the heater hose take off. Also think about a new radiator cap if it hasn't been changed in recent memory.

[geoff]

thanks for this reply, and for your Stainy. I have taken your info on board and decided to leave the stat in place and find out the true reason for the problem. I forgit to mention to you that I am using Evans waterless coolant. I have heard that this can lead to some engines running hotter but I would like to continue using it because I have seen the results of the corrosion caused by using water & anti freeze and what to reduce that.
geoff

[SteinOnkel]

thanks for this reply, and for your Stainy. I have taken your info on board and decided to leave the stat in place and find out the true reason for the problem. I forgit to mention to you that I am using Evans waterless coolant. I have heard that this can lead to some engines running hotter but I would like to continue using it because I have seen the results of the corrosion caused by using water & anti freeze and what to reduce that.
geoff

I think we are narrowing down your issue. I have not met anyone that is happy with this stuff.

As for the corrosion, as long as you regularly (i.e. every two years) swap out the coolant you should not have an issue. Antifreeze has plenty of Anticorrossive additives. The problem is that nobody ever does this and once the rust is in there, it's really hard to get it back out.

[geoff]

I hear you steinoncle but the corrosion was in the aluminium. It was not rust.
geoff

[geoff]

ok, I admit - perhaps I have the stat in the wrong way round ! I am not sure anymore.
On a normal system, the side of the stat with the wax pellet goes on the engine side not the rdiator side, so for this car that means to the top hose; right ?
The problem is I cannot identify which of the three ports on the stat that is.
Can anyone please point me to a clear diagram or photo please?
cheers
geoff

[aj81spider]

Here's a thread on it with a picture

http://fiatspider.com/f15/viewtopic.php?t=36651

[18Fiatsandcounting]

This might help as well: https://www.youtube.com/watch?v=m5Xnrfjc9qU

-Bryan

[RRoller123]

[geoff]

thanks all for all of this helpful input.
It is now installed correctly, filled and bled so we will see. I did install a bleed facility at the top of the heater hose but later I saw this device which I guess would have avoided the need to do that because as I see it, this device temporarilly raises the radiator cap to the highest point?
https://www.ebay.fr/itm/EPAuto-Spill-Pr ... Sw3uteeClj

[rridge]

A number of different external thermostats have been made for the Twin Cam over the years. You cannot judge orientation by internal or external detail. All external thermostats for this engine function by blocking the flow from the bottom of the radiator when coolant is cold. The port that is closed to flow when the thermostat is at room temperature is the port that connects to the bottom radiator hose. Blow into a port. If you feel your breath come out one of the other two ports you've found the cold recirculation path from top of head to pump. If your breath is blocked, you've found the port that shuts off flow from the bottom of the radiator.

[geoff]

good logic there rridge.
Once the system is bled and nicely filled, I am tempted to fun the engine and open the bleed valve i have fitted to the heater hose so that any more trapped air will be expelled. what to you think - is that a good idea,
cheers
geoff

[rridge]

A better test is to turn the heater full on, run the engine after filling to operating temp, let it cool then check the level in the heater fill port. Fill the port if needed. Run and cool the engine again. Check again. If you are still finding air in the heater port after several cycles you have a coolant leak somewhere in the system.

Even a properly operating cooling system traps small amounts air during refill and allows small amounts of air to enter in normal operation. Since the top of the radiator is itself a local high spot, sooner or later air collects there and when the radiator cap opens to vent excess pressure, the air travels to the coolant recovery bottle and escapes via the unpressurized bottle's open vent. In normal operation the water pump will eventually scavenge whatever air remains in the head after refilling and it will find its way to the top of the radiator although it may take several cycles.

When the engine cools and negative pressure begins to develop in the cooling system only coolant should return to the radiator. If the valve isn't working or if there is an air leak somewhere in the system (including the seals on the cap itself) the fluid in the bottle will not rise and fall with engine temp.

The coolant recovery bottle's is the normal path for excess air to leave the cooling system. Make sure it is working.