1931 355A v-8 temp thermostat

[Thomas B.]

Where is the temp thermostat located on this 31 v-8 and where can I get one?  I have a shop manual but it does not really show the location of the thermostat.Thanks.  T. Brown

[m-mman]

It is 'built into' the radiator and uses a rod to operate shutters in front of the radiator that open or block the airflow through the core.

It is located on the side of the radiator that faces AWAY from the engine. Closest to the front of the car. You should be able to easily see the shutters in front of the radiator core if they have not been removed. If you have an accessory chrome stone guard/screen you may not have noticed them.

Not uncommon for them to jam and the thermostat itself is not readily available, so many times they have just been wired into the full open position.

[31caddy]

Here's some pictures of one.

[Bob Hoffmann CLC#96]

I may have one available that I could test.
Bob

[Thomas B.]

Thank You Bob.  Yes, I did check the shutters yesterday and they are open, I think they are wired open like you said as they do not close when it cools down.  When the air temp is 85 and you drive the car at 55 or sixty she seems to run around 210 or 220.  I ran it this morning at an idle for 30 minutes and she got up to 180.  It seems to not run as well at these temps, yesterday after driving it she shut down and would not start, as if it was vapor locked.  We are running an electric pump at 1 1/2 pounds of pressure so I would think that the pump would still push the fuel through and not vapor lock.  I know that was a common problem with these cars.  I did check the radiator with the cap off while it was running and the coolant is flowing good.  I also checked the engine temp with a digital gauge against the gauge in the car and it was pretty accurate.  I personally feel 210 or 220 is way to hot for this engine.  Any thoughts?  Thanks.  T. Brown.

[31caddy]

I've owned a couple of these cars and they both never got over about 185 even on a hot day, and often ran cooler than that. Since the cooling system is not pressurized  (which would raise the boiling point), I doubt if you are reaching 220 if it is not boiling over, but it does sound as if it is running on the hot side. If the shutters are wide open all of the time, they are wired open, or the linkage rod/thermostat lever is frozen, because the shutters are spring loaded to the closed position by a spring inside the thermostat. As the thermostat heats up, it overcomes this spring pressure to gradually open the shutters.
As a side note, if you are driving that car routinely at 55-60mph, and you don't have an overdrive installed or non factory rear gears, your rod bearings will soon be done. It is really screaming at those speeds.

[m-mman]

Since you have a thermostat assembly accessible perhaps you can answer a question for me.

This is my link plate. I am currently freeing it up and creating new linkage. But I would like to know if the holes are supposed to be oval? or round?

My thought was that they should be round and are worn but maybe the oval shape had something to do with the geometry of the linkage. . . . ?
Maybe I need to remake the arms? or make a new bushing for it?

[Bob Hoffmann CLC#96]

Thomas,
It sounds like you're in good hands with the guys that have these cars. If you need a thermostat ,I have one to sell. I can test it first.
Thanks, Bob

[31caddy]

Attached are some more pics showing the area you asked about. The hole should be racetrack shaped as shown. It appears that yours has some extra wear, especially in your second picture. I am uncertain as to whether this is a problem. You can test the bellows/operation of the thermostat by placing in in a pot of water with a thermometer and heating it up. The arm should begin to move at around 160 degrees, and the spring should return the arm to the closed position as it cools.

[m-mman]

"Racetrack shaped" good description.
The pivot pins are stuck and the threaded clevis is broken, so I got some more work to do but at least I know it aint too bad.

I didnt know if I even had a thermostat to rebuild. Turns out the 'washer retaining nut' was missing so to seal up the radiator they covered over the entire thing with 1/4 inch of solder(!)
A torch and a wire brush to scrape out all the muck and surprise! I at least had one to rebuild. (As recommended -Jim Otto he did a great job) Now To get all the other little stuff replaced.

[Thomas B.]

That is some great information Bob.  Thank You very much for your help.  T.Brown.

[Thomas B.]

So, the saga continues with this fuel problem.  Now, with the electric fuel pump set up and bypassing the vacumn tank.  (Fuel pump set at 1 1/2 lbs), the car will drive down the road 4 or 5 miles no problem, but when if you shut it off, it will not start til it cools down.  I spoke with Bruce from Classic & Exotic Services about the float, the kit we installed in the carb has the new urethane float so that should not be an issue.  It seems as though the float is not letting fuel into the carb at high temps.  The only thing I can think of is the bowl that the float sets in is changing shape at high temp.    T. Brown

[Chris Cummings]

Tom,

I have a hunch that you should speak with Tom Young, CLC member in Paso Robles, California, who has made an intense study of the Cadillac updraft carburetors, of which yours is close to the final version.  There is something he was telling me about a thermostat that opens a passage to let vapor escape from the float chamber.  It seems to me that vapor accumulating with no way to escape could restrict the amount of fuel that could come into the chamber (and hence supply the engine).  Give Tom a call and feel free to blame me.

Hope that helps,

Chris Cummings

[Thomas B.]

Thank You Chris, I will do that.  That makes a lot of sense.  T.Brown.

[Thomas B.]

Chris, would you happen to know which CLC club Tom is affiliated with?  I searched a couple of them from CA but could not find his contact info.  T.Brown

[Chris Cummings]

Hi Tom,

National club.

See page 120 of the 2016 Directory.

Best regards,

Chris

[Thomas B.]

Thanks again Chris.  T.Brown

[Chris Cummings]

You're welcome.

[31caddy]

The carburetor has a 2in 1 thermostat located under a small sheet metal plate on the passenger side of the carburetor above the float bowl. Here is a description from an old manual: " The throttle pump discharges air in the pump chamber into the float bowl when the throttle is opened, increasing the pressure above the gasoline and causing an increased fuel discharge from the spray  nozzle. The throttle pump thermostat opens at 74-78 degrees F, providing a vent for part of the pump discharge and decreasing the float bowl pressure.
A second thermostat controlling a float chamber vent is set to open at 125-130 degrees F. Thermostats should not require adjustment."