Hello-POC family
I want to replace the thermostat in my 39 P-8-
I have had it for decades and it recently spit out coolant
after it was hot-Not from the thermostat
housing but through the tube attached to
the radiator-This is one part I have not replaced-in the decades
that I have owned the car.
#1- Gasket for the thermostat-? Make my own-? or-??...
anything to go onto the block side or the upper side
when reinstalling?
I read someplace that some guys put a thin smear of heavy duty
grease to help bridge the gap of unevenness on the mating
parts?
#2- I am thinking of draining the block-opening the block
petcock-...would I be opening a can of worms with that?
I hate to think that I would not be able to get that closed
when refilling ...
I have previously changed the coolant over the years but not specifically
drained the block-
Thoughts?
Thank you!
Dennis
You have a non-pressurized cooling system so a perfect seal on the radiator cap isn't really required.
Water expands when it gets hot. In modern cars with a pressurized cooling system there is an overflow tank that takes that extra volume of coolant when the engine is hot. When the engine cools down the radiator becomes under partial vacuum and the cap system allows fluid from the overflow to be sucked back into the radiator.
Your 1939 system deals with expanding and contracting coolant slightly differently: It simply has a much larger top tank and an overflow drain hose. When the coolant level is correct and engine is cold there is a lot of space above the coolant level and the overflow. As the engine warms up the coolant expands but as long as the radiator was not over filled it never reaches the level where it will drain out of the overflow.
But someone used to a modern car that simply fills the radiator to the top will always have coolant being released from the overflow. Basically the car is trying to get the coolant level down to the point where it was designed to be. Just saying that spitting out water from the overflow most likely means you are overfilling the radiator and the fix is simply: Don't overfill the radiator.
Regarding you second question, draining and back flushing the block and radiator are generally good things to do from time to time. If you don't then you can get sediment build ups that decrease the cooling capacity of the system. You may not get much flow from the drain cock on the side of the block, especially if there is some sediment build up. But removing the thermostat and the lower radiator hose will allow you to use a hose (and maybe some ad hoc fittings) to force water backwards through he block and the radiator to flush out some debris. If the cooling system is in really bad shape they you probably want to remove the core/welch/freeze plugs on the side of the block and use some stiff wire when you flush to break up the sediment. And if going that far, you probably ought to remove the water pump and pull out the water distribution tube and see how corroded it is. That tube directs coolant at the exhaust valve seats.
Tod- -I drained the radiator and the fluid looked brand new- I thought that the thermostat wasn't opening and-was all just from the radiator-it made sense (To me) that the thermostat didn't open- as the temp gauge was way over to the hot side-
I did probably overfill the radiator!!
-The hoses are old but I don't think they leak. I was going to take-
the opportunity of a thermostat change to change all the hoses too--to/from the radiator- It looks like the heater core hoses have been replaced- at least not as old as the radiator hoses.
If the thermostat did open then the fluid would not of looked new?-The coolant in the block would of run through the radiator-My thought that the coolant that was in
the block was "Stuck" in there as the Thermostat did not open-? and it showed hot. I thought
it didn't open-I appreciate your input here-you have helped me before-Any more thoughts here welcomed-!
Dennis
It sounds like the thermostat did not open properly. There are several possibilities but first, has that thermostat been on there a while and if so did it work at one time?
Assuming a new thermostat, it could be defective, it could be the wrong type (I think you might need a bypass type thermostat for your car), or it could have been installed upside down.
By the way, one thing the confused the heck out of me when I got my old Plymouth was that the water pump impeller had come free from the shaft so the pump was not working at all. The car would run pretty much okay if there was no thermostat. But if I tried to install a thermostat it would overheat and the thermostat would never open. Finally I noticed a little weeping from the water pump and took it off and found the real problem. Pretty rare type of failure I would think, but apparently it can happen.
Hey Tod-
I actually got 2 thermostats from the then 39 advisor- in Severena (?) Park, Maryland-- Roy...something.
He was great!!! I have the original boxes that they came in-After he passed, I dealt with Pat-? I think his wife.
Just great people.... That thermostat could be original? might be? I have had the car just short of 30 years.
I will change the thermostat out-I'll get/find/make a gasket for it. the hoses all have the wire type of clamps
and all the wires are cloth covered. It has 82K miles- I believe original. Thoughts on something as minor as a thermostat gasket? I see the type of gaskets that come with stuff today and they are thinner than paper.
Thanks again
Dennis
I actually stayed in Severna Park, MD for a while back in the 1970s.
For simple gaskets, I often just get some sheet gasket material (I usually have some in my garage) and cut out whatever I need. Valve cover gaskets, thermostat housing gasket, etc. You might be able to get by with the really thin material but with the usual "patina" on surfaces that old you are correct that a bit thicker material would make more sense.
Thanks Tod!!
I will go to the local parts store and get some gasket material-
Thanks again-!!!!
I life saver for me and no doubt countless others
Dennis