Do I need a new thermostat?

[wdoland]

Engine always runs about 189 degrees but it seems hot to me when I shut it off in the garage. Today I left it running and squeezed the upper hose and it felt like nothing was flowing through it. Then I carefully removed (I know, I know) the radiator cap and looked in with flashlight. Nothing was moving. The level is above the core but not too full since I read that is not good.

Went to drain the coolant, which has the proper anti-freeze by the way, and found that the little drain at the bottom of the radiator is missing or broken so I siphoned some coolant out of the top to get the level below the upper hose. Didn't want to make a mess when I took the hose off. But what I found out was the coolant was very hot. Not so hot that it would burn me but hot. If the thermostat was bad wouldn't the coolant be cool since it isn't flowing through the engine? And wouldn't I feel circulation in the top hose with the engine running?

[Merle Coggins]

At idle you may not be able to feel any flow by pinching the hose. Also, remember that the water pump is not a positive displacement pump. If you restrict the output you can stop the flow, especially at low RPM.

 

Merle

[Joe Flanagan]

It should take a while for the thermostat to open and until it does, you won't feel anything coming through the upper hose. Once it opens, you'll feel the hose start to heat up. I don't know how long you had it running, so it's hard to say. If you're in doubt, remove the thermostat and put it in a pan of boiling water and see if it opens. Putting in a new one is a relatively simple job.

[wdoland]

I ran around town for awhile and it was definitely up to temperature. Shouldn't I see the water flowing with the cap off?  Not sure what "positive displacement" is but I didn't restrict the flow that much. I just squeezed the hose a little and didn't feel any flow through it.  

I have an after market temp gauge and it's never gone above 189. Maybe everything is normal. I'm still getting use to the little "quirks" of this car. It just seems very hot when I park it in the garage. I raise the hood and you can just feel the heat coming off the engine. But there's no bubbling sound, no steam, just radiating heat. Keep in mind, I'm still learning and I just want to be sure I'm not hurting anything. Thanks for the advice.

Wayne  

[Joe Flanagan]

I'm not sure I've ever been able to feel coolant flowing through the upper hose. I think the most important thing is whether the hose itself starts to get hot. That tells you that water is coming out of the block and into the radiator. I don't think 189 degrees is all that hot for one of these things, but other guys who know a lot more about it can maybe chime in. 

[Tones52]

I'm with you Wayne in that I'm still learning, too.

 

An easy check for me to see if my dash Temp Gauge was reading right was to put one of the needle pointed kitchen thermometers into the radiator opening after running the car around the neighborhood. I had a 4 lbs. radiator cap and carefully removed it to check the temp with kitchen thermometer.

 

I also found that after shutting down the engine, the temp would go a bit higher.

 

I changed my thermostat and did check it before installing it by putting it into a a pan of water on the stove top (BTW - ask for an old pan that can be used for auto parts stuff LOL). The new one opened right at 160 in a nice smooth manner. I also checked the old rusty looking one and it also opened but not as much.

 

I hope that  drain plug is an easy enough fix, too.

[De Soto Frank]

You won't  feel the water flowing in terms of pressure, like you would kinkng a garden hose...  what you should feel is that the hose and the elbow into the top tank ofthe radiator are the same or nearly the same temperature as the cylinder head right around the thermostat housing.

 

If your MoPar has the "external bypass" cooling system ( short piece of 1" hose between the thermostat housing and the water pump),  you will not find a thermostat at the mdoern auto-parts stores.

 

You will need to get an old-stock stat from one of the specialists.

 

Good luck !

[wdoland]

I think my service manual says the thermostat starts opening at 157-162 degrees and is fully open at 183 so I'm not running too bad at 189. I'll keep an eye on it. Maybe it's just the way it is. There is a lot of getting use to this engine. It's super quite, sometimes I think it stalled. When I shut it off, there is no cooling down ticking like my newer cars. 

 

Now onto the drain plug...Do they screw in? or do I need a radiator shop?

 

On a side note, I had a 69 Firebird that started overheating after I parked it. Thought it was the water pump. Went to Advance Auto where an older guy told me to get a new radiator cap first. He said the engine continues to get hot after you shut it off. Got a new cap and problem solved. 

 

Just saw your post, Frank...yeah, I do have that external bypass so I'm gonna order a new thermostat from Andy Bernbaum tomorrow just to have it on hand if I do need to change it.

Edited September 22, 2013 by wdoland

[Young Ed]

You won't  feel the water flowing in terms of pressure, like you would kinkng a garden hose...  what you should feel is that the hose and the elbow into the top tank ofthe radiator are the same or nearly the same temperature as the cylinder head right around the thermostat housing.

 

If your MoPar has the "external bypass" cooling system ( short piece of 1" hose between the thermostat housing and the water pump),  you will not find a thermostat at the mdoern auto-parts stores.

 

You will need to get an old-stock stat from one of the specialists.

 

Good luck !

 

Not true. Napa has them in both 160° and 180° versions. I suspect any parts line can get them. They are basically a conventional modern thermostat that snaps into a brass spacer and then a large rubber ring to seal to the cast iron housing.

[De Soto Frank]

Not true. Napa has them in both 160° and 180° versions. I suspect any parts line can get them. They are basically a conventional modern thermostat that snaps into a brass spacer and then a large rubber ring to seal to the cast iron housing.

 

I couldn't find them in Stant  or any of the other lines...

 

 

Is the by-pass passage open when the stat is closed ?

 

If you can, please post some pics or a part #....

Edited September 23, 2013 by De Soto Frank

[_shel_ny]

I believe this thread shows one

 

 

http://p15-d24.com/topic/33566-thermostat-old-style-vs-new/?hl=thermostat

[Young Ed]

I think the napa part number is THM 55 and THM 155 but thats just off the top of my head.

[Rodney Bullock]

The easiest way to tell if your system is flowing is to remove the radiator cap and while the car is running rev the motor. If it's flowing you will see the water moving if you just look down the radiator opening at idle you might not see anything also make sure you have a non pressure radiator cap on your car. These systems are not pressurized. 189 is not hot for these cars.

[chopt50wgn]

Just a few facts about t-stats.........................they open at the given temp they are rated for, like 160 or 180 but they are not full open until they hit 15 degrees above the opening temp. Example- a 160 opens at 160 but is not full open until it hits 175.

 A t-stat may open and close many times while driving which can give you varying readings on the gauge. It is due to a variety of factors. On a hot day it will probably be open more as the hotter temps along with hotter air hitting the radiator will keep it open. On a cooler day it may open and close due to air temps being cooler .

[JBNeal]

something I learned about heat exchange is that different materials conduct heat energy at different rates, and that the mass that is storing heat energy acts as a capacitor as it transfers that heat to another mass in the presence of a temperature gradient.  Grandma's Diplomat's 318 was notorious for pegging out the temperature gauge after the engine was shut off, as heat from the lower areas of the engine radiated upward towards the temp.sensor, but once the engine was running again, the temperature would stabilize to normal operating temps.  On my '48 & '49, I can drive around at operating temperature for a good while, then shut off the engine and watch the mechanical temperature gauge rise to boiling temps.  When I first saw this phenomenon, I thought I was doing damage to the engine, so I would start the engine and rev the motor to get the water pump to moving coolant, which would bring the temps back down to operating temp.  Shutting off the engine would see that the temps rise again, so I stewed about it and let it shed heat on its own.  If it's overheating during operation, then ya have a problem, as the temp sensor is measuring a constant high heat radiating from the engine internals, and that's not always a good thing.  Heat generation is from the combustion process, but also friction from rotating & sliding parts, so if one of those heat sources is too high, then ya might have a charged air mixture problem or an internal mechanical problem.  Or in some cases, a blocked coolant passage will cause area of the engine to not shed heat at the same rate at other areas of the engine, causing hot spots that can do damage to the engine.  And if ya think about it, if ya boil water on a conductive stove top, then turn off the stove (heat), does the stove, water pot or water cool off right away?

 

As for the ticking noise ya hear when a modern engine is shut off, I'm purty sure what you're hearing is the various heat shields on the manifolds and exhaust pipes that are moving around from the heat.  They are thin sheet metal and expand quickly compared to cast iron.  If ya hear a ticking noise from a flathead, RUN FOR DA HILLS