nagging thermostat issue

[Aaron]

I know there are several thermostat threads out there, but I am struggling to find a 160 degree thermostat that will work with my housing. I just had Napa order me in # thm55, but as you can see in the picture, the bugger will not fit my housing. It won't even slide in half way.

I would probably consider a 180 degree at this point if 160 can't be found...

I included a picture of the thermostat that came out, which looks to be pretty old...

Any suggestions would be appreciated.

Aaron

[grey beard]

Aaron,

I really believe you would be happier with a 180 degree stat than a 160. The lower number stat harks back to the day when our Pilothouse trucks were built, and the only antifreeze was alcohol stuff that had to be drained out each spring, etc. and could not tolerate a higher operating temp because it would boil and dissipate down till it had no freeze protection. Today, when most antifreeze is ethylene glycol based, many newer vehicles carry thermostats made to open higher than 200 degrees, because the manufacturers want the engines to warm up quickly to get the computerized fuel delivery system into closed loop, where emissions are at their lowest.

With heavy engines like our flatheads, it is also good to get the operating temperature up near the 200 point. My own truck has a large size thermostat that is 195 degrees. When I drive the truck, the dash temp gauge never goes over 185, at least this time of the year. Maybe in warmer weather it will go up to 190 or 200, but with the overbuilt radiators and cooling systems built into our trucks, they seldom if ever had heating issues. Remember that these same engines were used in larger trucks that pulled their hearts out with heavy loads on a daily basis. AND if you keep a nice, clean 50/50 mix of antifreeze and water, the boiling point of the coolant is now up around 245 degrees. If we had pressurized systems - my 48 model does not have this - we would have boiling points over 250.

Having said all that, you can get the stat you need from (gulp) BurnBumm. Hate to recommend the guy, cause his bedside manner really lacks gravity, but sometimes you gotta' do what you gotta' do. Also, you could try Vintage Power Wagon, if you share the same aversion I have to businesses in Massachusetts.

Good Luck

[Don Coatney]

the only antifreeze was alcohol stuff that had to be drained out each spring, etc. and could not tolerate a higher operating temp because it would boil and dissipate down till it had no freeze protection.

Dave;

I recall my dad refreshing the alcohol mix weekly in the early 50's. And I recall a lot of cars with frozen radiators for those who failed to refresh the alcohol anti freeze mixture weekly. So there was more to it than draining each spring. Permanent anti freeze was available in those days but the "fear" was the ethylene glycol mixture would ruin an engine if a head gasket failed. Glad those days are behind us now.

[Aaron]

Thanks for the info Dave, I will let you know what I find...

[Young Ed]

Go to any auto parts store and don't tell them what its for. Just tell them you want a thermostat. There are too sizes big and little that fit cars for about 40 years. The thm55 you bought is the same thermostat my dakota uses minus the rubber ring and the brass adaptor.

[TodFitch]

Ethylene glycol anti-freeze is mentioned in the 1933's owners manual, so it was available way back. Also mentioned in the manual in addition to alcohol was "radiator glycerine" whatever that was.

You probably want a 180F thermostat as grey beard and Don Coatney mention. But you should be able to get a thermostat that fits at you local auto supply. My 1933 takes a thermostat that is identical in size and shape to those used in the 318 V8 engines that were in the 1963 Plymouth and 1963 Dodge truck that I once had. And the thermostat housing in your photo looks very much like the one on my car. Look for:

612048 Thermostat assembly (160F) (PC, PD, PF)

Interchange/Vendor:

Stant 13476 Reverse poppet thermostat

Stant 29706 Economy model

Tru-Temp 651

NAPA THM 91 “Regular”

[Aaron]

Are there separate thermostats for external bypass and internal bypass???

[Young Ed]

Yes the thermostat housings are different. The stamped steel one pictured is the internal one.

[Aaron]

I know the housings are different, but are the actual thermostats made specifically for internal or external systems?

[Young Ed]

Yes. The thermostat has to allow the bypass in the external system

[Aaron]

So if it is an internal system, will any thermostat work (external or internal?)?

[Young Ed]

No because the external ones won't fit in the housing. This is what you need.

[Aaron]

found a 180 degree thermostat that fit my housing at O'reilly's auto parts. Got it installed and took the truck out and within about 5 minutes she was going over 212!

Any ideas of what might be the problem?

Oh yeah, I also just put a new waterpump on...

[greg g]

Based on your first pic you installed it upside down. The spring goes into the head. So once you engin got up to temp, it actually closed the flow and went back to by pass.

[Zeke1953]

I had the same problem and found out my radiator was plugged. Luckily, the radiator from my parts truck was good. Also, have you removed the freeze plugs and cleaned out all the gunk from the block?

[Aaron]

Based on your first pic you installed it upside down. The spring goes into the head. So once you engin got up to temp, it actually closed the flow and went back to by pass.

That first pick just shows a thermostat that didn't fit my housing. the attached picture shows the type of thermostat I just installed. the spring goes down into the engine head, right?

[greg g]

yes and so should the other style.

[Aaron]

I hate to keep bringing this issue up, but I am at my wits end.

Before I installed a brand new water pump and a new 180 degree thermostat, my truck temp would run at about 200 with a 190 degree thermostat in.

After installing the new waterpump and 180 degree thermostat which is pictured, my truck would get up to 212 in which I would quickly turn it off. Even if I got the truck up to 200 and turned it off the temp kept on climbing...

Well tonight I drained the coolant again (which is a pain in the you know what) and took the thermostat out, boiled it and it opened at, you guessed it, 180 degrees.

Do you think it could be the temp sensor, style of thermostat? or what should I be trying at this point?

[Zeke1953]

I had the same experience. I replaced a perfectly good water pump and it still overheated in about ten minutes. Are you sure your radiator is ok? A local radiator shop will pressure test it for a few bucks. If you haven't cleaned out the gunk from inside the block, this might also be a problem. Finally, did you get the right water pump? I think the plate on the back is different for the internal vs. external bypass setups. Thinking logically (which I try to do at least once a day), your problem has to be caused by one of the above. Zeke

[Reg Evans]

If you still have the old water pump reinstall it and see if the problem goes away.

[H Suhling]

Aaron

Are you allowing the thermostat enough time to open? On my truck the heat guage will go up to around 200 degrees stays there about a minute then fall back to 180 and stay there.

Harvey

[MBF]

Assuming your radiator and water distribution tubes are both in good shape on the first run of the day it may appear to overheat for a bit. If I remember correctly the temp pickup is towards the rear of the engine and thermostat is of course at the front. The coolant in the block will warm up and allow the thermostat to open, and then when it gets the ambient temp coolant that was in the radiator on startup it may close again temporarily until the water that has entered the block comes up to a temp high enough to allow the thermostat to open again. My 78 Dodge slant six pickup does this, and so did an Astro van we used to have. Mike

[Aaron]

I think I might have figured out the problem. I will try to make this make sense...

If you look in the thermostat hole on top of the head of the engine there is a 'ridge' that is about 3/16" high. I'm not sure what the purpose of this is but maybe it directs the coolant a bit?

This 'ridge' is directly centered under the thermostat. I think I have figured out that the style of thermostat I was trying (pictured) hits this 'ridge' when it is trying to open. Becaue this style of thermostat has such a small hole compared to the originals, the 'plunger' thingy has to go down at least

1/4" further and then hits this 'ridge' which prevents it from opening all the way, therefore causing my engine to run really hot!

Does this make sense? I will take a picture of this 'ridge' tomorrow and post it.

P.S. My radiator has a brand new core, waterpump back plate is identical to my old one and had a different style 190 degree thermostat that had a larger hole opening that was working but didn't like the truck running at the 200 degree temp...

Aaron

[MBF]

Aaron: One other thing you may want to check is the thermostat. I'd put it in an "old" pot of water and bring it to a boil and see what temp it actually opens at. You may have a bad new thermostat. I've never used the newer type stat in my old stuff so I don't know if there are issues with this or not, but I do know my 36 Plymouth and 52 PH are the fastest heat builders I have-they're both up to at least 160 and able to put out heat in less than a mile and a half of driving. Both use the older type 160 stats. Mike