The Stovebolt Site Forums The Parking Lot Big Bolts engine temp issue

Does anybody know how I can get the engine temp in my '46 to get high enough for the thermistat to open. New water pump, block heater, misc. hose and some antifreeze/coolant and i can only get it to 165 F, the thermistat is a 185 F. By the way I work outside and its 20 degrees below zero.

Scott

Time for a trip South! Or, maybe put some paper or cardboard in front of the radiator.

Thanks, the trip south sounds like a good idea whats the weather like in your backyard? Some cardboard should work, I figured since it hasn't ran in twenty years it should run hot, I guess not.

Scott

yes, they did use "winter fronts" commonly in the day!

if your thermostat is in right and works at the temp called for [185] the engine HAS to get that hot before it opens and circulates water outta the engine and thru the rad - if the stat doesn't open the engine heat should continue to climb til the ol girl blows up - where are you reading the 165? have you actually tested the thermostat in a pan of water on the stove, w/ yer wife's good candy or meat thermometer?

Bill

My old 54 2-ton was supposed to have a 160 thermostat in it. You sure stat opens/closes right? Remove,use thermometer and pan of water on stove, check it's operation.

I did not check the stat before I installed it, on the head on the drivers side is a temp probe for water temp and it got as high as 165 F. The top rad hose and bottom had a temp differential of about 100 F all over the engine the temp didn't get any highe than 163 F. The hood is also off the truck (fell off) that might have something to do with low temp?

you've got a 165 stat if it's workin properly, and at 20 below I'd get a hood on and a potato sack on the front of the rad - don't use cardboard, that might bend the fan blades or cause belt slip and wear

Bill

Should I use a 165 or 185 stat up here in Edmonton?

160 deg stats were for Alcohol antifreezes...which boiled-off at temps above 160F...

(This is why Ethylene Glycol antifreezes were known as "permanent" anit-freeze...)


Use the 180 or 185 F stat . The engine will be happier.


Good luck !

Frank McMullen

165 should be fine for the engine, but 185 might be better for the heater to work well, and should be fine - just watch you don't use a modern high pressure rad cap, as the system was designed for no-pressure caps and an old rad might not like too much pressure

Bill

Thanks guys, your always a great deal of help.

I learned alot by just following along. I also want to say thanks.

If you have too agressive of a fan it can cause the temp. not to come up to the therm. setting.

So it turns out the stat is opening but flow might be an issue, after running and getting up to temp I shut her off, from the top of the rad down there is a distinctive temp difference. When running there is a 50 degree temp difference. Without pulling the rad what can I do?

Don't forget the dynamics of the radiator. I would think there would be a temp difference top to bottom. If you are thinking the tubes are plugged, short of pulling it and having it boiled, cooling system flushes would be the choice.

You can look into the filler neck and see the the top header and tubes..it's an old truck, they will probably be partially plugged. Pulling the radiator isn't a huge task. Make sure it is the culprit.

Stuart

Our local Bolt Store guy said it should be on about 20 degrees or so and if you run your hand down the core from top to bottom and it goes hot to cold that isn't good. The more advice I get the better, when you work outside at 15 below you got to be sure of your next move. Thanks.

Scott :confused:

Scott,

I think the cooling system pulls from the bottom of the radiator, through the engine, through the thermostat and into the top tank. If this is indeed how the systems functions, I would expect the radiator to be warmer on top and less warm on the bottom...how much of a difference I don't know.

Usually any blockage in the radiator results in OVERHEATING. You are saying yours is not reaching the proper temp...I don't know if this line of reasoning changes when you get into an area of 20 below...brrrrrrrrr!

Stuart

Well after running it for at least an hour I would think the temp would rise if there was a major problem. I had the hood closed and a tarp in front of the grill and it wouldn't get above 180 degrees on my temp guage, I suspect the stat is indeed opening and there is just a difference between my guage and stat. Is there some place on the engine directly that I can use an infared temp gun to confirm temp readings?

Scott,

I think the SOP is to remove the radiator cap and insert a household meat thermometer in the coolant...the water temp in the top tank should be a true example of system temp. Surface reflectivity can sometimes fool the infrared!

Stuart

Thanks again Stuart, my wife just bought a brand new meat thermometer I can break in, I'll try that.

scott

If the engine isn't getting hot, and your temp gauge dosent rise above 165, then my guess is the thermostat IS open.

An engine is a series of explosions.. hold a lighter to a spoon (even in sub 0 temperatures) and it isn't just going to stop getting hot at 165.. it's gunna keep on getting hot till something comes along and cools it.

For instance, drain all the coolant out of your truck and let it idle for an hour.. i'll bet it gets hotter than 165.. even if it's 20 below outside with no hood on it, in the wind.

For instance, drain all the coolant out of your truck and let it idle for an hour.. i'll bet it gets hotter than 165.. even if it's 20 below outside with no hood on it, in the wind.

not a good suggestion in my opinion

Well it wasn't meant to be taken literally, but used to illustrate my point that regardless of how cold it is outside, without a steady stream of "cooled" coolant, your motor will eventually exceed the operational temperature limit (in the case of a 1946 Chevrolet, thats about 212 degrees)

The fact that his engine temp dosen't get above 165 suggests that the engine is indeed getting "fresh" coolant.. if it wasn't, it would overheat.

My '46 1/2 ton has an aftermarket temp gauge installed under the dash, and even on warm days hasn't gotten much warmer than 130.

actually Joe, it's the other way round - the higher pressure caps came about to cope w/ engines that naturally ran much hotter and the higher pressure actually keeps it from boiling over - the earlier trucks ran NO pressure caps, and do run normally quite cool, which is why they use thermostats, because an engine is more efficient at certain temps, like created by a 180* stat

the pre-46 used a non-pressurized cap, the AD and TF trucks used 3 & 7# caps - all use 160+ thermostats - all run the risk of popping rad seams w/ caps over 7#, and the 60 year old rads may go w/ even a 3# cap

my 46 GMC 228 would run quite well & with a 185* thermostat required having the window or cowl vent open a bit to prevent making the cab downright tropical - my 57 235 w/ a 185* gets the heater cookin too, but the gauge won't get above 1/4 unless the rad is half empty

Bill

Have you checked your dash gauge? Remove the capilary bulb from the engine and stick it into a pot of almost boiling hot water with the wife's meat thermometer and compare readings?

If your dash gauge is good and you are really running cold then my guess is there is to much flow through the radiator. It's either a stuck open thermostate or the thermostat has a by-pass hole drilled in it, this would allow flow even when it's closed. The thermostats job is to stay closed untill the engine internal temperature reaches it's set point (ie. 160 degrees). By staying closed it allows the engine fluid to recirculate within the engine, bringing the engine up to operating temperature faster, which in turn helps reduce unnecessary wear. The engine needs to operate at temperatures above 150 degrees, otherwise proper metal clearences aren't achived.

Tell us what you have done or tried!

Happy Holidays!

Mike B

Sorry for the delay fellas, a new temp guage and the temp is the same, and the stat does not have a hole in it. So does that mean it's flowing and doing what it's supposed to do? Also with the stat out and less coolant in it the temp definately rises and rises, 200 F before I shut it down. I think things are good, let me know if I am confused.

Scott

sounds like a bad thermostat to me

Scott,

Why would you want to run your engine with "less coolant"? You run the risk of major engine damage (cracked head, blowing a head gasket or worse)...KEEP the radiator full!

Double check the thermostat to see is it's working (when you remove it from a cold motor it should be closed, put it in a pot of cold water and heat it up on the stove and watch it open). Also make sure it's installed correctly with flow > to > the radiator). If you run the engine without the thermostat the engine will have trouble getting up to operating temperature.

Have you tried putting a piece of cardboard in front of the radiator to block the air flow?

Mike B

Possible air pocket in cooling system. GMC Tech. Bullitin suggest, drilling a 1/8 hole, in the thermostat flange, to allow, for system bleeding, after cooling system work, has been done.

Hey Spanky,

Wouldn't an air pocket cause Over heating? 46GMC says he's running to Cold...

Mike

Had alot of dealings with air pockets,in the cooling systems, in these School Buses, over the years. They would have a hard time building enough heat, for the heaters to work correctly. Seemed to most often happen, after cooling system repairs, ie, rad., heater core, thermostat replacement.

Thanks for the info Spanky...I didn't know an air pocket could make an engine run cold. Learned something new!

Happy Holidays!

Mike B

Cover the radiator with card board if it warms up then its a bad thermostat

thanks for all the suggestions guys, even with a new temp guage installed it says about 178 -180, and infared at the stat housing varies between 168 and 179. The stat does open in a pot of hot water, could it be everything is working? there could definately be inconsistencies with the infared the new temp guage could be off? and the stat does open. Coving the rad helps it heat up quiker, I think the only thing left is drill the .125" hole in the stat flange or pull the rad. I think I'll drill the hole first, thanks again for all the help .

Scott