Engine Running too cold... change thermostat?

[MrSony]

My 350 is brand new, less than 4,500 miles on it. New radiator, water pump, hoses, etc. Because it was the middle of the humid hot summer and I was afraid to have the engine over heat breaking in, I put a 160 thermostat in it. Now that it's getting colder, my temp gauge stays at about 130 when I'm driving and when I shut the car off it goes upto 190 where it's supposed to be. Should I get a 180 or 195 thermostat to correct this? I have no fan shroud and a cheapy spectra aluminum radiator with plastic tanks. I can tell that since its gotten colder the car uses more gas, runs rich, and over all doesn't perform as well as it did a month ago.

 

[drogg1]

I would definitely change your thermostat. It almost sounds like its sticking open so it would be good to change it anyway. Pretty cheap insurance. Learned the hard way in my daily that it is always good to regularly replace cooling system components. I realize you rebuild it recently though. Generally a higher temp will run more efficiently.

 

[MrSony]

I would definitely change your thermostat. It almost sounds like its sticking open so it would be good to change it anyway. Pretty cheap insurance. Learned the hard way in my daily that it is always good to regularly replace cooling system components. I realize you rebuild it recently though. Generally a higher temp will run more efficiently.

Yeah, I was thinking the same thing. It only started acting weird, running rich/rough and using more gas since its been getting colder here. And once it hits sub 70 highs the car will probably be undrivable. It's only 7 bucks and I should change the coolant anyway. I see some floaty things in there, seems like dirt though. Nothing metallic.

 

[64nailhead]

Keep in mind that t-stats aren't like a light switch. They crack open prior to the rated temp. If working correctly they should be full open at their rated temp. Now consider if you have an aftermarket radiator that cools better than needed for your motor, a high volume water pump or lower water pump/crank pulley ratio like a 1:1. All of these increase cooling capacity and will aid in your issue. If this is what you have on /in your car, then electric fans will help you as you can have them turn on at different temps so that they are working or they aren't. I have the same issue at a higher temp. Going down hill I have a tough time keeping the temps above 160 with a 190 t-stat. I changed it twice thinking the thermostat was a dud. But it works just fine under load.

With all of that in mind, you could just have a bad thermostat as well - lol. You ought to be running a 180-195 as that is what you motor needs to burn the fuel more efficiently. And the best burn occurs around 205-215, but you have to be careful not to get to the point that cooling system begins to run away because it doesn't start cooling until it's too late.

You mentioned that when it sits after driving with tmotor shutoff it will heat up - that is normal - COMPLETELY - it's referred to as heat soak. And I'll bet that when you start the car it takes 2-5 seconds to drop 10-20 degrees - again,completely normal. No issues will develop until you start seeing 250+ (it just scares most people to see it that hot whether it's running or not.)

 

[MrSony]

Keep in mind that t-stats aren't like a light switch. They crack open prior to the rated temp. If working correctly they should be full open at their rated temp. Now consider if you have an aftermarket radiator that cools better than needed for your motor, a high volume water pump or lower water pump/crank pulley ratio like a 1:1. All of these increase cooling capacity and will aid in your issue. If this is what you have on /in your car, then electric fans will help you as you can have them turn on at different temps so that they are working or they aren't. I have the same issue at a higher temp. Going down hill I have a tough time keeping the temps above 160 with a 190 t-stat. I changed it twice thinking the thermostat was a dud. But it works just fine under load.

With all of that in mind, you could just have a bad thermostat as well - lol. You ought to be running a 180-195 as that is what you motor needs to burn the fuel more efficiently. And the best burn occurs around 205-215, but you have to be careful not to get to the point that cooling system begins to run away because it doesn't start cooling until it's too late.

You mentioned that when it sits after driving with tmotor shutoff it will heat up - that is normal - COMPLETELY - it's referred to as heat soak. And I'll bet that when you start the car it takes 2-5 seconds to drop 10-20 degrees - again,completely normal. No issues will develop until you start seeing 250+ (it just scares most people to see it that hot whether it's running or not.)

Thanks for the info. I have a lead on a job soon and if I get it that's one fo the first thing's I'll buy. I'll buy a 195 and a 180. I'll try the 195 first and some new spark plugs as well if mine look bad. If I like how it runs and drives after that with the 195, I'll return the other and vice versa. Plus a carb kit. That's what I love about this forum. So many cool people, someone is always bound to know something about something.

 

[pontiacgp]

If your engine's temperature is 130° then changing a thermostat will not help. The 160° thermostat is not opening at 130° so putting in a 195° or a 180° won't change anything unless the 160° thermostat is stuck open. Also I would suggest you confirm the temperature so that you know the gauge is accurate.

 

[MrSony]

If your engine's temperature is 130° then changing a thermostat will not help. The 160° thermostat is not opening at 130° so putting in a 195° or a 180° won't change anything unless the 160° thermostat is stuck open. Also I would suggest you confirm the temperature so that you know the gauge is accurate.

How would I do that, buy another gauge and try it? The gauge itself seems fine and dandy, never gave me any trouble. I have the sender in a port on the intake as I think my Buick doesn't have ports on the heads. There are two ports on the intake for the sender though, the two threaded holes on either side of the water neck hump. I used the slanted hole for the heater hose. Also does it matter that my heater/heater core is not hooked up atm? It just has a hose looped around from the water pump to the intake. never had a problem with it and coolant is certainly circulating through it. The thermostat I think would still be benefited from being changed out to a 180/195 (I'll try the 180 first) to allow the engine to run hotter. When it was warmer outside and after a few pulls on the highway, the engine would run better idle better, and what not. And that was with my good carb before the one I have on their now that has fuel drainage issues. Gonna address that soon. I think the engine isn't getting as hot as it should and therefore is fouling out the plugs, or at least not burning off the carbon deposits like it should for clearer combustion when not running hard and hanging around 130-160 degrees tooling around town. Regardless the thermostat will be coming out anyway.

 

[MrSony]

If your engine's temperature is 130° then changing a thermostat will not help. The 160° thermostat is not opening at 130° so putting in a 195° or a 180° won't change anything unless the 160° thermostat is stuck open. Also I would suggest you confirm the temperature so that you know the gauge is accurate.

And I don't know if I was clear on this, the engine is not at a constant 130, just when I am at high speeds and a lot of air is moving around or now all the time that it's getting colder here in Iowa. Unless I drive it hard at WOT (interstate driving to and from school, weekend dicking around) it never gets up to 190F on the gauge. Hell, it seemed like it was running like a new motor (yes I know its kind of redundant) when it was overheating at 230 when the belt flew off.

 

[pontiacgp]

And I don't know if I was clear on this, the engine is not at a constant 130, just when I am at high speeds and a lot of air is moving around or now all the time that it's getting colder here in Iowa. Unless I drive it hard at WOT (interstate driving to and from school, weekend dicking around) it never gets up to 190F on the gauge. Hell, it seemed like it was running like a new motor (yes I know its kind of redundant) when it was overheating at 230 when the belt flew off.

The thermostat restricts the water flow until the temperature is high enough to open it. Once the engine temperature gets up to the the temperature rating of the thermostat the temperature on your gauge would always be higher or close to it. If the coolant temperature cools down because of the ambient temperature and air flow the thermostat closes up to keep the temperature of the engine at operating temperatures and it would never get to 130°. I'm not sure where you have your sender but it needs to be before the thermostat. To properly check the temperature I use an infrared heat thermometer.

 

[MrSony]

The thermostat restricts the water flow until the temperature is high enough to open it. Once the engine temperature gets up to the the temperature rating of the thermostat the temperature on your gauge would always be higher or close to it. If the coolant temperature cools down because of the ambient temperature and air flow the thermostat closes up to keep the temperature of the engine at operating temperatures and it would never get to 130°. I'm not sure where you have your sender but it needs to be before the thermostat. To properly check the temperature I use an infrared heat thermometer.

I have it in the only place that I can, which are the two ports on either side of the water neck opening. If that wasn't the place to use, why are they there? I don't remember seeing any passage ways in the head for one and I would notice coolant dripping everywhere if there was. The big bump on the front is where the thermostat goes.