Over cooling!

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boomslack

boomslack

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Hey guys, I tried a search through the forum and couldn't find anything concrete so I'll start a new thread. Lemme detail out what I have/know:

'66 Barracuda, stock everything, /6 (of course).

I did radiator work during the summer b/c it was having issues overheating. I replaced the thermostat to the stock 160 and after that in never overheated. The radiator held pressure with a water test, and it was flushed by a professional so I'm confident that's fine. The thermostat is brand new, only 2000 miles on it tops(I regularly drive across the state). All this work was done in August.

Recently, especially after this past weekend(outside temps low 20's high teens), the thermostat temperatures drop drastically, and stay cold. Normally it stays just on the inside of the operating range on the cold side, but this time it dropped below. The defroster reflects the temperatures on the gauge(when it's very low the heat coming out is lukewarm at best) I'm not sure exactly what's causing the issue. It starts out pretty warm as well, it's only after I'm on the highway for 30+ minutes. It doesn't do this when the outside temps are >40-ish degrees.

I was thinking of putting in the 180 thermostat, but not positive. If I put any extra fluid in the radiator it gets immediately dumped through the overflow.

EDIT: felt it was important to note, I was getting ~17mpg this past trip.
 
A higher temperature stat won't raise the temperature if it can't get up to the thermostat temperature of the 160.

Also, there's no guarantee the 160 is still good, even being so new. That's the best place to start..

..or toss a chunk of cardboard in front of your radiator to see if reducing some of the flow helps the temps come up in the frigid weather.
 
Two things to check. Thermostat and radiator cap. Both are so cheap, I'd just replace them both. I have had a thermostat open and then jam itself open. No heat, unless I put cardboard in front of the radiator.
I concur that you should get by just fine with a 180 thermostat.
 
I've heard about the cardboard trick though, to prevent air-flow. I might try that. I thought it was odd though because it never had any issues in warmer weather.

Like I said, I'm pretty sure the thermostat is still good ... I got one of the better ones b/c I didn't want to replace it (after going through two of them within 50 miles). And the radiator cap? I never thought of that, how come?

I'm not sure the 180 might be the way to go. Back when I had the 180 in it, it always operated on the high side of the temp gauge on my dash-board. Not sure if the dash is just screwed up or not(it is on the 'to-fix' list as it is). Though with it acting so cold, maybe the high end is what I need!
 
160 is too cold, use a 180. That is the sweet spot for wear and performance. Too low and your cylinder bores will wear faster, too hot and youll lose power. In your case, just drop a piece of cardboard in front of the rad with a softball size hole in it. 20 is cold, -30 is very cold and cars still start and work fine.
 
Thermostats keep an engine from running too cold, your system may not have had enough cooling power to get the temperature down to 160 until it got cold outside.

so put a 180 in it and it should be fine.
I don't think you need the cardboard.
 
boomslack said:
I've heard about the cardboard trick though, to prevent air-flow. I might try that. I thought it was odd though because it never had any issues in warmer weather. And the radiator cap? I never thought of that, how come?
Click to expand...

I had to do the card board thing on a Dodge Avenger. The T-stat broke, the round disk broke free and turned sideways. I just didn't have time to change it right away.
My sister had an old Comet that would not generate any heat. This was before I really knew anything about cars. The guy at the parts store said to change the cap, it needed pressure (pressurized water can get hotter before it boils) to be able to generate heat.
I thought he was full of crap, but I tried it because it was a cheap part. I was surprised when it worked. I have since heard that radiator caps are generally only good for a year or two before they start losing their pressure rating.
I feel, the part is cheap, easy to swap, and really can't hurt to try. Just my 2 cents worth.
 
I had this same issue in a /6 dodge truck I put an a/c radiator in and never could figure it out before i sold it.
 
The gauge being at the hot end of the normal range with a 180 t'stat is not unusual for the older temp sensors and gauges; in fact, there were service bulletins about them in the very early 60's. You may just have the wrong temp sensor; the newer ones available tend to read hotter. So don't depend on the gauge to be absolutely correct. Borrow an infrared temp gun or use a candy thermometer to check the actual temp of the coolant as it reaches normal operating temps. My '62 Dart with /6 always runs towards the upper end of the scale with a 180 F t'stat; I have calibrated the temp sensor resistance and the coolant runs truly between around 185 to 200 F in summer with the engine good n' hot; that is with the gauge getting right to the top of the normal range, and maybe a bit over worst case.

I have used the cardboard in front of the rad before with later A body /6's, when I lived in northern IN and it was consistently -10 to 10 F in the dead of winter. But cardboard was never needed in winter in Salem VA growing up, or when I went to VPI, with any of the 5 A bodies that my family owned in that area.

And as old as your rad is... 50 years!..... flushing by a profession or anyone is not likely going to get it really clean and open. Rodding it out after all these years is probably needed.... hopefully the tubes survive that. I'll be rodding out my '62 rad soon.
 
Losing interior heat AND a dropping temp guage, CAN be a sign of low coolant level as well. I know you said it blows out any fluid that you add, but if you have air trapped in the system, it COULD do that. SOMETIMES a heater core is hard to bleed.

I agree with a higher rated stat. I have run a 205 for many years in my 360FormulaS,in summer, and my other cars never run less than a 195 up here in Southern Manitoba. And I run a 7psi cap, whenever I can. The hoses last forever, and it's easy on the old rads.In your hotter summer climate, that might not be enough, but our heat waves usually only last a week in July, and even then, only during the part of the day when the sun is directly overhead;while I am at work,not on the road.heehee
Yeah so, also up here, running cardboard on these old engines is very common. The stat only sets the minimum operating temperature.My 1980Volare slanty absolutely has to have cardboard from December through Febuary, the rad being covered about 90%. For November and March I might run 50 or 60%. This is more to prevent ram-air from cooling the block, as it comes through the rad, cuz the rad itself is often cool, as the heater core is extracting a lot of heat. Those slantys have a whole lot of surface area to radiate heat, so the rad in January, barely gets warm. even though the airtemp coming out the heater might be 140 to 150*F. I have often taken off the 4-blade fan as well, to reduce air-cooling.
 
AJ/FormS said:
Losing interior heat AND a dropping temp guage, CAN be a sign of low coolant level as well. I know you said it blows out any fluid that you add, but if you have air trapped in the system, it COULD do that. SOMETIMES a heater core is hard to bleed.
Click to expand...

Very true. A temperature sensor surrounded by steam doesn't read the same as when it's in water. A recovery system is never a bad idea, and these days the parts are easy to find and pretty affordable.
 
This is some awesome stuff, on top of what everyone else said as well. once it gets warmer, I'll take a look at the different t'stats and see what they look like compared to an external heat sensor.

nm9stheham said:
The gauge being at the hot end of the normal range with a 180 t'stat is not unusual for the older temp sensors and gauges; in fact, there were service bulletins about them in the very early 60's. You may just have the wrong temp sensor; the newer ones available tend to read hotter. So don't depend on the gauge to be absolutely correct. Borrow an infrared temp gun or use a candy thermometer to check the actual temp of the coolant as it reaches normal operating temps. My '62 Dart with /6 always runs towards the upper end of the scale with a 180 F t'stat; I have calibrated the temp sensor resistance and the coolant runs truly between around 185 to 200 F in summer with the engine good n' hot; that is with the gauge getting right to the top of the normal range, and maybe a bit over worst case.

I have used the cardboard in front of the rad before with later A body /6's, when I lived in northern IN and it was consistently -10 to 10 F in the dead of winter. But cardboard was never needed in winter in Salem VA growing up, or when I went to VPI, with any of the 5 A bodies that my family owned in that area.

And as old as your rad is... 50 years!..... flushing by a profession or anyone is not likely going to get it really clean and open. Rodding it out after all these years is probably needed.... hopefully the tubes survive that. I'll be rodding out my '62 rad soon.
Click to expand...


^^This is very applicable because I drive past Salem almost every month! my 'cross-state' trips are across VA. I had to try and beat the storm yesterday, that was a trip!
 
BTW, since your older A body likely does not have an overflow tank (it would not have had one new), then you cannot fill the rad to the top or it will indeed blow out some coolant every time when it gets hot. The FSM states that you have to leave the coolant fill in the rad about 1-1/4" below the lower edge of the rad cap opening in the top of the rad. That air gap inside the top of the rad HAS to be there for coolant expansion in a non-overflow system. Filling a non-overflow rad up to the top GURANTEES that it will blow out the excess coolant until a sufficiently sized air gap emerges in the top of the rad. I had that happen over and over when I first got my '62 Dart; I FINALLY read the FSM and learned to not fill the rad too high!

Man, I hope you get all the salt washed out form under your nice A body! We came back from Salem to Augusta County Sunday eve in that early snow fall towing a trailer; it was a bit nasty in places. People sure drive foolishly in small amounts of snow....
 
As a general rule for people that don't have a lot of experience with it, your car isn't running too hot if it doesn't blow fluid out when you stop. (The coolant temp in the engine increases when the engine is shut off) and that is when you know for sure it's running on the hot side.

I also agree that 160 is too cold and increases engine wear.

Personally I run a 190 year round here in AZ.
 
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