radcap or thermosat

[brad mcintyre]

my 383 runs hot dose not over heat but runs 200 -210  but a quart of antifreeze comes out overflow. have 16 lb rad cap do not want to pull thermostat if it is just rad cap. I think it runs that hot because it is low on anti

[Charger1970]

Replacing the thermostat is pretty easy. A word of advice; Don't get a thermostat from Advance Auto or Auto Zone. I went through 3 of those in the span of about a year. I got #4 at NAPA and it's been working great for several years. My 383 runs cool as a cucumber. 

[myk]

If your engine is spitting that much coolant then you're having a boil over. Do you have a way of verifying the temperature of your coolant?  Your stock gauges may be woefully inadequate.  Replacing a t-stat and rad cap are easy attempts; you might as well try those things first.   What is the status of the rest of your cooling system?  What type of radiator, water pump, fan, clutch or direct drive fan, electric fan, fan shroud, etc...

[brad mcintyre]

it is mostly stock direct drive fan original water pump and rad. rad redone last year and they beefed it up

[brad mcintyre]

has aftermarket temp reads about 200 210

[RallyeMike]

The only way to test the thermo is to remove it. Just looking at it from a logical perspective, since you don't want to pull the thermo, then replace the cap. 50/50 you will solve it

[green69rt]

Has it been running hot before the radiator work, after the work or just recently?  Was the thermostat and or pump changed out recently?  Any other work done?

Some possibilities:
If before then it could be thermostat or cap.
After the work then I'd look at the radiator, maybe the folks who "beefed" it up screwed it up.
Recently then I would look at the thermostat again or make sure the coolant system is not air bound somewhere.

[brad mcintyre]

it ran hot. but after recore seemed good last year .this year antifreeze come out of overflow but never got that hot car or weather yesterday was about 31 or 32 c it got hot. I think the cap lets out to much coolant for it to keep cool .is 16lb cap what I should have or should cap have more presure

[cdr]

unless you have a coolant recovery tank, the system is designed to push out the excess coolant when it heats up, when cold the coolant should just cover the tubes in the radiator, when it gets hot the coolant expands , if the radiator is full to the top when cold it is gonna spit it out when it gets hot. 

[daveco]

Is there an overflow/recovery bottle installed?

[brad mcintyre]

no but there will be

[cdr]

no but there will be

the rad cap for recovery system is different, so get the correct cap also.

[Mopar Nut]

How old is the thermostat? Two or three years or more, replace it with one that has a bleed hole in it. Is the lower radiator hose collapsing?

[myk]

Is 210 considered too hot for these cars?  Modern cars running modern garbage gas run hotter than that by design...

[6spd68]

Is 210 considered too hot for these cars?  Modern cars running modern garbage gas run hotter than that by design...

Really?  I used to go into panic mode once my 302/347's would hit that temp.

[myk]

Is 210 considered too hot for these cars?  Modern cars running modern garbage gas run hotter than that by design...

Really?  I used to go into panic mode once my 302/347's would hit that temp.

Normal running temperatures for my 4th Gen F bodies is 230* .   My 90's Mustang runs at about 215* consistently.  Again, what temperatures are considered normal for our cars?  I can't see why they would be any different, asides from smog considerations of course...

[brad mcintyre]

I start to panic 210 to 220 what temp do I start to think shut it off

[green69rt]

Quote from Answers.com

"Brian Mette    

I am a ASE and Chrysler certified master technician with over 17 years experience working at a Dodge/Chrysler/Jeep dealer.

Engines vary. The normal operating temperature for a modern (e.g., 1996+) automobile engine, manufactured for sale or use in the US, will fall between 200 and 250 degrees F. Smog equipment and computerized combustion control favor a 'hotter' running engine. The proper amount and concentration of coolant in your engine will protect it.
The thermostat plays a big part in controlling it. If you buy a 185 degree thermostat it opens at 185 degrees. Same with a 195 & so on. Average engine temp (as no specific given) would be around 195 - 205 degrees. The cooling fans come on around 210 degrees approx. The temperature will vary according to driving conditions, ambient temperature etc..

Some newer engines will run in the 220 to 230 deg range."

I don't know if this is really true, but it comes off the internet so it must be!   

[myk]

250?  Wow that's hot...

[c00nhunterjoe]

The 60 year old engines where not designed to run at those temps. Will it blow up at 200 or 210, no, but its hot for the engine, it will ping, it wont make optimal horsepower. The rad needs to be filled no higher than an inch below the top on a stock system.
   Now, on to questions-
1: does it run that hot at idle and cruising down the road or just one or the other?
2: if its only at idle, does it have a shroud, how far from the rad is the fan blades, what fan is on it.   specificly.
3: on top of whatever else is answered or discovered, i would reccomend a 160 stat

[crj1968]

My 383 (stock-ish) with new alum radiator seems to hang right at 190.

I always wondered what temp others here were seeing.   

[myk]

The 60 year old engines where not designed to run at those temps. Will it blow up at 200 or 210, no, but its hot for the engine, it will ping, it wont make optimal horsepower. The rad needs to be filled no higher than an inch below the top on a stock system.
   Now, on to questions-
1: does it run that hot at idle and cruising down the road or just one or the other?
2: if its only at idle, does it have a shroud, how far from the rad is the fan blades, what fan is on it.   specificly.
3: on top of whatever else is answered or discovered, i would reccomend a 160 stat

I'll answer.
1. Cruising down the road it's 140*.  After about an hour and a half of stop and go it slowly creeps up to 210*. 
2. Stock shroud, fan is about 1/3 into the shroud.  Fan is a 17" Summit thing with 6 blades and spun by a Hayden 2765 clutch.
3.  Really?  I just swapped out my 160* for a 180* because I became convinced that my cruising Temps and warm up time are too cold and take too long.  I'm so confused...

[brad mcintyre]

I don't think 66s had shrouds .I am going to put recovery tank of some sort on it. now I have a couple deferent rad caps ?I have electric fan that would go between rad and grill . but  I like the stock look . but only the people who know something will notice .go figure that is the only ones you want to talk to

[c00nhunterjoe]

The 60 year old engines where not designed to run at those temps. Will it blow up at 200 or 210, no, but its hot for the engine, it will ping, it wont make optimal horsepower. The rad needs to be filled no higher than an inch below the top on a stock system.
   Now, on to questions-
1: does it run that hot at idle and cruising down the road or just one or the other?
2: if its only at idle, does it have a shroud, how far from the rad is the fan blades, what fan is on it.   specificly.
3: on top of whatever else is answered or discovered, i would reccomend a 160 stat

I'll answer.
1. Cruising down the road it's 140*.  After about an hour and a half of stop and go it slowly creeps up to 210*. 
2. Stock shroud, fan is about 1/3 into the shroud.  Fan is a 17" Summit thing with 6 blades and spun by a Hayden 2765 clutch.
3.  Really?  I just swapped out my 160* for a 180* because I became convinced that my cruising Temps and warm up time are too cold and take too long.  I'm so confused...

I was aiming that at the op, but now your response has me pondering more questions.... cruising at 140 and idling at 210 tells me you have an airflow problem at idle and plenty of capacity at cruise. In comparison, my car will warm up in a few minutes of idling to 180, idle all day at 185 to 190 on a 100 degree summer day, and cruise at 180.

[brad mcintyre]

if I am driving at 30 to 40 mph it is around 160 170 stopping starting 200 .sat was very hot it stayed 200 at 60 mph .when stopping it would go up

[brad mcintyre]

I am also going to change stat its a couple years old. if its under 90 its not a problem 

[myk]

The 60 year old engines where not designed to run at those temps. Will it blow up at 200 or 210, no, but its hot for the engine, it will ping, it wont make optimal horsepower. The rad needs to be filled no higher than an inch below the top on a stock system.
   Now, on to questions-
1: does it run that hot at idle and cruising down the road or just one or the other?
2: if its only at idle, does it have a shroud, how far from the rad is the fan blades, what fan is on it.   specificly.
3: on top of whatever else is answered or discovered, i would reccomend a 160 stat

I'll answer.
1. Cruising down the road it's 140*.  After about an hour and a half of stop and go it slowly creeps up to 210*. 
2. Stock shroud, fan is about 1/3 into the shroud.  Fan is a 17" Summit thing with 6 blades and spun by a Hayden 2765 clutch.
3.  Really?  I just swapped out my 160* for a 180* because I became convinced that my cruising Temps and warm up time are too cold and take too long.  I'm so confused...

I was aiming that at the op, but now your response has me pondering more questions.... cruising at 140 and idling at 210 tells me you have an airflow problem at idle and plenty of capacity at cruise. In comparison, my car will warm up in a few minutes of idling to 180, idle all day at 185 to 190 on a 100 degree summer day, and cruise at 180.

Not to steal the OP's thunder but what do you recommend?