Over Heating issue

[Grant MacPherson]

I had a 402 Monte from 71 through 81, and it ran hot from New. Never boiled over but 220 was normal in stopped traffic,  used to put it in neutral and bring the revs up a little. My 70 SS I have now is the same but I have a Gen 5 454 in my 87 GMC and it runs at 180 and has an180 Stat. Not sure if there was any casting differences,  running same heads on both.

[LS65Speed]

On 4/14/2023 at 6:43 PM, Jsd454 said:

Hello Everyone,

A little background, I recently got my 1972 MC matching numbers 454BB rebuilt and back in the car. I had a new aluminum radiator installed. It has a 16 pound cap. Was going to get a lower pound cap. I also at this point do not have a clutch fan. The car is running around 200 and hotter when sitting.

I have the original style clamps but the bottom radiator hose blew off so I am also assuming the clamps are not the quality as the originals. I want to order a clutch fan along with a seven blade fan. Do I need a fan spacer since at this point the fan sticks out slightly from the shroud? It is an A/C car but have not added freon to run it at this point. I want to get the car to run cooler. Living in Florida with the heat doesn't help.

Any suggestions would be greatly appreciated!!

Here is a link of my car as of now:

 

 I have some data, general as it may be, that outlines something that worked for me. As a kid I bought a crate  L-79 and loaded it into what was once a 6 cyl 64 Impala. It got hot quick just running a few minutes in the driveway or running around the block while we checked the install over for things we might have overlooked. I knew the 6 cyl radiator was not gonna cut it but the objective was to have everything ready before I picked up a new radiator the following Monday. Went the radiator shop and asked my friend John for the largest radiator he could get me. He came up with a radiator for a 64 409 ci A/C equipped Impala station wagon. It was a copper core radiator that might even have been specified for A/C 409 and towing package. I will never know about that part of the story.

Point is it ran at 180 no matter what the ambient temp was and no matter how long it was stuck in traffic. I even ran the 4 blade fan blade from the 6 cyl engine with the setup I outlined. It worked just fine cause the rad was way oversize for the engine. I am not saying this strategy contains your answer because I think you only said a "2 row aluminum radiator" is in your car.

All the suggestions are valid in responses above but in my experience the solution is usually related to the heat transfer capability of the cooling system. If you engine is hot your cooling SYSTEM cannot off load sufficient quantities of heat per unit of time, at least that theory is my bottom line. You have A/C and that in and of itself effects the systems ability to off load heat load because of the condenser. Clutches and holes in t-stats and larger fans are IMHO ways to make marginal gains but only if (and I am not saying this just to be a pecker head) the radiator is up to the job. 

Along with some of the suggestions above I wanna add one more thing. Where is your timing? If it is retarded that alone will add to you woes. Back in the day we retarded the timing to pass required emissions inspections. Ya hadda get in, get tested and get out pronto before things overheated. You raced down the street outta sight of the test station bumped the timing back and went on your way.

Hope this helps........just my $.02

Edited July 23, 2023 by LS65Speed

[TheBMan]

I recently talked to the folks at Milodon and installed a Milodon 16210 high-volume water pump and Robert Shaw high flow 180° thermostat. I just got it back together and running today. It's about 88 humid degrees here today and the temp slowly climbed when sitting still. It got up to 215° before I drove it to cool it down to 190°.

I believe this car should have more than enough cooling system capacity so I'm completely baffled why it's getting hot. The temperature should sit on 180 to 190 (variations in where the thermostat is located vs where the sensor is located) and not go any higher. That's exactly what the purpose of the thermostat is - vary its opening/flow-rate based on temperature in order to maintain a constant temperature.

Man, I hate to bite the bullet for the 4-row radiator. That thing is $1100 and what if it still gets hot? ARGH!

@LS65Speed Thanks for your input. I don't have A/C and my timing is set at 12° BTDC (initial). My radiator is a full size copper/brass 3-row, brand new.

Frustrated.

[MC1of80]

Try a 160 degree thermostat. 

You should be running 180-190 max. 

[TheBMan]

51 minutes ago, MC1of80 said:

Try a 160 degree thermostat. 

You should be running 180-190 max. 

I tried a 160° thermostat before the high flow water pump. It behaved the same.  

[LS65Speed]

7 minutes ago, TheBMan said:

I tried a 160° thermostat before the high flow water pump. It behaved the same.  

Thermostat rating 180 / 160 etc.etc etc. only determines the point at which the stat opens not necessarily the point at which the engine will run. You shouldn't assume that the t-stat rating is the temp at which the engine will run. That is not always the case. If the radiator is too small or all blocked up a 160 stat will open at 160 but the engine operating temp will go up until the cooling system reaches a stasis point at what ever temp the system is capable of maintaining. If the system can maintain 160 it will stay at 160 if it can maintain 180 it will stay at 180, if it can maintain 225 it is gonna go to 225. End of story

Edited July 26, 2023 by LS65Speed

[jft69z]

I have a Griffin aluminum radiator that they made up for me. FWIW, they were very specific to avoid high-flow water pumps, saying it doesn't allow enough time for heat exchange. It's a large, 2 row unit.

[MC1of80]

I have the original, not new, but the 1970 4 core brass radiator in Big Red with a high flow milodon water pump and a 160 t-stat and SOMETIMES reach 190 sitting in traffic and soon as I start moving, 175-180.  496 big block. Joe T and others saw it drive to and from Carlisle and out for dinner in town with no complaints and I wasn't putt putting around. Lol

[TheBMan]

5 minutes ago, jft69z said:

I have a Griffin aluminum radiator that they made up for me. FWIW, they were very specific to avoid high-flow water pumps, saying it doesn't allow enough time for heat exchange. It's a large, 2 row unit.

I've heard this philosophy before (heat exchange). What Milodon told me is that being in the radiator longer means it's also in the block longer (getting hotter).

I don't want to go to an aluminum radiator because I want to keep it stock fitting and appearing.

[TheBMan]

3 minutes ago, MC1of80 said:

I have the original, not new, but the 1970 4 core brass radiator in Big Red with a high flow milodon water pump and a 160 t-stat and SOMETIMES reach 190 sitting in traffic and soon as I start moving, 175-180.  496 big block. Joe T and others saw it drive to and from Carlisle and out for dinner in town with no complaints and I wasn't putt putting around. Lol

I'm afraid I'm going to have to bite the bullet for the 4-row radiator. I'm not sure I should have to do that since this is a stock small block without A/C but I may have no choice. You guys may have to peel me off the wall if it still gets hot after doing that. 😝

[jft69z]

14 minutes ago, TheBMan said:

I've heard this philosophy before (heat exchange). What Milodon told me is that being in the radiator longer means it's also in the block longer (getting hotter).

I don't want to go to an aluminum radiator because I want to keep it stock fitting and appearing.

Depending on the system though, it could be an endless cycle. Too much flow, less heat exchange thru the radiator, equals higher temp. Possibly vice-versa with less flow, longer time in the block, etc. (the factory never saw the need for a high flow water pump though, but...the cooling capacity was engineered as a system). The radiator ultimately has to have the capacity to cool the system, the thermostat will help regulate it from there. 

I had them make my rad with stock sized upper & lower hose fittings, and I also spray a light coat of trim black paint on the front core & side tanks to blend in better and not be noticeable. It fits perfectly in the factory location, with the factory rubber upper/lower mounts as well.

[LS65Speed]

2 minutes ago, TheBMan said:

I'm afraid I'm going to have to bite the bullet for the 4-row radiator. I'm not sure I should have to do that since this is a stock small block without A/C but I may have no choice. You guys may have to peel me off the wall if it still gets hot after doing that. 😝

Has the block ever been flushed?

[MC1of80]

7 minutes ago, TheBMan said:

I'm afraid I'm going to have to bite the bullet for the 4-row radiator. I'm not sure I should have to do that since this is a stock small block without A/C but I may have no choice. You guys may have to peel me off the wall if it still gets hot after doing that. 😝

Not posting this to make you sick but, (Always a but) lol, my brothers 71 "COVID" monte has a 355, stock water pump, an auto parts store 2 core aluminum with plastic tank (for an 80s Caprice) radiator, 160 thermostat and NEVER gets hotter than 160! In the winter my brother has to let it warm up for over 45 min and it still only gets to 140. Wanna talk about cooling and a freak? Never had a car run that cool. And have tried different mechanical gauges and my temp sensing gun. All verify the 160. 

[TheBMan]

12 minutes ago, LS65Speed said:

Has the block ever been flushed?

Yes, as part of the restoration. It has very few miles on it.

[TheBMan]

1 hour ago, MC1of80 said:

Not posting this to make you sick but, (Always a but) lol, my brothers 71 "COVID" monte has a 355, stock water pump, an auto parts store 2 core aluminum with plastic tank (for an 80s Caprice) radiator, 160 thermostat and NEVER gets hotter than 160! In the winter my brother has to let it warm up for over 45 min and it still only gets to 140. Wanna talk about cooling and a freak? Never had a car run that cool. And have tried different mechanical gauges and my temp sensing gun. All verify the 160. 

Thanks Thomas. I hate you. 😆🤣

[TheBMan]

I ordered the 4-row radiator today. I'll update here after I install. I appreciate everyone's feedback!

[LS65Speed]

10 minutes ago, TheBMan said:

I ordered the 4-row radiator today. I'll update here after I install. I appreciate everyone's feedback!

What did ya order?

Edited July 27, 2023 by LS65Speed

[TheBMan]

12 minutes ago, LS65Speed said:

What did ya order?

US Radiator reproduction 4-row high-efficiency brass/copper. It has 1/2" tubes 3/8" on center compared to the typical (and what I have now) 1/2" tubes 9/16" on center. It's something like 40% more cooling capacity than what I have now. If it doesn't solve my problem, I may commit hara-kiri. 😵‍💫

[riverdogs00]

On 7/27/2023 at 1:46 PM, TheBMan said:

US Radiator reproduction 4-row high-efficiency brass/copper. It has 1/2" tubes 3/8" on center compared to the typical (and what I have now) 1/2" tubes 9/16" on center. It's something like 40% more cooling capacity than what I have now. If it doesn't solve my problem, I may commit hara-kiri. 😵‍💫

Bryan, where did you order from?  I'm in that phase now as well. Got the LS=7 fired up, and am buttoning all the little details up. Installed the wrong 3 row that came with the car, but used a BB shroud to get it on the road before I bit the bullet on a nicer 4 row M/T rad, but of course it leaked while filling today......

[EVC]

To add my thoughts:

I run two water temps gauges.. One directly in the thermostat housing and the other in the stock position on the passenger side of my 350… There is usually a variance of 20 to 25 degrees between the two … Naturally the one in the housing is hotter… 

Typical readings are as follows:        

Using ambient air temp 90 to 95 degrees,,, as baseline. My Radiator is a 3row copper/brass stock type, stock fan and fan clutch. 

At idle,,,,In heavy traffic,,, w/AC on ,  the temps can read as much as 210/220 at the stock position and 230/240 at the upper housing when in heavy traffic. 

When rolling, the water temps will appropriately drop back to a comfortable 180 to 190 with AC ….Every car I've owned during the past 60 plus years of driving has run similar temps and like many other members here I am always concerned. The bottom line is, if it doesn't boil, then move on and try to treat the engine gently. 

I'm sure everyone here has their favorite setup, but I'm a big fan the 3 row radiator opposed to the 4 row or aluminum. (another discussion )

When the ambient temps go above 100 degrees I expect the numbers to increase and scare the crap out of me, but I've never lost and engine because of heat. Try driving a 63 Pontiac Bonneville 389 or and old Cadillac 472 in the Arizona desert. The temps will go off the charts.  They seem to run better without mechanical gauges..  

On cool days with average of 75 degrees she will run at about 160 on the open road (actually too low for me), but it really doesn't matter much whether you use a 160 , 180 or even a 195 degree thermostat, as long as it opens on time. Running a car too cool  in the winter can be worse than running it at 220 on a hot day. Good oil with Zinc, proper coolant, hoses/belts and timing is everything… My fuel economy is best when the engine is 195 to 210.  

I use a vacumn gauge to drive and it really helps me from putting the foot down.. I picked this up back in the early 60s when Pontiac installed them in some their cars… 

EVC 

 

 

 

[TheBMan]

10 hours ago, riverdogs00 said:

Bryan, where did you order from?  I'm in that phase now as well. Got the LS=7 fired up, and am buttoning all the little details up. Installed the wrong 3 row that came with the car, but used a BB shroud to get it on the road before I bit the bullet on a nicer 4 row M/T rad, but of course it leaked while filling today......

US Radiator

[TheBMan]

8 hours ago, EVC said:

To add my thoughts:

I run two water temps gauges.. One directly in the thermostat housing and the other in the stock position on the passenger side of my 350… There is usually a variance of 20 to 25 degrees between the two … Naturally the one in the housing is hotter… 

Typical readings are as follows:        

Using ambient air temp 90 to 95 degrees,,, as baseline. My Radiator is a 3row copper/brass stock type, stock fan and fan clutch. 

At idle,,,,In heavy traffic,,, w/AC on ,  the temps can read as much as 210/220 at the stock position and 230/240 at the upper housing when in heavy traffic. 

When rolling, the water temps will appropriately drop back to a comfortable 180 to 190 with AC ….Every car I've owned during the past 60 plus years of driving has run similar temps and like many other members here I am always concerned. The bottom line is, if it doesn't boil, then move on and try to treat the engine gently. 

I'm sure everyone here has their favorite setup, but I'm a big fan the 3 row radiator opposed to the 4 row or aluminum. (another discussion )

When the ambient temps go above 100 degrees I expect the numbers to increase and scare the crap out of me, but I've never lost and engine because of heat. Try driving a 63 Pontiac Bonneville 389 or and old Cadillac 472 in the Arizona desert. The temps will go off the charts.  They seem to run better without mechanical gauges..  

On cool days with average of 75 degrees she will run at about 160 on the open road (actually too low for me), but it really doesn't matter much whether you use a 160 , 180 or even a 195 degree thermostat, as long as it opens on time. Running a car too cool  in the winter can be worse than running it at 220 on a hot day. Good oil with Zinc, proper coolant, hoses/belts and timing is everything… My fuel economy is best when the engine is 195 to 210.  

I use a vacumn gauge to drive and it really helps me from putting the foot down.. I picked this up back in the early 60s when typo Pontiac installed them in some their cars… 

EVC 

 

 

 

Thanks for the input. Interesting that you find the temp is higher at the thermostat housing than at the sensor position in the cylinder head. For me it's the opposite and I would expect that since the sensor is installed very close to the combustion chamber.

I'm hopeful that increasing the capacity of the cooling system solves the problem. I realize this is an older car using older "technology" but at the end of the day if any cooling system has adequate capacity, the thermostat should regulate engine temp and hold it at a steady number. That's the entire purpose of the thermostat, after all.

Others have said that they don't have run-hot issues even in hot climates so I'm hoping that I'm not expecting too much from an old car. 🤷‍♂️

[EVC]

48 minutes ago, TheBMan said:

 Interesting that you find the temp is higher at the thermostat housing than at the sensor position in the cylinder head. For me it's the opposite and I would expect that since the sensor is installed very close to the combustion chamber.

The thermostat housing should logically be the accumulation point for the hottest water in the engine. If you're water is hotter in the cylinder head on the passenger side then you possibly have other issues.  Every car I've owned had hotter water temps inside of the thermostat housing when driving.   Which water pump are you using ?    I doubt it, but the horror of reverse flow is always there. 

 My 63 Bonneville, 60 Pontiac Ventura with 389s, and two Cadillacs, 472/500 and both Monte Carlos, 350s,  all had hotter water temps in the thermostat housing.    I'm no engineer, but it makes sense to me that's why the thermostat was placed there to begin with.  

The same thing applies to transmission temps. The oil in the pan should always be cooler than the converter.  To get the average tranny temp always gauge from the pan. To get the scare the crap out you numbers gauge the temps as the fluid returns to the tranny cooler….    Same thing with your water,,, To get the scare the crap out of you numbers gauge the temps at the return point. Otherwise measure from the input average point and enjoy your car. 

All of my numbers are with actual water gauges installed in the engine, not with the little red dot. Using external measurements can be deceiving because of exhaust manifolds and other influences…  

Ed C

 

 

[TheBMan]

36 minutes ago, EVC said:

The thermostat housing should logically be the accumulation point for the hottest water in the engine. If you're water is hotter in the cylinder head on the passenger side then you possibly have other issues.  Every car I've owned had hotter water temps inside of the thermostat housing when driving.   Which water pump are you using ?    I doubt it, but the horror of reverse flow is always there. 

 My 63 Bonneville, 60 Pontiac Ventura with 389s, and two Cadillacs, 472/500 and both Monte Carlos, 350s,  all had hotter water temps in the thermostat housing.    I'm no engineer, but it makes sense to me that's why the thermostat was placed there to begin with.  

The same thing applies to transmission temps. The oil in the pan should always be cooler than the converter.  To get the average tranny temp always gauge from the pan. To get the scare the crap out you numbers gauge the temps as the fluid returns to the tranny cooler….    Same thing with your water,,, To get the scare the crap out of you numbers gauge the temps at the return point. Otherwise measure from the input average point and enjoy your car. 

All of my numbers are with actual water gauges installed in the engine, not with the little red dot. Using external measurements can be deceiving because of exhaust manifolds and other influences…  

Ed C

 

 

I'm currently using a Milodon high flow stock direction water pump and Robert Shaw 180° high flow thermostat. This combination has the same behavior as the stock setup.

[EVC]

45 minutes ago, TheBMan said:

I'm currently using a Milodon high flow stock direction water pump and Robert Shaw 180° high flow thermostat. This combination has the same behavior as the stock setup.

Good luck Bryan,, sounds like you have the right parts…  

Thanks for the tip on the thermostat…  Water Temps of 220 from the passenger side head are not uncommon in traffic, especially with the AC on and the air temps above 80… We live in the hill country and it amazes me to watch people speed up on the hills and race to the top… I'll never get it… !!!  

I can only imagine the exhaust temps and stress that puts on the engine and transmissions…    But what do I know ?

I've been behind the wheel of my Monte, Pontiacs and Cadillacs for well over 50 years and logged perhaps over a million miles of seat time. Driving cross country with the family, often with a trailer, makes one weary and alert in those long desert drives.

300 miles to the next gas station on the original route 66 was common….  Breaking down wasn't an option. 

Ed C..