Need help from you smart folks..car still overheating, got any clues?

[71 RT]

I have posted a few times that my stock 440 magnum is running hot.  I need one of you really smart folks to help me come up with what it may be that I am missing.  Here is the scoop, I can drive 40 MPH all day and nothing heats up.  If I start driving 55-60 the temp slowly starts climbing.  I have replaced the water pump, temperature sending unit, radiator cap, all hoses to and from the radiator, and heater core.  I thought the lower hose might be collapsing, so I bought a new one with a spring in it to prevent this from happening.   I had my radiator "gone through" about 600 miles ago.  I have a 22 inch radiator (stock that came with my non-AC car).  I fear that the radiator was not worked properly, or that the fan might not be operating correctly.  I have a fan shroud, and a temperature controlled fan clutch.  The car really is heating up that badly, for a while I questioned if it really was getting as hot as the gauge said, and I did confirm the gauge is correct. 
Before I try to find another stock radiator or buy a re-punched one for way too much, I would like to see if anyone as any ideas.  Car runs and drives great, just tends to run hot.  If you continue to drive 60 MPH, it will eventually peg the needle, and boil over when you shut off the car.  Very frustrating, any help would be appreciated.  Thanks for your time. Should I try another fan blade?  Could the automatic transmission be causing the heating up?  HELP!
71 RT

[FLG]

Have you tried changing the thermostat?

[67_Dodge_Charger]

Are you using the heater core?  How about the overflow?  Timing maybe,......  Check the oil for antifreeze.  Could be a head gasket but I would think timing is the problem.  22 inch radiator might be a little small for a 440.

Robert

[Tilar]

I'd try another fan clutch. Some fan clutches have a spring on the front that you can turn and lock then so they run all the time and not slip. If that is the type you have, you could lock it for testing.

[RECHRGD]

I'd be looking at the radiator size or flow restriction.  At 60mph the fan and shroud should be a non-issue.    Bob

[maxwellwedge]

Have you tried changing the thermostat?

I hope you are running a thermostat...If so, what temp?

[green69rt]

I'd be looking at the radiator size or flow restriction.  At 60mph the fan and shroud should be a non-issue.    Bob

I agree with this guy.  If you had you radiator worked recently then I would make a small bet that they didn't do it right and the flow is down.  Only way to check that is with a flow test and a lot of shops don't have the equipment, especially small general service garages.

[FLG]

maxwell,

I dont have a T-stat on my 400 because the one i had quit and i just havent felt like buying another one. No issues though.

[Rolling_Thunder]

maxwell,

I dont have a T-stat on my 400 because the one i had quit and i just havent felt like buying another one. No issues though.

I was always told not to run with no thermostat - moves the water through the cooling system too fast apparently...   I run restrictors myself (cut out the plunger of a thermostat) and it slows flow...     again just what i was told but makes sense with a high volume water pump pumping at higher RPMs 

[FLG]

Yep. I mainly drive it on the street so i guess its not much of an issue..but even on the highway no problems. Makes sense though with a HV pump at high RPM's I plan on putting it back.

[flyinlow]

In the words of Forest Gump" I know I am not a smart man  " .


You said its a stock engine and runs well.  Timing set properly ,idles smooth, not smoking out of tail pipes. Makes normal power.?

If transmission was not working right I would think the trans. fluid would be burnt and smell bad.

I am assumming you are not in Death valley , diving with the brakes on , pulling an other  Charger on a trailer behind you, or running a 5.13 gear on the street.

Car runs at 40 mph all day:  Trans in third gear, engine speed and power output is low. Radiator keeps the engine cool. If the thermostat was stuck it would overheat in this condition. At this speed you could drive with out a fan/shroud , there would be enough airflow thru the radiator. Probably not the fan or clutch.

Car gradually overheats at 60 mph:  Engine speed and power output has increased to the medium range. Airflow thru radiator should be increased also.
At this point I suspect poor radiator circulation or blocked airflow.

You said no A/C. Can you see thru the cooling fins? some radiator shops slop on the asphaltic paint . Maybe blocked to much airflow?

You said you replaced the waterpump and lower hose . With the cap off and engine warm can you see water circulate thru the radiator?
Can you feel  airflow thru the radiator?

When was the last time the car work normally?

Craig

[Corellian Corvette]

I agree with above. The differences between 40mph and 60mph are SO similar from a car perspective then really I'm not sure that the problem is with your cooling system. If your car can TRUELY run at the proper operating temp at 40mph all day long, then the problem is something else.

What about idle? Idle is actually the hardest on your cooling system because you have NO airflow; MOST people have overheating problems at idle.

I would start looking elsewhere.

First, make sure that your system has been "burped" - raise the front of the car on ramps, and run the engine w/o the rad cap and make sure you have all the air out of the system.  Second, is your upper hose getting hard? If not, rent a radiator pressure tester and make sure you don't have leaks in the system.

My guess is that you have some external issue - brake drag going on, you are running too lean or too rich, or your car is not actually shifting into 3rd gear.

You can check your plugs and see what the internal condition is. How do your plugs look?
Second - have you tried manually shifting your trans to make sure you're getting 3rd gear (I'm assuming you have an auto). True story - Imy Buick was exhibiting EXACTLY the same problem as you are describing, and I found out that same problem - the car wasn't shifting. Around town everything was fine, but get on the freeway and I was having all kinds of problems.

[71 RT]

Thanks everyone.  It appears that I have to have that radiator looked at one more time.   Yes, I am running a 160 degree thermostat.  I do not have oil in the antifreeze, and I am running 3.23 gears (just to answer a few questions you all had).  I really do appreciate your input.
If a guy wanted to try and find another Mopar radiator that was the correct 22 inch radiator from Mother Mopar (Number 3443 938) any clues except eBay as to where a guy could find one?  I would obviously have to have it rebuilt, but mine might not be able to be repaired.  Is there a good place for old stock radiators?  Thanks again, that is why I love this site.  Lots of friendly folks, with lots of brain power
71 RT

[green69rt]

If you say yours may be beyond repair then that leads me to think you are centering in on the problem.  Old radiators that you can find may have as many problems as you already have.  How would you know??  Last time I bought a rebuilt radiator it ended up coming from a plant in Mexico and was cr*p.  I think you need to think about a new one or else find a shop that you have confidence in and ask their advice.  Good luck, and don't give trying.

[Tom Q]

First off after we solve you problem  you will get rid of the 160 thermostat and put a high flow 195 in there - today's gasoline requires the 195 thermostat. Please don't make me write about the operating temp any further as your problem is what I would like to solve.  Use 60% distilled water / 40% antifreeze and a bottle of water wetter. You need a good water pump like flow cooler or edelbrock.   

I am assuming the timing is good and the fuel mixture is not lean.

Remove the drain plugs from the block and back/forward flush the block.  DO NOT pass go or collect the 200 dollars until you do this.  I am not kidding.

Fill the car with water only after the flush, bring car up to operating temp.   Shut the car off and check the radiator for cold spots or hot spots. An infrared temp gun is really what you need but your hand should suffice. The condition of the core is suspect and the info on the radiator is sketchy but I suspect the block is full of crud and subsequently center of the core is restricted.

[Moparman01]

71 R/T, this is EXACTLY the same situiation i'm havin with my 440 powered Charger! I've been dealin with it for the last 2 years now and still have not figured out the problem. The temp will stay ok if i run the car around town for a little while at speeds under 40, but once i get out on the highway the temp slowly rises to the point when i pull into a car show or something i'll be seein temps between 220-230*. I too run a 160* t-stat, but i've also tried a 180* stat with no luck. Hoses are all fine, i have a larger than stock fixed fan and a shroud. I run a Mopar 26" radiator that i had rebuilt (re-corded), and yes i've tried all the "water wetters". I have a Mopar Performance hi-flow aluminum water pump on the motor, which is what i asked about in a thread i posted about A/C vs Non-A/C water pumps (thread "Water pumps, what's the difference?"), i was told by a local Mopar buddy of mine to get rid of the "hi-flo" and get a water pump for an A/C car (mine is not A/C). I will probably try that first, before i go out and spend several hundred bucks on a new radiator, especially since i spent $300 having my old one rebuilt. And yes, mine runs just fine and has been professionaly tuned, timing and carb seem to be right on. Like i said this has frustrated the hell outta me for 2 years now  , if you get any thing figured out please lemmie know!!! Good luck!

[flyinlow]

Cooling system facts of life:    4 decades ago when our mopars were new ,our (scratch that, your) numbers matching Radiators were at their prime.
                                         They have been going downhill since.
   
                                       The cooling jackets in the block and head probably have some scale built up.


An engine gets rid of heat in several ways.  Out the tailpipe. We usually improve this part with less restrictive exhuast. In to the oiling system. Some of use put coolers or bigger pans on. Radiant heat. Keep your engine clean and paint it black. The colors not that big of a deal. And finally the coolant system.

Ma Mopar, sometimes refered to as Chrysler, Plymouth and cheap , was not overly generous with radiator capacity. What was OK then does not cut it today.


If your 440 Charger gets 12mpg.... At 40mph you are burning 400,000 btu's per hour. At 60 mph you are burning 600,000 btu's per hour. Somewhere above 40mph you are passing you coolant systems ability to keep up.

Sorry Buddy, you need a new radiator or recored.

If it was me I would flush you cooling system with the radiator you have. Take block drain plugs out get all the scale out you can . Then rinse. Then rinse. Did I mention rinse. Then get the biggest aluminum dual core radiator that will fit. I have a 31 by 20 in mine. Fit a shroud and clutch fan and you should be ready for Death Valley.

If you want stock you can recore if the tanks are good with 3 or 4 core. It is getting hard to find a radiator shop that can handle this.

The stock AC car waterpump seams to work well . That's what I use.

[oldkimmer]

...............U need 2 have a 195 t stat, anything less and it will overheat.....there is nothing wrong with running 195 all day long, but there is everytime u overheat it.......especially on marginal cooling systems...............which is 90%  of all muscle mopars............kim...........

[Bossman963]

had the same problem w/ my 70 383 and this may sound stupid - but I was having the exact same problem with it and above 45mph it would get hot and never cool down - so make sure all the timing is correct and make sure the fan is installed the correct way- as i found out as i had mine backwards so it was oushing air back @ the radiator instead of pulling it through.
Put a paper towel in front of the radiator and make sure it stiks to it, if it doesnt fans on backwards- switch it and all the over heating problems went away.
Mike

[flyinlow]

had the same problem w/ my 70 383 and this may sound stupid - but I was having the exact same problem with it and above 45mph it would get hot and never cool down - so make sure all the timing is correct and make sure the fan is installed the correct way- as i found out as i had mine backwards so it was oushing air back @ the radiator instead of pulling it through.
Put a paper towel in front of the radiator and make sure it stiks to it, if it doesnt fans on backwards- switch it and all the over heating problems went away.
Mike

Had a guy with a Nomad with an electric pusher  fan and had installed it as a puller.  Blew air forward and was wired to run any time the ignition was on. Cooled fine in traffic , got hot on the road. At 60 mph the fan was nuetralizing the wind and no airflow thru the radiator.