'70 Charger Overheats after 40 minutes on highway today [but before this it did not overheat at idle or shorter trips]

[Some Car Guy]

Get it warmed up and go over the radiator with a heat gun. If it’s plugged you will find hot and cold spots. If you find some get it boiled out. I’d replace the stat too if you find out this is the issue. I don’t like crud getting in them and it’s gravy to install since the system is open.

another easy but unlikely item here is the tightness of the fan belt.

 

[Sixpactogo]

I too agree with the thermostat being the culprit here. They will constantly open and close while the engine is running. Their only job is to try and keep the temperature at there rated temperature. It may have stuck closed keeping all the fluid in the engine or stuck open not giving the fluid time in the radiator to cool down. Before doing anything else, I would replace the thermostat.

 

[stushug]

I would change the thermostat first. Simplest, least expensive item to change in the cooling system. If that doesn't help you can always move forward, and you didn't spend a ton of time or money.

 

[matchek]

Whether your mechanic thinks so or not I would do as Jerry Hall suggested & put a thermostat in the car..

I agree and I am going to replace the thermostate for sure once it comes in.

By the way, as far as the flush, would you just empty out the radiator and then add 50/50 solution or would first flush it with an additive like "Blue Devil Radiator Flush" , empty and then refill with water/coolant?

 

[matchek]

By the way, I opened the radiator cap and took a closer look at the holes inside the radiator and some holes do look corroded and would reduce flow. I am thinking about replacing the radiator. Is there a brand you recommend (70 Charger 440 engine)? Also why do I see so many people talking about "re-coring"? Would you just want to get a new one and be done with it?

 

[1 Wild R/T]

By the way, I opened the radiator cap and took a closer look at the holes inside the radiator and some holes do look corroded and would reduce flow. I am thinking about replacing the radiator. Is there a brand you recommend (70 Charger 440 engine)? Also why do I see so many people talking about "re-coring"? Would you just want to get a new one and be done with it?

Is your car an R/T or a 70 Charger with a 440? If your a "Numbers guy" the radiator has a very visible part number stamped in the top tank....

If it's a 70 Charger with a 440 I'd throw a replacement radiator in it without a second thought...

BTW I'm not meaning to disparage a non-R/T with a 440, I have owned & currently own Mopars that are personalized... But collectors often chase numbers so if you have a real R/T it might be worth trying to keep a numbers matching radiator in the car...

 

[1 Wild R/T]

I wrote about this with one of my cars too:

Overheats on the freeway but not when cruising around town?

I haven't figured out exactly what is to blame. I've replaced the thermostat and radiator and added a shroud. I've yet to take it out on the road.
It didn't overheat while cruising around or even hot rodding it. It only did so on the freeway.

Yeah, but that's so last month...

 

[matchek]

I see. For the 70 Charger 500, it came with a 318 and the replacement engine is a 73 440 so the engine is not even matching. So I don't care about a numbers matching radiator. I could not find a number on it with a quick look. The radiator looks great from the outside but on the inside I had to take a screw driver to open some radiator tubes. I would bet others that I cannot see are probably corroded too.

 

[1 Wild R/T]

I see. For the 70 Charger 500, it came with a 318 and the replacement engine is a 73 440 so the engine is not even matching. So I don't care about a numbers matching radiator. I could not find a number on it with a quick look. The radiator looks great from the outside but on the inside I had to take a screw driver to open some radiator tubes. I would bet others that I cannot see are probably corroded too.

Yup, your looking at the tops of the tubes.... Gravity sez theres a lot more further down in the tubes....

No numbers means it's not an original radiator so nothing to worry about there... See how free having a modified car is? OE you got to sit and analyze the fix... Modified you just fix the damn thing...

 

[gtx6970]

Sudden spike in temps is most likely T Stat or more likely a gauge, especially the fact at supposed 250 degrees and hood open you got nuttin boiling over

Replace the stat with a high quality piece and install a mechanical gauge then go from there.

 

[matchek]

Sudden spike in temps is most likely T Stat or more likely a gauge, especially the fact at supposed 250 degrees and hood open you got nuttin boiling over

Replace the stat with a high quality piece and install a mechanical gauge then go from there.

Btw , a little water was dripping from the front license plate area after I pulled over. My hunch was it from the radiator overfill hose but I did not get close to observe.. There was a puddle maybe 1.5 feet x 1.5 feet and stopped.

 

[Some Car Guy]

Well you can pretty much get anything you want to replace it. Aluminum. Recore it. Whatever. Getting it boiled is probably the cheapest route, but I have seen them fall apart after that if they are too far gone already.

 

[WileE]

Either boil-out or recore the radiator, replace the thermostat. A common repair methodology we did back in the day, and it applies today as well.

 

[Geoff 2]

If you are going to replace the rad, get an alum one. They are more efficient.

 

[matchek]

Standing outside my car, facing it, the my top hose (where connects to thermostat) is on the top right of the radiator and the water exits on the bottom left side of my radiator. I can add water from the top center.

Is that where your radiator opening are? With my quick internet searches, a lot of pictures on websites where to to order them have the either backwards from what I have or both ports on one same side. Just wanted to check if I have anything different.

 

[HawkRod]

Standing outside my car, facing it, the my top hose (where connects to thermostat) is on the top right of the radiator and the water exits on the bottom left side of my radiator. I can add water from the top center.

Is that where your radiator opening are? With my quick internet searches, a lot of pictures on websites where to to order them have the either backwards from what I have or both ports on one same side. Just wanted to check if I have anything different.

Sounds like you have a 22" radiator, which makes sense if your car originally has a 318 (and no A/C). The heavy duty cooling radiators that are 26" wide have the top return hose on the left as you look in the engine compartment.

 

[Don Frelier]

Sounds like you have a 22" radiator, which makes sense if your car originally has a 318 (and no A/C). The heavy duty cooling radiators that are 26" wide have the top return hose on the left as you look in the engine compartment.

Your water pump housing must have the inlet on the passenger side as well which is an "odd ball" for a big block.

They did make 22" radiators for a big block with the opposite arrangement on the hose connections compare to what you've described.
But you would need to replace your water pump housing if you choose to get that style.
I'm curious how you find the correct hoses?
Can you post some pictures of how it looks today?

 

[matchek]

Sounds like you have a 22" radiator, which makes sense if your car originally has a 318 (and no A/C). The heavy duty cooling radiators that are 26" wide have the top return hose on the left as you look in the engine compartment.

I thought that too. But I when out and measured, the current radiator is 27" from flat edge to flat edge width. (I measure 3 times so don't know how it is that long). Also it is fits snug to the drivers side and there is only 1" gap of space on left on the passenger side so the radiator take most of the space. And it is a 3 row.

The manual says the standard for a 440 is a 26" and a 318 is 22" (but it also gives up to upgrade to a 26" for "maximum cooling") .

In addition, how many rows do you have ? It looks like one can get 2, 3 or even 4 row radiators.

 

[matchek]

Your water pump housing must have the inlet on the passenger side as well which is an "odd ball" for a big block.

They did make 22" radiators for a big block with the opposite arrangement on the hose connections compare to what you've described.
But you would need to replace your water pump housing if you choose to get that style.
I'm curious how you find the correct hoses?
Can you post some pictures of how it looks today?

My top hose from the thermostat is on drivers side and the water pump connection is on my passenger side as shown in the pictures below. The top braided hose goes to the thermostate where at the very bottom you can see a corrigated hose which connects from the water hose to the engine block.

FYI my engine block is stamped Oct 1972.

Is this port arrangement standard for 70 Charger 440?'

 

[HawkRod]

I thought that too. But I when out and measured, the current radiator is 27" from flat edge to flat edge width. (I measure 3 times so don't know how it is that long). Also it is fits snug to the drivers side and there is only 1" gap of space on left on the passenger side so the radiator take most of the space. And it is a 3 row.

The manual says the standard for a 440 is a 26" and a 318 is 22" (but it also gives up to upgrade to a 26" for "maximum cooling") .

In addition, how many rows do you have ? It looks like one can get 2, 3 or even 4 row radiators.

People add larger radiators all the time, and since yours is not original, maybe they did for your car as well? You should first check the core support opening width. A car originally equipped with a 22" radiator has a smaller opening than one with a 26" radiator. I just very quickly and roughly measured my 70 Road Runner (that was built with a 26" radiator). The opening was about 26" across.
My original radiator was re-cored by Glenn Ray radiators and they added an extra row of cooling.

In my humble opinion, bolting a 26" radiator in a car designed for a 22" radiator likely provides limited additional cooling, as some of the heat transfer fins are blocked by the core support.