Cooling issues 69 Dart GTS 340

-
Mattax said:
'69 Dodge FSM says 190* thermostat and 16 psi cap. 14 -17 psi acceptable when testing.
Click to expand...

Pardon my ignorance, but why/how does a radiator cap's pressure rating affect the cooling system? How can you tell what lb rating your radiator cap is?

Also, I have the MP viscous fan package that puts the fan's clutch approximately 1/4" - 3 /8" away from my new (last spring) radiator (Spectra).
 
Last edited:
DartGTDan said:
Pardon my ignorance, but why/how does a radiator cap's pressure rating affect the cooling system?
Click to expand...
I'll give it shot. I haven't had to explain this or think about it in a while.
Increasing the pressure of the coolant raises the boiling point. That is improved the ability of the coolant to carry heat away from the cylinders.
With the system open to atmosphere, the coolant's boiling point is lower. Lets say its just plain water with a boiling point of 212 F.
When the coolant next to a cylinder hits 212° the vapor bubbles can push away liquid coolant. This especially happens if the little bubbles join into big ones.
That results in less coolant and super hot vapor (steam) in the system.

DartGTDan said:
How can you tell what lb rating your radiator cap is?
Click to expand...
Caps have their pressure painted or stamped into them.
upload_2020-4-16_20-15-28.png


upload_2020-4-16_20-18-53.png
 
Last edited:
DartGTDan said:
Also, I have the MP viscous fan package that puts the fan's clutch approximately 1/4" - 3 /8" away from my new (last spring) radiator (Spectra).
Click to expand...
That's a good package and a should work fine.
That's cutting the distance really close.

I had a similar setup on my car until a couple years ago. The radiator was a semi-custom '70+ style. I was able to get more clearance of the tank and the core by resoldering the mounts so the top tank was as far forward as possible. Got about 1/2" to the top tank.
upload_2020-4-16_20-30-1.png


upload_2020-4-16_20-33-44.png


A hood seal and a fan shroud helped a lot when idling in hot weather (ie stuck in traffic).
Unfortunately the shroud I had on there was damaged by the previous set up - a Chrysler flex fan that came apart.
All I could do when caught in a bad traffic situaiton is keep the rpms up a little and try to keep rolling slowly rather coming to a dead stop. Obviously turn the heater on if needed. But that was only in the worst situations.
The car has shroud again now, along with a new radiator. Expect this one will last at least as long as the one in the photo (18 years) since it will get better care. :)
 
Last edited:
Update on heating issues. Changed to a 16lb cap. This stopped the overflow problem. Pulleys have been changed 6 on crank and 5.2 on fan. Took it for a cruise Saturday. Ran 210 for long time then started to crawl up to 225. Not happy with that result. Has any one run a Flowkooler high flow water pump? Thinking about trying that next.
 
A 2 row radiator is not heavy duty cooling or for A/C/.
 
Maybe I missed it somewhere you mentioned 7 blade fan. Is this on a clutch or flex fan? If on a clutch make sure your using a heavy duty clutch as the resistance of the 7blades over a 5 blade fan normally used with the std duty clutch causes the clutch to slip to much at low speeds. The results will be heating up gradually at idle and low speeds. Also as mentioned make sure there is a shroud installed.
 
I hate to be 'that guy' but in my first post I saw plenty of ways to bring the temps down without buying a new radiator. With the mods you've made, I will now go on record to say you need a bigger radiator. :) I'll go so far as to guarantee you can bring temps down 20+ degrees.

I'm not saying some of the other ideas wont help but now you are starting to spend some dollars and time on repairs. The radiator can cure some other inefficiencies that you may or may not be able to find.
 
Last edited:
Ccas said:
I hate to be 'that guy' but in my first post I saw plenty of ways to bring the temps down without buying a new radiator. With the mods you've made, I will now go on record to say you need a bigger radiator. :) I'll go so far as to guarantee you can bring temps down 20+ degrees.

I'm not saying some of the other ideas may help but now you are starting to spend some dollars and tome on some expensive repairs. The radiator can cure some other efficiencies that you may or may not be able to find.
Click to expand...

That might be true, but if I'm not mistaken, heavy duty and A/C applications were three row. If what he has is a small tube two row Mopar radiator, it ain't enough and there's no sense in trying to band aid around it.
 
RustyRatRod said:
That might be true, but if I'm not mistaken, heavy duty and A/C applications were three row. If what he has is a small tube two row Mopar radiator, it ain't enough and there's no sense in trying to band aid around it.
Click to expand...
I think we're saying the same thing. :)
 
Keyeserin said:
My Dart does not have A/C. I will have to verify the clutch for the fan.
Click to expand...
Start with the basics.
Must have a fan shroud
Check that the lower radiator hose is no collapsing at cruz rpm
Use the correct cap
Remove the water pump and do a thorough inspection, make sure it is the correct pump for your application. The water pump needs to be overdriven from the crank.
Is the fan clutch functioning, they can be problematic.
Check out the thermostat is it correct and functioning.
Ignition timing can effect engine temps
Your radiator should cool your engine if it is stock
If you do end up replacing components do your homework and make sure you use quality parts from a reliable American manufacture that provides a good warranty.
Stay away from off shore suppliers that offer up some kind of marketing gimmicks that cant be supported by solid engineering at a cheap price.
Good luck
 
512Stroker said:
Start with the basics.
Must have a fan shroud
Check that the lower radiator hose is no collapsing at cruz rpm
Use the correct cap
Remove the water pump and do a thorough inspection, make sure it is the correct pump for your application. The water pump needs to be overdriven from the crank.
Is the fan clutch functioning, they can be problematic.
Check out the thermostat is it correct and functioning.
Ignition timing can effect engine temps
Your radiator should cool your engine if it is stock
If you do end up replacing components do your homework and make sure you use quality parts from a reliable American manufacture that provides a good warranty.
Stay away from off shore suppliers that offer up some kind of marketing gimmicks that cant be supported by solid engineering at a cheap price.
Good luck
Click to expand...
Thanks. I'm going to pull water pump and inspect next.
 
You must log in or register to reply here.
-

Back
Top