Over heating issue

Moose440

Member
Joined
Oct 5, 2019
Messages
67
Reaction score
12
Location
Robesonia. Pa
Hey guys my 68 Newport 440 overheats at idle it just creeps up I have a 26 ac radiator in it the motor was just rebuilt it aluminum heads rollers all that. Since I got the car last summer it’s been doing this I put some electric fans on it that didn’t help granted they where garbage they really didn’t move air. I put a factory fan shroud on with flex fan still doing it. I’m at the point where I think either the radiator is clogged up or it’s the underdrive pulleys. Because my crank pulley is small. What do you guys think.

EFBBF203-4AA7-4C50-96CB-5CB299421F94.jpeg
 
that is a small pulley. do you have any charging issues? looks like a long spacer behind the fan. do you have a shroud? is the fan half in and half out of the shroud?
 
What do you have for water pump, water pump housing and thermostat?

Where is your base timing set? Do you have the vacuum advance connected, and to a timed or constant vacuum source?
 
Yes I have a shroud and it’s half in maybe a little more then half in. I have a 75 amp alt and it still dims at idle. That’s what I’m thinking it’s either the crank pulley or clogged radiator
 
What do you have for water pump, water pump housing and thermostat?

Where is your base timing set? Do you have the vacuum advance connected, and to a timed or constant vacuum source?
It has an Edelbrock aluminum water pump housing with a mopar performance water pump. Timing is 15 initial 38 all in. And yes my vac advanced is plugged in and timing comes in fast. I only have the problem at idle or below 35 mph. Highway it’s fine.
 
When was the last time your radiator and block were flushed, or your radiator boiled out?
 
When was the last time your radiator and block were flushed, or your radiator boiled out?
I think I found the problem the crank pulley I have on it from March is a perforMince pulley it’s 5-3/4 and they have a high flow water crank pulley that’s 6-1/2 I’m going to order it tm
 
When was the last time your radiator and block were flushed, or your radiator boiled out?
And my motor was just rebuilt two weeks ago there’s no sludge in it and the radiator was recorded in 96 and had 6000 miles put on it since. I have a feeling I’m going to need a radiator as well but I’m pretty sure the crank pulley is the issue
 
Get down to Harbor Freight (or similar) and get an IR "heat gun" to check the radiator core with. They can look good at the top and be clogged at the bottom. The heat gun will illustrate that quickly. "Creeping heat", at any speed, is usually a radiator issue, from my experiences.

As far as the "high flow" stuff, remember that the head gaskets have flow restriction holes in them to slow things down enough that the water picks up MORE heat from the engine. Chrysler a/c and non-a/c engines had DIFFERENT pulley ratios for the water pump pulley. The a/c pump had fewer vanes than the normal pump, but it was turning a bit faster with those fewer vanes. The under-drive pulley "trick" might be "trick" to have, but I also suspect it can be contributing to the low-speed issues you're having. Just my suspicion.

How much fan noise is coming from your flex fan? Consider that when the flex fan "flexes" and flattens with the higher rpms, it just MIGHT be blocking air flow through the radiator at those road speeds. Whereas a fan clutch with just let the fan turn as the air coming through the radiator will make it turn all by itself.

Just some thoughts,
CBODY67
 
Flex fan needs to be replaced with a clutch and stock 7 blade fan...

May not solve all your problems but at least help out.
 
I fought for a year overheating on a new rebuild 440. The only thing that has given me a chance is a hayden clutch and derale 18" no-flex fan and going back to OEM shroud. Also milodon 160* hi flow thermostat. cold case electric fans were not enough and the electric demand to run any electric fans is insane.

that pulley ratio may be goofin with you too. its critical. look in the FSM there are different pumps and pulleys for A/C and non A/C on 440, and you are probably underdriving that non A/C WP pulley as you are currently with that smaller crank pulley.

try not to die -

- saylor
 
It has an Edelbrock aluminum water pump housing with a mopar performance water pump. Timing is 15 initial 38 all in. And yes my vac advanced is plugged in and timing comes in fast. I only have the problem at idle or below 35 mph. Highway it’s fine.
In my experience, overheating at idle and in-town, but ok on the highway, is low coolant flow at low RPM. Sounds to me like you've addressed the obvious with the flex-fan and shroud. I tried that and they didn't help either. Your underdrive pulley could be the culprit in your case.

Some aluminum water pump housings have very restrictive passages which have caused some people grief. I presume Edelbrock would be a quality piece but I don't know from experience. Similarly with the MP water pump. I personally like the Milodon high volume pump. That and a high-flow 180* thermostat ultimately fixed my identical problem.

One thing you didn't mention was the thermostat. I recommend 180* high flow, and I always test thermostats in a cup of boiling water and a thermometer to ensure they are opening and closing properly when they should. (I don't recommend the cheaper Mr.Gasket high flow thermostat. I had one which failed in the open position, and others on the internet have complained about the same thing.)
 
I just ordered the new pulley I have a 5 inch crank pulley it even said on March website the performance pulley can cause overheating in slow speed conditions lol. So I got there 6.5 inch pulley it’s says it’s a high flow water pulley hopefully this is the fix. If not I’m getting a champion radiator with 2 12 inch spal fans.
 
And my motor was just rebuilt two weeks ago there’s no sludge in it and the radiator was recorded in 96 and had 6000 miles put on it since. I have a feeling I’m going to need a radiator as well but I’m pretty sure the crank pulley is the issue
14 years and 6000 miles ago is a long time since it was flushed and no sludge doesn't mean a thing, but you're the expert! Flush it good before buying. Good Luck
 
Last edited:
I just ordered the new pulley I have a 5 inch crank pulley it even said on March website the performance pulley can cause overheating in slow speed conditions lol. So I got there 6.5 inch pulley it’s says it’s a high flow water pulley hopefully this is the fix. If not I’m getting a champion radiator with 2 12 inch spal fans.
that might help your charging too.
 
14 years and 6000 miles ago is a long time since it was flushed and no sludge doesn't mean a thing, but you're the expert! Flush it good before buying. Good Luck
I did flush it and used radiator flush as well nothing really came out. And if the radiator was clogged wouldn’t it overheating all over the board?
 
I did flush it and used radiator flush as well nothing really came out. And if the radiator was clogged wouldn’t it overheating all over the board?

If the bottom half of your radiator is clogged with crud, the flush with chemicals won't remove it. I would pull the radiator, take it to a good radiator shop, have them boil it out clean, and pressure-test it. Also, I would get rid of all the non-stock pulleys, water pump, w/p housing, thermostat, etc.
 
Back
Top