Overheats on the freeway but not when cruising around town?

[Kern Dog]

I myself would make sure to remove as much air from the cooling system as possible before driving it again.

I have seen this in print before but still don't understand.
When I refill a cooling system, I squeeze the upper hose as the radiator gets close to full to burp out as much air as I can.
I'll often run the engine with the cap off to watch the flow and then top it off as needed. I will get it up to operating temperature and check the coolant level occasionally. If there is some other way to rid the system of air, I'm willing to learn.

The radiator arrived last week.

Pretty nice looking unit for a beat up car!

Transmission cooler at no extra charge….

Nice thick mounting flanges:

I went through my stash and picked a shroud. I have 2 from the 85-89 Chrysler Fifth Avenue cars. They had 26" radiators but also used bigger fans. The opening in the shrouds that I have are approximately 22", compared to around 20" in the stock shroud I have in the red car. I'll be using a bigger fan and shroud with this radiator. I've used a 19" 5 blade fan but I'm switching to a 20" 7 blade fan from that Fifth Avenue.

Since the shroud isn’t stock, I had to clearance it a bit where the hoses will go.

 

[Don Frelier]

I've never had a problem with air stuck in the block.
I doubt that's part of your problem.

 

[copper67sat]

I didn't read all of the posts so apologies if this has been mentioned...I have had a thermostat stick closed and I have also had ones that either opened slowly or not enough, all of which caused overheating at speed. The ones that opened slowly or not enough were not obviously bad until I put them in a pot of hot water with a new one and then I could clearly see the difference.

 

[Kern Dog]

The thermostats that opened slowly or not enough were not obviously bad until I put them in a pot of hot water with a new one and then I could clearly see the difference.

This is an excellent point.
Mine did open fully but I don’t know at what rate it opened. I watched it move, it took maybe 10 seconds to go from fully closed to fully open. Just a guess but I suspect that is within an acceptable range.

The larger fan that I bought with this shroud….

I wondered about the gap to the shroud around the fan. There are people that say the clearance shouldn’t be more than an inch. Some say the fan should be partly within the shroud and partly outside of it. When I get conflicting information, I sometimes look at cars or trucks that are 100% stock.
My 2007 Ram 1500 has never overheated and it has about 1 1/4” clearance and only about 1/4 of the fan sits outside the shroud.

I can feel the suction of air from the front of the radiator in the truck as well as my red car. A sheet of paper sticks to both quite well.
I feel some pull with this current setup but not the same amount.
I expect the bigger fan with more blades and the shroud to change that.

 

[RemCharger]

I have seen this in print before but still don't understand.
When I refill a cooling system, I squeeze the upper hose as the radiator gets close to full to burp out as much air as I can.
I'll often run the engine with the cap off to watch the flow and then top it off as needed. I will get it up to operating temperature and check the coolant level occasionally. If there is some other way to rid the system of air, I'm willing to learn.

The radiator arrived last week.

View attachment 1463121
Pretty nice looking unit for a beat up car!

View attachment 1463122
Transmission cooler at no extra charge….

View attachment 1463125

Nice thick mounting flanges:

View attachment 1463124



I went through my stash and picked a shroud. I have 2 from the 85-89 Chrysler Fifth Avenue cars. They had 26" radiators but also used bigger fans. The opening in the shrouds that I have are approximately 22", compared to around 20" in the stock shroud I have in the red car. I'll be using a bigger fan and shroud with this radiator. I've used a 19" 5 blade fan but I'm switching to a 20" 7 blade fan from that Fifth Avenue.

View attachment 1463127

Since the shroud isn’t stock, I had to clearance it a bit where the hoses will go.

View attachment 1463129
View attachment 1463130

Hard to say if the shroud will gain much other than finger protection. The hole is as big as the rad!!

 

[1 Wild R/T]

When filling the radiator if you pop a heater hose off it will allow air to escape... Back in the day cars often had a flushing tee in the heater hose, that works great for bleeding air...

 

[66 Sat]

I was thinking on Monday when I was driving my car whether the heater being partially blocked could cause overheating. The reason this popped in my head was I was struggling to get the car up to 180 degrees and my car only has a 22" radiator with the 4 blade fixed fan and no shroud. It doesn't ever run hot, even on the very hot summer days we get here. I realize it's only a stroked small block but I was wondering whether my car not having a heater box makes the system more efficient?

Might be something to consider if this new radiator doesn't fix the issue.

 

[Chargerjase]

I mentioned the funnels earlier. Here is a video explaining the process. It worked great for me.

Yeah I know its a Chevy and the guys voice is nauseating, but it's good info.
Another method is to elevat the front of the car slightly to allow air to work itself out because it will travel to the highest point.

 

[Kern Dog]

The radiator fit but the opening in the core support had to be opened up a bit.

Making non stock parts work together often results in a few conflicts. The shroud fit the radiator when it was out of the car. When installed…..

The rim of the shroud was too deep. The power steering pump was inside of it, the alternator was really close and it was about 3/4” from the crank pulley. The shroud was for a 318 car.
I cut an inch off of the outer rim edge and it fits much better.

 

[Kern Dog]

Awhile back I wondered why the fan always seemed to be closer to the radiator at the bottom. I learned that with a stock radiator, fan clearance is better because the side mount brackets for the radiator are angled to account for the angle of the engine and fan. Aftermarket radiators don’t have this so it is possible to have adequate clearance for the fan at the top but be too close at the bottom.

I wanted to use the 7 blade fan for more air movement. Unfortunately, with the Hayden 2747 stubby Fan clutch, the fan blades wanted to hit the hub on the power steering pump. Why? The pitch of the blades was too sharp.

I have three of these fans and they all have the same steep pitch. I tried using a standard fan clutch to move the fan forward but the blades touched the radiator at the bottom.
I had no choice but to revert back to the 5 blade fan and shortie fan clutch.
Even the 5 blade fan is close to the pump

Almost done.

Just a few more details and I’ll add water and anti freeze and warm it up.

 

[RemCharger]

I probably missed it, but what's the reasoning for the antifreeze down there? Straight water and a water wetter would work better, no?

 

[1 Wild R/T]

I probably missed it, but what's the reasoning for the antifreeze down there? Straight water and a water wetter would work better, no?

Where Greg & I are does still get temps down below freezing every year so you need at least some protection.... Through the years I have seen a few engines with cracked blocks due to freezing...

 

[Kern Dog]

Does "Water Wetter" have anti-corrosion properties in it?
This engine was first started in Spring 2021. The inside of the thermostat housing has slight rust residue and it was new when I built the engine. I should have put anti freeze in it after break in but I got distracted and forgot.

 

[RemCharger]

 

[72sunroof]

I probably missed it, but what's the reasoning for the antifreeze down there? Straight water and a water wetter would work better, no?

If you read the bottle it is called antifreeze /coolant it also raises the boiling point of water above 212 without the pressure cap.

 

[Kern Dog]

Repost...

 

[5.7 hemi]

Did you lift the front of the car or put the front tires on car ramps? That helps with getting rid of air pockets

 

[Kern Dog]

Man, that sounds like a snipe hunt.
All the vibrations and motion these cars make during normal driving should be enough to rattle out any air bubbles.

 

[Bighouse]

I just scanned thru this and didn’t see if there was an answer to the lower hose having a spring in it. Sorry if I missed it.

Did we find out if there is one? Without it the lower hose will suck itself closed at higher rpm.

 

[Kern Dog]

There was no spring before. There is now.