Just TOO cool

[TrailBeast]

This kinda sucks because I have this issue that everone say's "Gees, I wish I had that problem"
I had the original 18" radiator and all OEM cooling on my Dart 318 and it would get pretty warm (210-220) in parking lots and slow block to block driving.
I replaced the radiator with a 26" Extra cool 2 row model and got a Jegs 17" electric fan, 8 impeller water pump, and a new 195 thermostat.
The fan controller starts the fan at 210 degrees and shuts down at 195.
All this works great around town block to block and idling around parking lots at low speeds.

Now here's the problem.
Even if it's 80 degrees outside if I drive down the hiway for even a mile or two, the engine temp drops to 165-170 degrees.
I blocked off the bypass from the water pump to the intake thinking "maybe it just cooling enough that the bypass was letting cooler fluid past the thermostat"
Didn't help.

I've been through all the guesses and thought I would ask if anyone KNOWS why it gets down that cool with a 195 thermostat in it.

Thanks

 

[RedFish]

Doesn't make sense to me. Unless the thermostat is upside down or stuck open.
The bypass hose allows water to circulate inside the engine while the thermostat is closed. It shouldn't be blocked off. You may have water pressure forcing the thermostat open.

 

[caferacerx]

thermostats are notoriously inaccurate, as are gauges to a lesser extent
first you need to verify the accuracy of your gauge
then you need to find an accurate thermostat

 

[TrailBeast]

This is the second new thermostat (the first new on was a 180)
I blocked the bypass after I couldn't get it to warm up all the way.(so I don't think the pressure is pushing past the thermostat, as it didn't change a thing)
It was however quite the pain to get it filled with coolant when blocked, and I expected that.
My thermal electric fan controller has marked temp settings on it, so I know the guage and actual engine temp are pretty darn close. (I can set the contoller to come on at 210 and it does come on when the gauge says 210.)
Thermostat upside down would make it overheat instead of over cool.

All the above are great thought's, but I've already been there.

 

[bohica2xo]

This overcooling is a problem I usually see on fords. My F150 would overcool so bad in the winter I had to block 75% of the radiator with cardboard.

The cure is relatively simple. Drill a bleed hole in the thermostat. Usually 3/32 is big enough.

That will stop the thermostat surge. I bet you can watch the thermostat open on the gauge. With a small flow across the thermostat, there is no surge of cold water from the radiator into the pump when the thermostat opens. It acts to damp the swings.

Now, what year is this Dart, and what exactly is this radiator & it's source?

B.

 

[TrailBeast]

This overcooling is a problem I usually see on fords. My F150 would overcool so bad in the winter I had to block 75% of the radiator with cardboard.

The cure is relatively simple. Drill a bleed hole in the thermostat. Usually 3/32 is big enough.

That will stop the thermostat surge. I bet you can watch the thermostat open on the gauge. With a small flow across the thermostat, there is no surge of cold water from the radiator into the pump when the thermostat opens. It acts to damp the swings.

Now, what year is this Dart, and what exactly is this radiator & it's source?

B.

Thanks for taking the time.
1973 Dart Swinger, 318/904
Stock cast 2 barrel intake.
Stock air cleaner.
Stock manifolds.
Fresh block flush, Radiator is 26" from Checker Auto (Looks refurbed) 2 row.
Brand new (second one) 195 thermostat.
17 inch electric S-blade fan at 2500 CFM pulling and directly mounted to the center of the rad.
Heater core comes in tomorrow so that's not even hooked up yet.

 

[bohica2xo]

The heater core should not make much of a difference. Lots of Mopars shut the flow off on that circuit with the A/C on.

The bypass circuit on the LA engine is huge compared to other makes. One of the reasons you can block the heater flow without issue.

You have very little heat to get rid of, and a huge radiator. In the winter you may need a bit of cardboard if it snows where you are.

When you open the system to add the heater core, drill a 3/32 hole in the thermostat in the flat part near the opening. This creates a small flow past the thermostat, and makes the system easier to fill too.

B.

 

[TrailBeast]

The heater core should not make much of a difference. Lots of Mopars shut the flow off on that circuit with the A/C on.

The bypass circuit on the LA engine is huge compared to other makes. One of the reasons you can block the heater flow without issue.

You have very little heat to get rid of, and a huge radiator. In the winter you may need a bit of cardboard if it snows where you are.

When you open the system to add the heater core, drill a 3/32 hole in the thermostat in the flat part near the opening. This creates a small flow past the thermostat, and makes the system easier to fill too.

B.

I'll be putting the heater in tomorrow afternoon, and will drill the thermostat flange.
I don't have big swings in temp so I don't see how it's going to make any difference, but I'll try it.
It gets down to single digits in the winter, and 100 or so in the summer here.
Will let ya know, thanks