Chasing this cooling issue for months

[godfatherofchry]

If you have significant flow in the upper hose when the thermostat is closed, you have an issue with the thermostat bore / housing.

With the engine cold, pull the radiator cap, and take the speed up to 1500 to 2000 rpm. If you see coolant flowing, it is bypassing the thermostat.

Unless you have been installing the thermostats upside down, there is no way water pump pressure can push one open.

What can happen is a mismatch of parts, or a poorly machined manifold / water neck allowing significant coolant flow to bypass the thermostat.

Through the years, mopar went from a 2.500 OD thermostat to a smaller one. The water neck bolt spacing changed, but I would not bet that some aftermarket parts were made with a mix of the two dimension sets...

Really the only place to get water into the radiator from the engine is the thermostat. The bypass, heater, etc all work against any flow heading to the radiator.

Check to see if you have upper hose flow on a cold start.

B.

x2 on if the stat is upside down.

 

[TrailBeast]

well the first thing I would do is get rid of the electric fan and go with a regular fan be it 6or7 blade with a fan shroud.your elect. fan is only cooling the spot that its in. this being the resin for it getting to 210 and then I would go with a 180 or 185 stat I think that would regulate you temp. better...I have never had any luck with using an elec. fan for the only source of cooling.and I think 180 is an ideal temp.for an older motor....this is my thut and its worked for me.........Artie

That's not going to happen, sorry.
The fan only comes on sitting in traffic, running and not moving, or heavy sustained load at low speeds (Like up a big hill in a residential area)

If you have significant flow in the upper hose when the thermostat is closed, you have an issue with the thermostat bore / housing.

With the engine cold, pull the radiator cap, and take the speed up to 1500 to 2000 rpm. If you see coolant flowing, it is bypassing the thermostat.

Unless you have been installing the thermostats upside down, there is no way water pump pressure can push one open.

What can happen is a mismatch of parts, or a poorly machined manifold / water neck allowing significant coolant flow to bypass the thermostat.

Through the years, mopar went from a 2.500 OD thermostat to a smaller one. The water neck bolt spacing changed, but I would not bet that some aftermarket parts were made with a mix of the two dimension sets...

Really the only place to get water into the radiator from the engine is the thermostat. The bypass, heater, etc all work against any flow heading to the radiator.

Check to see if you have upper hose flow on a cold start.

B.

There is no flow at cold startup, and I noticed the diameter differences and sealed around the thermostat to make sure nothing was getting by it.
As far as bypasses, there are none, or at least I blocked them all in testing to find out if they made any difference.

TrailBeast;
A 195* degree thermostat should maintain an average engine temp of 175* with a good cooling and air circulating system. Remember that it isn't like a light switch on/off. You have a bypass hose and most likely a bypass built into the T~stat as well. 195* is the full open temperature but that stat will partially open at 175* try one in a pan of water and watch it. That partially opened position with highway speed airflow should give you the 175* operating temp you are experiencing. It is this exact same reason that I used to recommend to my diesel customers to run a 203* t~stat to maintain a 190* engine temp. Since the 195* is the highest I know of for your car all you can do is install a system that blocks airflow through the radiator at speed. The louvers you mentioned with an electric motor controlled with the same type of thermostat as your fan should do the trick.
~Michael

This one explains it.
I didn't think about it that way but "thermostats don't work like a light switch."
It was exactly that phrase that, shall we say "Turned on the light"
When it's cooler out I need to block part of the airflow through the radiator core.
I can do that.
The electric controlled louvre system is interesting to consider also.
Thank you Dartman1969 and everyone else that offered suggestions.

 

[67Dart273]

That fan is not effective. Fans MUST HAVE a full radiator shroud. If you look at ANY factory electric fan setup, they have a shroud covering the entire core. Even if the fan is pulling "enough air" it is only using a small part of the rad.

Earlier you mentioned that "if the gauge is wrong" it means that the engine is running too hot (230) at low speed. This may very well be---a cooling system that is leak tight and with a good cap CAN run at 230, and without an accurate gauge, you would never know it.

I would get something else to check your engine temp.

 

[TrailBeast]

The only time that fan ever comes on is when the guage reads 210 and then it brings it back down to 190-195 and I mean right now.
The ONLY time the car ever gets to 210 is sitting in traffic running on a really hot day.
I have two separate electric devices that agree that the temp is right where they say it is, AND I have seen my oil pressure at 230.
I drive it in Phoenix when it's well over 100 out, and never even gets close to overheating, so I don't understand why people tell me that it won't work when it works so well.
Let's don't apply the fan shroud(which I agree most peoples cars need) to every car out there.
Otherwise I would have to say what I said to the last person that told me that. "Then I must have a giant icecube in the motor somewhere that is cooling it indefinatly when it's over 100 outside."
This one simply does not need it.
I have overcooling issue's at hiway speeds not overheating issue's.

Thanks though.

That fan is not effective. Fans MUST HAVE a full radiator shroud. If you look at ANY factory electric fan setup, they have a shroud covering the entire core. Even if the fan is pulling "enough air" it is only using a small part of the rad.

Earlier you mentioned that "if the gauge is wrong" it means that the engine is running too hot (230) at low speed. This may very well be---a cooling system that is leak tight and with a good cap CAN run at 230, and without an accurate gauge, you would never know it.

I would get something else to check your engine temp.

 

[BillGrissom]

TrailBeast;
A 195* degree thermostat should maintain an average engine temp of 175* with a good cooling and air circulating system. Remember that it isn't like a light switch on/off. ~Michael

Agree. For anyone who wants to investigate further search "proportional offset". It is common to any control system that is not on-off, but rather has a proportional output. As the load increases, the error increases (difference between setpoint and actual value). The error can be decreased by increasing the control gain, but that makes the control touchier and can even oscillate. The "final solution" is to add "integral action", but that adds it's own problems. If you get into electronic fuel control, you may run into the full PID controller (Proportional - Integral -Derivative, since 1940's). The Holley FI manual has you tune the PID loop for the IAC. All engine coolant controls I know of are simple "thermostat spring - proportional" types. My 2 Mercedes have a complicated passenger heat proportional controller. They usually fail and you get no heat at all (or sudden bursts). Often simple is better.

 

[Frank Mopar]

One thing oft overlooked in cooling issues is carburetion. A lean set-up tends to build head while a rich set-up does the opposite.