Ford Mustang Forum banner
1 - 16 of 16 Posts

·
Premium Member
mostly 1966 coupe with pny package
Joined
·
3 Posts
Discussion Starter · #1 ·
My '66 289 2bbl, no air or p/s, fails to reach, what I believe, to be a good operating temperature. When running, either in town or highway, the gauge will just barely reach the bottom of the safe zone arc. It will move up, as expected, to just shy of mid point after shut down. Which I hope is sufficient to boil the acids and crud from the oil.

The car has a 160 degree thermostat, a high flow Mr Gasket water pump, new U S Radiator 3 row, 5 blade fan and coolant recovery system. The fan is 1 1/2" from the radiator, no fan shroud. I was thinking about going to a 4 blade factory fan, but don't know if it would make enough difference to warrant the switch. The ambient temperature here has been running in the mid 80's or so. Should I be concerned? Any thoughts from those more experienced would be appreciated.
 

·
Registered
Joined
·
7,112 Posts
160F thermostat is too low. Use at least a 180F. I used to run a 195F.

The "correct" coolant temperature is 200F. The goal is to keep the oil temperature as close to 212F as possible, since this is when it boils off moisture and is at the designed viscosity.
 

·
Tech Advisor
1967 Mercury Cougar XR7
Joined
·
3,272 Posts
The thermostat in your engine works exactly like the one in your house. It sets the temp, when everything else is working fine. But setting it to 150 degrees doesn't mean your house will reach 150 degrees during the winter. Neither will setting it to 30 degrees in the summer get it that cold. Your engine's cooling system has limitations. So long as it's working, and opens properly, the thermostat will just try to hit the temp it's set up for, and your radiator, fan, shroud, cooling fluid, and water jacket are all able to do the job.

The "right temperature" for your engine is just as Yadkin said: a 192 degree thermostat allows your oil to get up to proper temp. If you go colder, water and acids will build up in your oil, making sludge and rust. Not good.
 

·
Registered
Joined
·
102 Posts
I am assuming an electrical gauge, as I am not familiar with your vintage of Mustang. You may want to confirm the operation of the gauge first, either by temporarily hooking up a mechanical gauge or using a temp sensor gun on the top hose or thermostat housing. I suspect you may have too much cooling with what sounds like an rad larger than original. Since the existing thermostat will be fully open at 160 (as will a 192 at that temp), the cooling is a function of the rest of the system, which means the best you’ll see with the 192 will likely be temps around 190.
 

·
Registered
Joined
·
1,296 Posts
Before doing anything use an infrared thermometer hand held gun and check the temp when the car has so called warmed up.
Then it will identify where the problem may be.
 

·
Premium Member
mostly 1966 coupe with pny package
Joined
·
3 Posts
Discussion Starter · #7 ·
Yesterday I pulled the 5 blade fan and put a factory 4 blade on and went for a spin. The fan swap made no difference. Upon arriving back to the car barn, I took Tony 64's advice and got out my infrared thermometer and took a look. Highest temp I shot was 180.6, which I know is too cold. I went to parts house and picked up 180 stat to swap the current 160.

I plan to install the 180 today and see what happens. Hopefully this will fix it. That bottom housing bolt is a king size pain to get in and out with my old hands which don't bend so good anymore.
 

·
Registered
Joined
·
102 Posts
Yesterday I pulled the 5 blade fan and put a factory 4 blade on and went for a spin. The fan swap made no difference. Upon arriving back to the car barn, I took Tony 64's advice and got out my infrared thermometer and took a look. Highest temp I shot was 180.6, which I know is too cold. I went to parts house and picked up 180 stat to swap the current 160.

I plan to install the 180 today and see what happens. Hopefully this will fix it. That bottom housing bolt is a king size pain to get in and out with my old hands which don't bend so good anymore.
I suspect that you will see no difference with the hotter thermostat. At your indicated 180.6 temp the 180 thermostat will be fully open, as was the 160. Your rad is efficiently shedding the heat generated by the engine. In order to have temps around 200 (if that is your goal) you would need a thermostat which opens and closes close to that temp. And, if you go that route, you will likely see movement on the gauge as the thermostat cycles open and close, as opposed to the steady temp of a fully open one.
 

·
Premium Member
mostly 1966 coupe with pny package
Joined
·
3 Posts
Discussion Starter · #11 ·
I got the stat changed. As noted by jonnybeerotten, it opens 20 degrees higher than the 160. After a run, I once again checked with the laser. The temp was 190.3. Also as stated by 07redstang, the internal temp of the engine would be some measure higher. At this point I feel the problem is solved.

My supposition is that with the 160, the efficiency of the other components kept the temp from rising to a proper level. Now with the 180, the other components efficiency remains obviously the same. But they do thing at a higher starting temperature, more appropriate for proper oil contaminants burn off.

To answer Yadkin's question, all other gauges appear to read as they should. The temp gauge now reads about 3/16" right of the low end of the safe operating arc upon warm up. A location which looks more correct. The ambient air temp was about 70.
 

·
Registered
Joined
·
77 Posts
My '66 289 2bbl, no air or p/s, fails to reach, what I believe, to be a good operating temperature. When running, either in town or highway, the gauge will just barely reach the bottom of the safe zone arc. It will move up, as expected, to just shy of mid point after shut down. Which I hope is sufficient to boil the acids and crud from the oil.

The car has a 160 degree thermostat, a high flow Mr Gasket water pump, new U S Radiator 3 row, 5 blade fan and coolant recovery system. The fan is 1 1/2" from the radiator, no fan shroud. I was thinking about going to a 4 blade factory fan, but don't know if it would make enough difference to warrant the switch. The ambient temperature here has been running in the mid 80's or so. Should I be concerned? Any thoughts from those more experienced would be appreciated.
Replace the 160 with a 180
 

·
Administrator
Joined
·
8,160 Posts
1 - 16 of 16 Posts
Top