Vintage Mustang Forums banner
1 - 20 of 24 Posts

·
Registered
Joined
·
44,119 Posts
My Mustang is running warmer on the freeway than it does around town.

Would this point to an issue with timing?
It could be. It could also be a partially plugged cooling system, water pump with a worn-out impeller, defective thermostat (failing to open all the way) or radiator with poor fin conductivity. Timing could also be an issue... improperly calibrated distributor advance, bad vacuum advance diaphragm or leaky supply, defective Spark Control Valve at the carburetor, vacuum leak somewhere, etc.
 

·
Premium Member
1966 Convertible 6cyl 4sp
Joined
·
171 Posts
Discussion Starter · #4 ·
Is it overheating?
It hasn't overheated but the needle goes from near the C around town to near the H on the freeway. And on a warm day it's really close to the H.
I did put a new 180 T-Stat in recently and want to try to make sure I'm seeing normal operation or if I need to chase down an issue before I end up with a real problem.
 

·
Premium Member
1966 Convertible 6cyl 4sp
Joined
·
171 Posts
Discussion Starter · #5 · (Edited)
It could be. It could also be a partially plugged cooling system, water pump with a worn-out impeller, defective thermostat (failing to open all the way) or radiator with poor fin conductivity. Timing could also be an issue... improperly calibrated distributor advance, bad vacuum advance diaphragm or leaky supply, defective Spark Control Valve at the carburetor, vacuum leak somewhere, etc.
Thanks
I have recently done a new:
  • Water pump
  • 180 TStat
  • Cap
  • Carb Spacer
  • Heater Core
  • All Hoses
That's why I was leaning towards timing - especially since it's primarily an issue at freeway speed.
 

·
Registered
Joined
·
2,107 Posts
Putting in a low temperature thermostat will not keep your engine from overheating if your cooling system has a problem. The total amount of cooling is not affected. So, unless your old thermostat was sticking 'closed', the new thermostat will not change the situation if you're boiling over.

The thermostat's job is to determine when to open, and try to maintain a constant temp. If you put one in that's too cold, water and other impurities in your oil will often never get warm enough to boil away, and that will cause rust and corrosion to the precision parts in your crankcase.

If you are overheating, it's a good idea to start with simple things first, like checking to see if your radiator cap holds pressure, low coolant, and make sure your timing's right. If you're overheating at idle and low speeds, that's most often a problem with your shroud. If you overheat more on the highway, that favors problems like corrosion in the cooling system, improper timing, or even a soft lower radiator hose that's collapsing at high RPMs.
 

·
Registered
1966 Convertible 200/C4 Silver/Red
Joined
·
600 Posts
What kind of rpm do you run at on the freeway? If that 4 spd isn't original maybe you're geared kinda low. Anyway, I have a 6 cyl 66 vert too, and I finally replaced the original radiator last year. It didn't leak and looked real clean inside, but just wasn't cooling as well as it used to. And it used to cool really well because it was an ex-AC car with a 6-bladed fan and a radiator with more fins per inch. I suppose it was the old loss of fin conductivity syndrome. She runs so cool now I'm going to go back to the old 190 'stat next time I've got the cooling system open.
 

·
Premium Member
1966 Convertible 6cyl 4sp
Joined
·
171 Posts
Discussion Starter · #8 ·
What kind of rpm do you run at on the freeway? If that 4 spd isn't original maybe you're geared kinda low.
Running the original Dagenham 4sp and 3:20 gears. I've got a tach installed but not quite wired up yet - so not sure yet what my RPMs are. Just put on some new shoes 195/70/R14

Land vehicle Speedometer Odometer Vehicle Tachometer
 

·
Registered
Joined
·
330 Posts
Recent brake job with shoes dragging on the drums? or out of adjustment, stuck wheel cylinder, etc.? Seems odd, but on freeway it would make it work harder. Around town there would be some cooling time during idling at stop lights.

When I was living in E. Texas the bugs would get so bad in the grill side of the radiator from their suicides, I'd use high pressure car wash to clean them out several times a summer to allow air to get thru the radiator.

All this said, I'd check the lower radiator hose. Make sure it has a spring in it to prevent high rpm collapsing. Some of the new hoses don't include spring. If needed be buy a universal hose of the right diameter & cannibalize its spring.
It will be something simple.
 

·
Premium Member
1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
Joined
·
2,497 Posts
Running the original Dagenham 4sp and 3:20 gears. I've got a tach installed but not quite wired up yet - so not sure yet what my RPMs are. Just put on some new shoes 195/70/R14

View attachment 846166
Just tell everyone that tach is pegged 🤘
 

·
Premium Member
1966 Convertible 6cyl 4sp
Joined
·
171 Posts
Discussion Starter · #14 ·
High rpm/high speed excessive heat is usually crap in the radiator. If it’s ever had stop leak in it, that’ll do it for sure. That stuff sucks.
Hard to know what's been poured into the radiator over the years or what work has (or hasn't been done to it). From what I can see of the inside it looks pretty good - but before I take it too far from home on a warm day I gotta chase this down.

Pretty sure there's no spring in that lower hose - need to get that squared away.
Motor vehicle Automotive tire Rim Gas Engineering

Motor vehicle Automotive tire Hood Automotive exterior Automotive design
 

·
Registered
Joined
·
401 Posts
C6ZE - is that the original radiator?

For me it was a partially plugged radiator. Could go 30-40 miles on interstate, then would heat up. Let cool down for a bit, and then it'd do it again. Wasn't so hot in town though at low speeds. Replaced radiator, problem solved.
 

·
Premium Member
1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
Joined
·
2,497 Posts
Hard to know what's been poured into the radiator over the years or what work has (or hasn't been done to it)
Exactly. Unless you’re the original owner there’s no telling what it’s been through for almost 60 years
 

·
Premium Member
1966 Convertible 6cyl 4sp
Joined
·
171 Posts
Discussion Starter · #17 ·
C6ZE - is that the original radiator?

For me it was a partially plugged radiator. Could go 30-40 miles on interstate, then would heat up. Let cool down for a bit, and then it'd do it again. Wasn't so hot in town though at low speeds. Replaced radiator, problem solved.
I was told that it had been "recored" and the top of the radiator was saved and welded to the new cores. I know nothing about radiators - can anyone tell from the pictures if that looks to be true ?
 

·
Premium Member
1965 Mustang GT. 11.898 @ 113.646, all motor, three pedals
Joined
·
2,497 Posts
I was told that it had been "recored" and the top of the radiator was saved and welded to the new cores. I know nothing about radiators - can anyone tell from the pictures if that looks to be true ?
I would say you’re absolutely correct.
 

·
Registered
Joined
·
2,840 Posts
You need a higher degree stat in there. I put a 190 in my 67 vert 200 6 during cold weather because it ran so cool it kept falling out of the learn mode on the Sniper, below 160. It stays pretty consistent about 190 now , but on my last trip out I got hung up in a little traffic in some 90 degree heat & it got up to about 204. Kicked it in neutral & run the eng speed up some ,she dropped back down to about 193.
Like some guys said check that lower hose for a spring ,unless it a flexible type hose. You don't have it that thing will suck flat with a lot of sustained speed.
 

·
Registered
Joined
·
44,119 Posts
You need a higher degree stat in there. I put a 190 in my 67 vert 200 6 during cold weather because it ran so cool it kept falling out of the learn mode on the Sniper, below 160. It stays pretty consistent about 190 now , but on my last trip out I got hung up in a little traffic in some 90 degree heat & it got up to about 204. Kicked it in neutral & run the eng speed up some ,she dropped back down to about 193.
Like some guys said check that lower hose for a spring ,unless it a flexible type hose. You don't have it that thing will suck flat with a lot of sustained speed.
How is a higher temperature thermostat going to make it run COOLER on the highway?
 
1 - 20 of 24 Posts
Top