Cooling system issue
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
Yeah a more aggressive cam would increase operating temps as its going to pull in more fuel and make more power. The cam you selected matched with stock (ish) heads, carb and intake should not produce significantly more heat to the point where its an issue.
This is worded in a way that confuses me.
does you onboard temp gauge display match the temp shown by the IR temp gun on the thermostat housing? If you are going to answer yes then the following example should be true: Gauge displays 210, T stat housing shows ~210 on IR, the sending unit in the intake that feeds data to your cockpit gauge shows ~210 on IR temp gun, The radiator hose running to the top of the radiator shows ~210 on IR the top of the radiator shows ~210 on IR.
Make sure to take all measurements at the same distance ideally about 2 to 3 inches away. An IR temp gun does not measure in a laser type line rather it measures in an ever expanding cone and temperatures quickly become an average after just a few inches.
I did also check thermostat housing temperature vs temperature at the intake where sensor is screwed into intake with ir thermometer. Temperature vs virtually the same at any operating temperature.
does you onboard temp gauge display match the temp shown by the IR temp gun on the thermostat housing? If you are going to answer yes then the following example should be true: Gauge displays 210, T stat housing shows ~210 on IR, the sending unit in the intake that feeds data to your cockpit gauge shows ~210 on IR temp gun, The radiator hose running to the top of the radiator shows ~210 on IR the top of the radiator shows ~210 on IR.
Make sure to take all measurements at the same distance ideally about 2 to 3 inches away. An IR temp gun does not measure in a laser type line rather it measures in an ever expanding cone and temperatures quickly become an average after just a few inches.
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
Gentleman's Relish
Joined: Feb 2005
Posts: 13,187
From: AZ
The push test verifies 1) the fan clutch is being turned the correct way (more resistance in the direction of rotation) and 2) the fan clutch isn't worn out by just spinning freely when you give it a push.
It's just like it sounds, you literally push the fan in the expected direction of rotation and see how many free turns you get. 1 or two revolutions is good. 3 or more you have a fan clutch that's either worn or spinning in the wrong direction.
I worked in auto parts stores for like 10 years (pep boys, Napa, Autozone formerly Kragen/Check/Shucks, and Oreliy's formerl Chief auto parts). Most engines turn clockwise but there are some that spin counterclockwise. Had a number of customers that would buy the CCW on accident because it was cheaper and the parts guy before me didn't know/care/or see it said CCW.
It's just like it sounds, you literally push the fan in the expected direction of rotation and see how many free turns you get. 1 or two revolutions is good. 3 or more you have a fan clutch that's either worn or spinning in the wrong direction.
I worked in auto parts stores for like 10 years (pep boys, Napa, Autozone formerly Kragen/Check/Shucks, and Oreliy's formerl Chief auto parts). Most engines turn clockwise but there are some that spin counterclockwise. Had a number of customers that would buy the CCW on accident because it was cheaper and the parts guy before me didn't know/care/or see it said CCW.
Last edited by Derf00; Aug 24, 2020 at 01:24 PM.
Gentleman's Relish
Joined: Feb 2005
Posts: 13,187
From: AZ
He's run fan diret? Crap, I missed that!
Welp, next item, running lean would cause overheating. You can run lean even if your timing is dead-nuts because you're starving your engine for fuel....Any stickies or clogs on the carb primaries? how the plugs look? White? That's lean.
Maybe try adjusting your idle/air or reduce your ideal timing.
Welp, next item, running lean would cause overheating. You can run lean even if your timing is dead-nuts because you're starving your engine for fuel....Any stickies or clogs on the carb primaries? how the plugs look? White? That's lean.
Maybe try adjusting your idle/air or reduce your ideal timing.
Joined: Aug 2020
Posts: 2
From: California
Late to the party, just joined.
The stock system was marginal, at best.
When you throw in:
- We run wider tires now than before
- Highway speeds are higher
- There's far more traffic than before
The stock 17" radiator just can't keep up
Early Mustang cooling problems are COMMON. In fact, almost all of the classic Mustang parts houses have no fewer than 100 parts on hand to sell you without guiding yuo
Early Mustang cooling components are some of the best selling items these houses stock. I am dead serious. And a LOT of it is snake oil.
I've had a 1965 with overheating problems for 15 years. Let me break down some of my trial and error
Back story
1. My engine was rebuilt sometime in the 80s and it seemed like it was bored .040 or .060 over. No documents. I used my Harbor Freight caliper when I had the heads off and it was definitely at least 4.040 in each cylinder.
2. The PO-before-the-PO removed the thermostat. The car lived in San Francisco its entire life, but I was further out east where the temperatures regularly climbed into the 90s-100s in the summer. The PO was a friend and never had any overheating issues. Weather is between 40-65F in SF year round.
Now, in my travels I've done the following:
1. Anti-collapse spring in the bottom radiator hose. I noticed when I revved the engine testing total timing advance (like you guys) I was seeing the hose flex/cave a little bit
2. 180F thermostat. Tested in boiling water on the stove before installed. Drilled 3 x 1/8" holes in it to allow more coolant bypass than the little hose afforded
3. Timing as everyone has said. You want to be 36 degrees all-in at or around 3000rpm. The factory calls for 6 or 8 degrees at 700rpm idle with the 2V 2bbl autolite carb I had. However, with the pertronix Ignitor II in the distributor I could never get it to run right and
always found that 10-12 degrees was the primo spot
4. Fan: You need a shroud, period. If you have A/C you need (at least) the 17" 7 blade fan and a shroud. This is how they came from the factory with the old factory installed AC. The fan should be 1" from the radiator core. In my opinion the thermostatic clutch fan is the way to go. Don't waste your time with flex fans.
5. Water pump. This will go hand in hand with what I have to say below. If you replaced your water pump with a high volume water pump you may be making the problem worse.
6. Radiator: now, this is a very important, often overlooked issue based on the number of cheap radiators out there. This is what was happening to me and I didn't even know it: The inlet/outlet are on the same side of the radiator. I had picked up a run-of-the-mill $150 Northern Radiator replacement from Summit Racing and installed it (was branded as a Summit Racing brand part). The original factory radiator had a baffle, which forced the coolant to go into the radiator, through the rows and then out the bottom outlet. I thought I was doing right by a high volume water pump (see above), and a nice new aluminum radiator. What was happening was coolant was entering the radiator and being sucked straight down into the outlet. When I ran the infrared thermometer over the radiator, the 6" or so above and below the outlets was at the approximate temperature of the coolant -- and the remainder of the radiator was registering at ambient temperature. I was effectively only using 1/3rd of the radiator and did not even know it.
I knew something was wrong when I had the radiator cap off and there was no flow. The coolant was just sitting there at the fill line not moving.
7. The original radiator cap was something like 7lbs. You want a 13lb cap.
Every lb of pressure the radiator cap is rated for raises the boiling point that much higher over 212F
8. Coolant: This is subjective and every guy will tell you different. Basically: If you are not in a freezing environment you don't need to run anti-freeze. Water is the best heat transfer liquid but it is also the worst for corrosion inhibiting. Running plain distilled water, with a water wetter and/or an anti-corrosion formula will be just fine if it does not freeze there.
The best thing to do is to run Evan's Waterless Coolant. It never needs to be changed. Pricey ($40/gallon) but again, never needs to be changed
9. Go to another doctor for a second opinion: I have found that not all temperature sending units are created equal. Using some hardware store acquired parts I plumbed multiple temperature sending units into the system. The differences were wild. The factory gauge in the dash (at the time) was the old ambiguous factory C ____________________H gauge. I kept that but also added two aftermarket gauges. The aftermarket gauges ran on the same type of sending unit (same ohm resistance range) and so I was able to swap them out. One sending unit was regularly registering 25F over the other. So one was around 180-195F and the other was 205F-220F. Swapped the sending unit each gauge was using and the problem followed the sending unit.
10. Check your brakes. In an old Mustang e-mail list I was on a gentleman was overheating after some engine work and traced it back to his rear brakes dragging. You may need to screw in a pressure gauge to one of the bleeder valves to test this. If you have front discs/rear drums check your proportioning valve.
11. As others have said check your idle mixture screws, and check your vacuum. With a mild cam you should be 15+ inches of vacuum at idle -- the higher the better.
I hope this helps. I've thrown so much money at this problem over the years, I finally realized my engine was rebuilt poorly and replaced with a crate. I also cut the radiator core and installed a 24" radiator found in the 1967+ cars with AC (also big block cars) along with a pair of electric fans.
Good luck, and I am here to answer questions if you need it.
The stock system was marginal, at best.
When you throw in:
- We run wider tires now than before
- Highway speeds are higher
- There's far more traffic than before
The stock 17" radiator just can't keep up
Early Mustang cooling problems are COMMON. In fact, almost all of the classic Mustang parts houses have no fewer than 100 parts on hand to sell you without guiding yuo
Early Mustang cooling components are some of the best selling items these houses stock. I am dead serious. And a LOT of it is snake oil.
I've had a 1965 with overheating problems for 15 years. Let me break down some of my trial and error
Back story
1. My engine was rebuilt sometime in the 80s and it seemed like it was bored .040 or .060 over. No documents. I used my Harbor Freight caliper when I had the heads off and it was definitely at least 4.040 in each cylinder.
2. The PO-before-the-PO removed the thermostat. The car lived in San Francisco its entire life, but I was further out east where the temperatures regularly climbed into the 90s-100s in the summer. The PO was a friend and never had any overheating issues. Weather is between 40-65F in SF year round.
Now, in my travels I've done the following:
1. Anti-collapse spring in the bottom radiator hose. I noticed when I revved the engine testing total timing advance (like you guys) I was seeing the hose flex/cave a little bit
2. 180F thermostat. Tested in boiling water on the stove before installed. Drilled 3 x 1/8" holes in it to allow more coolant bypass than the little hose afforded
3. Timing as everyone has said. You want to be 36 degrees all-in at or around 3000rpm. The factory calls for 6 or 8 degrees at 700rpm idle with the 2V 2bbl autolite carb I had. However, with the pertronix Ignitor II in the distributor I could never get it to run right and
always found that 10-12 degrees was the primo spot
4. Fan: You need a shroud, period. If you have A/C you need (at least) the 17" 7 blade fan and a shroud. This is how they came from the factory with the old factory installed AC. The fan should be 1" from the radiator core. In my opinion the thermostatic clutch fan is the way to go. Don't waste your time with flex fans.
5. Water pump. This will go hand in hand with what I have to say below. If you replaced your water pump with a high volume water pump you may be making the problem worse.
6. Radiator: now, this is a very important, often overlooked issue based on the number of cheap radiators out there. This is what was happening to me and I didn't even know it: The inlet/outlet are on the same side of the radiator. I had picked up a run-of-the-mill $150 Northern Radiator replacement from Summit Racing and installed it (was branded as a Summit Racing brand part). The original factory radiator had a baffle, which forced the coolant to go into the radiator, through the rows and then out the bottom outlet. I thought I was doing right by a high volume water pump (see above), and a nice new aluminum radiator. What was happening was coolant was entering the radiator and being sucked straight down into the outlet. When I ran the infrared thermometer over the radiator, the 6" or so above and below the outlets was at the approximate temperature of the coolant -- and the remainder of the radiator was registering at ambient temperature. I was effectively only using 1/3rd of the radiator and did not even know it.
I knew something was wrong when I had the radiator cap off and there was no flow. The coolant was just sitting there at the fill line not moving.
7. The original radiator cap was something like 7lbs. You want a 13lb cap.
Every lb of pressure the radiator cap is rated for raises the boiling point that much higher over 212F
8. Coolant: This is subjective and every guy will tell you different. Basically: If you are not in a freezing environment you don't need to run anti-freeze. Water is the best heat transfer liquid but it is also the worst for corrosion inhibiting. Running plain distilled water, with a water wetter and/or an anti-corrosion formula will be just fine if it does not freeze there.
The best thing to do is to run Evan's Waterless Coolant. It never needs to be changed. Pricey ($40/gallon) but again, never needs to be changed
9. Go to another doctor for a second opinion: I have found that not all temperature sending units are created equal. Using some hardware store acquired parts I plumbed multiple temperature sending units into the system. The differences were wild. The factory gauge in the dash (at the time) was the old ambiguous factory C ____________________H gauge. I kept that but also added two aftermarket gauges. The aftermarket gauges ran on the same type of sending unit (same ohm resistance range) and so I was able to swap them out. One sending unit was regularly registering 25F over the other. So one was around 180-195F and the other was 205F-220F. Swapped the sending unit each gauge was using and the problem followed the sending unit.
10. Check your brakes. In an old Mustang e-mail list I was on a gentleman was overheating after some engine work and traced it back to his rear brakes dragging. You may need to screw in a pressure gauge to one of the bleeder valves to test this. If you have front discs/rear drums check your proportioning valve.
11. As others have said check your idle mixture screws, and check your vacuum. With a mild cam you should be 15+ inches of vacuum at idle -- the higher the better.
I hope this helps. I've thrown so much money at this problem over the years, I finally realized my engine was rebuilt poorly and replaced with a crate. I also cut the radiator core and installed a 24" radiator found in the 1967+ cars with AC (also big block cars) along with a pair of electric fans.
Good luck, and I am here to answer questions if you need it.
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