[Woodchuck]

1. Shroud.
2. Vacuum advance to manifold vacuum.

A/C equipped cars used a Hot Idle Compensator.

4V 4100 - on the air horn...

2V 2100 in the PCV line...

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[jebsen]

I had a similar cooling problem with my 66 project (363, ACP maxcore stock size aluminum radiator, thermal clutch, 6 blade fan, OEM shroud, no A/C) . When I first got it together it would overheat on a warm day when idling. Revving it to 2000 and holding it there would bring the temp back down. I got it under control by going to a HIPO 7 blade fan and reducing the waterpump pulley from the stock 5" to a 4" aftermarket one. Where I am now I think the radiator is still a little too small but I didn't want to go straight to a bigger one. I think it's manageable - we'll see.

 

[Spedy7]

To the OP, I read that at one time stop leak was used. If you are concerned about blockage, do a citric acid flush. It’s easy to do and it’s works. Don’t use chemical flush as it is milked down and doesn’t work.

Hmph, wish I saw this earlier. Added a small bottle of Peak's flush and letting cycle through until Tuesday.

What about your water pump? Personally I’m suspicious about today’s stock replacement. I think most of them are using a stamped steel impeller that are poorly designed and inefficient. I’m using a PRW nick offasss of a Edelbrock pump. I ordered it by accident. I thought it was a repacked unit. Anyway it seems to work pretty well. I have a thermostat clutch fan with no shroud and I haven’t had any cooling issues. I’m using a cheap EBay aluminum 2 row radiator.

Last I remember it was an Autozone pump possibly? Its been on since we built the motor 4-5 years ago. No leaks or play in the shaft bearing, but may warrant a replacement with a slightly higher flow and a high flow t-stat.

The shroud will likely fix your problem, but if it doesnt, then you should consider adding an AC idle solenoid as a reasonably cheap, easy solution. On my car, when the AC kicks on it drags the motor down by a couple hundred RPMs. With lower RPMs and a mechanically driven fan, you are getting less air flow through the radiator, so your temps go up. The AC idle solenoid will compensate for that lowered RPM by kicking the throttle up a tad, helping you maintain normal idle speeds and thus better air flow.

It is a pretty basic part - it mounts on the front of your carburetor and features a plunger that, when activated (12V applied), pushes your throttle up a bit. You just wire it into the compressor wiring so when the compressor is on, the solenoid is active. Supposedly you can find these idle solenoids on a few junkyard vans, IIRC Woodchuck knows which ones.

I bought one as a precaution since I have a Holley on it, haven't added it yet though.

Swapped to manifold vacuum for the advance, may have made a difference, but hard to tell. Without the a/c on, it takes some time but will eventually creep up at idle. Read ~200* on an IR thermometer, so I'll add the shroud on Tuesday and see how it goes.

 

[Asm109]

Just to set expectations. 200 at idle is not too hot. Heck 200 anytime is not too hot. 230 now that is too hot.

 

[1967pony]

ugh , i gong thru the same issues ,i got a .40 over 351W in a 67 mustang ,stock 2 core 20 inch rad. it got so hot it blew the seams out of 2 rad.s i got a new stant 180 thermostat 17 inch flex type fan from a 351 cougar new water pump it creeps up to 3/4 way ,shut the pony off come back pegged but then it does drop down now

 

[stephen_wilson]

ugh , i gong thru the same issues ,i got a .40 over 351W in a 67 mustang ,stock 2 core 20 inch rad. it got so hot it blew the seams out of 2 rad.s i got a new stant 180 thermostat 17 inch flex type fan from a 351 cougar new water pump it creeps up to 3/4 way ,shut the pony off come back pegged but then it does drop down now

Coolant, no matter how hot, will not rupture a radiator. A faulty cap that's not relieving the pressure would though. You probably just had 2 poor quality radiators.

 

[Spedy7]

Put the shroud on today with half the fan in the shroud, seems like it made a small difference, but will still slowly creep up when idling for longer than a couple minutes. I wonder if putting a fan on the condenser may help push some more air at idle? I can fit a 7.5-inch Spal one without having to modify the latch support.

Wish I had a '67 or '68 now :|.

 

[fraso]

If your hose nozzles are on the same side, Badass Racing suggests that having them on opposite sides will help improve cooling.

See Badass Racing: My early Mustang runs hot, Why?

I think it would be easier to move the upper nozzle and use an universal rad hose than it would be to move the bottom nozzle.

 

[stephen_wilson]

I believe that's a popular myth. The coolant won't just "shortcut" the far side of the radiator. The header tanks are distribution manifolds, and the flow will be divided according to the restriction and pressure drop in each individual coolant tube. If what they claimed truly happened, greater flow would have to travel through the near side tubes, but that would increase the pressure drop, which forces water to the far side (with low flow & pressure drop). There is probably some uneven flow distribution, just as there is on a poorly designed intake plenum, but not enough to substantially reduce cooling.

 

[fraso]

I wouldn't have thought staggering the nozzles would make much of a difference either. With nozzle staggering, if flow short circuiting was actually occurring, you could easily have a similar situation. You would have to measure tube temperatures across the width of the radiator to have a good idea of how evenly the flow is distributed.

Is there any truth to Badass Racing statement that 1969 & newer vehicles do not run as hot as earlier cars? If so, what is different in the cooling systems between the 2 eras?

 

[GT289]

Wish I had a '67 or '68 now :|.

No you don't. I haven't found them to be that much better in the stock cooling dept.....

Put the shroud on today with half the fan in the shroud, seems like it made a small difference, but will still slowly creep up when idling for longer than a couple minutes. I wonder if putting a fan on the condenser may help push some more air at idle? I can fit a 7.5-inch Spal one without having to modify the latch support.

I'm guessing you don't have enough air transfer THROUGH the coreS.

 

[MrFlash]

Is there any truth to Badass Racing statement that 1969 & newer vehicles do not run as hot as earlier cars? If so, what is different in the cooling systems between the 2 eras?

69-70 have the water pump inlet on the drivers side. Thus the bottom radiator outlet is on the drivers side.
The top radiator inlet is still on the passenger side.

Most modern radiators are cross-flow. Where coolant flows side to side rather than top to bottom.
But that’s not really applicable to early mustangs.

 

[Palo Alto Car Guy]

I have a 65 A code fastback with AC (stock with fan shroud). After several years I began having overheating issues. Switched to an aluminum radiator from ECP (http://www.speedcooling.com/1964-1966-Mustang-Aluminum-Radiator-For-289-V8.html) and the car runs super cool. I replaced the radiator on my 65 C-code convertible as well with great results. I chose this radiator because I couldn’t find a brass one, the price was good <$200, and it looks really well made. No, I don’t work for ECP but it’s nice when a product works as advertised. Totally satisfied. Good luck.

 

[Spedy7]

I'm guessing you don't have enough air transfer THROUGH the coreS.

My thought exactly. Even on my dad's '66 Sprint 200, it runs hot and it has a stock motor with my old flex fan. I did notice that with the electric fan I had on before the a/c would stay consistently cold, especially once the temp switch grounded and would have the fan run constantly. I think it was running ~210 or 220 though, but I feel like more than 210 is too hot for a carbureted motor.

If I had another inch of space between the radiator and pump, I could fit a better puller fan, but I haven't seen anyone solve that issue besides a 2 core radiator (or I'm not searching enough?).

:shrug:

 

[1ofAMillion+]

Wish I had a '67 or '68 now :|.

You can have a piece of one. https://forums.vintage-mustang.com/...tage-mustang-forum/1134489-cooling-issue-throwing-kitchen-sink.html#post9917353
Like President Pence, you know its needed, sooner than later the better, put it behind you and move on.

 

[LSG]

cooling

Spedy, I don't think you have a problem.

Flash, you and BadAss are mistaken, the 69 302 and 351W have the rad hoses both on the right hand side. LSG

 

[Spedy7]

Well, today isn't a 110* day, but pulled the clutch fan off and put my electric fan back on as well as going to a roughly 80/20 mix with water wetter. Everything was working fine until my Edelbrock pusher pump died , had to warranty that. Didn't get past 3/4 of the gauge though, added the high idle solenoid I had and it all works better than before...for now anyway. I think I will just move up to a 24" radiator next year with duals to cut headaches.

Just another question though, can a 289 shroud work on a 200 car? I'm certain my dad would like to put it on his as well as my "old" fan+clutch.

 

[LSG]

wrong approach

Spdey, going to the larger rad will help, but you should use a mechanical clutch fan and a shroud. That'll move alot more air than wimpy electrics. LSG

 

[ripped]

There is a lot of good advise in the posts before me. I was the victim of probably everything that can go wrong, before I sorted out my cooling system issues. I'd say get a hold of a pressure tester that will do both your system and rad cap. That was very valuable to me is helping finalize my issues

Electric fans are nice, but you are dealing with apples and oranges. Modern cars run a much higher pressure cooling system. And if you want to try it, great, but then you are putting more stress on rad hoses and heater cores that were not designed for that.

So here are some tips;
Test the thermostat in boiling water. (I bought a name brand high-performance one - out of the box new it failed this test)
Drill a 1/8" bleeder hole in the top of your thermostat flange. This will ensure there are no air pockets in the system, should you have a system that overflows a lot and doesn't siphon everything back.

Get a clutch fan or similar and shroud. Overheating badly can damage your engine severely, and the teeny horsepower gains of an electric don't balance out in the long run.
Test the clutch portion - yep mine failed

Once the system from rad through heater core is verified, pressure test it.

Pressure test that rad caps (I had two fail)
Check the seals
Get a good catch can/overflow and check it to see that it's working both in overflow, and that overnight it takes the excess coolant back into the rad

Start with the engine stone cold. With the rad cap off, wait until the thermostat kicks in and look for really good coolant flow across the radiator (through the hole) - PLEASE don't do this with the engine hot

If you are making a lot of HP or have a big overbore, step up in rad size.

If you want extra cooling, then you can add an electric pusher fan or fans. I have 2 and they regularly kick in via a thermostat, in stop and go traffic in the summer. It does give you peace of mind

My 2 cents