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1965 Mustang overheating

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New User

Sep 10, 2018, 10:33 PM

Post #1 of 7 (668 views)
1965 Mustang overheating Sign In

Here's the car basics:
- 1965 Mustang
- The car was originally built for a 200 but had a 289 dropped in before I got it
- It will run fine, but if it gets to stop and go traffic, or just sits at a light, it will get hot quick.

I'm thinking to get the cooling system flushed, but I don't know that's going to fix it. What would be the next step? New aluminum radiator or an electric fan or both? Any other ideas ?

Thanks in advance for any help you might be able to give.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 11, 2018, 4:06 AM

Post #2 of 7 (659 views)
Re: 1965 Mustang overheating Sign In

? Tcop: There isn't much that more straight forward than how to diagnose this not sure why you are having a problem. Proper size radiator for a 289 should have one made for A/C whether it has it or not just because IMO. Thermostat right up front and top hose just feel it stay cold and slowly go warm to hot from a cold start.

These are not hard to bleed air out of the systems if you have a fan at all most were non A/C just 4 bladed fixed to water pump wasn't an issue.
It's totally antique now should be no reason to not have new water pump, thermostat, hoses and proper coolant mix. Only thing is if the water pump or engine is somehow shot already or thermostat just a maybe fit in backwards is the problem. Tolerant engine and layout this really should be basic if you want to own stuff like this plus ever last screw on these is available in no time they'll never quit,


Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 11, 2018, 9:19 AM

Post #3 of 7 (652 views)
Re: 1965 Mustang overheating Sign In

If it is running hot only at stops, you probably have issues with not enough air behind drawn through the radiator for some reason. Do you have a picture of the cooling fan set up on this?

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

New User

Sep 11, 2018, 10:15 AM

Post #4 of 7 (644 views)
Re: 1965 Mustang overheating Sign In

I had this car back in my early 20s... sadly, that's about 25+ years ago. The car went to a family friend and is now coming back. I'm not sure all the upgrades they did, but it had the same issues I had back when I had it. It might be worse now -- i'll know when I actually get the car.

Back when I had it, I did my very amateur job of trying to flush the cooling system and I put in a new bigger radiator. I don't remember that it helped all that much. But, like I mentioned, it was 25+ years ago.

And to clarify, it doesn't get hot if you are driving on the freeway at speed, it was only when you got to a situation where you were at a stop or going really slow.

I don't have a good picture to show yet for what's actually there right now, but I can probably get one in a day or so if you thought that would really help.

New User

Sep 15, 2018, 12:02 PM

Post #5 of 7 (597 views)
Re: 1965 Mustang overheating Sign In

In Reply To
If it is running hot only at stops, you probably have issues with not enough air behind drawn through the radiator for some reason. Do you have a picture of the cooling fan set up on this?

I think this is the best that I have..

New User

Sep 15, 2018, 12:15 PM

Post #6 of 7 (593 views)
Re: 1965 Mustang overheating Sign In

I always thought it should be straightforward too; however, it's been problematic since I got it and has continued with the current owner who had much more money to throw at it than I did back in the day.

As far as I recall, the following has been done:
- bought a new bigger radiator (back in 1986?)
- got a new fan (the flex fan that's on there is new since I had it)
- changed the thermostat
- done a piss poor coolant flush

Stuff I don't know if it were done or not would include:
- change the water pump. I'd say there is a 25% chance this was done, but I just can't recall either way.

After that, I don't know what else I could do that's specific to the cooling system.

I'm likely to replace the current radiator and replace with an aluminum one with an electric fan. I'm hoping that should do the trick.

But, other stuff I will be doing as soon as I get it:
- A major tune up
- A proper cooling system flush

I'm sure the car needs both.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 15, 2018, 1:01 PM

Post #7 of 7 (589 views)
Re: 1965 Mustang overheating Sign In

That fan was used in the 70s for assorted Fords was great IMO but quit only because a couple threw off the fiberglass hurt one person ends those.
Looks like a newer water pump another time at least clear coat it or Ford Blue.

Shroud looks good now from cold feel that top hose the engine end is the thermostat. It will stay cold until it reaches temp rating of the thermostat and open a little to a lot but not an open hole. It needs a thermostat.
If that isn't doing that or feels warm BEFORE it's warm enough (will or should be too hot to hold so careful) that has to go.

Flush: If unknown just do it. Suggest taking out lower side bolts around or below people call "freeze plugs" I think a 9/16th bolt/plug make sure. No water will come out if not done it's full of junk will clear out with stiff plastic or carefully with a coat hanger type wire for flushing yuk, rust or junk will pack in the bottom should NOT want that. Lots of decent techs wouldn't go that far for you have a problem do that! Refresh > LOOK for those they are there for flushing out water jackets fully!

Back, I'm out of order: As it warms up and feel upper hose hot enough should feel just warm air blowing backwards. Careful now the lower hose should be easy to tell it's cooler than the upper if not it isn't flowing enough these water pumps if anyone ran it with just water could rust out the fins the pushes coolant around. You do want 50/50 only carefully less % for other reasons not too much antifreeze is a TERRRIBE product for heat exchanging always mixed - know that.
That straight forward also know it stays full of coolant. Turn heater on lowest both hoses pretty warm to the touch.

Start somewhere don't let it be getting hot any more than for testing. It can but isn't known as a head gasket eating engine even better if done already is better than the ones that came with it new.

You should be able to do that much without much for tools if not sure of yourself there's always dangers in working on an engine test and feeling as I suggested if not sure default is don't. Your hands are more important than the engine!

(edit) See if the blades of that fan are pushing air towards the engine? IDK it's wildly unlikely but if backwards it was meant for another vehicle used same pattern into the later call 302 and 5.0 engines some truck were counter rotating would be opposite/wrong for this car if so...…..
(edit 2) OMG fixed lots of my own typos! Sorry - re-read pls...…

(This post was edited by Tom Greenleaf on Sep 16, 2018, 1:09 AM)

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