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Dreaded over heating topic again...I know guys sorry

23K views 159 replies 49 participants last post by  PA_cob 
#1 ·
I hate to bring this back up but it seems like no matter what I do eventually it comes back around. I recently installed AC on my 65 coupe with a stock 289 in it. I have been monitoring temps while driving. Today it was 90 degrees here in San Antonio. Driving temps on the highway were about 200-205. But when I stop and idle they will creep up. No AC running temp at idle hits 220-225 and hangs there but turn the AC on and it starts climbing. I let it cross 235 today and it showed no sign of stopping, turned off AC and it slowly went back to 225. I am running:

195 degree thermostat
fan shroud
17 inch clutch fan
thermal clutch
flowtek high flow pump
aluminum 2 core radiator
Engine is timed at 18 intial with 38 total
600 cfm holley
Weiand Street Warrior intake
Stock cam
Stock heads
Coolant is 60/40 water/antifreeze mix
Water wetter added

Engine has been flushed several times with citric acid and thermocure. I really can't think of anything else to help short of installing a auxiliary electric pusher fan or going to an all electric set up. When I high idle about 1500 rpm temps will come down some with AC on. Temps don't shoot right to 235 but if I idle for like 5-10 minutes they will get there. If anyone else has and idea I would love to hear it but otherwise my next step will be trying electric fan. It's just going to get hotter here in San Antonio..
 
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#2 ·
Im not a fan of high flow pumps. My 65 with a 289 and AC has a stock radiator and 5 blade fan with a 180 thermostat. So far so good, but 81-82 is the highest we have had here this summer.
 
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#5 ·
Is your 65 an early aluminum pump without the backing plate? That is a high flow pump straight from the factory. Also are you running AC. The addition of the AC condenser has upped my temperatures even when the AC is not on. I am guessing due to the fact that it's harder to pull air through the condenser and the radiator.
 
#23 ·
Try switching to manifold vacuum. My '68 has the thermal switch ("distributor vacuum control valve") that changes the vacuum advance from ported to manifold above a certain temperature. This advances the ignition timing at idle which does two things. First it increases the idle speed to increase the water flow rate. Second, the earlier ignition results in better combustion. Remember, the ported vacuum set up was done for emissions with the later timing sending hot but un-burned gas into the manifold where it was greeted with additional air from the smog pump for complete combustion.

The biggest change I've ever seen in any vehicle was a larger radiator. The 67-68 radiators are wider and that might be your eventual solution.
 
#6 ·
Ditch the mechanical fan for a nice electric with thermostatic switch (make sure to upgrade your alternator to 3G to compensate) and I’m a little suspect that your thermostat is opening. For the cheap cost of a new thermostat you can have peace of mind.

/thread haha
 
#7 · (Edited)
@Acooljt this is a brand new thermostat. Just replaced it like less than two weeks ago. Everything to do with cooling this engine is 6 months or less old. If the thermostat wasn't opening I would over heat no matter if I was running down the highway or idling. I am running the 195 because that is the recommendation of some very smart people on this forum. It's the OEM installed temp. I have considered changing to the 180 but really don't see how it can help..yeah it will open sooner. But once open will not flow anymore than the 195 so eventually the temp will go up. BTW, already running a 3g alternator. So if I do go with electric fan I should be good to go.
 
#8 ·
Ive been through almost all that, elec fan with an original engine. Every single thing helped a little bit but it would eventually reach overload and runaway in temps ~90*, ie. half the year.

Adding a generic '67 size 3 row radiator solved it overwhelmingly and I have a feeling it would have if it was done 1st.
 
#9 ·
I've got everything in place, just have not installed the A/C lines yet. Sanden compressor, factory condenser, aluminum water pump, original 5 blade flex fan w/o clutch (factory set up), factory style shroud. Aluminum 24" 3 row radiator. 180 thermostat. Evans Waterless coolant. Auto trans using the cooler built into the radiator. I've let it sit and idle at the house (not in traffic) and it will get up to around 219 max. I'm sure it will go up once I get the A/C lines installed and the system charged up and running, which should happen by next month. Its been in the upper 80's here lately and that is going to do nothing but go up in the next couple of months.
 
#14 ·
How do you know the temps you are quoting are accurate?

Your symptoms sound like you need more air flow at idle. Do you know the thermal fan clutch is working?

The only vehicle I have ever had that used a thermal clutch was an 84 F250. One time I was driving across Arizona in July. Temps were triple digits. I slowed down for a freeway clover leaf. All of a sudden there was a Cessna on a takeoff run under my hood. It was a sound I had never heard before. About 3 or 4 minutes after I was back up to highway speed the sound suddenly died away. I finally realized the fan clutch had gotten hot enough to lock up and it was moving serious amounts of air.
 
#15 ·
I have an aftermarket mechanical guage installed on the car. And I have used laser temp gun to verify temps on the car. The fan clutch is only 6 months old. When I spin it by hand when the car is off it spins one to two times and stops. It's moving air at idle just not enough. I do notice that it seams to spin the same wether it's hot or cold so maybe it's not working correctly.
 
#16 ·
What is a Flotek high flow pump? Assume you mean FloKooler water pump.
Don't care for those personally. A cast iron factory pump and factory (closed)
impeller would have been just fine.... But that's not your actually problem.
You answered your own question actually- you're probably not getting enough
air flow through the radiator core and condenser core. (I don't care for aluminum
radiators either, BTW. Too much other stuff has to be changed for them to work
correctly. And yes I have been there..... with a $700 custom Fluidyne no less)

Air flow. Probably a puller arrangement if you can fit one. That should do it.
 
#17 ·
@GT289 yes I meant Flokooler sorry I was writing off the top of my head and confused the name. And there is no cast iron pump for my engine. It's an early 65 289. It came from the factory with the aluminum pump, no back plate. It's the same pump used on the 289 HiPo clear into 67. That pump had a cast impeller with 6 vanes. I had a parts store pump on it with a stamped star shaped impeller. The Flokooler is real similar to the original. (Which I no longer have). My parts store pump literally came apart on me two weeks ago. So I replaced it with the flokooler. Just curious by what you mean has to be changed to make an aluminum radiator work. I had a three row copper radiator on it until about 6 months ago, and it never cooled. I have seen cooler temps since adding it. Just with the AC added it doesn't seem to be enough.
 
#37 · (Edited)
It's your air flow through the core(s) that is the issue. (two of them, since you have a condenser)

I've told this story before about my experience with a pricey aluminum radiator.... only thing replaced, when my 4-row copper brass bit the dust.
For me aluminum was a complete joke. Took awhile to heat up and then the engine temps stayed up, way up. And back in the pits, the temps didn't
come back down. I don't like to see any temp gauges nearly pegged all the way on "H" when I'm on the track. I got home from the track, removed
that POS, sourced a copper/brass 4 row and magically my temps went right back down to where they normally were. No changes other than a radiator.....
Fortunately I was able to get someone to take the aluminum off my hands- he seemed overjoyed to get it actually, because the rumor is aluminum
radiators magically cool better. Total BS.

If I had to guess (not being a thermal engineer) my thinking is that aluminum doesn't dissipate & absorb heat
at the same rate as copper or brass (which I know is factual) and MIGHT have different airflow requirements
across the core. There are some differences in the various year Mustangs as far as what size radiator you can
fit- therefore differences in air flow through that area.
 
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#19 · (Edited)
When I spin my clutch fan by hand it doesn't make 1 full turn. I got a 6 blade mechanical fan to go with it too. It moves some air. It might turn a couple of fan blades is all. I am by no means a clutch fan expert but I would suspect that if you can spin the clutch fan around 2 turns by hand that the clutch has seen better days or it was BOTB.
 
#21 ·
I am cranking on the fan pretty hard. It spins one turn. Starts the second and stops. If anything the clutch is locked open as it's spins fast from cold to hot. I never can see or hear a difference..but it is moving lots of air. I may get a new one just in case.
 
#24 ·
Without a shroud that actually forces air to come through the fan and radiator, you might as well be putting pinwheels on your bumper to cool things, especially when the A/C is on.

If it doesn't overheat when moving, but it does when sitting still, I think you have your answer.

If it overheats while moving, then your issue is likely something to do with timing, or possibly a vacuum leak. 18 degrees initial does sound a little high!
 
#25 ·
I am running on the 10L side of the reluctor arm of the distributor. So I am already at 18 BTDC. If I go to the manifold vacuum I am concerned that I would run to much advance at idle. But I may switch it over and see what happens. I am probably going to get a new clutch and see if that makes a difference. I have seen people talk about an HD clutch vs a standard duty but can't seem to locate one online that is for my application. If anyone has that info I would appreciate it.
 
#28 ·
Sorry, PA - I should've been more clear. Not all shrouds are created equal. The early pre '67 Mustang shrouds with a big gap there at the radiator, that look like a little steel strip held on with some brackets? It's a 'shroud', but it's not a SHROUD.

I saw that you mentioned you're running one, but I don't know what you have! Maybe it *IS* a good shroud, but if it's not, this could definitely be a culprit. Being able to suck air from the hot engine side of things means your fan might just be thrashing hot air around, without forcing it through the air conditioning coils and radiator.

It's important to have one that makes a good seal with the radiator, and forces circulation.

Hope this helps!
 
#29 ·
No worries. I am not running an early shroud. I am actually running one that I fabricated myself. No gaps but it is probably a little wide as it covers most of the fan. That being said by installing the shroud I noticed a decrease in temperatures then before I was running it. So it is working. I actually took the advice of a couple of others in here and moved to manifold vacuum. It bumped my idle up as well as smoothed it out a little. No AC temps are stable at about 210. With AC on it stayed at 225 for about 20 minutes. Of course it was only 87 today. It's going to get warmer and I still think I need to move more air and when I can will get a new clutch for the fan, and if that doesn't work I may install a pusher from the front to supplement.
 
#30 ·
Fan shroud should only cover 1/2 of fan blades. Maybe you should step up to 24 inch radiator and mod the core support, but as a last resort. What you have should cool it. When we hit 102-105* this summer you will need to do something to keep daily driving it. The Taurus electric fan fits a 20 inch radiator perfectly. Might have to hit one of the junkyards on the south side.
 
#31 · (Edited)
I am not a fan of electric fans, but the Taurus fan/shroud moves some air. More than most aftermarket. I had clearance issues trying to install on my son’s 68 with 200/6. It would have been overkill in that application. Not sure if your 65 will have the same clearance issues. I did have one laying around, but loaned it to a friend for his model A. He has not used it yet. It’s been 2 years.
 
#32 ·
@coupster stepping up to a bigger radiator is definitely a last resort. I would have to change mounts for the condenser and everything. I am going to trim the shroud when I pull the fan for a new clutch. I think a Pusher fan on the front pushing like an additional 1000-1200 cfm should be enough.
 
#33 ·
Alrighty then...

1. I doubt whether you have the "hot idle compensator" that was originally installed on A/C-equipped cars to increase the curb idle at high ambient temperatures so you are probably suffering from a lack of airflow and coolant flow at idle.

2. Using ported vacuum for a spark advance signal you're not adding any spark advance at idle so the lean fuel mixture (closed throttles) is still burning when the exhaust valve opens, wasting heat that could have been converted to linear motion. The use of ported vacuum or "timed spark" was a method of increasing exhaust gas temperatures to lower hydrocarbon emissions.

So, either swap your vacuum advance over to full manifold vacuum or add a thermostat housing with a bung and add a DVCV (distributor vacuum control valve) to modulate the vacuum advance signal based on coolant temperature (IMHO that only complicates things so....). Run as much initial spark advance as the engine will tolerate. Make sure your distributor advance curves (centrifugal and vacuum) are correct (I recommend Dan Nolan at The Mustang Barn for a recurve). This should improve your engine cooling by reducing the heat load that must be handled by the radiator.

With regard to the hot idle compensator there are really only a couple options. While the HIC for the Autolite 4100 is readily available and inexpensive, the one used on 2V and factory Holley applications is rare and, when available, wicked expensive. The option is to use a DVCV as a HIC by plumbing it into the cooling system somehow. This can be done by drilling/tapping the intake manifold, the heater outlet fitting in the intake manifold (won't work on later models using a heater control valve), using an adaptor in the upper radiator hose, adding a bung too the radiator upper tank or using a thermostat housing with a bung. Instead of plumbing the DVCV to modulate the vacuum advance signal, it is used to vent vacuum from a full manifold vacuum source to the atmosphere when the coolant gets very hot. This can be done using either a 2-port or 3-port DVCV and an aquarium air line filter.
 
#34 ·
Ok, I would go for two things:
1) New radiator cap.
2) Back timing down to 15-16*. 18* is really high for a stock cam, 14 is more the norm on today's pump gas but you probably wouldn't get enough total timing if you set it for that.

It is surprising how frequently bad radiator caps are overlooked. I know because I overlooked my bad radiator cap for like a year once. I had the same symptoms - temps would slowly creep up at idle, but once under way the car was totally fine. I flushed the radiator, put on a new rebuilt HiPo pump, screwed around with timing, and got no improvement. Then I found another cap laying around in my parts bin, put it on the car, and lo and behold... rock steady at 195* now, all the time. With AC on she'll hit 202* in traffic in the summer. I felt really dumb after that one.

FWIW, my 289 is bored 0.040" over and has a pretty rowdy cam. I am running a nearly-stock cooling system - 195*F thermostat, stock shroud, stock fan clutch+fan, stock HiPo water pump. The only aftermarket part is my radiator, which is a 2-row aluminum that is the same thickness as the old radiator. Only reason I've got an aluminum radiator in my car is because it was on sale when I blew the stock 3-row brass radiator full of rust (put it on someone else's car, their motor was full of rust). It ran fine with the brass radiator, and it runs fine with the aluminum radiator. Never runs hot, even in the worst of Texas temps.
 
#35 ·
Most everything I would advise has been covered, manifold vac. advance, hot idle compensator (by the way, if you keep an eye on eBay, you can score one of these for reasonable money sometimes, and I actually have a few in surplus, because they are hard to get when you need one), Thermocure, etc.

I know the general sentiment is that thermostats cannot fix an overheating problem, and I took that fact for granted as well. I was reading somewhere a comment about using a high-flow thermostat (one with three crossbars on the front instead of two). I really wasn’t familiar with those, and figured all thermostats were the same other than temp ratings and quality of manufacture. The person was insistent that these was the only way to fly, and made a huge difference. I was building an engine at the time and needed to replace my intake manifold gaskets on another car, so I figured I’d just try a couple of these for the heck of it. My car with the manifold gasket leak had always run on the verge of hot. In the summer, the stock temp gauge would creep up to the P in TEMP more frequently than I liked. In IR thermometer said I was about 212-220* at my upper radiator hose. (By the way, this is a concours, low-miles C-code 66 coupe, automatic, no A/C, had Ford 195* factory thermostat).

I used the Mr. Gasket 4364 180* High Performance Thermostat:

https://www.amazon.com/dp/B000BWAPA2/ref=cm_sw_r_cp_api_i_sCdXCbVF1G9NT

Keep in mind that this was the only variable I changed. For the first time ever, my car runs very cool, arguably too much so. The gauge never even reaches the half-way mark, and generally hangs out between T and E of TEMP. I estimate this has reduced my engine temps by at least 15*, maybe 20*, and I’d have never thought it could.

I thought about all the overheating threads that come up in the forum and I believe that this should at least be included in one’s quest to cool things down. If it works like it did for me, it really has to help.
 
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