Helping a friend on his Mustang this weekend. The car overheats at expressway speeds, but around town it is running cool. 67 Mustang with 289, auto. It has a flex fan. A racer friend said to change to stock fan blade. Anyone have one? I know taht this belongs in the classifieds, but need is immediate. Will post there. OR some ideas?
kind of sounds like the water is flowing too freely. I think I would start with a new thermostat to see if you can keep the water in the radiator a little longer
Fan makes little difference at hiway speeds. 3 possiable problems 1 no thermostat,2 iginion timing not advancing, 3 partially plugged radiator core either inside or outside.
The Thermstate is new--yes--I know new parts can be bad--just replaced a new Napa condensor that was keeping us from getting the car to start!! We are going to go with the bottom hose and install a new Flex hose as the are built with a spring. Then flush the cooling system and do a test drive. --details on flushing--- We are going to do a flush to the cooling system as this was a Navada Car and offen ran just water. I'm going to do the old Arm and hammer Backingsoda Detergent boaster and distilled water treatment. It works great--add all new distlled water with 1/2 of the box and run around town for a week. Then drain--the water will comeout looking dark red(brick red)! Repeat for second week and drain. Depending on color of second drain it may take 3 tratments to get all the rust and crap out of the system. If it still overheats at highway speed we will replace the flexfan with a stock Ford fan and see what happens. I'll keep everyone up to speed. Thanks for the feed back! Still looking for a stock 289/302-non AC fan!! Dutch
If putting all the right equipment back on it doesn't get it done- he may have a cracked head- i had one that ran great till i hit the hiway, and she'd go Chernobyl on me- exhaust seat had a crack that wouldn't expose in town. The car does have a hood on it, right? -rick
I had the same problem with my Comet, stock 289, flex fan W/no shroud. I flushed the cooling system with oxalic acid (wood bleach) replaced the clogged radiator and added a coolant filter. It now runs 180 all day long.
I agree with the above-"DUMP THE FLEX FAN"-It's blocking air at hiway speeds. Its a EZ fix to remove the radiator and have it flushed rather than go to several weeks of flushing. You can plug the botton hose and install block flush and let it set while the radiator is being flushed. Use the garden hose to clean the block/heads ect. Seems a better way to fix a cooling problem-just my thoughts and 2cents worth.
A 99¢ gasket and 3¢ worth of gasket sealer could be the answer, I've seen it happen more than once and goes with it overheating at highway speeds. Other than that, I'm with the stock fan and a possible collapsed radiator hose. Bob
When a car over heats at speed it's almost always a partially clogged radiator reducing the efficiency. Fans are only affective at idle. You can spend a lot of money on fans, shrouds, T stats and other wild goose chases. Get the radiator flushed or rodded out. I had it happen to me. Around town at low speeds when the engine is not working hard everything is fine...out on the interstate under a load it starts to heat up due to the lost capacity. It's a 67 Mustang not a chopped and channeled large V8 hotrod.
I'm with Mr Evans, radiator plugged possibly. My wife had a 93 Grand AM, drove me nuts, tried everything. Around town, ran ok, as soon as you hit the hi-way, up the temp went. Radiator was new looking up top, but plugged at the bottom. I tried thermostats, waterpump ect... like I say, radiator was nice and clean in the top so I figured bottom was clean also. WRONG. Make sure you have a spring in that bottom hose also. Lippy
All true and quite possible, no telling what was dumped into the cooling system over the years. Leak stop, old coolant not being changed can gum up a radiator. Bob
I had the same problem. A bit hot in town, and worse on the highway. After much screwing around, I tested the thermostat found it was not opening all the way, although at the correct temp. So at highway speeds more heat built up and couldn't get out. A new thermostat is cheap.
A friend of mine built a '65 Mustang to race in the Targa Newfoundland road race a few years ago. He had this exact same problem. First thing they did was replace the t-stat. Didn't solve the problem, so they went down the list, repairing and replacing, then came back to the t-stat. They even pulled the engine and had Holman-Moody take another look at it (HM built the motor). Replaced the fan, replaced the radiator. They ended up replacing the thermostat FOUR times... When the put in the 5th one, everything was perfect and they went racing. I just had a thermostat go bad on my Suburban: I ran the engine lean for 290 miles (the whole way home from a trip--the fuel pump died, so I just zip-tied the choke closed and drove home, pulling fuel through the vacuum secondaries). When i replaced the fuel pump, the engine still ran hot. The spring in the t-stat took a set and was malfunctioning. I replaced the t-stat, and it's right back down where it's supposed to be. -Brad
Had a thermostat go bad in my ranger pickup--last winter--so I had one of the local Napa shop I go to, do it (as the street rod was in the way of getting in and I wasn't working on it in 20degree weather outside). They didn't let the rtv setup and when they put it back together the thermostat slipped and was cocked in the housing. Worked for a while then the stat went out and blew the gasket out--lost most of the coolant in the engine. Got it fixed the next day-but missed work as I was in Wis. and had my Boss at NAPA wright me up for not getting to work. Even thougt it was the repairshops falt! Now he's my X Boss and I'm so glade. Been in parts for a long time--and new out of the box goes bad all the time. Doen't matter any more if it's AutoZone,Pep boys, checker, Or Napa they are all building parts cheaper and we pay for it in poor parts! Thanks for all the feedback. The thermestat is working fine on this as it opened up after we did the flush and added the water. We'll run it around town with the Arm and Hamer baking soda detergent booster and distilled water for the rest of the week and then drain it. It should come out nice and red as it will eat away at all the rust that's clogging the system. I am doing it this way as 1) it's cheap 2) I have done it in the past on cars that ran only water and it works 3) It's easy to do and it doesn't heart the hoses or seals! Sometimes it takes a couple of flushes to get it supper clean--but it's worth it. We'll probley replace the fan with a stock one just to make sure--but after seeing what came out when we flushed it--I'm leaning toward a cloged rad. core! Dutch
First we need to catagorize the overheating. If it occurs at stop lights it is fan and often idle, pump speed related. One of the best solutions is to speed up the fan with the pulleys. ie Smaller pump pulley or bigger engine pulley. Even a change of a 150 RPM which does not take much pulley change can make a huge difference. HOWEVER at highay speeds the fan has nothing whatsoever to do with anything. You must keep this in mind when diagnosing overheating problems. Sometimes the rad has insufficinet flow or is becomng blocked. A rad shop can do a flow test for you. Sometimes you do not have sufficient system pressure . Raising the pressure 1 lb raises the boiling point by 3 degrees F. Anything you can do to eliminate the formation of steam or steam pockets will go a long long way to eliminating heating problems. Older cars will run with a 4 lb cap. I mean OLDER real old. 60s cars run with a 7 lb cap or a 13 lb cap. Some new car like a car i just traded in run with a 26 lb cap. When i get a car with a overheating problem and by car i mean hot rod or racecar I check first of the system will hold pressure usinga stantrad pressure tester. If that is good I use the adapter to test the pressure cap. I run as much pressure as I believe the system will stand comfortably. Now for a real life example. My friend Mike had trouble with his 41 Willys. It has a warmed over 331 Hemi in the 300 range for HP. It has a 47 Plymouyh rad. It would stay cool at idle and in short trips running betwen 150 and 180F but if pushed hard above 70 mph or stouck in taffic for a while in 90F weather it would push towards 210. That is too hot in my books for that engine . it would also puke when shut off afterwards. Mike was about to spend $800 for a special rad. I went down with my stant tester and persuaded him to let me test. Rad would hold about 1/2 pound pressure as the pressure relief on it would not hold. This cap would hold nothing. While listening to the constant banter of all "the experts" (Folks who dont understand what they "know" so to speak) I persuaded Mike to seal off temporarily the tube from the relief valve. Using some rubber adapters in my pressure kit i adpated a 13 lb cap i had brought with me to the 47 plymouth rad. I told Mike to drive the long way to my place and i would meet him there. Normally this would have produced rad puke and 200+ temps. He drove in quite awhile later and hollered "I cant get it over 160. An hour later he was still driving it around and waved going by. Mike a talented old school plumber immediately made the changes to his rad needed sealing of the relief , repairing on small (tiny) leak and replacing the old 47 rad neck with one from a 70s chev truck rad he and in the back yard. He bought a 7 lb cap i believe. That was now over 8 weeks ago . He drives it everyday unless it rains and has even had it to the dragstrip. Not even a hint of trouble. overheating problems are not magic. You need to sit down and understand how the system works. Steam pockets can form under hard use if the system has insufficient pressure. Or if the rad is too small for the HP. Remember the fan is not used at highways speeds. Even at 30 mph it is not functional. Sometimes in a high outpt engine the thermostat can become an obstacle. Switching to a restrictor will often help as well. A restrictor can quickly be made by removing the centre from a thermostat and reinstalling it to see what happens. I hope this helps you sort through the problem. Skip no steps is the trick and understand how your system really works which is a far cry often from how the cruise night "experts" think it works. Don
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