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Go Back   ClassicBroncos.com Forums > 66-77 Ford Bronco > Bronco FAQ > Engine FAQ's

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Bronco Overheating Bronco Overheating
Some common reasons for your engine to run hot
As with a lot of older vehicles, the Bronco cooling system is prone to overheating, if not properly kept up. Some of the sources of overheating are listed below:

Not enough coolant in the radiator. You should check the coolant level every 200-300 miles or so. If you have the coolant recovery reservoir, mounted on the passenger side front wheel tub, you can judge the level from the markings. If its below the low mark, check the radiator after its fully cooled. It should be 3/4 to 1 inches below the radiator neck and add coolant to bring the level up. If the level is really low, then there may be leaks in the system.

Where to check for leaks: radiator hoses, heater hoses, hose clamps, bypass hose, heater core, thermostat housing, water pump, freeze plugs and the radiator. It also wouldnt hurt, if you do have a leak, check your engine oil to insure its not watery, which would give you an indication of a blown head gasket at the minimum to a cracked head or cracked block.

Another cause for overheating which Ive had happen to me before, the fan belt not being adjusted properly or the belt is bad.

If the radiator is blocked (dirt, mud, (Nebraska)bugs), this can lead to overheating. The radiator should be hosed off every so often.

If youve been working on the engine, incorrect timing could be a issue, causing overheating.

Another source of overheating is a bad thermostat. To test it you can pull the thermostat out and heat it in a pan of water and if it opens its good, if it doesnt open all the way or not at all it should be replaced.

Damaged fan blades can cause overheating. Depending on how your bronco is set up, running just an electric fan, may not be enough to keep your bronco from overheating. Running without a fan shroud is a biggie also.

Sometimes its the radiator cap that goes bad, I've dealt with this, you can have the coolant system pressure tested, but sometimes that's a hassle, I've just replaced the cap before and that has been all it took to cure the problem.

Insuring that your C-4 (or other auto transmissions) has plenty of tranny fluid and that the lines aren't leaking, could also be a preventive measure to insure that you avoid overheating.

Putting in a beefer engine (hi-po) can be a cause for overheating, if running the stock radiator.

Any one of the above could cause overheating and driving your bronco hot for any period of time could cause severe damage. Checking hoses, water pump, hose clamps, coolant levels (and getting that faulty gauge fixed), could prevent blowing a had gasket, cracking a head or the block.

For this article I browsed the 66-77 Chilton's and my own personal experience. While not all inclusive and detailed, this should give an idea of what is some possible problems and some solutions.  

Last edited by admin; 07/30/06 at 12:43 AM..
tomcleveland on 05/04/07, 05:47 PM
I have found that the oil runs extremely hot at highway speeds and low trail speeds. I ran a 302 and the oil temp was tha cause of the overheating. The oil temp would climb to over 250 degrees cruising or trailing riding. I have had the oil temp to 280 degrees. I now have a 1973 Ford 400 in the bronco and the oil temp does the same thing. I believe that the oil temp is the cause of the overheating problems with the Broncos. I will be getting a cooler.
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ransil on 05/20/07, 06:27 AM
Running lean and too much timing can cause overheating too.
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jake633 on 11/08/07, 01:56 PM
i have a 1976 with 302 runs hot at low speed however increase rpm and it cools down it has ac but even with it off does same thing new water pump and therostat maybe i need a better raditor or and electric fan????????
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bronko69er on 11/08/07, 02:22 PM
Originally Posted by jake633 View Post
i have a 1976 with 302 runs hot at low speed however increase rpm and it cools down it has ac but even with it off does same thing new water pump and therostat maybe i need a better raditor or and electric fan????????
or a smaller WP pulley
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skid on 12/20/07, 08:30 PM
I recently had a problem with the 302 in my 1972 Bronco overheating at idle after it had not been started for several months. (water was circulating in the radiator) I first thought it was the thermostat, but the problem continued even with the stat removed.

It turned out to be sludge in the ports of the aluminum adapter to the water pump. It was apparently caused by electrolysis.
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jake633 on 01/07/08, 04:06 PM
I still am not sure how to fix the heating at low RPM I can go with a better raditaror but would like to know if it will work first (not trying to save money) wildhorse has one three pass I am looking at plus a tranmisson cooler I understand this a common problem so I was looking for someone with the same problem THANKS
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brad4043 on 04/25/08, 06:29 PM
I just bought a 72 Bronco that overheated badly on the 5 mile drive home. Is a 16" puller cool a 351c good enough for that size of engine or is sometihg else necessary?

Last edited by brad4043; 06/24/08 at 05:30 PM..
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hodge's 69 on 06/17/09, 05:07 PM
I just put on a 4 barrel carb w/intake that I know is out of adjustment(will be adjusted on friday) and my bronco was over heating with a thermostat, I removed the thermostat and my bronco still runs at around 190f. To me 190w/o a thermostat is funning hot. Is it possible the the carb being out of tune would cause it to run hott?
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ljktup on 08/22/09, 10:34 PM
I just rebuilt my 302 in my 70 bronco with new intake and 4 barrel carb headers ect.... mine was running hot at 190 to 220 depending on the driving i was doing... very uncomfortable feeling. I do agree with you guy's that the timing and Idle mixture can cause overheating with a whole realm of other things. I spoke with Chuck at BC Bronco's and told him my problem..Chuck said that Ford ran the Harmonic balancer and the water pump pully the same size (6")....basically 1 to 1 ratio. So i ordered a new water pump pully 5 3/8 On normal driving I cant break 170 degrees on a hot day now when it's a stop and go situation (traffic) it climbs to 190 but cools right down once i start moving. I can't believe how simple of a problem i had....I'm thinking Bigger radiator, electric fan....simple fix.
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bingen on 03/14/10, 01:24 AM
here's one more

am in the Philippines and did not need a heater system, so in the process of rebuilding, I removed the heater core and condemened the syste! Under load up hills, I started to overheat, even with a locally built 4 core radiator system.
I put an auxiliary radiator on the fender with its own fan. Got it from a Nissan Patrol, connected to the old heater system.
Solved the overheating problem, actually its running a little too cool at about 130 degrees.
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Cali Orange on 08/06/10, 02:20 PM
I am new to this forum but I am currently experiencing an overheating problem only at highway speeds and it gets worse when i am climbing even the smallest grade. I have a '91 5.0 a 3 core aluminum radiator from WH and an 18" Derale electric fan(puller), 180' thermostat, A/T has separate cooler (mounted away from the radiator)with its own Derale electric fan, Flowcooler wp. This is a relatively new porblem and nothing in my cystem has been changed other than I added a Summit Racing elec. fan thermostat because I would sometimes forget to turn it on. A friend said his Bronco would overheat then he discovered that his C-4 was slipping because a bolt on the side of the tranny that puts tension on the bands had backed out. He said the slipping was causing the tranny to heat up and also heat up his engine temp. Anybody have any ideas??? I am stumped. BTW all parts listed are brand new within 2 years.
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