Thermostat or Module Issue
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Joined: Sep 2015
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Thermostat or Module Issue
Ok I purchased my 79 Bronco about a month ago. Long story short I've been messing around trying to get it running correctly before I start messing with bigger and pricier things. Starts just fine has a 400 in it, Edelbrock carb, both installed by the previous owner. He also pulled the carpet and rhino lined it which is fine. Problem is if I drive it out of town for 20 miles it starts to stall out. After talking to a couple people I've decided it is one of three issues. Basically engine gets too hot and it starts to stall out. It idles and runs fine while I'm in town though. In fact it idled 20 min the other day and the engine was fine. Never stalled when I drove home or anything. The friends I've talked to and research I've done seem to think it could be the ignition module or thermostat. I've also thought it could possibly be vapor lock. I'd like to say I use gas without ethanol but the only gas station around that sells it is about 30 mins away. Any ideas? This is the only nagging issue before I can actually start on the other things that I plan on fixing over the next several years.
Cargo Master
Joined: May 2004
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Next time it happens, see if spraying ether in the air box gets the engine to run.
Check for combustion gases in the coolant, might be a blown headgasket.
Might be a magnet getting two hot, that might be in the distributor, I don't know enough about 79's to be sure.
Check the whole cooling system, not just the thermostat, is the radiator in good condition or is it being blocked in some tubes?
is the fan working correctly?
Check for combustion gases in the coolant, might be a blown headgasket.
Might be a magnet getting two hot, that might be in the distributor, I don't know enough about 79's to be sure.
Check the whole cooling system, not just the thermostat, is the radiator in good condition or is it being blocked in some tubes?
is the fan working correctly?
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I'm leaning away from the head gasket solely because the engine has been rebuilt less than 5k miles ago. Started to happen this morning right after start up. Gave it some gas going to the store and it acted like it wanted to stall out but didn't. Distributor has crossed my mind as well.
Laughing Gas
Joined: May 2011
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From: SoCal
Thermostat or Module Issue
Hello I've been lurking on this forum for a long time. I have a 78 Bronco with a 351m motor and I also owned from new a 1980 f350 with a 400 motor. Heres what I've learrned. I had the vapor lock problem on both vehicles due excessive heat. On the 400 it turned to be a faulty aftermarket thermostat housing allowing air to leak into the system(one of those chrome jobs). On your Bronco make sure you have the correct themostat. Some parts stores will list the same thermostat for the Cleveland(351c) and Midland(351m) motors. They are not the same. The Midland motors have unique water jacket the ciculates water in the block until it warms up. When the engine reaches operating temperature the themostat closes the passage to allow radiator water into the flow. The thermaostat has a hat on the bottom to close the return orifice to the engine forcing cooler radiator water into the engine block. Also make sure the orifice is clear and the seat is clean. You can see it when you remove the thermostat. hope this helps.
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