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Overheat like I’ve never seen..


Rlindgrenii

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1985 bronco ii 2.8L v6 -
Odo: *58000 could be 158, surely not 258.
Carfax showed no mileages at all, so who knows.

Bought the bronco about 2 weeks ago and drove It back to my place which was about 40 miles. Reached 65 eventually, and topped out about there. Didn’t overheat, didn’t stall, ran okay.

Had some snow so really got to look under the hood and adjust my idle ect just the other day. After some tweeks It fires up after a week and i drove It to the car wash, let It sit and idle while i washed, then drove back no issues.

Note i made sure It was full of coolant. And had maybe an inch or two in the overflow.

Today i planned on testing It on a small hill outside of town to watch the mountain sunset. I jumped the bronco and let It idle with nothing attached. Went inside for 5-10 minutes or so and got caught up talking to my girl friend. I walked out to move my truck to take the bronco to get gas, and to my surprise the bronco looked ON FIRE. I immediately panicked and yanked the keys and popped the hood only to realize It was steam. My coolant resivour was full and violently boiling. I pulled my mister that was handy and put a light mist out up high to help It cool down. It boiled for a solid 5 minutes before It began to settle. I let It sit and cool and went to the store. Waited a while and came back to It. Felt my hoses and my TO heater core was almost too hot to touch. My return was cold. Upper and lower hoses were also very hot.

My initial thought is my heater core is clogged. So i bypassed the Core by removing the hose INTO the core and putting It where my return hose went to. I yanked the hose out that was the RETURN hose. Cold and BONE DRY. I feel i have solved this.

I fire up the bronco again and let It idle. Before ieven could check the temp, coolant began boiling over again. All hoses hot.

All i can think of at this point is thermostat or water pump. I ordered a water pump and plan on grabbing a thermostat as well.

Will also do a full flush and burp the system.

If anyone has any input on this I’d appreciate It.
 


alwaysFlOoReD

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Thermostat is cheap. I had a waterpump impeller come off the shaft and caused the same symptoms you have.
 

Rlindgrenii

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Thermostat is cheap. I had a waterpump impeller come off the shaft and caused the same symptoms you have.
So you’d suspect that changing the water pump should be the fix to this? I’ll replace the thermostat while I’m at It either way.
 

alwaysFlOoReD

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What type of fan is on it? If it's a clutch fan and the clutch fails that would also give the same symptoms.
 

XTC90BII

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If it got that hot I hope you did not crack a head? Those early bronco's were really bad about that.

Dennis
 

Rlindgrenii

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Sorry for the delayed response, been a few days, i opened up the thermostat housing to find no thermostat. At this point I’m assuming water pump, or fan clutch. I appreciate the input guys.

I have a new water pump in hand but weather has put me off for awhile. I’ll replace that and see where i am.

I’m not sure what fan i have, it’s a whitish tan color and is badly cracked. It ran fine as far as i remember, never noticed the cracks thanks for mentioning that
 

alwaysFlOoReD

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I've read that no thermostat can cause overheating too, the water goes thru the engine too fast to pick up heat and too fast thru the rad to lose the heat. And XTC mentioned the heads cracking, not the fan. But replacing the fan is a good idea. The fan is bolted to a viscous clutch which thickens up when heat from the rad hits it. That was what I was talking about, if that fails it can lead to over heating. They usually fail on rather than off tho.
 

Rlindgrenii

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I've read that no thermostat can cause overheating too, the water goes thru the engine too fast to pick up heat and too fast thru the rad to lose the heat. And XTC mentioned the heads cracking, not the fan. But replacing the fan is a good idea. The fan is bolted to a viscous clutch which thickens up when heat from the rad hits it. That was what I was talking about, if that fails it can lead to over heating. They usually fail on rather than off tho.
That makes a lot of sense now that you mention about water going too fast.

And yes XTC did mention the heads cracking (biggest fear) but after the over heat It fired back up immediately and sounded like It was solid still. The bronco did not turn off on its own at least.

When i bought this bronco not long ago It was caked with gunk all over the engine. While It hasn’t been running I’ve been slowing cleaning the bay and noticed a pretty significant leak on my front main seal. It drips to the ground every 30 second shift or so. Not sure if this was the cause of the gunk, as if cleaning It just allowed me to see the source, or if this recent over heat caused It.

The driveway of my house is a ice rink, so hopefully tomorrow after work or some point this week I’m taking It less than a 1/4 mile to a buddy’s shop to put the pump in, install the thermostat (one i have is set to 190°F) i did just order a fan as well. So i guess here’s new questions if y’all can help you’ve been awesome so far.

If I’m replacing the fan should i replace the clutch?

Should i flush the cooling system before or after the water pump and thermostat are installed?

Should i try to do all of the above, as well as regasket my main seals before even trying to see if It still over heats?

Feel like throwing in the towel on this 2.8...

Frankenstein wiring harness with loads of connections not hooked up, as well as a black green and tan vacuum lines plugged. Resistor leaded to my coil off a green wire.

The resistor tells me my ignition system isn’t stock, but I’m having a hard time identifying what i have.

I’ll try to add some photos so you can see what I’m talking about. Tomorrow I’ll take some and add them. Sorry for the long posts, i try to be as descriptive as possible. Thank you
 

alwaysFlOoReD

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See if you can borrow a pressure tester for radiators from a parts place. The system needs to hold a couple pounds more the marked on the rad cap.
I would flush before changing the pump.
In the following thread is a description on how to test the fan clutch;
 

Shitbox

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Man I had a bronco I just bought over heat on the way home and the cooling system was so rough I replaced the entire thing. Hoses and every single component.
 

wildbill23c

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No thermostat, obviously whoever you got it from had overheating issues as well. Could be a clogged radiator, water pump, hard to say and with the unknown condition of the system I'd start with a known good radiator, thermostat, hoses, etc. The fan clutch really doesn't do much at an idle and it shouldn't be overheating while its just sitting in the driveway idling anyhow. The fan clutch should be replaced if its of concern, usually if they fail they fail in an engaged status so under acceleration the vehicle would sound like an airplane taking off LOL, that clutch when engaged makes that fan scream.

If it were bubbling in the coolant reservoir I'd be worried about blown head gaskets. Do you have any signs of coolant in the oil?
 

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