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Bronco overheating and hesitation under load (NOT MINE)

Dabba

Dabba

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So me and my friend just bought a boat and we were backing it up a driveway with a small incline. (its a 16ft, nothing big, trucks a 91 with a 302) While in reverse the truck would hesitate and almost stall while trying to back the boat up the driveway. After we got the boat up we shut the truck off and after about 10 seconds, he heard a hissing, pop and then antifreeze everywhere. The full cap popped off, good thing it wasnt a hose but what should we be looking at? Easy fix? hes sick of it and dosnt wanna deal with it if its involved, thanks
 
you should be looking for this little thing on the front of the truck somewhere, it's blue in color, sort of oval shaped,,,the problem is circled right in there somewhere.... :D
 
It overheated or it blew a head gasket.

And if it overheated, it may have blown a head gasket anyway.

Let it cool down for a while and then see how it runs.

I'm going to go out on a limb here and bet that the temp gauge in this truck doesn't work ;)


My bet is on a head gasket.
 
In all honesty i had an 84 bronco that had a very f'd up overheating situation. It had to do with a thermal actuated heat riser that froze up on one of the exhaust manifolds..... It took me several attempts to figure out the problem


So naturally I bought a chevy and "did the basic chevy build. Took off the radiator cap and swapped everything else out" to paraphrase a sig line on here :D
 
forgot to mention we let it cool and drove it home fine after topping it off with water. just popped the fill cap to the fill cap to the resivor, no blow headgasket, wonderring why
 
well it wasnt the radiator cap, it was the resivor cap, poppedd and boiled over but hmm, never occured to me
 
I'd start with the small stuff. Thermostat. Is it the upper hose rock solid while the truck is warm and running???
 
remember them replacing the thermostat a long time ago, not sure with what one though. couldnt tell you about the hose just yet. he said it overheats on the beach too, in reverse too. maybe the fans not moving enough air?
 
well, it definatly sounds like its overheating (duh) the question is why.

what year is the bronco? carbed or fuel injected? full stock or modified? if its modern enough, have you run it for codes?

my brother has a 1973 that has a similar problem, I think its just a screwed up carb adjustment, wrong jetting or something like that. Ive attempted to set the adjusting screws to no avail. but a lean mixture would cause high combustion temps that would lead to overheating. My brothers main problem we think is actually vapor lock, the fuel line is pretty close to the header.
 
Is the radiator shroud intact? Is the fan clutch working properly?

My 429 Bronco does fine, at low speeds, but highway speeds the temp gauge starts creeping up.
 
its a 91 FI 302. radiator shroud appears intact. dunno bout the fan clutch, was wondering that too. how would you check? just see if the fans turning too slow?
 
not really sure how to check the fan without loosing fingers. maybe with the engine off, put a heat gun on the clutch thermostat, heat it up, and then try to spin the fan, if its locked up the clutch is working, if its spinning free, then you need a new one.

also, id take it to.... crap its either autozone or advance auto parts, that scans your car for codes. its always a great diagnosing tool on the newer cars.

could also be a collapsed radiator hose. you said youve done the thermostat already, check the lower radiator hose to see if that internal spring is still in there, it keeps the hose from being sucked closed by the water pump. Makes sense because it seems like the truck only overheats when its under load, if youre on the throttle, the water pump is gonna be pulling harder, and can produce enough vacuum to collapse the lower hose if it dosnt have the internal spring to keep it open. lack of flow would definatly cause the overheating.
 
Probably the fan clutch if it overheats when idling or moving slow.
Let it get normal temp or a little hotter, pop the hood and grab the fan.
TURN IT OFF FIRST.
Try to spin the fan.
It should turn, but not move after you let go.
If it spins more than a couple of inches when you try to sling it around, the clutch is bad.
Its a fluid type clutch, not a solid lockup, so you should be able to move it. It just will be really dampened.
If you see oil stains or a wet place on the front of the clutch or around the shaft, its bad or about to be.

They basically have three failure modes.
Loss of fluid, truck overheats at idle or in traffic, but does ok on the highway.

Lockup, the bearing seizes. Truck runs nice and cool, never overheats, but has lots of engine noise on the highway and gas milage sucks.

Total failure. Fan comes off, goes through hood, radiator, or richocets off the pavement and takes out the oil pan. Rare, but I have seen it.

J.
 
Fordum said:
Probably the fan clutch if it overheats when idling or moving slow.
Let it get normal temp or a little hotter, pop the hood and grab the fan.




TURN IT OFF FIRST.
Click to expand...

lets hope he reads through the whole post before taking any action, and dosnt go step by step :D



Fordum said:
Total failure. Fan comes off, goes through hood, radiator, or richocets off the pavement and takes out the oil pan. Rare, but I have seen it.

J.
Click to expand...

not sure why but i was actually laughing about the mental picture of this in my head.
 
yeah, it would be funny to watch the fan fly out the hood. It would be one of those "shoittt thats not good" momments. And yeah so, just to recap, warm engine up, grab fan, then turn off engine. Check..
 
I've actually seen two of the scenarios.
Saw a slight leak in my waterpump. Went to Pep Boys and got a reman. Installed it, checked for leaks, hit the highway.

5 minutes later, 70 MPH, the water pump bearings seized and the shaft snapped off even with the pump body. HEAVY fan.

Snapped so cleanly there was no sideways torque. Fan helicoptered straight into the radiator.
Ate the radiator, fan shroud, belt wrapped around the tensioner and snapped it off.

Pep Boys said I must have overtightened the fan belt. No explanation when I mentioned it was an automatic tensioner.

Riding with a friend, again at about 70, started noticing a vibration that seemed to change with the engine speed.
Asked each other " do you feel that?"
Drove a little farther, said:
"Maybe we should pull over and check that out."
"All the gauges are ok,"
"Yeah, but sometimes the gauges"....WHAM!! Whole truck shook.

I grabbed a hand hold with one hand, my rifle with the other. Sounded like someone had shot the truck.
Truck running fine. Even the vibration gone.

"Did something hit us?"
" Didn't see anything."
" Well, did you hit something?"
"No"
"Should we stop?"
"Lets drive on a little, if someone threw something at us I'd like to put some distance between us."

Actually drove OVER A Mile looking around!

Finally,
"Uh Don?"
"Yeah?"
"Don't want to alarm you, but what is that sticking up out of the hood?"
"WHAT THE HELL IS THAT??"
"Looks like a fan blade....."

Funny how you can overlook something like that. The blade was all the way through the hood up against the hub on the underside. Never saw it for about almost a minute or so.
Pulled over, determined that the water pump was ok, and the belt was still on. Drove all the way into town, never got to the hot mark. Kept the speed up though.

I begged him to just saw the fan off under the hood and leave the blade sticking up, but he wouldn't.

I havn't had the oil pan one yet, but I have seen an oil pan with part of a blade embedded in it.

Of course, with lots of today's fans being light aluminum or plastic, that takes a lot of the fun out.

J.
 
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