Overheating 1968 289

[johnny_nv]

Hi All!!!
My bronco is up and running on the road.
Over the past month, I have.....
Replaced the rear main seal
replaced the timing chain
replaced the timing chain cover and all seals
replaced the oil pan seals
new radiator
replaced the distributor ring seal

Still left to install, new harmonic balancer and new vacuum advance diaphragm on the distributor.

Now, when i drive this beauty, the engine temp gauge buries the needle.
With that being said, the fan works, the radiator got very hot too, so I know my coolant and circulation are ok. My father and I believe that it is a timing issue.
Any input or suggestions on what to have a look at??????
As always, thanks in advance! FYI, just put the top on and Daisy is a sight for sore eyes!

 

[Justafordguy]

Timing issues can certainly cause overheating. Fix your vacuum advance and set the timing correctly and hopefully that's all it is.

 

[Crush]

Does the temp needle immediately peg out or only after it runs for a while and warms up? If it immediately oegs then it is a ground or sending unit issue. I would get an ir temp gun and check actual engine temps while you are at it

 

[bknbronco]

put a new thermostat in and a sending unit....or the gage is off. My 289 is the most cold blooded bitch i have driven....takes miles and miles and miles for it to get up to temp. Mine only burys the needle on a warm july day whenever i shut it off to run into a store.....when i come out its hot as hell but imediatly drops below 190 once its running and few seconds

 

[taipeichris]

Hi Guys,

STOP! Before you change anything, take it to a mechanic when the Bronco is HOT and with a "non-contact infrared thermometer gun," measure the actual engine and radiator temperatures.

Maybe is the problem. Maybe it's the thermostat, the gauge is broken, the sender is broken or maybe someone plugged in the wrong wire to the sender.

After you're sure it's over heating, drain, flush and install a filter in the coolant line. You wouldn't believe the amount of "metal-rust-flakes-crap" that were floating around in the coolant when I first got my Bronco.

Good luck and keep us posted!


PS Inline coolant filter thread... enjoy!
http://classicbroncos.com/forums/showthread.php?t=192915

PSS You can also get a 20% off coupon for Harbor Freight and get yourself this tool.
https://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-60725.html

 

[johnny_nv]

Well so far nothing. Harmonic balancer is replaced. Vac advance diaphragm too.
Set the idle timing to 6BTDC
She runs at the correct temp at idle. But at soon as she revs up the needle starts climbing.
Both the block and the radiator get too hot to touch.
But when I park and idle the temp drops again.
Kinda stumped.....

 

[Broncobowsher]

Look at the fan. The blades will have a concave side to them. Is the concave side facing the engine or the radiator? Engine is good, radiator is bad.

You have taken the radiator cap off (when cold) and checked that it is actually filled? That burned me once. Thought it was full, started driving, got really hot. Found it burped the air and was actually very low on coolant. And everything was very hot in doing so.

 

[B RON CO]

Hi, put your hand on the front of the radiator or use a temp gun to check for cold spots. If most of the radiator is cold it is plugged up and needs to be boiled out, or rodded at a radiator shop, or replaced.
If you do not have a plugged radiator I would suspect the timing is retarded. Advancing the timing and a good vacuum advance should help. Maybe the breaker plate in the distributor is stuck. Make sure it moves. Check for spark advance with a timing light. When you give the engine gas the timing mark should move off the scale, up under the water pump. Good luck

 

[Rustytruck]

how many blades are on your fan? 4, 5, 6, or 7?

I would pull the thermostat and suspend it on a wire in a pot on the stove. Start the burner on the stove and if you have a thermometer check the water temperature at 180 or so it should be starting to open by 200 or just before the water boils it should be wide open. when the thermostat is properly installed in the intake the bail or hoop end should be towards the radiator hose. The heavy brass or copper slug end should be inside the intake manifold.

https://www.youtube.com/watch?v=kNrBud_Fh-8

 

[johnny_nv]

Well problem has been solved everyone.
And usually the simplest problem is the answer!
Last night, I fired her up. that 289 sounds amazing even with stock exhaust.
let her warmup on idle and used an infrared thermometer to measure.
Block is 155ish
Passenger side of rad was around 60F

Went for a nice drive, came back shut her off and took new readings.
Block was 200-210
while the passenger side of the rad was a cool 65-70.

So when she was 155F the gauge was showing 210ish
when she was 205, the gauge was buried in the red.

Therefore, the temperature sensor must be off.
If I hadn't been a dummy, and started with the easy fix, I could've saved myself a lot of headache!

Thanks to all who replied! I might be a little bit ahead of most of you, but here in Toronto Canada, I have my top on and winter tires on and ready to go!

Keep yer rig on the road!

 

[Justafordguy]

Sounds like the sending unit and a new thermostat is what you need. At least it is an easy fix.

 

[Broncobowsher]

Heads up when shopping sending units. They are paired with the gauge, not the engine. If the Bronco is a '73 and the engine a '93, you will want a sending unit to match '73 gauge. Not the '93 donor vehicle.

 

[johnny_nv]

Didn't know that, great advice, but not an issue!
Mine is 90% original, and numbers matching.
It was a lucky, great find