'67 Mustang 289 Cooling issue.

Hi, Wow!
Yeah, Radiator bursting is an understatement, fortunate you/anyone weren’t severely burned.
A 3 row Radiator & Clutch or Flex-o-lite Fan should have no issue in keeping a 289 cool. It’s not had any issues, previously & nothings been changed, (Change or alter anything, was it hibernating?) happed fairly sudden, idling.
General causes, less what you’ve done).
Check your Oil, Oil Pressure...
1) Severe restriction in the cooling system, heater core, chunk dislodged.
2) Distributor advance issue, spring-broken, perforated diaphragm, Ignition timing incorrect.
3) Combustion chamber (Cyl) leaking superheated combustion gases into Coolant, I.E.; Head gasket, Cracked head, block.
4) Carb debris causing obstruction yielding a very lean running condition at idle, dirt in main jet, annular booster orfice(s) clogged.
5) Exhaust system has a blockage, sudden rusted piece of muffler falling in the path of exhaust gases.
- I’d suggest, initially..
- Put the car on stands & burp it, highest point will be radiator cap. For safety, replace radiator cap with 15lb pressure cap & add an overflow tank.
1) Verify the Coolant is not bubbling at idle, in Coolant. Cold start, cap off. Careful view of Coolant emitting small bubbles within may indicate a combustion chamber leak. Confirmation is checking Coolant for presence of Hydrocarbons from the combustion process. Exhaust have a sweet smell. Cross contaminated, check for Coolant in oil, oil in Coolant.
2) Thermostat is replaced. Verify orientation is correct, functional (verify you can feel it opening via flow in upper Rad.hose as temp rises).
3) Heater core plugged, obstructing coolant flow..Pull the lines & run h20 through with a hose. If plugged, bypass one line by making a loop, if resolved..that’s the issue.
4) Pull the Dizzy cap, rotor & verify advance works smoothly & not hanging up. If vacuum, test diaphragm with a MityVac or any vacuum source to verify it holds air, watch it actuate advance, look for binding. Mechanical advance, check that Springs & advance limit bushings are intact, not binding, rusty- in place w/proper functionality.
-Vac advance removed, clean & mark balancer at TDC, and 10 Degrees. Set timing conservative at 10-12 degrees with a light. Running points? Set Dwell.
-Pull all plugs, look for evidence of high temperatures, lean condition, Coolant contamination (White, grey, shiny). Optimal Tan to slightly Carbonized (Black). Look for unusually colored electrode(s) vs. others.

Something to think about...
This is the acute issue, but you may wish to consider correcting these..
Radiator shroud appears to be cut, or modified. Shroud should be a 360 degree circle with proper shroud to fan blade clearance, fan to radiator clearance, blade angle, proper blade rotation direction & correct shroud depth.
I’d listed above- for safety, why not now..Cap on the radiator a 15lb relief type- cap? Replace the cap with one rated for your weakest link (15lbs) & install a puke tank. It’s cheap insurance & will generally be enough to gain attention to shut it down. (Usually prevent a radiator explosion.).
Was that an aftermarket, non OE Radiator? Even the B.B. Fords have high crowns in the material for strength on top, uncertain if due to damage(?)
No Coolant ever noted on fins of radiator from leakage, previously?
Good luck! Try the list & we’ll go from there.
- John

Hi,
No prob’s!
Glad your on the right track, and you’ve got a Pressure release cap on the new radiator, think that’s about the worst I’ve seen, lol! Above all, glad nobody was hurt!
Realistically, a mild 289 with a good fan & Pump, clear block are good about running cool even without a shroud with a 3 core radiator, others a bit more needy.
Roger that regarding your shroud.
Good luck!
-John