rebuilt 390/ severe overheating!
Mountain Pass
Joined: Feb 2018
Posts: 108
Likes: 0
My 390 didn't want to restart when it was hot. I bought a Powermaster starter with gear-reduction. Also new battery cables from "Battery Cable USA". Also I paid a starter-rebuild shop to replace my regulator with a shiny little chrome thing about the size of a cigarette lighter that screws onto the alternator and does the regulator's job. Now it starts every time.
Mountain Pass
Joined: Aug 2014
Posts: 162
Likes: 21
https://www.youtube.com/user/Myvintageiron7512 has a nice series (8 or 9 parts I believe) covering a FE rebuild. I think it's in part 8 where he discusses what Dave mentioned about head gasket orientation.
If you have verified there is no trapped air in the upper area of the cooling passages via "burping" the system with whatever hose is the highest (heater core hose usually works for me) and the cooling system passes all the usual tests (thermostat opening, holds a pressure test, you can see flow in the radiator when the thermostat is open, etc) ... Silly question, any chance the water pump is spinning the wrong direction from a serpentine drive added up front?
If you have verified there is no trapped air in the upper area of the cooling passages via "burping" the system with whatever hose is the highest (heater core hose usually works for me) and the cooling system passes all the usual tests (thermostat opening, holds a pressure test, you can see flow in the radiator when the thermostat is open, etc) ... Silly question, any chance the water pump is spinning the wrong direction from a serpentine drive added up front?
Mountain Pass
Joined: Aug 2014
Posts: 162
Likes: 21
Yeah, that's what I was referring to. Instead of the impeller vanes pushing the water through the cooling system, the impeller is cupping/scooping the water, resulting in less flow in the wrong direction. Off idle low speed driving it's less noticeable, highway speed the temp could just keep climbing.
Tuned
Joined: Jun 2018
Posts: 334
Likes: 9
This might not apply but I had a similar situation at rebuild breaking in my cam I'm surprised the motor even runs I did everything wrong air in the cooking system bad flowing water pump.i used the old one that was on it before rebuild timing wrong I have 150 psi on all cylinders so couldn't of hurt it that bad well Iim.not running a heater core I had factory air and the heater cores are very hard to find for that unit so I bypassed it or simply plugged off the port on the water pump that went to the heater core and put a plug in the intake were the return valve was . It got Hot immediately 5 min it was up in the 200 range once I looped them together problem went away although it takes forever to warm up now since the water pump is putting cool water passed the thermostat before it opens I don't know why this is still tell myself no it was my imagination the thermostat didn't open yet that's why the.temo was so high no way that could matter but it did on the 390 or at least mine .
New User
Joined: Oct 2021
Posts: 1
Likes: 0
I'm having the same problem, less than 1000k on fresh professional rebuild. Starts great, slowly gets up to 175 the electric fans kick on, the 180 degree thermostat definitely works as the temp then drops down into the low 170s initially, but then just keeps creeping up! I haven't driven more than 20 miles at a time because of this,. Around town anywhere from 195 to 212 driving, as I'm putting the car back in the garage, 222 and up!
high flow water pump ( tuff stuff) and matching 180 degree high flow thermostat. Head gaskets are flush on both sides of front of motor and do not stick out under exhaust manifolds. Aluminum 3 row radiator and 3 electric fans pulling 2500cfm. Fitech fuel injection system.
I've switched out the water pump and thermostat again, same result. I use a vacuum tool to refill the system. I also just changed the oil and it looked good. Definitely a knock on driver's side front.
I'm running out of ideas!!!
high flow water pump ( tuff stuff) and matching 180 degree high flow thermostat. Head gaskets are flush on both sides of front of motor and do not stick out under exhaust manifolds. Aluminum 3 row radiator and 3 electric fans pulling 2500cfm. Fitech fuel injection system.
I've switched out the water pump and thermostat again, same result. I use a vacuum tool to refill the system. I also just changed the oil and it looked good. Definitely a knock on driver's side front.
I'm running out of ideas!!!
Hey did you ever resolve this issue. I'm have the same issues with all new cooling system parts in a 68 F250. No logical reason for it overheating.
More Turbo
Joined: Nov 2007
Posts: 703
Likes: 3
From: Western Washington
That's right, the head gaskets need to be installed so the front water port is blocked and the rear is open, sending the water to the rear of the block.
I can only guess if the gaskets are reversed, the water will only go to the front of the engine and out, never reaching the rear of the block and cause overheating.
I can only guess if the gaskets are reversed, the water will only go to the front of the engine and out, never reaching the rear of the block and cause overheating.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Use a digital point-and-shoot temp gauge. Start it up and watch the temps from front-to-back on the block and heads. If the back of the block/heads get hotter than everything else, that's it.
What you should see is, block is cooler in front, warmer in back, back of heads the same temp (or close) as the back of the block, and heads a little warmer in front than the front of the block.
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1st Gear
Joined: Jun 2023
Posts: 1
Likes: 0
390 overheating
need some help to figure this out, i,m startin to lose it !. had the 390 rebuilt, bored .040, new bot end, heads redone, installed new 4 core rad ( cross flow ),new hoses,belts,thermostat (180 superflow),temp. sender, new battery , rad cap ( 13 lbs & tried 7lbs ) problem i,m havin is while driving she runs in the mid range of temp. gauge when i shut it down within 5 min. the temp gauge is pegged and the motor wont even turn over, i removed thermostat and ran for a bit , same thing, installed another new thermostat, 2 -16" electric push fans & removed bush bar ( figured it may be distorting air flow ), checked the timing, AFTER all this the motor still overheats after shut down , 
, IS there anything i can check or could this be something to do with the rebuild ?
thanx
, IS there anything i can check or could this be something to do with the rebuild ?thanx
Last edited by Archangel137; May 29, 2024 at 11:50 AM.
Cargo Master
Joined: Oct 2020
Posts: 2,675
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5th Wheeling
Joined: May 2023
Posts: 28
Likes: 12
Almost every engine will increase in engine temp. after shut down.Maybe up to 20 degrees or more. No coolant is flowing through the engine to remove residual heat. Make sure the starter is up to par. Worn bushings cause starter drag and worse on a very hot engine. Good ground connections and larger cables are a must. If headers are installed, header wrap and a shield on the starter is a must. Worked in a Ford Garage in the seventies and solved most of these problems.
Good luck.
Good luck.
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