Overheating
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Junior User
Joined: Feb 2004
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Overheating
Got an 85 F-350 with a I-6. I just rebuilt the motor (less than 100 mi since rebuild). She's been running a little warm since rebuld (about R/M in NORMAL), but progressively getting hotter and hotter. I replaced EVERYTHING (besides the gauge) in the cooling system and she still almosts pegs out at H. I read out the resistance at the temp gauge switch and it reads 20 ohms, which according to O'Reilly Auto where I bought it from, 24 ohms is H.
I talked to Napa and the guy pointed out that the 300 has a nasty tendency to trap air in the head and is extremely difficult to get it out. This made sense since this was my first rebuild, and I didn't burp the system well enough. He suggested installing a back-flush adaptor and running the hose to flush the air out. It seemed to work for a few minutes (the gauge was reading mid-range with the water hose on). Thats when the wife noticed coolant inside the cab - aka heater core leaking. Heater core's replaced, and tried to bleed out the steam trapped in the top radiator hose. It looks like most of the air is out, but it still overheats.
What's the best way to get it out and how can you be sure its all gone? I checked the timing and it looks set on 6 btdc. Any other suggestions of what else could be the problem?
I talked to Napa and the guy pointed out that the 300 has a nasty tendency to trap air in the head and is extremely difficult to get it out. This made sense since this was my first rebuild, and I didn't burp the system well enough. He suggested installing a back-flush adaptor and running the hose to flush the air out. It seemed to work for a few minutes (the gauge was reading mid-range with the water hose on). Thats when the wife noticed coolant inside the cab - aka heater core leaking. Heater core's replaced, and tried to bleed out the steam trapped in the top radiator hose. It looks like most of the air is out, but it still overheats.
What's the best way to get it out and how can you be sure its all gone? I checked the timing and it looks set on 6 btdc. Any other suggestions of what else could be the problem?
Last edited by navyflyinggreg; Mar 12, 2004 at 06:47 PM.
Senior User
Joined: Feb 2004
Posts: 116
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From: Northwest
Take the thermostat out and drill a 3/16 hole in it. When you reinstall it make sure the hole is in the 12 o'clock position. This will act as an air bleed........ that way no air can get trapped in the head behind the thermostat.
Elder User
Joined: Apr 2001
Posts: 772
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From: Glen Burnie Maryland
Agree with Patrick. You could also put an aftermarket gauge on the engine and test for actual vs. perceived temp.
On the thermostat drill the hole about 1/2 way between the outer edge and the inner edge for the valve. Make sure the retaining arms are at 3 & 9 when ya do this. then install it at 12 or when Mickey's hands are both at the top!
This is a Mark 1 Mod 0 field modification. Yer on yer own bucko, but don't let the Chief hear about it!
Just remember there are more planes at the bottom of the ocean than there are FLYING SUBMARINES!!
"Any boat can submerge......ONCE!"
Larry
On the thermostat drill the hole about 1/2 way between the outer edge and the inner edge for the valve. Make sure the retaining arms are at 3 & 9 when ya do this. then install it at 12 or when Mickey's hands are both at the top!
This is a Mark 1 Mod 0 field modification. Yer on yer own bucko, but don't let the Chief hear about it!
Just remember there are more planes at the bottom of the ocean than there are FLYING SUBMARINES!!
"Any boat can submerge......ONCE!"
Larry
