Heater issue that has me perplexed
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Joined: Jun 2004
Posts: 35
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From: Indianapolis
Heater issue that has me perplexed
As many trucks as there are like ours out there, I don't think any problem, no matter how odd, is unique. Maybe someone here has had this before, and hopefully, this will benefit someone in the future.
'96 F150, 302. 147K miles. Cap, stat and hoses all replaced at the last coolant flush and change 3-4 years ago. everything else in the cooling system has been on the truck since 25K miles (probably original, but I got it at 25K)
For 11 years, this truck has consistently run with the temp gauge never going above the "O" in "normal" on the gauge.
Monday, when taking my daughter to school, after 20 minutes of highway driving, the heater went cold. I moved the temp lever to cold to see if it was putting out anything warmer than outside air. It IS warmer, but not much. Temp gauge was at the leading edge of the "M" in normal. This is warmer than normal for my truck, but not close to hot. Kept an eye on the gauge as I drove home. It seemed to fluctuate between where it normally runs and this new slightly higher temp. When it runs normal, the heat comes back. When it goes to that new higher point, it goes chilly again.
I also suspected the blend door, but when you go to warm, you can hear the door closing. Actually hear it hitting the stop.
I Was petrified about a head gasket. Got home, and when it cooled down, checked the coolant level. About 1-2 cups low. Not enough to cause lack of heat. No sign of oil in the coolant. Checked oil, no sign of coolant there.
I Also noticed that the radiator cap will move with the safety lever locked down. Ok, I need a new cap, but that shouldn't cause a loss of heat.
Tuesday evening after a ten minute drive (after truck was fully cool), I noticed a small puddle of coolant. I found the radiator leaking at the seam between the aluminum and plastic. Minimal loss of coolant- two days driving empties the overflow, but the radiator is still full. This leak does not happen after longer drives, but is very consistent after ten minute drives. (I live ten minutes from work, so I do a lot of those) No sign of any coolant in the cab, either.
I'm a bit baffled. If it was a stat sticking open, it should take forever to heat up, but stay warm once it did. If it was sticking closed, the truck should overheat. Boiling it down to basics, I'm either not flowing water through the core, or the water flowing isn't hot. But not consistently.
If the core was clogged, it should be cold, and stay cold. It shouldn't be intermittently clogged. The temp fluctuation isn't enough to cause that drastic of a drop in the heater temperature. This is a Ford, it's suposed to have a butt-kicking heater (it has for the last 11 years)
I really don't think I have a blown head gasket. I doubt that the radiator leak could cause it, either. The leak started when I said it did, too. I'm consistent enough about where I park, and am also consistent about looking for stains and puddles in the places I park. But it would be odd for the two not to be related.
My plan of attack is this: Flush it out, new coolant, cap and stat. I'm gonna try to milk the radiator through until past the holidays, if I can.
If anyone has any thoughts, I'd be interested in hearing them. I'll post the results so anyone having the same problem can benefit.
'96 F150, 302. 147K miles. Cap, stat and hoses all replaced at the last coolant flush and change 3-4 years ago. everything else in the cooling system has been on the truck since 25K miles (probably original, but I got it at 25K)
For 11 years, this truck has consistently run with the temp gauge never going above the "O" in "normal" on the gauge.
Monday, when taking my daughter to school, after 20 minutes of highway driving, the heater went cold. I moved the temp lever to cold to see if it was putting out anything warmer than outside air. It IS warmer, but not much. Temp gauge was at the leading edge of the "M" in normal. This is warmer than normal for my truck, but not close to hot. Kept an eye on the gauge as I drove home. It seemed to fluctuate between where it normally runs and this new slightly higher temp. When it runs normal, the heat comes back. When it goes to that new higher point, it goes chilly again.
I also suspected the blend door, but when you go to warm, you can hear the door closing. Actually hear it hitting the stop.
I Was petrified about a head gasket. Got home, and when it cooled down, checked the coolant level. About 1-2 cups low. Not enough to cause lack of heat. No sign of oil in the coolant. Checked oil, no sign of coolant there.
I Also noticed that the radiator cap will move with the safety lever locked down. Ok, I need a new cap, but that shouldn't cause a loss of heat.
Tuesday evening after a ten minute drive (after truck was fully cool), I noticed a small puddle of coolant. I found the radiator leaking at the seam between the aluminum and plastic. Minimal loss of coolant- two days driving empties the overflow, but the radiator is still full. This leak does not happen after longer drives, but is very consistent after ten minute drives. (I live ten minutes from work, so I do a lot of those) No sign of any coolant in the cab, either.
I'm a bit baffled. If it was a stat sticking open, it should take forever to heat up, but stay warm once it did. If it was sticking closed, the truck should overheat. Boiling it down to basics, I'm either not flowing water through the core, or the water flowing isn't hot. But not consistently.
If the core was clogged, it should be cold, and stay cold. It shouldn't be intermittently clogged. The temp fluctuation isn't enough to cause that drastic of a drop in the heater temperature. This is a Ford, it's suposed to have a butt-kicking heater (it has for the last 11 years)
I really don't think I have a blown head gasket. I doubt that the radiator leak could cause it, either. The leak started when I said it did, too. I'm consistent enough about where I park, and am also consistent about looking for stains and puddles in the places I park. But it would be odd for the two not to be related.
My plan of attack is this: Flush it out, new coolant, cap and stat. I'm gonna try to milk the radiator through until past the holidays, if I can.
If anyone has any thoughts, I'd be interested in hearing them. I'll post the results so anyone having the same problem can benefit.
Member
Joined: Dec 2006
Posts: 56
Likes: 0
From: Bowling Green KY
i run a radiator leaking at the seam your talking about for years. Would just have to top off the reservoir every once in a while. Finally replaced with a new one at $150 bucks. As to the temp change your having it sounds like a start to a blowed head gasket. Happened to my 302 on the way home one night. Stopped to get gas and i was missing on one cylinder and steaming out the exhuast like a freight train. After getting back on the road the temp gauge would go up and down and the heat would go in and out. Hope this is not the case for you. Time will tell. after doing head job i still didnt have heat. come to find out when the head gasket blowed and pressureized my coolant system it swelled up my heater core so little to no warm coolant could flow through, had to replace the core and i got my hot air back!
