on a 99 f150 4x4, 4.6L w/128,000. I can smell antifreeze through the vents when i first turn on the heat. and from what i understand this is probably a bad heater core. BUT the smell goes away after a couple of mins and there is not leaking on the inside. But when i get on the gas pretty hard (whether the heat is on or not) a strong antifreeze smell will come into the cab.. i checked under the hood and noticed that there was a small amount of antifreeze that had accumulated around the spark plug next to the fire wall on the passenger side. not sure where it came from.

also my heat is not as hot as it used to be. at times it will be hot and other times it will be luke warm at best.

if anyone has any ideas i would love to hear them....thanks guys.

 

I think I would get one of those system leak tests done. Something doesnt sound right there, and the leak of antifreeze on the motor seems to tell it has a leak.

 

The 5.4L engines are known to have leakey heater connections. Start by checking the clamps where the heater hose connects to the heater core. Second, check your coolant level. If you have had a leak for some time, then your level could be low and that could produce erratic heater performance. Lastly, these trucks (and Ford in general) are known for having heater cores go bad. If it has a small leak, a can of "stop leak" might get you thru the winter. By brother has been living with a leaky core in his 1991 Ford Ranger for several years.

 

Tighten the heater hose on the firewall just above the spark plug. These clamps are known for being lose. Also, depending on whether you have COPs or plug wires, clean out the spark plug well. Antifreeze down in that well will cause the spark plug/COP to fail if not tended to.

 

what is the best way to clean the spark plug well???

 

Quote:

Originally Posted by cneagle87

what is the best way to clean the spark plug well???

Compressed air nozzle.

 

I found the leak. it was the heater core connection above the plug. The plug was soaked with antifreeze, so i replaced it and sprayed out the wire and plug well with air. i dont smell antifreeze anymore which is great....thanks

 

Glad you got it fixed! Enjoy your truck and have a Merry Christmas!