Hello, Looking for some help.

I have a 2002 F150 Lariat Supercrew with a 5.4 Triton. When the temp needle rises past the thermometer on the panel coolant blows out of the cap on the reservoir. Have changed caps 3X, installed a new radiator, thermostat, and hoses with all new clamps and even a new coolant reservoir. Still getting the same issue. Any help would be appreciated.

 

There are some things that can cause those problems among which could be ,
Air trapped in the system (There are procedures to reduce that)
Compression getting into the system (Sometimes with the radiator cap off before starting, and watching for compression bubbles coming up, Best to remove thermostat to see this problem or have combustion indicator verify this)
Water pump seal allowing air to get sucked into the system due to a bad water pump seal, (doesn't have to leak externally)Low pressure at seal creates a vacuum where air can get in.
Water pump impeller loose on it's shaft (Only physically checking can verify this)

Some people have managed to install the fan backwards.
How about a little more history regarding original problem , any overheat condition that might have been ignored. Some engines have a protective system to prevent excessive overheat by disabling every other cylinder from firing and using the disabled cyl to just move cooling air.

 

Thanks hanky for the quick response. There have been some issues with high temperatures. But before it overheated I shutdown let it cool and added coolant. Then 4 weeks age it started loosing coolant. No leaks noted other than the cap area. changed the cap out and it worked for a week or so. Then it started really spewing coolant from the cap. Enough that I changed the reservoir one weekend, still had coolant blow out issue so I changed the radiator, top and bottom hoses and thermostat the next weekend. Had a flush and fill done at Precession Tune along with a pressure check of the coolant system. No leaks noted. The next day same issue again. Took it back to Percussion Tune and Dye was added to coolant UV light used all over with no leaks found. Now when the temp needle rises past the thermometer on the panel coolant blows out of the cap on the reservoir. If I let it heat up for about 30 minutes and don’t get above 40-45 mph no coolant blows out of the cap. (5.4 v8 closed coolant system.)

I’m looking at changing out the water pump based on you response.

 

Also have burped the top line as the Hanes manual stated multiple times.

 

Also having a misfire on #1 & #6. Rich on bank 1 and 2. And an emissions warning.

 

There may be some differences of opinion on this, but this is what I would consider doing.
Remove the plugs for cyls 1 & 6 and look for coolant contamination. Depending on what we find would determine next move.

Also, can have a shop do a check for combustion gasses from the cooling system, which if found in there would confirm compression is getting into the cooling system.

Keep in mind normal pressure in cooling system is around 15psi. while compression pressure in the cyl can be over 100 psi so that might be why no pressure drop was observed when doing the cooling syst press. test.
Don't want to be overly pessimistic, but could be head gasket or intake manifold problem.

 

Thanks for your guidance. I’ll check the plugs in the morning and go from there.

 

Classic head gasket issue.