2003 4.6L Supercrew. No error codes at this time:

Recently I got a P1299 code which was caused by a failed Cylinder Head Temperature (CHT) sensor so I replaced it. At the same time I drained and flushed the cooling system, then I installed a new 195 degree thermostat, G-05 coolant, and distilled water. Then I disconnected the battery for a while to clear the error codes.

When I drove the truck again after this service it seemed to run fine initially, and I have not had any new error codes so far. However, I have twice watched this sequence of events which concern me:

After the truck is warmed up, the temperature gauge needle settles midway between H and C. This is its normal operating position. But after a while I might see the needle start to move higher, and if this happens the needle keeps climbing until some coolant is boiled/forced out of the overflow cap. Then the temp needle returns to its normal position and everything appears fine again.

Is coolant being forced out of the system because there's too much in it? If so, this seems strange because I only fill it to the cold fill mark on the overflow reservoir when the truck is cold.

Or does this indicate some other problem? And if so, what could it be? The Check Engine light does not come on when this occurs, so I have no error codes to help me to figure out why this is happening.

Also note two possible related issues:

1- I do not always get heat inside the truck. Sometimes it starts blowing warm/hot air but then it just switches to blowing cold air even though the climate controls are still set to full hot.

2- Sometimes I hear what sounds like water sloshing / gurgling on the passenger side near the firewall. Would this water be inside the heater core? And if so, why would there be air in there?

Any help you can provide on this matter is greatly appreciated.

 

I can't help but think "head gasket" when I read this. Air lock in the heater core is one of the things that gets my attention. That and multiple coolant expulsions, although you said after it "burps", the temp comes back to normal. If you go to an auto parts store I think you can get a simple hydrocarbon test kit which will tell you if you have combustion gasses in the coolant.

Once or twice in my life I've heard stories of a freak water pump seal failure that will allow it to suck air when cold/unpressurized but not leak externally when hot and under pressure. I've never seen it but I suppose its possible.

 

PerryB, can you please explain why you suggest "head gasket" as a possible cause of this problem? There is no oil in the coolant , no coolant in the oil, no leaks anywhere in the engine compartment, no strange sounds (other than the gurgling water sometimes) and no obvious power or compression issues.

 

Dont panic yet- these trucks are notorious for air trapped in the cooling system after service is done-

 

You might check out the heater cutoff valve if you have one.
The valve is vacuum activated when A/C is selected, but even though the arm moves the valve may be stuck/clogged.
There is sometimes a restrictor in the heater supply line right where the hose exits the engine that might be clogged.

 

Gurgling sound is from low coolant level

But this dont make it relieve coolant

Vapor generation in the circulation loop will

Either by failed hg or overnpheating coolant somewhere.

If you have poor flow, and actually boil your coolant you can, but youve cooked your heads then too at 265f. Hg failure isnt far behind

 

It's just trapped air in the system. It's creating a hot spot. Your system needs to be burped. You've done everything correctly, sounds like you did a good job in fact. But yea, like user Bear posted above, - they are a PITA to burp or purge. I usually jack the front and lower the rear when I do it anymore. There's other ways to burp, -I just do that on the refill so I don't have to bother with purging through the core lines in the end. And yes, they will gurgle, at times quite often. They also do it a lot after shut down inside the cab lol...if there air in the system.

So there's a lot of air trapped, enough to create a hot spot...that's not good, -too much!

I'll post the Ford solution, but it's much easier nipping this in the bud on the refill, -

Coolant Fill Procedure, -

 

Earlier today I bought one of those Prestone Flush and Fill kits because it comes with a tee fitting that installs permanently into one of the heater hoses. My plan is to install it in the highest physical location in the highest heater hose. Then I can pour new coolant into the system from there, and if I'm correct the excess air should come out the same opening.

This may not get all the air out the first time I try it, but with the tee installed it should be much faster and easier for me to repeat this"air purge" process any time I need to from now on. I'm hoping that if I do this two or three times, then drive (or at least warm up) the truck and let it cool down in between each try, I can actually get rid of most of the excess air.

Can you think of any reason why this won't work?

 

This morning I installed one of the tees (it comes with 3 different sizes) from my new Flush and Fill kit into the top heater hose after first uncapping the coolant reservoir to release pressure, then recapping it. I cut the hose that comes from the front of the engine. This is the hot water supply hose to the heater core, not the return hose to the engine.

No coolant came out where I cut the hose -- which told me that there was definitely air trapped in the highest part of the cooling system. After securely installing the new tee I slowly poured almost 1/2 gallon of distilled water into it before it wouldn't take any more. Then I put the cap on the tee, started the engine, set the climate controls to max heat with the blower on low, and let it idle until it reached full operating temperature.

During this entire time I did not get ANY hot air out of the blower. It blew cold air the entire time ...

So I turned the engine off, opened and closed the cap on the coolant reservoir again, and opened the cap on the new tee. This time I added another 1/4 gallon or so of distilled water before it would take no more. I capped the tee, started the engine, and let it idle again. This time I immediately began getting hot air from the blower, so I knew I was making progress.

I revved the engine to 2000 RPM for about 30 seconds, thinking that this might help force some of the remaining air bubbles around in the system until they eventually got trapped in the heater core or maybe in the top of the radiator. Then I let the truck idle again for a few minutes before shutting it off. Once again I uncapped and recapped the coolant reservoir before adding more water to the Flush and Fill tee ...

This time I was able to add only about one cup of water before it was full.

Bottom line: After repeating the purge-and-fill procedure 3 times I think I have successfully removed most of the air from my cooling system.

At the moment I'm letting the truck cool down so it will suck some more coolant from the overflow reservoir if necessary, and maybe release any remaining air bubbles into the overflow reservoir from the top of the radiator. Then I will know how much coolant I should add to the overflow reservoir to bring it up to the cold fill line.

I hope I'm close to the end of this project. It's been fun learning all these new facts about my truck, and fixing it. But now I have some work to catch up on, so I'm hoping to just "use it" again for a while -- without it overheating!

 

^^^ This...sounds like you got an air pocket in system...quit common when a flush has been done.