I have a 2000 F150 with the 5.4 in it. I'm having a strange problem that I can not seem to pinpoint. Upon initial start up every morning I will drive approximately 5 miles and my temp gauge spikes and light comes on. It stays that way for anywhere from 2-10 seconds then drops into normal range. I have absolutely no heat until this happens. It is forcing coolant out of my res. bottle. I've changed the thermostat and water pump. Both hoses have been replaced. I took it to my local ford dealer and had them flush the heater core. They couldn't get it to act this way as it only does it once a day. After it does it early in the morning it won't do it again until the next morning. It is getting very frustrating. Any ideas?

 

You have a small head gasket leak. Pressure in the radiator bleeds down each night into the combustion chamber. Have an air pocket in the water sytem at the top. When you startup in the morning, after a few minutes, the thermostat opens and soom the temp probe is uncovered and spikes way up. Drops back to normall in a few seconds. When you have no heat is because there is air inside the heater core, which sets up high. You probably have to add 2-3 cups of antifreeze after that , right ? I had the same thing. I use a Bars Leak head gasket and block sealer in the antifreeze and that fixes it. Have had the problem for 3 years. I have to retreat it about once per year. Originally i used the Bars Copper block seal for $10. This last time i switched to the more expensive 1111 for $30. to see if it will last longer as they claim.

 

Head Gasket Fix (p/n 1111) | Products | Bar's Leaks & Rislone - Premium Automotive Chemicals

 

read this little story about Cadillac...

https://secure.steelseal.com/index.php/northstar

 

Check the intake manifold cross over tube that runs from the front left to f ront right corner, behind the alternator... No external leaks at the ends, right ?

 

I put that 1111 in a few weeks ago and the dealer told me that it caused my heater core to plug up. They flushed it out and I still have the problem. Should I put this product in after it has overheated in the morning and continue to drive normally? I don't want to put it in there only to have it blow back out when the A/F is forced back out of the cap.

 

I have no leaks externally. I have watched it actually force the A/F out of the cap. I had a technician tell me that it could be something with combustion gases getting into the system.

 

I put a garden hose fitting in the heater hose above the right valve cover. I put the hose on there and flush the old antifreeze / crap out the radiator drain and let it overflow the radiator tank. Then i close the radiator drain, put 2 gallons of antifreeze into the tank, take off the top radiator hose at the radiator and pour the 1111 into the hose and reinstall. Top off the tank with 1 gallon of water or whatever it will hold. I then start up and let it idle for a few minutes (radiator cap off) . Park with the truck nose up so the antifreeze runs back toward the garden hose cap. Stop motor and loosen the garden hose cap and let out any air untill antifreeze comes out. Finish filling the radiator to normal level and install cap. Go run around for 5 minutes and come back and park. Pressure is now in radiator. Let truck set overnight so PSI will push more of the 1111 into any small crack in gasket. Next morning, remove radiator cap and top off with water if needed. Problem solved. THe BARS did not plug your heater core.. i have done this 3 times in 3 years and heat is great. I do flush each time prior to adding the NEW Bars, not just adding to last years work.

 

You know the proper level is a couple inches from the top of the tank ? THere has to be an air pocket on top of the tank for expansion. If you overfill it will burp out.

 

Have you changed the rad cap? It works in two directions. Allows coolant into the reservoir under heat and draws coolant back to rad under cooling. If the draw back to the rad valve is stuck the reservoir keeps filling but won't return to rad.

 

Let's walk through a few things.
The pump draws coolant from the' bottom' of the radiator into the block and heads where it's flow is controlled by a thermostat at the outlet back into the top of the radiator where it falls to the bottom again.
The thermostat blocks/controls the flow on the output side.
If it take 5 miles to heat the coolant, you won't get any heat to speak of until the system temperature is high enough to make the thermostat begin to open and allow flow.
The only exception is the bypass that takes place to feed the heater circuit..
If the gage is peaking then come back to normal, it is likely responding to high temperatures detected by the CHT sensor.
With it coming back down, the coolant is beginning to be allowed flow by the thermostat opening up and be cooled by the radiator as cooler fluid enters the pump from the lower hose.
Be awhere the thermostat does not open full and close fully like a switch but slowly according to coolant temperature or a modulation process according the outside air temp , how fast your driving, fan clutch operation etc.
Another point is moving onto the road with a cold engine delays it's full heating due to 'over cooling' from the outside air movement through the radiator until the system stabilizes under the conditions.
This also delays allowing the transmission going into overdrive until it's fluid has raised to about 100 degrees as sensed by a sensor on the valve body plate. The fluid also goes through the radiator in a seperate coil on the left side.
The cooling system normally operates at some pressure to raise the boiling point of the coolant.
When the system cools it normally developes a vaccum in the system.
The pressure cap has to handle both these actions as a two way deal.
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Back to the problem; what light comes on? Is it the CEL or an overheat indicator?
If a CEL you need to have a scanner attached to catch the code when it is present.
For coolant to be pushed out of the Resviour there would have to be a rise in system pressure above the Cap rating to cause this to happen.
Several possible causes are a thermostast failure causing overheating making the temp gage rise, restricted radiator or a cylinder leak that is present until it seals from heat expansion.
I know a cooling system seems simple enought but it can offer some elusive problems until you get lucky or think about the causes and find it.
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I don't know what you have but these are the points to think about.
Be sure there is no air in the system, observe the cold engine as it heats by feeling the top hose to tell when the thermostat has opened by the fast rise in it''s termperture.
Consider the radiator may be restriicted in it's lower section impedding flow.
Is the thermostat in in the right direction?
Is the pressure cap known to be good?
Test coolant for presence of Exhaust.
You can test fan clutch operation by using a timing light triggered by any cylinder and pointing at the fan blades.
As the thermostat modulates the temp and the clutch responds the blades will sync with the light and appear to stand still then go out of sync as the temp changes. This proves both actions.
Good luck.

 

Look for combustion gasses in the coolant. Blown head gasket or cracked head is my bet. U may even be able to hear gurgling and bubling after you shut it off good and hot.

 

I have changed everything except the Rad and head gaskets. I am going to try sealing it with some sealer prior to tackling the head gaskets. That does not appear to be a fun job.

 

U might hear the heater core gurgly away with your ear up next to it. Shut off all the sound so it is good and quiet.

 

This worked. I also flushed the heater core seperately as I also had no heat. 2 days without overheating and losing a/f. I now also have heat. Thanks to all who gave advice.