This overheating issue has me baffled. I believe a possible head gasket leak now. When the car is warmed up you get that antifreeze smell, yet noe exterior visible leaks, yet it uses some coolant, seems to air lock in the circulation, so frequently bleeding to keep coolant flowing through especially in the interior heater. I think now that as the engine warms up there is a slight leak on one of the head gaskets that is oushing small amounts of air into the coolant side and then when the engine is shut off it leaks small amounts into a cylinder. This is the only left that I have not checked.

 

Did you check the oil color yet. If it is light brown don't run the engine until the gasket is repaired. I have the same engine in my 2000 s-type and over heating can warp the engine parts. Also the plastic "T" stack or thermostat housing can develope pin holes. Are you checking the exhaust for what seems like extra steam which would tell you if she is leaking coolant int the cylinder. Good luck in sniffing out this one.

 

You got it. My F150 Ford did it too. Do not run. Your heads might still be unwrapped or shavable.

 

Before you jump to any conclusions do the simple stuff first?
Check for combustion gases in the coolant. The kits are all over and around $40.

How did you fill the cooling system? I now only use a vacuum filler and after you use it once you will never use any other method. No air bubbles at all.
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Tkx clubairth1. My wrench, (I prefer diy but 73,) uses one. I am getting thisi 00 with two cyl getting head gasket leaks into them at 131k.

What to do best practice on a vet's budget while open and awaking CORRECT head gaskets. Tensioners seem the highest priority. Something, 3rd gen... Non-plastic????

 

Head gasket leaks into the cylinder seem not all that uncommon on these. My 00 leaks into 2 cylinders, teardown shows. At 131k mi I'll do updated tensioners also.

 

The reason cars overheat when a head gasket fails is because the leaking water does turn to steam and does move back into the water jacket with piston pressure. Water pumps pump water and when enough steam builds, the water no longer moves and the engine over heats. You also have to test for a casting crack in the heads or block when you blow a gasket (pressure test). If it isn't a head gasket or cracked casting, it is something else like water pump, thermostat, expansion tank, broken hoses and fittings. It is much more difficult to repair a car engine with this issue verses a boat. No room to work!!!

 

Remove the spark plugs and perform a compression test after checking for combustion gases in the coolant.

 

I believe "leak down" is the test desired. Not compression

 

Could the valley coolant hose be leaking? I had to replace my 4.0’s valley hose last winter(pretty time consuming job). Is the fan working correctly? Had similar issue with the thermostat housing leaking few years ago. Replaced it with aluminum one. Sorry didn’t realize the post was a decade old