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2003 Explorer Coolant & Heat Mystery!


dsturch1

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September 2, 2008
Messages
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City, State
Pennington, NJ
Year, Model & Trim Level
03 4.0 XLT & 98 5.0 XLT
Anybody with input is greatly appreciated at this point as I am getting extremely frustrated with my truck. I have a 2003 Ford Explorer XLT with the 4.0L 6 cylinder. The truck has been having coolant loss issues for the past month or so and I for the life of me can not figure out what is going on. I have done everything to make sure I keep coolant in the truck as to not overheat.

I had a couple of issues in the past with the truck losing coolant but I have had them since addressed. When this all started last summer, I saw the leak, the trail was evident and the water pump was leaking. I had the issue fixed and the system bled out and refilled with coolant. That water pump then had a defect and was also leaking again. I then had it repaired (under warranty) and everything was back to normal. The second water pump also blew a seal at which point I had that repaired (yet again under warranty) and now I am on the third pump. At the point the third pump was done, I also had them do a thermostat just in case that was also an issue. As I said before, I don’t see any evident leaks of any sort or have any stains in the driveway from losing coolant.

Now recently (a month or so since the last repair) from a cold start the truck will start fine, run fine, etc. and then all of a sudden the temp gauge will rapidly go up and peg at hot, stay for about 5 seconds maybe, and then kick back down rapidly to normal operating temperature. After doing so, it will do this about 2 or 3 cycles typically and then my heat in the truck will get hot and warm up. I am assuming this would either be air in the system, or a bad coolant temperature sensor.

I am also losing coolant rapidly, however I have zero smoking out the back. I filled the system up earlier this week (Thursday) and now on Saturday I am already low on coolant with only about an inch in the overflow bucket. I don’t have any obvious leaks, or any stains in the driveway and haven’t noticed any wet spots underneath the truck or in the engine compartment at all.

From here on out my buddy who is an recently retired Ford mechanic told me a few things to do. First was to change the thermostat to ensure it was actually changed. Second was to drain all of the coolant in the truck at the moment. Third was to refill the coolant myself to ensure it is full. Finally was to replace the overflow bucket cap to ensure its releasing pressure and to make sure I don’t blow seals on that water pump again just in case in the event it was from a faulty cap.

Does anyone have any additional input, help, suggestions, comments, or has anyone heard of any Explorers having similar symptoms and what the outcome was? Thanks for any feedback in advance!
 




jahzwolf

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December 26, 2009
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City, State
Seattle
Year, Model & Trim Level
2000
I have just successfully overcome a cooling system MULTIPLE leak issue.

The key is REPLACE the thermostat HOUSING Assembly.. do it now.. that plastic must have sprung 10 leaks i fixed before i finally replaced it.. and when i did looking at the plastic INSIDE the housing I could see clearly why.. the plastic has become crystalized throughout.

on your truck like mine the housing routes the HOT water directly to the heater core and returns to the water pump.. so if using your heater on full makes a difference you may have issues with your thermostat being stuck or your radiator not getting the water cooled down, or the pump not driving the water thru the block..

I would start with the housing assembly. Mine is a 2000 6 cylinder SOHC I would see if you have the same unit or not..
 




dsturch1

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September 2, 2008
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City, State
Pennington, NJ
Year, Model & Trim Level
03 4.0 XLT & 98 5.0 XLT
I think I fixed it, the clamp on the lower radiator hose looked like it was kind of loose. I replaced that as well as the thermostat and the gaskets. I let the truck warm up and didn't have a single bit of overheating at all and the heat got hot as soon as the truck read at normal operating temperature.

I took the truck for a good 30 mile ride just to let it run at temperature, burp out any air in the system hopefully, and see how it was. The truck never read anything above normal operating temperature and the coolant level only dropped maybe a quarter of an inch on the overflow tank. Keeping my fingers crossed.
 




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