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Coolant leak

Mark Freeman

New Member
November 6, 2016
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City, State
Year, Model & Trim Level
2003 Explorer Sport
Looking for some help... just did an oil and filter change on an 03 Explorer Sport. Moved the vehicle to do the same for my daughter and found coolant stain on th pavement. Coolant is dripping/pouring off the back of the oil pan, below the bell housing. Some research on line lists freeze plug, or intake manifold gasket. Really can't see anything from top. Just topped off radiator with water and fluid started steady stream of fluid again. Fluid running off passenger side of oil pan. I think it's a freeze plug.... what's best way to repair this?

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I second that, it likes to collect in the valley, then when you go up an incline it rolls down the back of the block. Hard to see under the intake but if you grab a flashlight and look underneath you should see it.

Check the LOWER thermostat housing.
How low is it? Are you talking about the front thermostat housing leaking at the bottom, or is there a, "lower thermostat" which has a housing?

ps, I also had rain coming in the windshield wiper cowling and puddling on the top of the engine.
Mine is all fixed.:)
The only thing that pees now is the air conditioner drain.:cool:

Thank you for the insight. I'm not seeing any sort of fluid at the thermostat housing, nor in the valley. I borrowed a small scope so maybe I can get a better look at th valley and back of the block.

Could be a rusted out frost plug on the back of the block too. Not as common though. Rads really like to crack on these things too. Also the plastic fittings on the heater lines like to develop cracks on occasion.

The people who owned my Explorer before me had never heard of following instructions or doing repairs, so mine didn't have anti-freeze in it and the thermostat housing leaked. I had that awful feeling about pulling the tranny to get at the freeze plugs in the rear.:(

What I had to do was wash off the top of the engine with water and blow-dry it with a wet&dry vac, then wait. It took 2 or 3 hours for the coolant to start seeping out around the thermostat housing bolts. Gotcha!:shoot:

Two days later, the valley was full of water again.o_O
It was the prongs that hold the windshield wiper cowling on that were leaking. Six pieces of new sponge didn't fix the leaking so I took it apart again and bedded the prongs in black silicon caulk.
Finally fixed!:chug:

Found the coolant leak. Turned out be a freeze plug on the front passenger side of block. Coolant was running down the mounting flange for the oil pan to the back. Has any one replace one without pulling the engine. Looks like I could get access by removing tire and inner fender liner. Any suggestions, past experince.

Not sure what they look like on the explorer, but any I have replaced you just swat one side with a punch until it turns sideways, bend it and pull it out with a pair of pliers. With the block drained of coolant first that is. Then you can tap in a new one with a hammer, or install a block heater if you need it.

I've seen freeze plug replacements made of brass, with a sealant coating on them, and I think I saw some with an expander bolt, a very long time ago. I never did one but it seems if you can just fit a rather big socket into the freeze plug and bonk the freeze plug into the hole, you're home free.

I assume cleanliness is important, and following the instructions about whether it comes with a sealant or needs some from you. I would never trust a rusty hole in a cast iron block to seal against 15 PSI without some kind of sealant goop on the freeze plug.

Thanks for the info. I got the old plug out and initially went with brass plug , but it was not as deep as original, shook I went with the rubber bolt-in expansion type. Goes in dry, no sealant. Filled with coolant and no leaks. No time to bleed out the air and top it off. Thanks again for the feedback.

I've used a rubber expansion plug on my 94 once. after a week it blew out. luckily my wife was driving it and was close to home. Happy she did have enough common sense to stop where she was. would never use one again even though the correct freeze plug is a pain to access.