Coolant Leak: Is it the intake manifold gasket?
 

This 4.2L is in a 2001, 2wd, F-150, that I bought new. It has 130+K miles.
About 500 miles ago I noticed the reservoir was about 1/4 inch low so I added 1/4 inch - didn't smell or notice any leaks. Tailpipe was wet but not unusually.
Engile idle has been a little strange lately (going up and down slightly for no apparent reason).
About 100 miles ago I found the coolant reservoir dry. So I filled it up. Still cant see or smell any leaks (except now the tailpipe seems more wet than usual).
Yesterday, when I jacked the truck up to change oil and rotate tires - a puddle about 8 inches in diameter formed under the end of the tailpipe and now there is liquid leaking (a bigger puddle from a rust spot I guess) at the back of the muffler. These puddles seem to be just water - no green color or coolant odor.
Does this mean the intake manifold gasket(s) needs replacement?
Is this something I can do myself or should I take it to a shop? (I have rebuilt engines before but on much older vehicles).
How much can I expect to pay to have it done?
I need to make a 500 mile run up north pulling an inclosed utility trailer - will the engine be roached if I don't fix it first? (There might be a heated garage to use up there).
Sorry for rambling on. Any help is appreciated!

Based on what you describe, a leaking lower intake manifold gasket is a strong possibility.
The external puddle may or may not be related.

One way to check is drain the oil and look for signs of contamination by coolant. The coolant/water can turn the oil milky brown if there is enough and it gets emulsified.

IF YOU WANT TO You can touch your finger in the puddle under the exhaust and then touch it to your tongue. If it tastes sweet, it is coolant.
Condensation water is kinda common when the weather turns cold, so the taste test should help you there.

Yes, you can do the work yourself if your are a reasonably skilled mechanic. It ain't rocket science.

I had to have the work done on my 2000 model way back when. (It was at 150K when mine failed). I paid to have it done due to timing and logistics. Pricing could be all over the map, but I'd expect something in the $350 - $450 range, parts and labor.

One word of caution, if it is a leaking LIM gasket, you could go out at any point in time and attempt to start the truck and ruin the engine in the process. If coolant leaks into a cylinder that happens to be ready to start the compression stroke, well.... water doesn't compress very much and you can easily bend a rod.

Not a problem as long as the engine is running. But each start up might be the last.

Here is my story from Feb 2005.
https://www.ford-trucks.com/forums/3...hydrolock.html

best of luck with it!

Everything Brian said is correct.If you do decide to change the oil do it when the engine is cold.If coolant is leaking by the LIM gaskets the coolant will settle at the bottom of the oil pan.Remove the drain plug very slowly letting the oil just seep out.If there is coolant in it you will see it immediately!

I had just changed the oil and didn't notice any coolant but the old oil was going directly into an enclosed drain pan. It will be worth it to loosen the drain plug a little, in the morning, before starting the truck - as you suggest.
Thanks for the great advice!

same symtoms I had. check your heater hoses where they conect to the alumium lower intake, mine is leaking there. its a steel nipple with a 90deg elbow by the thermastat housing. its pressed in I plan on drilling mine out and threading the hole and using a brass nipple.

Quick question for red01 - were you seeing coolant at the fitting you mentioned? Cause I'm not seeing evidence of a leak there.
I made the 500 mile trip with no problems. I brought 3 gallons of new coolant with me thinking that I would be adding it at every rest stop. Surprisingly to me - it didn't loose a drop. After it sat a day or two at the end of the trip I noticed the level was slightly lower. Now, for the first time, the Check Engine Light is on. My brother is coming over tomorrow with his code checker and a coolant system pressure gauge. Hopefully by then I'll have a spot in the garage and the kerosene heater fixed. It's a whopping 6 degrees out there this morning.

Just wanted to say thanks to "BrianA" for the link. It was very helpful reading!

Just trying to find out as much information as I can before tearing into this problem.
The code reader came up with P0171 & P0174 (lean bank 1 and lean bank 2).
My thinking now is that coolant is used to somehow heat the intake air. And that somehow this coolant is getting into the exhaust and corrupting the O2 sensors. I'm going to try and find a schematic of the coolant flow that might show where this leak is occuring.

Have you replaced your intake manifold gasket yet ? If so how long did it take ? Parts should be less than $100 for everything including new isolator bolts.

No, I haven't dug into it yet for two reasons. I'm waiting for my finances to catch up and also - it hasn't lost any (noticeable) coolant for quite some time. I know there is still a problem because occasionally the idle will raise and lower for no aparant reason. I've driven almost a hundred (city) miles since resetting the check engine light and it has remained off.