Bad water pump causes check engine light??

Hello. I had an issue w/ the daily driver today and I'm not really thinking clearly right now. This is kinda wordy, but I wanted to make sure I don' tleave anything out. Any help you can give me would be appreciated.

The car is a 1999 Ford Explorer Limited( 5L V8 w/ AWD) and has 215K miles on it. Aside from what I thought was a bad alignment, its been running fine lately. I have about a 60mile round trip commute, and have lately been trying to see how far I could go on each fill up. Meaning slow starts and stops, cruise control set at speed limit or 5 below, etc( nothing major...kinda painful but getting easier).

Fri I was rushing to get home cause my wife had to be somewhere. So, naturally I drove home that day like I normally do(meaning 10-15over and somewhat "efficient" but not overly aggressive).

Truck doesn't move all weekend.

Mon am I drive my usual route to work at my new "thrifty" pace. Nothing unusual. Run out briefly for lunch, still fine. Stop by WallyWorld after work, and as soon as I get on the interstate heading home the check engine light comes on. I pull over asap, cut the engine off and pop the hood. The upper rad hose was as warm as I expected for having only been running for a mile or two, but felt only about half full. I don't notice any obvious leaks, but the coolant overflow bottle is bone dry. I add what little water I had in the truck to the overflow, turn the heater on and get back on the highway. I can feel a very slight miss as I get closer to home, but aside from the check engine light which was still on, a different driver probably wouldn't notice anything wrong. The temp gauge wiggled a few times on the trip home, but no big spikes. A few hours later, I go out, top off the overflow , and check the actual rad itself. Didn't see any leaks, but the level was alittle lower than it should be. Water immediately started flowing back from the overflow, and the soon filed back up. I could also hear air escaping from the rad cap when I squeezed the upper rad hose. I started the truck and the check engine light stayed lit. After it warmed up, the upper hose got full and very hot, but the lower hose only got slightly warm.

Now, after all that my question is does this sound like a water pump or head gasket or both? And why the check engine light if it is the water pump? I'm assuming water pump b/c it appeared that there wasn't any water in the oil. Can't really afford another car right now and I don't have the time or skills to do any major repairs either. Any guidance or info you guys could give me would be appreciated.

Thanks again. Will

What code did it set?

Yep, find out what the CEL is telling you. Water pump could be leaking, there have been cases where the impeller disintegrated. How dirty/old is the coolant ? Evidently you are losing coolant, find out why. No, the CEL won't tell you the water pump is bad,just the effects it could cause.

also need to check the thermostat

Thanks for the info. I wanna apologize for being in a spaz when I posted last night. It's been kinda crazy lately, and I reacted w/o thinking enough. Thanks for putting up w/ my rants. I drove in this am, and I noticed a slight hesitation while driving w/ the cruise control on. Temp gauge was alittle higher than normal, and floated around enough for me to turn the heater on to drop the temps. Smelled antifreeze for the first time after I parked, and I also noticed coolant leaking from somewhere but couldn't pinpoint where. I'm going to run to autozone during lunch to get the codes pulled. Not really seeing leaks near the rad, I'm leaning towards the water pump. Will update as I find out more.

Thanks again.

I kind of doubt it's the water pump causing the check engine light. But let us know what code is read when you get it checked!

Overheating will cause detonation, which would explain the misfire and the light. Air pockets in the system could cause overheating without knowing because the air could be right at the temp sender, giving a false reading on the gauge.

VWs will set a code for "cooling system performance", but I doubt your 99 Ford has the same fault code in it's library.

I stopped by autozone during lunch and the codes came up as: P0401( EGR system fault )

According to the reader it can be caused by: - blocked egr passage - bad egr valve - bad egr soleniod - bad egr pressure sensor - bad egr position sensor

I haven't had alot of time to dig for info while at work, but I did purchase a new rad cap( mine was the orig. ), but now I'm thinking if it is a rad leak it will come w/ one anyway. I haven't gone very far under the car, but I saw water directly under the rad. I assume that if it was a water pump leak, water would be pushed by the fan towards the back of the car. I'll get online to dig more once we get our son to bed tonight.

its a dpfe sensor almost sure of it. which is the egr position/pressure sensor. notorious on all fords. considering you had misfires/hesitation tho i would rec a new egr valve also. remember to clean the ports in the intake manifold also when you do this. to make sure there isnt a blockage. generally a can of brakeclean and a soft bristle round wire brush are enough.

In reply to KATYB:

Thanks for the info. I just found this and it points to exactly what you said.

http://www.explorerforum.com/forums/showthread.php?t=164517

I used to be in the habit of cleaning the throttle body and intake using deep creep, but I haven't done it in awhile(young kids and spare time don't mix). Is there a way to check the egr valve w/o a scan tool?

Also, if the check engine light is egr system related what caused it? Could leaking from the front of the engine get into the vac hoses on the top and rear of the engine? I guess I need a better idea of root cause.

I think you have two seperate problems. egr and a coolant leak.

well just replace the dpfe... to check the egr use a vaccuum pump directly hooked up to it. if when u apply vaccuum the engine runs different possible dieing and it holds vaccuum without a problem then egr not the problem but i think yours may be stuck open lil