My 1997 Explorer with a 5.0L AWD is leaking coolant.

[Steve Eastham]

I have a 97 Ford Expl 5 liter AWD. It has 250,000 miles on it. It has started to leak coolant. Appears tp be running down from somewhere to right of water pump (pass. side) and drips off bottom of oil pan. It doesn't appear to be coming from water pump (replaced 2 yr ago) or a radiator hose. Any one have any ideas before I start dismantling.

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 95-01 section. Connect a cooling system pressure onto it to help pin point the leak.

 

[jlsparky7]

Double check the hoses and the thermostat housing. if the pump was replaced properly i doubt thats the problem again.

 

[SoNic67]

Under the intake manifold are two water conduits that take the water thru the firewall to the passanger side heater. See if there are leaking.

 

[Steve Eastham]

Thanks for all the responses. How do you pressurize the coolant system to help pinpoint a leak? One unusual thing I have noticed since this leak started is that even when engine cold there seems to be some pressure beneath the radiator cap. Not a great amount but enough to cause a small amount of coolant to spill over when cap is removed. And it can't be due to overfill. The reservoir is actually low on fluid probably due to the leak.

 

[BrooklynBay]

http://www.explorerforum.com/reviewpost/showproduct.php/product/231/cat/all

 

[SoNic67]

One unusual thing I have noticed since this leak started is that even when engine cold there seems to be some pressure beneath the radiator cap. Not a great amount but enough to cause a small amount of coolant to spill over when cap is removed.

That's normal. The system is pressurized to keep the water from boiling in some parts of the engine - the cap even has a pressure rating. Above that rating will overflow in the tank. It will "suck" back coolant while the engine is cooling - in this way the cooling circuit is always "full" with no air pockets.

You can apply pressure with an air hand pump on the tube that connects the overflow tank with the radiator.

 

[SmoothJimmy]

AutoZone will loan you a coolant pressure tester with a deposit. You get the full deposit back if you return it within the agreed time period.

 

[OneLever]

Double check the hoses and the thermostat housing. if the pump was replaced properly i doubt thats the problem again.

jlsparky is on the right track. I have the same engine you do and had the exact same problem crop up last winter. It was a small coolant leak from under the bottom of the thermostat housing onto the top of the water pump. The gasket between the thermostat housing and lower intake manifold had gone bad, and the thermostat looked like it needed to be replaced.

I recommend using Permatex "Right Stuff" instant curing gasket maker instead of a paper gasket. I tried a paper gasket the first time and it didn't seat fully. Had to take everything apart and seal it again, by which point I didn't have enough time to let blue rtv cure. That "right stuff" allows you to test everything immediately after assembly. Instead of waiting 24 hours to find out you need to rip it apart again. If on the other hand time is not an issue then by all means use blue rtv.

While you're in there you might as well replace the bypass hose as well. It's a PITA to get on and off. If I have time I'll try to do a write up soon on this since I took a ton of pictures.

 

[Steve Eastham]

After investigating it appears that it was the gasket on the thermostat housing. I noticed a pool of green coolant on top of manifold just to right of water pump. I did rent the pressure tester from autozone but it did not have the right adapter with it for the radiator fill tube. I was able to test cap and apparently it was bad. Wouldn't hold pressure at all. I bought a new housing from AZ but it was not same shape as OEM. Was not as thick where bolts go in and long bolt was bottoming out and would not tighten down on housing. So I just cleaned original housing and reused it with paper gasket and blue RTV. Ran engine to normal temp and did not see any leakage. I guess time will tell if I did good enough job. Thanks to everyone. You guys are great!

 

[BrooklynBay]

Thanks for the update!

 

[InnerLimits]

Did you ever make a write up on the bypass hose. It is the devil to replace it. thanks,
Angel