I have a 1995 F-150 5.0 (302).

From looking under the hood (top of engine) there is no visible leak. When looking from under the truck, there appears to be a small coolant leak some where on the lower half of the engine. It almost looks like the coolant is coming from the oil pan gasket. I know that can not be the case. Is there a sensor or something that I am not seeing which could be causing this. The coolant can be seen dripping from the crossmember directly under the oil pan. It looks like it could be coming from the passenger side. This leak is very small right now. I would like to fix it though before it causes problems. I have been looking for this leak for a few months now. Any theories are appreciated.

 

Had the same problem on my 88 w/302... Always a little puddle under it all summer, couldn't ever find where it was coming from. Then when it snowed there was always a green circle about 4 inches around in the snow... One day it finally let go, water pump seal was on the way out for 4 months and 4000 miles. Supposedly had a new water pump from previous owner about 6000 miles ago - stupid reman junk!

Sometimes if the bottom of the thermostat housing is leaking it is hard to see too.

I would take a real close look at the little weep hole on the bottom of your water pump for starters...

 

The small leak could be comming from a freeze plug! Causing the appearance of antifreeze on the pan! Not uncommon for one to rot through even with regular cooling system flushes! Also do you have a factory block heater? The element fits right into the freeze plug opening, it has a small o-ring, they do fail on occasion.
If there is a leak at the blockheater (if your truck has one) There is a bolt offside of the element next to the plug, try and tightening this up a bit and see if the leak goes away!
Just a few things to look at, hope this helps!
Rayolight

 

Get a cooling system pressure tester (loaners available from AutoZone) and pressurize the system to about 15lbs. The leak will become apparent. I could only see my leak at the oilpan as well and I had several leaks.

 

Texas -

Had a similar mystery leak - sounds like it may be in same location- check my earlier post :

https://www.ford-trucks.com/forums/s...hreadid=189708

I added Stop Leak, it took about 3 weeks to work - no more coolant drips (for now). Guess I'll not worry about it unless/until it comes back. Weather getting warmer here in NC - maybe that we change things. No overheating - just a slow drip.

 

To TexasGuy001, The coolant leak could be coming from a number of area's. But check the thermostat housing first. Mine leaked on a 95 F-250 for over a year. I had a garage change my thermostat and they never tightened the bolts up! I changed it myself this last time, used a metal gasket & a thin bead of sealer. Hasn't leaked since. Good Luck.

 

one other option, do a compression leak test, run 13 lbs for 10 min, then see if it leaks

 

I had a similar problem. A nice little drip of green from the oil pan gasket. Traced it back to the water pump. Only a small nightmare to change it. No more little green drips. Hopefully good for another 140,000+ miles. '91 f150 XLT Lariat

 

check where the radiator hose bolts into the engine block, I had that go on a friends truck. THe flange broke.

 

TexasGuy001, A pressure test will also find the leak. But Be very careful with the pressure tester! If you pump up the pressure to much, you could blow the Rad, Heater Core, Even the Head Gasket! If your engine has high mileage, tread lightly bro. Or your could end up with more problems than your trying to fix. A good Mechanic told me to drop the Rad pressure cap down to 7-8lbs on a higher mileage engine. Thats 1/2 of the factory cap. I did that, and my engine dosen't leak, overheat, and you could cook bacon on the defroster! It still pumps out awesome heat. It's worked for me for 5+yrs now. My Truck is a 95 F250 HD, has 202,000 miles on it. And the Engine has never been apart!...It has Original everything! Starter, Water Pump, Hoses, Exhaust, etc,etc,..Its the best truck I've ever owned. Has Outlived my Toyota by 100.000 miles trouble free. By, The way I'm in NY (upstate) and its colder than Alaska up here!

 

Same symptoms on my 90, also turned out to be the water pump.

 

Hey All,

Thanks for the input. The thermostat housing isn't the problem that used to be a problem though. LOL... I have been doing some more looking and I believe that it could be the water pump. I think it is called is the weep hole seems to have traces of coolant showing up in it. So, I'll give that a shot and try fixing that tomarrow. Since the water pump has never been replaced its probably due for replacing anyway. I would have never found that small leak had that not been brought to my attention. If that doesn't fix the problem then I'll try a pressure tester. Does any one else know anything about changing the radiator cap? That sounds like an interesting idea. Thanks again!

 

Texas, i did replace my radiator cap, but with OEM specs rated at 13lbs, this is because i replaced the radiator....always replace radiator cap when replacing the radiator. I had my water pump replaced at 125,xxx just because the other part of the cooling system was new, but i knew it wasnt going to be long before it went anyway, and about the lower lbs rated caps on an older motor, and still get good heat????