Occasional Coolant Leak?

[MaxxAction]

Hey guys...

new to the forum, and I want to say up front I REALLY would appreciate some help with this issue.

1998 expy 5.4 4x4, 108k miles. Last January, I was on my way home from a friends hose about 75 miles away, I turn on the heat, and immediately my windows fog up til I can't see, heater core was bad.

So I had the heater core replaced at a local shop, all seems well, till about two weeks ago, I start smelling coolant in the truck. No fogging of the windows, no dripping out the vents. I get to looking, and the valley under the intake had a couple inches of coolant standing in it, and underneath, there is coolant dripping down right about in line with the firewall, rapidly. I got under the truck, and the coolant is dripping off the top of the catalytic converter heat shield. I checked the heater hose connections, no leaks, so I am assuming it is the under intake heater pipe that is so common on these trucks.

So I change that pipe. Refill the coolant, let the truck run for an hour, go drive it about 20 miles, come home, no leak. All is well for about a week. The wife put about 200 miles on the truck this week, and the antifreeze smell if finally starting to go away. Today, I started the truck, and moved it 30 feet so I could mow, and when I went to move the truck back, I see dripping, in the same place, with the truck off, having run for 90 seconds a half hour earlier. Not much, but it is dripping.

I started the truck, and let it run until it got to operating temperature, and the dripping stopped. Shut the truck off, which should increase the pressure in the cooling system and make it leak, watch for five minutes, no drip. I went back out and checked it again an hour later, no drip. I don't get it.

Does anyone have any idea what could be going on?

 

[1955moose]

Sounds like your plastic intake manifold is probably leaking. What I would do rather than guess is pressure check system. Their are so many possibilities as to the leak, it may be at multiple spots. Keep us posted what you find.


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[MaxxAction]

Sounds like your plastic intake manifold is probably leaking. What I would do rather than guess is pressure check system. Their are so many possibilities as to the leak, it may be at multiple spots. Keep us posted what you find.


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early 98 model, aluminum intake.

 

[1955moose]

My bad!


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[1955moose]

Still could have gaskets leaking.


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[1955moose]

Besides cost why would Ford switch to a plastic crappy intake?


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[docraymund]

They sell a UV dye which can help pinpoint coolant leaks.

 

[1955moose]

True, but if he has a leak, or potential leak, pressure testing will bring it out now instead of later. It may make a little leak big, but you want it to leak now, not later at the worst time, when it's raining/ snowing with the wife and kids driving it. The fact that it leaks, then doesn't, you might want to change your expansion tank cap. Their cheap enough. Sounds like your building pressure, then losing it. More than likely your losing coolant only when hot, most leaks get worse when hot. Theirs a lot of forum members that have reported leaks on our site. Besides doing the pressure check, read up on their findings. Report back what you find.


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[MaxxAction]

Still could have gaskets leaking.


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I guess it's possible, but I would also believe that if it was a gasket, it would have leaked from the first minute the cooling system began to build pressure. When I look in from the side through the fender, there is no coolant on the back of the motor/exhaust/trans dipstick tube.

 

[1955moose]

Borrow a pressure tester and find out for sure. On this forum we try not to do too much guessing. It ends up costing too much, replacing parts that weren't bad. That and we end up looking bad! Some leaks only show up with pressure, or when engine is stressed. I was working on a friends Honda accord years back, that had a leak I couldn't find. It turned out to be a small bypass hose that I discovered by moving the hoses back and forth while the car was running. It started spraying when I did that, but not before. Report back what you find, for our journal.


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[MaxxAction]

No guessing left....

the heater core is leaking again. Drove it today, when it was in the upper 30's, and as soon as there was heat, I got that slimy, foggy film on the windows. The leak underneath is the same place where the AC drips when it's hot out. So it's leaking out the core, and dripping out the drain.

 

[1955moose]

Well at least it's under warranty. See if they can switch brands of heater cores. I've had good luck with 4 seasons brand in the past. Or ideally if available maybe one direct from Ford. Sorry you had to do same job twice, but at least it's not you doing labor.


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