98 Trans Sport Mystery Coolant Leak

[KBM3]

I have a 98 TRANS SPORT with an odd coolant leak. I first noticed the leak yesterday when my wife was backing out of our driveway (first time the van had been started for the day after a night with temperatures below freezing). As she was backing up a stream of fluid was pouring from the very front drivers side of the vehicle. The stream stopped however before I got to her as she sat at the end of our driveway perplexed as to why I was waving to her to stop. There were no apparent drips or anything under the vehicle. She proceeded to the store and back (4 miles round trip) and no more leak. I put cardboard down and tried to trace the problem with no luck. A 1/2 hour later there was a small spot where a drop of coolant came from the very front drivers side. I let the vehicle cool for a few hours, fired it up and still no leak. This morning the spot where it dripped was about the size of a quarter but was essentially a stain and not visibly wet. I then started the vehicle, went inside to get changed for work, came back out about 10 minutes later and sure enough there was a large wet puddle under the drain petcock side of the radiator but nothing was obviously dripping. I opened the hood to look inside but again nothing stood out. My wife drove the van back and forth while taking the kids to school (short 3 mile round trips) with no leaks and the reservoir is still full. I suspect that the leak wont occur again until it sits overnight and completely cools off. I should note that I have been periodically topping off the coolant reservoir a few times since this summer but didn't think twice about it. Any suggestions as to where to look would be greatly appreciated. Thank you.

[maxwedge]

A simple pressure test on the radiator will reveal the source.

[FXIT]

The leak is likely coming from the intake manifold gasket. These commonly fail on this vehicle -- I know because I have one and the gasket failed at 72,000 (just 2,000 past warranty). The two sides of the intake manifold face each other and slope to the center of the engine block. As the fluid leaks from the gasket it collects in the pan on top of the engine. This low spot is quite large and can hold a fair amount of fluid. Then when you move the car (is your driveway sloped?) the fluid can run out as a stream. I experienced exactly the same symptoms and had to replace the gasket.
You can tell if this is the case by using a flashlight to look just below the temperature sensor, it's hard to see the pan area. Look for a pool of coolant. Also look at the other end, just to the right of the serpentine belt.
It's a time consuming repair. Unfortunately mine just started leaking again and I will have to do the fix again -- but I have put 60,000 miles on it since the first repair 4 years ago. Personally, I think the gaskets are too narrow around the edges of the manifold.
If could sell this van and get much out of it I would but looks like I'll be driving it into the ground.
Other problems have included: Slider door won't close, driver window won't close, exterior vent control motor malfunctioning, rear hatch handle (interior) broken, oil fill cap actually traps dirt in a groove around the fill neck then comes loose and allows dirt to fall onto rocker arm assembly (just bad design), I could go on but won't. Suffice it to say I won't buy GM again.

Good luck

[amexjoe]

Here is my 2 cents!
I have used stop leak for years with great success. Best fix was an old Dodge van with a leaky water pump bearing seal, I put in a can of stop leak and the leak stopped, ran all summer until I finally replaced the water pump. amazing. Now I am using the stuff to stop a leak in my '96 Trans Sport.