99 venture coolant tiny leak - sometimes

I just had my lower intake manifold gasket replaced at 150,000 miles. When I got home I noticed a couple drips under the radiator cap area on the floor. I felt under the cap and there was a little coolant there. I topped off to the coolant-cold “full” line on the reservoir and kept watching the floor every night. Every night a couple more drips.

It seems like when the coolant level is about a half inch below the “full” line the leak stops, so I stopped filling to the “full” line.

I could buy a new cap, but I’ve never had one go bad. I watch the area when the van is running and I don’t see any leakage at all.

Is this anything to worry about? Is the cap probably bad?

Rad caps aren’t expensive. If I were you I’d change it as it doesn’t seem to be holding pressure. Make certain to get a cap properly pressure rated. (I think it designates the pressure spec on the cap)

Also, check the coolant return hose from the reservoir to ensure it isn’t leaking at the rad end clamp.

The coolant reservoirs in these GM vans are not pressurized so the rad cap has to work properly.

FWIW, you got pretty good mileage out of the original gasket. Most didn’t, including me.
My 2000 Silhouette went at 45K miles.

The radiator cap can certainly start leaking and they are cheap/easy to replace. If the level is staying steady a little below the full line, I wouldn’t lose any sleep over it. If the level continues to drop, or there is any coolant leaking around the engine, I would bring it back to the shop that did the work.

The original one went five years ago at 66,000. The dealership gave me a break and replaced it for $100. That one just went. They did not use the “fel-pro” metal gasket, which is what I have now.

I went ahead and replaced the cap. I noticed the lower gasket on the old one was about 1/32 of an inch thinner than on the new one, and it had a permanent round indentation within the rubber that looked a little bumpy. The upper gasket also didn’t lie flat. It was warped.
Hopefully that takes care of the leak.
Thanks, Bri

remember the coolant gets hotter after the engine turned off. and the pressure raises. you have the cap tested.