A 1998 Peterbilt 379 gave me a full Friday of coolant leaks from three different spots.

Found the usual suspects, a cracked heater hose and weeping water pump seal, but the third leak was a pinhole in the upper radiator tank that only showed up under load. What's your go-to method for finding those hard pressure leaks without making a huge mess?

2 comments

2 Comments

ericgonzalez16d ago

Man, those pinhole leaks are the worst! I had one on an old Freightliner that drove me nuts. My go-to is that UV dye in the coolant. Run it up to temp with the pressure cap on, let the system work, then hit it with the black light in the dark. That green glow doesn't lie, and you can spot a tiny spray from a mile away. Saves you from hosing down the whole engine bay with a pressure tester and making a slippery mess.

jason52416d agoMost Upvoted

Just watch out for that dye gunking up your heater core later on.