2005 Honda Civic - Unknown Coolant Leak

mattscherer5198_167569
Fri, 22 May 2020 23:32:32 +0000
Maintenance/Repairs

So here’s the issue I’ve been having and I’m out of ideas, a quick summary is at the bottom:

I’ve had my car for 4 years. After about 2 years, I happened to be checking the coolant level and noticed it was pretty low, maybe one to two cups short of coolant. I filled it up not thinking much about it; maybe 3-4 weeks later I checked again and about the same amount was gone. I continued to check every few weeks and it seemed to be missing the same amount. I didn’t pay much mind to it because I never had any issues with overheating or anything else and I’d been driving like this awhile apparently.

Fast forward maybe another year and a half, I topped up the coolant again, but this time I noticed some steam coming out from under the hood near the radiator cap area. I figured that I filled it up a bit too high and the extra liquid was coming out and boiling up. Big mistake there apparently; a week later or so, while driving on the highway, I must have overheated and blew cracks in the radiator, fluid everywhere.

After that, I put in a brand new radiator. Then the next day driving, the check engine light came on with a thermostat code (P0128) and I noticed my heat was going high. Checked the thermostat, it was stuck open, so I replaced it. Two days or so later, the light still hadn’t gone off, and I was beginning to overheat again. Checked my coolant, missing like one to two cups of coolant again…

Basically I’ve found now that I ONLY lose coolant when driving. I’ve let the car idle for over 40 minutes while occasionally giving it some gas, I’ve checked my system with a coolant system pressure tester, both of which I see literally only a couple drops over 40 minutes to 2 hours. No where even close to the 2 cups of coolant disappearing in about 10 minutes of driving.

The leaking seems to be burst all over, not just from one specific spot. It’s also not leaking from the water pump side of the engine, and it’s not mixing with my oil or being burnt off that I can notice while driving, which makes me think it’s not a head gasket or water pump.

TL;DR

Symptoms:
Leaking 1-2 cups of coolant within 10 minutes of driving
Only a couple droplets while idling 40+ minutes
Only a couple droplets while under coolant pressure system tool
No leaking below water pump side of engine
No coolant visibly mixing with oil or coming out of tail pipe
No coolant on inside floor of car

What I’ve done already:
New radiator
New thermostat
New radiator hoses and clamps
Tried three different radiator caps

I’m just out of ideas now and don’t want to spend a fortune getting it checked and getting everything changed out if I don’t have to. Only thing I can think of is maybe it was a faulty new radiator? Any help would be appreciated.

11 posts - 5 participants