Long story short, have a coolant leak that doesn't show up anywhere. No leaky drips or wet areas anywhere. I can smell a little coolant when the engine is hot, but no visual signs. It leaks so slowly that I've only had to top off the radiator once in the last 6 months. Engine temp runs fine, but I knew the coolant was down last night because when I'd come to a stop , the temperature of air from the heater would blow cold. Then when I'd start moving, the temp would come back to warm. I don't want to just add a sealer to the radiator. Would rather find the leak. I know it's not a head gasket. No signs of water in exhaust. Do they make a pressure tester that fits the radiator cap for Hondas? Any suggestions appreciated.
Duane

 

Yes they make a pressure tester.

There are small hoses and stuff on the back of the engine and the intake manifold that contain coolant. These are often best seen from underneath the car. Also check the radiator very carefully, it is hard to see the whole thing.

 

How to Tell if a Car's Water Pump Needs Replacement: 8 Steps

Chances are this small leak is a sign of your water pump beginning to fail.

 

I hope it doesn't turn out to be the water pump. I just had it and the timing belt replaced about 6 months ago. The new one should last another 100,000 miles as did the first one.
Duane

 

go to advance auto and rent their pressure tester, will set you back around $180.

It'll come with the right adapter to fit your radiator and you just pump to radiator cap limit which should be around 16psi. It might say on the cap but I don't have one to check.

obviously once you reach whatever psi and it drops you're leaking coolant. Check both radiator hoses, the heater hose that runs to the firewall, the heater bypass hose, the coolant temp sensor, the water neck that runs under the head behind the block, or the radiator itself.

You'll see wet spots somewhere or at least look for signs of a previous leak where dirt might've built up on the wet spot before.

A few years ago before I replaced all my hoses I had a little leak in both heater hoses.

The only time I'd consider it being the water pump housing is if you started smelling coolant right after you had it replaced, not months later.


***Forgot to mention if you rent the tester to check for cracks where the pressure relief valve is at. The plastic housing is sometimes cracked and you'll always have a leak when testing.

And once you do return it, I think it's within 30 days, you'll get ALL your money back.

 

Have you properly bled the cooling system?

Just to clarify, it's a free rental for the pressure tester at many auto parts stores.

 

Well, for anyone following this thread, I have some results. Apparently the radiator cap was bad. It was allowing the radiator when hot to relieve its pressure into the coolant reservoir. That 16 pounds of pressure in the reservoir cracked the bottom of it where the hose attaches, and that is where the leak occurred. Didn't show up when I pressure tested the system because the overflow tank isn't part of that system. I got a new radiator cap and replaced the overflow tank and everything seems fine now. Thanks for all the help suggestions.
Duane