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Coolant leak mystery

Car parked overnight on slightly sloped driveway (nose up). This morning, small coolant puddle under water pump area, with slow drip continuing.
Reservoir looked empty, and check under radiator cap showed full. But slow drip seemed to pick up speed. I quickly put cap back on and put a pan under the drip. Had to do other things for a few hours.

Came back to car and pan only had maybe 6 ounces of coolant in it. Started it up and moved it into garage (level surface).

The leak stopped!

Reservoir is definitely empty, and I haven’t opened the radiator cap again in case it vents and lets coolant stream out (although reservoir leaves an air path to do that as well).

Poked around the water pump (OEM after about 175k) and it looks like it is the leak, although I cannot completely rule out connection with lower hose, which is right under the pump.

What happened to stop the leak?

You don’t have much choice. If the water pump is leaking you will need to get it repaired. Might as well get the timing belt replaced at the same time.

You might want to dry it off with an old rag around where you suspect the leak. Top off the coolant and run the engine for a few minutes. Do it on your driveway. Look for leaks around the water hose. Replacing a water hose is a simple DIY job, replacing the water pump is not.

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You really need to do a pressure test, My best alternative scenario, you have a pinhole leak in the upper radiator hose, that makes the water pump look like the culpret. So it would leak when there is pressure, and lack of pressure by engine being cool, on possibility, the other parking flat the fluid was now behind the level of the hole.

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You didn’t mention what year your Town & Country is or which engine it has, but from experience changing the water pump on mine (2005, 3.8 L V6), take the right wheel off when you do the repair to get those last few millimeters of space to fit the water pump. My father-in-law was helping me with the repair (we have a trench cut out in our garage floor to access the underside of the car so we didn’t have it jacked up to replace the water pump) and we were having trouble getting the pump in until I physically used a prybar to pull the wheel out of the way far enough to get the stupid thing into place. We replaced ours between 135-140k right after we bought it (no maintenance records from previous owner(s)) when it decided to crap out on the way home from Tennessee. While I agree with @Barkydog that a pressure test is the best test to do to give you a definitive answer, I wouldn’t be surprised if the pump is toast due to the number of miles on it.

FYI, moving a car from the driveway into the garage shouldn’t heat the engine enough that you shouldn’t be able to remove the radiator cap if you just drive it up the driveway then immediately turn the engine off.

You could use one of these to find the exact leak path. They’re cheap, easy to use, readily available, and make the coolant light up light a Halloween necklace.

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If the seal around the shaft inside the water pump is failing and allowing it to drip coolant out the weep hole , it is not unheard of for the leak to stop if you just start it up and shut it off without running the engine enough to get up to temp and pressure. The pump still needs to be replaced. If you look at the weep hole, the inside of it should be the same color as your coolant if it has been leaking.


Sounds like this explains my situation. Thanks!

Thanks. I already removed the passenger front tire and wheel well liners to reach the water pump. I’m expecting to replace it.

I didn’t open the cap because it might be maintaining a vacuum that stopped the leak. It wasn’t hot.

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I don’t know what’s causing your leak, but I had a similar problem on my Corolla a few months ago. A small amount of coolant would appear on the floor after parking overnight. Wasn’t losing much, maybe 1/2 cup a month. But it was annoying. So to figure out what was leaking, I drove a few times around the block, then put the car in the driveway and looked for leaks. Nothing. Nothing on the water pump was leaking. Water pump weep hole, nothing. So I jacked up the front passenger side b/c that’s whet the water pump is, removed the wheel, crawled under there with a flashlight. Not a drop. So I returned that side back to normal and jacked up the driver’s side, removed the wheel, crawled under, no leaks.

So I’m thinking somehow the leak must be fixed. I’m good to go! Yipee!! No way, next morning a small puddle of drops of coolant. Eventually it occurred to me that the reason I could see no leaks in my first experiments was b/c the driveway is tilted a little so the front end is higher. But where I park is level. So next set of experiments I backed the car into the driveway, so the front end was lower, did the jacking thing and very quickly saw where the leak was happening. On the Toyota 4afe engine, there’s a coolant return hose that returns coolant from the back of the engine (where the thermostat is) to the water pump on the front of the engine, and where that metal hose attaches to the water pump there’s an o-ring, leaking o-ring was the problem.

Congrats on getting yours fixed, George. Good work… but I know you know your stuff, so while I’m happy for you, I’m not surprised. :grin:

Thanks TSM. The other problem I had, the door latch/key lock, that was actually a tougher one to solve. Technicallly more difficult. The coolant leak was very annoying though.

Looks like @oldtimer_11 gets all the points. I was draining the coolant while removing the belt and then turned the water pump a little by hand to look for play. The leak came back.

Thanks again!

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I’ve run into those kinds of situations

I’m assuming that o-ring was flat and/or hardened, causing the coolant leak

When I suspect such a thing, I attach a coolant pressure tester. Those faulty o-rings will often start to leak under a little pressure