Couple of months ago a co-worker came in to tell me my car was leaking something. I went out to check and there was a large puddle of what I determined to be coolant under the car and it was dripping from somewhere but I could not see the source. I added about a quart of water to fill up the radiator and drove it home. It sat all weekend until I could get it to my mechanic on Monday. I was surprised to not see a big puddle under the car on Monday but drove it to my mechanic. He flushed and filled the system twice, said there was a lot of rust and didn’t want to pressure test it since he said it would likely cause it to leak in places that were fine now. He said he could not find a leak though. Next day I drove it to work and when I got there, sure enough, there was a heavy dripping of coolant under the car and I was able to see a small puddle in one place on top of the engine. I immediately took the car back to my mechanic, but by the time I got there it had stopped dripping. He opened up the radiator cap and showed me some whitish gunk which he said was from an additive he had put in to clean out the rust. He refilled the radiator, closed it up and commented that the system was under pressure now so if there was a leak we should be seeing it. He said I should keep an eye on it and bring it back for another flush and fill.
It has not leaked since, as far as I can tell, and I haven’t taken it back for another flush and fill yet.
So any ideas about the leak?
And is it bad that I haven’t taken it back for another flush and fill for 2 months?
So I’ve stumped everybody with this one?
If there’s a leak, a flush and fill will not fix it, and a pressure test will find it. I question your mechanic’s logic. Mine leaked from the upper hose fitting on the radiator, caused by bad engine mounts allowing the engine to rock back and for. This cracked the radiator, requiring replacement. Yours might be somewhere else, but a pressure test is required to find it.
Are you sure it was a leak, and not an overflow of coolant caused by overheating? When was the last time this car had a new thermostat installed? Are the cooling fans working correctly?
If it was leaking it would still be leaking. Cooling system leaks don’t go away all by themselves.
Is there still “whitish gunk” in the radiator? There should be nothing but antifreeze and water in the radiator. If you see anything but green, I suggest another flush and refill.
On the hand, if it’s not leaking and the engine is operating at normal temperature, it may be best to leave well enough alone.
“Cooling system leaks don’t go away all by themselves.” I disagree. I once had a T-bird that leaked at the seam of the side tank for the radiator. It started while it was still in warranty, but I couldn’t get Ford to fix it because it wouldn’t leak while they were watching. It wouldn’t leak during a pressure test. It would only leak if the temperature was just right (not fully warmed up, but not cold, and not fully pressurized), and the planets were aligned just so. I finally gave up and replaced the radiator myself - end of leak problem.
That said, it is non-sense to claim that a pressure test would cause leaks where there were none.
The concept of pressure causing leaks in areas that are fine now is bogus. If the system cannot hold the test pressure, how is it safe to use the car. When the engine builds pressure, that is when you want the system to hold. If the system leaks while hot and blows all the coolant out, you risk overheating the engine, blowing a head gasket, and warping head(s).
One area that can leak intermintantly is the water pump. You definitely have enough mileage on this car for that to be the case. You should have had it replaced at the last timing belt change.
Hope that helps.