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Sneaky Coolant Leak

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    MILES:Approx. 165000
    ENGINE:3100 V6
    DESCRIBE ISSUE....Coolant leaks but later on after sitting. Go outside and there is a big wet spot of coolant under the car. I fill up the reservoir tank, get it up to temperature and watch for leaks but there is literally none at all. Turned the heat on and off full blast here and there to have coolant going through the heater core but still nothing. It did do this a little ways back when it was cooler outside but then stopped for awhile during the summer and was unable to find the leak then because of it just not doing it anymore. It was cooler outside this morning when my girlfriend took the car so I am somewhat stumped on this one. In almost every coolant leak case I've dealt with, it has revealed itself but not this one. Any suggestions would be greatly appreciated. Thank you.
  2. These engines were notorious for lower intake manifold coolant leaks. Look for a plug with a clamp hold down for what used to be the distributor mounting hole. You should see some antifreeze around there most often than not. Probably an oil leak also, so be mindfull to change the o-ring on that plug for the old distributor hole while your in there.

    Also, to help you pin point the leak if it is not coming from the rear portion of the lower intake, go out and rent a pressure tester from autozone.

    Look here for their tools available in your area. Most likely they have one for loan. http://www.autozone.com/landing/page.jsp?name=loan-a-tool

    Since you say it leaks over time, it is probably leaking as the different engine metals such as aluminum intake, iron block etc are working at different expansion rates. So putting pressure on a cold engine is your best bet since you can't do that with a hot engine. As when you let the engine build up it's own pressure as it's gets hot, it basically seals itself due to expansion. Then you have exactly what you are experiencing.

    I have done so many of these, I would be pretty surprised if that intake was not leaking.
  3. Here are some snapshots of the area I want you to check. Screenshot (103).png Screenshot (104).png
  4. Some of those V6's had a plastic fitting hidden behind the alternator with a mid-size hose connected to it. I fixed it in a campground for a stranger, probably 10 years ago, so I don't remember details other than to say we couldn't access the fitting till I took the alternator off. Then we found the broken plastic fitting. It came out easily and we took it to the auto supply. They didn't have the right size, but we went on to a big box home store and their plumbing department did. Took two pieces, and maybe one was from the auto supply plus a size adapter from plumbing supplies. I replaced plastic with iron, sealed with Teflon tape.

    This car had a MAJOR leak. I don't know if it started gradually like yours or not. Just thought I'd mention something I'd seen.
  5. Thanks for all the info. I had the lower intake gasket replaced like 3 years back I think it's been now. And I put a new water pump and thermostat in it a little bit before that. But any of that stuff can fail no matter how new. I did not get a tester yet, but did leave the radiator cap off of it and got it up to temp. Both upper and lower radiator hoses got hot, but I did not see any circulation through the radiator at all. Only thing it did was pour water out the top of the radiator, then drop back down, start to over heat, I'd fill it a little with water, temp would drop, then water come back up a bit but again, no water coming out the water jackets in the radiator at all. Coolant is definitely leaking from the water pump area but it did the same thing when the intake gasket was leaking and it's all pretty hidden especially from the top. My Sis has the same engine pretty much but it's the 3400 and it leaks everything but brake fluid. Friggin annoying.
  6. Water pump is the most likely on-again off-again leak point.
  7. Paul "ScannerDanner" had major problems with one of those recently --- presented as a crank no start after an overheat, it took him a while to realise it was a major coolant leak into the manifold.
  8. Or...go the old-fashioned shade tree route: use some coolant dye and use a black light.