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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.
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.