Frustrating coolant leak


Old 12-02-07, 12:52 AM
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Frustrating coolant leak

2001 Ford Escort ZX2 with 62,000 miles.

I experience an off and on coolant leak which occurs while the car sits overnight. It may go weeks without a trace and when the leak does appear it is maybe a couple of tablespoons. The location is always on the drivers side beneath the thermostat housing. There is a heater hose running from the rear of the housing to the heater core and a shorter u-shaped hose from the front of the housing to the head. After the leak appears there is usually no real evidence of leaking around the hoses or the thermostat housing. Last spring I took the car into a repair shop where they pressure tested the system and found no leaks at all. They suggested replacing the hose clamps, which I did myself at home. After repalcing the clamps on each end of the thermostat housing and tightening the screws holding the housing together (they were loose) the problem seemed to be solved for until a few weeks ago.

I'm wondering if the thermostat housing seal is going bad. At present the leak is so miniscule, is there any risk in just watching it and waiting? It seems that I lose only a small amount and I don't see how I could lose any more that what remains in the housing when I park the car overnight. From what I can gather the housing comes apart and goes back together with rtv sealant. If it needs to come off and be resealed I don't think I want to mess with it, I'll just take it back to my mechanic. I would prefer to just take the wait and watch approach. What do you think? Thanks for any input.
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Old 12-02-07, 03:43 AM
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If the system is pushing coolant out, then it is sucking air in when it cools down, and you have a closed system. This, although minuscule, is not good for the system. BUT, you have to find the leak in order to fix it. I would just keep an eye on it daily until you are able to actually locate the problem, THEN fix it.
Old 12-02-07, 09:56 AM
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Thanks for your input. I check the garage floor every morning for leaks. There was a spot yesterday, none today. My worry was a catastrophic sudden failure but this has been an off and on dribble for so long I guess thats not a big worry. I also realize its foolish to blindly go replacing parts until the problem is diagnosed. Finally, I don't want to waste my mechanics time and my money going back for another pressure test which is unlikely to reveal anything until the problem grows. I like your advice.
Old 12-02-07, 10:14 AM
Join Date: Dec 2007
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t-stat housing

if the t-stat housing is made of black plastic(ish) material, then its the housing with out a doubt. they crack inside at the lip that holds the thermostat and seal. replace it with an updated part.
Old 12-02-07, 01:00 PM
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Thanks. You described the housing exactly. I'm still thinking I'll watch it and nurse it along for a few months, unless things get worse. I'll be taking the car in before 70,000 miles for a new timing belt and I'll ask my mechanic to replace the water pump, thermostat and housing at the same time. In my original post I overstated the leak amount, it is more like 1 or 2 teaspoons when it occurs. Thanks for the info.

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