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Old 10-05-2012, 08:30 PM   #55
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Join Date: Jul 2012
Location: upstate NY
Posts: 1,105
My Ride: 2002 330 cic
Originally Posted by TerraPhantm View Post
Hmm... Honestly, I think you're both right. If a crack already exists, then a pressure test will reveal it - either by coolant showing through, or by the pressure slowly dropping. If a crack has not yet formed, then perhaps the mixture of heat and pressure will throw it over the edge.

But simply increasing the pressure slightly beyond what would be seen in a real-world scenario should stress it to a similar extent as heat.
I agree, I think they both might be right.
It is possible for a leak to start when a part gets hot and expands (it is also possible for a leak to seal when a part gets hot and expands).
Likewise for a part that cools, a leak could start, or seal, as the part contracts.

But any real leak almost always seems to show up in a pressure test. Hot or cold. It might not be a visible leak, it could be an internal leak. If the leak is slow it might take a few minutes to show up on the gauge (and then you always wonder, is it a real leak, or just a leak between the gauge and what you are testing - soapy water can help show this kind of leak). You might have a slow leak that the people doing the testing did not wait long enough to see on their gauge.

Did they also pressure test the cap? Maybe the cap is leaking. Or, maybe the cap does not seal well to the tank.

Probably the smart thing to do is replace both tank and cap - at least.

But before you do that, you might want to find out if you actually have a leak.
The light on the dashboard can be useful, but it can also be wrong. You do not say what the float tells you the fluid level is. You might want to add a little distilled water to bring the level between min and max. Shouldn't take much.
You want to keep it BETWEEN min and max - don't go under min, don't go over max. Be careful, at least on my BMW the float will not go above max, but, you could fill it above max if you wanted - don't do that, keep the level just a little below max.

I've read someplace that cooling level sensor and windscreen fluid level sensor are the same part on our cars. This could be useful information if you determine the problem is the sensor, and not the actual fluid level. Switch sensors to determine if it is a sensor problem or a wiring problem.

FWIW I bought my car used this summer. Service records show the thermostat was replaced at about 23K, or 28K can't remember right now. Presumably warranty replacement. Car has about 80Kmiles and 10 years on it. Belts were replaced about 10Kmiles ago. I hate to replace parts that seem to be working OK, but, think I will replace ET and cap since they seem to be common points of failure at about this age. I might do the whole mango thing on the cooling system just because it is easier and cheaper to deal with at home than it is to wait for it to fail. Duct tape and bailing wire will not get you home if the ET explodes.

Last edited by dknightd; 10-05-2012 at 08:36 PM. Reason: typo
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