Join Date: Feb 2011
Location: San Francisco Bay area
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Re: Coolant puzzle
You're talking about a coolant recovery tank, which catches coolant that passes through the pressure cap if it releases. What I'm talking about is a header / expansion tank, which is in the cooling system and is pressurised. It has a second pressure cap on it. It should be the highest point in the system.
If you have a header tank, the pressure cap on it should release at a lower pressure than the one on the exhaust manifold, which is thus not functioning as a pressure cap. It's just a plug.
You can of course have a coolant recovery tank, AND a header tank, which is what I have. The coolant recovery tank is connected to the cap on the header tank, NOT the exhaust manifold one.
You need a coolant recovery and an expansion tank to minimise the air in the system, if you are going to use modern long-life coolants. They hate being exposed to hot oxygen and then begin to crystallise. If you don't have either, better stick to the old 2-year green coolant.
However, the OP asked why coolant gushes out of the cap on the exhaust manifold. Answer : because there is a header tank he hasn't found yet.
"The overflow tube is capped off" : Because it's doing nothing, because the overflow tube that actually works is connected to the header tank.
Bristol 31.1, San Francisco Bay
Last edited by MarkSF; 06-11-2015 at 02:49 AM.