So the previous owner did a special version of clamping on the expansion tank, and it seems it's leaking. If these 2 hose clamps can't keep it from leaking, what am I missing? The hose definitely seems like it's made for it, but it also clearly doesn't seem like it fits. It's been remarkably difficult to find pics which makes it tough to tell what hose I should be looking for.

 

It's supposed to be held on by two pinch clips

 

If you have a supercharged the part number is C2Z1373 BUT ITS DIFFERENT FOR THE NON

 

A lot of times if an underhood hose won't seal it's because the rubber has become stiff from time and heat exposure.

Best to replace the hose instead of trying to clamp the crap out of it.

 

Yep. It's an easy replacement and the connector on the other end of it (if it's an S/C) above the throttle body is prone to failure anyway. Also check there isn't a hairline crack on the plastic pipe of the expansion tank itself.

 

It's likely that your tank nipple is cracked/broken and the clamps are trying to keep it sealed up. It is VERY common. I have broken two different tanks. It's extremely annoying and the supercharged tanks are more expensive and harder to find. The hose should be a bit longer and have some fender support to prevent this. As the engine revs it pulls on the hose and over time it breaks the tank nipple.

Does anyone know if the 5L supercharged tank is different? Looking at pictures back to back they look identical in every way but the part number for the 2009 Supercharged is: C2Z11937 and the 5L models have this part number: C2Z22872. The 5L version is a bit cheaper. I think the 5L tank is the same but the part number changed over the years.

 

I have a 2009 4.2L S/C. Sounds like I need to buy the hose and the reservoir both, huh? There are 3 separate part numbers so far in the thread, so maybe I'll start by calling the *********** and seeing how much it would be to buy from them.

BTW, the reason this came about was because I got an error code Code P0128 - Coolant Temperature Below Thermostat Regulating Temperature. When I saw the little leak out of the reservoir, I figured loss of pressure. Think I should be replacing the thermostat too?

Edit: Really? steal-er-ship is edited out?

 

I would get the tank first and try that. It's probably leaking at the cracked nipple. Check the hose over but I've never had issues with the hose on mine.

I'd recommend getting some extra hose a hose barb and some clamps to extend the hose a bit and attempt to support it nearby so the engine movement doesn't break the nipple off the new tank in a year.

 

Just ordered a tank from eBay. Dealer wanted $250, this was $150, so we'll see if it works out. I also got a replacement hose from the dealer, (since it was only $18) but I'll probably use a bit of the old hose to build the extender you're talking about. I'd rather do a bit of preventative if possible.