C900 Coolant Expansion Tanks

[DrewP]

Spend the extra money and buy OEM ones! I replaced this one a few months ago with the aftermarket MTC expansion tank eEuro lists: eEuro - 7549876A

When I installed it, I actually had to drill out the center because the hole was too small for the hold-down bolt to fit thru, and there was sharp flashing around the boss where the water pump supply hose connects that I had to trim down with a razor blade. It also has "MADE IN INDIA" molded into it.

I probably had 1,000 miles of street driving, and then 18 minutes into the endurance rallycross I went to over the weekend the tank split right under the threaded boss for the radiator cap (new cap). Granted, it was ~92*F out on the lake bed, and the temp gage was pinned a knick or two under the red after the first few laps and I had the heater on full blast. Will address cooling issues in another thread...

The good news is that it split facing the engine, so my engine is all nice and steam cleaned now....

I can't believe this burst before one of the radiator / heater hoses. The hoses on this car are at least 5 years old, and are all Gates from when I could get the expensive hoses for short money when I worked at the shop.

[Powar]

That's awesome. I have the same aftermarket one in my C900S. The cap doesn't seal properly and was spraying slightly when under pressure at track days. Pretty sweet feature for a brand new part.

[Jordan]

MTC's motto should be. "Usually better than nothing"

[DrewP]

LOL

It was better than nothing, that's for sure!

[Geoff]

Interesting failure point. You can see in the photos that the threaded section is a separate component from the bottle section, indicated by the clean break. What the supplier probably does is mold the threaded portion (since it's common to many coolant bottles, brake fluid too) and then blow mold the bottle. Then they probably ultrasonically weld the threaded portion onto the bottle. Ultrasonic weld joints can be brittle, especially when they're not done right, which would explain the separation. A poor ultrasonic weld could warp the part and explain the cap fit issues some people talked about - or it might just be a sh*tty part to begin with. Other leakage people have seen could actually be at the threaded part-to-bottle interface due to a bad weld too.