The humble coolant expansion tank... odds are you've not given the one on your C5 Corvette much more though than "does it have coolant in it". Unfortunately though with Corvettes starting push 20 years old now the plastic these are made of is starting to really show it's age and fail for many owners.
The most common source of failure is where a hose returns from the radiator. That hose has no strain relief on it, so every bounce and jounce or vibration transfers right through it and has to be absorbed by the plastic provision above, which isn't terribly thick being a 3/8" hose provision. Multiply that strain times 20 years, a few hundred thousand miles, and some spirited driving, it's going to fail. Driving your corvette on the track? Just straight up divide by zero, it's going to fail you!
The above video is a good example of that very failure, which had occurred on our author Shred Jesse's C5 Corvette. The provision mentioned failed with a mild crack. Coolant would then begin to spurt out form the failure, both draining the system slowly and preventing it from pressurizing. A system that can't pressurize can't cool as well, and now you've got an overheating problem.
While catastrophic failures are currently rare on the Corvette, as the plastic continues to age on more and more of these vehicles the odds only go up that failures will be more severe... and if a Pressurized system were to fully fail... it's going to burp a lot of coolant out, if not outright pump all the coolant out of the failure point!
Suffice it to say... it's worth looking at your Coolant Expansion tank and formulating a plan.
Coolant Expansion Tank Repair & Modification
So let's start with the basics... can these be repaired or modified to prevent this failure, or other failures? Unfortunately... not really. Plastic welding only further compromises this area of the plastic. Per the picture above... JB weld Plastic isn't a solution either (no surprise though right?).
Strain relief in theory could be added to the hoses coming and going from the expansion tank, which would buy you some time. You could probably utilize a cable clamp to at least secure the hose going from the radiator to the expansion tank...but good luck securing the bottom hoses.
Suffice it to say, we're unaware of anyones long term success story doing a repair or modification... but if you've done it, reach out and let us know! We'd love to add your information here!
Coolant Expansion Tank Replacement Options
So you either need to replace your tank or have made the wise decision to get ahead of replacing your tank. Wise choice! Here's the options we're aware of, along with some success stories from folks!
First on our list of options is the OE replacement, manufactured by Dorman. It lasted 20+ years on most of these cars, even if the replacement only goes 10 years it'll last longer than most folks will own the car so why not make it the next owners problem? We don't agree with that mentality, but it's how some folks operaet. At around $105 or so on amazon, it's a fair enough deal. You unfortunately will lose the connection for your low coolant sensor it would appear, so it's not a perfect replacement, but it's OEM shape and connections and will bolt right up without a fuss.
One solid and tested option is the True Focus Fabrication coolant expansion tank. Coming in at a stout $499 price difference, this will definitely be the most expensive unit we share as an option... but it is a solid and tested good option both on the street and on the race track! Our author Shred Jesse utilizes on on his C5 Corvette after a failure and it's worked great for him. It fits all factory mounting locations, it's easy to work with, and it even has AN connection options if you're looking to get really fancy. The only qualm Jesse has had with this unit is that the one singular non threaded replaceable hose provision on the unit... is the exact same one that failes on the OEM unit. This unit being aluminum and notably more stout however has thus far meant it's fine, and since it's aluminum, should it fail a new threaded provision can be added on at that time.
Next up, is the Moroso Expansion Tank for the C5 Corvette. Coming in at $372 at the time of writing this article, it's cheaper than the True Focus Fabrication unit. Moroso also has a massive history of doing great work for a variety of different vehicles various tanks. Moroso even has great install directions with PICTURES in COLOR! Few manufacturers of aftermarket parts can claim that!
That said, there are few differences between the Moroso unit and the True Focus Fabrication unit that give us pause. The big one being that none of the connections are threaded and thus replaceable. While this does improve clearance a bit in some areas... if something fails on here you can't just replace it, it's an outright failure. Also, like all aftermarket units it would seem, you lose the low level coolant level sensor provision.
The Moroso unit also lacks a sight glass provision allowing you to check the coolant level at a glance. For us, that's a deal breaker since you'd never know if a leak somewhere else in the system had consumed some coolant.
Last on our list are the various generic offerings from Amazon. Unfortunately... all the reviews are fairly poor for these, with inconsistent fit, low quality connection provisions that can leak... in general we'd say these are to be avoided.
The specific expansion tank pictured above is available for $85 with prime shipping at the time of writing this article... but only has 3 reviews and they are all one star so suffice it to say... we're only sharing this to steer you away!
In fact... when we looked at all the options available on amazon, they rendered as a 3 star rating, but when clicked only had 1 star ratings from folks confirming that the part does not actually fit the Corvette. So, steer clear of expansions tanks from amazon!