Can you patch a cracked coolant reservoir tank

You can patch a cracked coolant reservoir tank, but you may be better off replacing it

Car makers have used plastic coolant reservoir tank for a long time. But the older versions were never pressurized. If you have a cracked coolant reservoir tank and it’s not pressurized, you can patch it. But if yours is pressurized, I strongly recommend replacing it and not trying to fix the old one. Here’s why.

There’s only one way to patch a cracked coolant reservoir tank

Coolant reservoir tanks are made from high density polyethylene. NOTHING sticks to polyethylene. Well, nothing stick for very long to poly. In other words, that plastic epoxy will stick for a while. Then it will leak. So will FlexTape. So will silicone. Trust me, nothing sticks to poly.

The only way to seal a cracked coolant reservoir is by melting the crack closed with a soldering iron or meting in additional poly from a plastic repair kit.

The Poly Welder Pro 200 Watt Plastic Repair Kit comes with 10 sticks of polyethylene repair material and a 200-watt welding iron and stainless steel reinforcement fabric

Use the welding iron to melt the edges of the crack into the middle. Then add more poly material to fill in the crack.

Never try to patch a cracked coolant reservoir on a pressurized system

In the past, the coolant reservoir was just a place to store extra coolant. As the engine heated up and the coolant expanded, it would flow into the reservoir. As the engine coolant, it would flow back into the radiator.

But on late model cars, carmakers changed the system. Now, the reservoir is part of the cooling system and it’s pressurized. Crack repair never lasts in these reservoirs because of heat and pressure expansion and contraction. If your fix fails, the coolant will leak out, the pressure will drop and your engine can overheat. Worse yet, an overheated engine can damage the head gaskets, costing upwards of $3,000. It’s just not worth it.

Where to get a replacement coolant reservoir tank

Find an aftermarket coolant tank at dormanproducts.com

You would think that the engineers would spend a little extra time to make sure the coolant tank could withstand the constant pressure. But they didn’t. So we’re seeing a LOT of broken seams on these molded tanks. You may think you can seal it, buy you’d be wrong. You can’t. No matter what glue or epoxy you use, the coolant tank will leak again.

You have three choices:

1) Buy a used one from a junk yard. But why replace a defective design with another defective design?

2) Buy a new one from the dealer. Hopefully they’ve updated the design

3) Buy a replacement coolant tank from an aftermarket supplier. Dorman Products makes them. Enter your vehicle information on their site and find the part number. Then do a google search for that part.

©, 2013 Rick Muscoplat