Is there a tool or technique for repairing crushed heater core connections, or sealing a hose to imperfect fittings?

This is in regard to my 2002 Daewoo Lanos, but I am sure other people have this problem from time to time with other models as well.

So when I replaced the original heater hoses, back in 2021, they were difficult to get off, and I might have crushed the fittings somewhat, twisting the hoses off. Or perhaps, the hoses are not the correct size. The OEM parts list shows that one heater hose is 18 mm and the other is 20 mm. In this country, the only choices are 3/4" and 5/8". I used 3/4" for both, and one leaked so badly upon initial startup that I had to cut off the end, and put a short length of 5/8" hose and a 3/4" to 5/8" stainless fitting.

I have a leak, which results in coolant running down the firewall, and I have to add a cup of coolant every 2-3 weeks. I am tired of wasting coolant, and I want this car to be reliable enough for even a long-distance drive, so I want to resolve this.

It would be too difficult to replace the heater core, and quite possibly there is nothing wrong with it, and it’s just a matter of getting different hoses. On this car, the hoses MUST be molded hoses, with a 90 degree elbow on one end, which goes to a plastic crossover pipe.

Assuming I get hoses of the proper size, and the fittings themselves are somewhat distorted, could I apply sealant to the fitting, before installing the hose, which would prevent a leak? Would that be clear silicone, black silicone, or something else?

Any advice would be appreciated.

You might try Oatey Plumber’s Epoxy.

Pesky rubber hose-to fitting leaks, suggest to try some easy ideas first

  • Verify you are using the correct hose inner-diameter and material for the application
  • Apply a little plumber’s pipe dope to fitting before pushing hose on.
  • Wrap fitting with a few layers of teflon plumber’s tape
  • Try a different type of hose clamp
  • Silicone caulk often works if fitting is kept dry until it cures, but can make removing hose later quite difficult.

When working on rubber hoses that have been in place a long time, if hose is difficult to budge, cut it off rather than attempt twisting methods.

I have straightened heater hose pipes with alignment punches or a smooth shaft like a 1/2" socket extension.


I was thinking of tapping in an alignment drift pin as well. Anything cone shaped of appropriate OD to fit the tubing. However, another potential option for DIY pipe expander/distortion removal tool for copper or aluminum tubing might be something like a rubber plug for the hull drain on a small boat. I have a bunch of them. The rubber expands as you tighten the screw and it compresses the rubber between two washers. Might be enough to make the tube round again if it’s crimped down a bit…



There may be a better way. A radiator repair shop may be able to order or adapt something new. I have had leaky heater cores after changing hoses. Mostly on Fords. If you bent or distorted the tubes you can expect trouble.

I’ve seen those as a replacement for engine block plugs when the threads are too mangled to accept the OEM plug.