I had a custom exhaust slapped together on my car several years ago. Recently, it started running badly. I noticed that the rubber hose connecting the catalytic converter to what I believe is the EGR tube had split. I got the hose off and went to the parts store to find a replacement. The guy at the parts store told me it was coolant hose (Gates Blue Line) and had no business being on the exhaust. I only drive the car a few hundred miles per year so that's probably why I've gotten away with it for so long. What can I replace this with? Given that I got years out of that one hose, I'm not against replacing it with the same and treating it as a consumable but I want to do it right if possible. I do not have the ability to weld.

The hose was about 10 inches long and 3/4" ID. The EGR tube is 3/4" OD, the catalytic converter's outlet is 1/2" OD. The hose was cranked down with a hose clamp and some hardened foam-like material over the catalytic converter's outlet to bring it down to size. Attached is a picture of where the hose was.

EGR pipe and cat outlet where the hose was

2 Answers 2


If coolant hose is nearly perfect except for its short life, blue silicone "heater hose" should last longer. It's heat resistant.

If you're looking for something to wrap around the 1/2" tube on the cat so it fits the 3/4" hose, thin silicone sheets are available as a kitchen item.

If you're feeling ambitious, you could find a way to extend the 1/2" tube 2-3 times longer than what it is using metal tubing, perhaps with a compression fitting. This will reduce the temperature at the open end and slow down the degradation of whatever hose you attach. A 1/2" to 3/4" adapter would also make for easier fitting to the silicone tube. Remember that exhaust systems tend to bounce and swing, so leave plenty of clearance and slack hose between the EGR tube and the cat tube.

  • Thanks. I was also considering exhaust wrap to increase the diameter of the cat outlet. Commented May 10 at 15:38

While this might seem a little janky, something you could do is get some 1" stainless flexible exhaust pipe used for small diesel heaters, then get reducer adapters for each end going to the right size. Like I said, janky, but you should be able to get it to work and seal up. NOTE: the products I've linked to are only examples so you know what I'm talking about ... please find the right ones for your application.

  • I was considering trying to find a 3/4" exhaust for a diesel heater, but I didn't have time to research them fully. The whole car is janky so I'm not against some JB-Welded tubes. Commented May 10 at 15:45

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