# Red Cats

**URL:** <https://community.cartalk.com/t/red-cats/48935>\
**Category:** Maintenance/Repairs\
**Tags:** explorer, ford\
**Created:** [May 16, 2010, 4:12pm UTC](https://community.cartalk.com/t/red-cats/48935 "2010-05-16T16:12:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![techrob](https://avatars.discourse-cdn.com/v4/letter/t/779978/32.png) [@techrob](https://community.cartalk.com/u/techrob)\
**Post date:** [May 16, 2010, 4:12pm UTC](https://community.cartalk.com/t/red-cats/48935/1 "2010-05-16T16:12:05Z")

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I own a 00 Explorer 4.0 ltr. but the engine was replaced wa 01 4.0 ltr.I also replaced the cats, but one of them is still getting cherry red. What could be the problem & fix?

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**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\
**Post date:** [May 16, 2010, 4:18pm UTC](https://community.cartalk.com/t/red-cats/48935/2 "2010-05-16T16:18:50Z")

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When a cat turns red hot it means unburned fuel is reaching the cat. You have to figure out why unburned fuel is reaching the cat. Otherwise it’ll melt the subtrate inside the cat and destroy it, if it hasn’t already happened.

Tester