Weird heating issue

[JCTJ]

So my TJ ( 98 manual 4.0) does absolutely perfect in town and sitting at a stop. 200-205F, but the second I start going over 65 it gets up to 215-220. I’m thinking it may be a radiator issue and the radiator does look kinda cooked as far as rust or mud or whatever in it lol. I’m thinking flushing with thermocure and doing a lot of flushes after will fix the issue. Has anyone experienced this and fixed it?

It has a new thermostat (195° stant), a new stant cap, and pretty new hoses

Thanks!

 

[KennethS]

That is the classic sign of insufficient radiator flow. Try the flushes, and if those aren't successful, search for the new radiator threads (there have been a few, with many, many pages of information).

 

[Ithaca]

Definitely sounds like it's having flow issues. When doing the flush, also make sure to remove the block plug on the drivers side in between the cats. It'll gush out so make sure to be ready and out of the way. Some people say thats unnecessary, but I don't see how you'd do it proper without that step. Flush it with hose water first a few times then the cleaner with distilled water, then just distilled, then add your coolant. I ran the engine until it was up to temp with the distilled/cleaner then just the distilled a couple times to completely clean it before adding coolant mix. After all of that my temp dropped about 30 degrees and engine sounded a lot healthier.

This is also a good time to flush the heater core. I was shocked to see the amount of "mud " that came out the core. Blew my mind, but now I have heat again.