Below are what my temperature guages look like. In order
1. after driving in some stop and go traffic and rolling through parking lot. Typical temperature or at the 210 mark.
2. & 3. Car sitting with AC on in parking lot at 108. Once the electric fan kicks on it goes to 210 then creaps up to just above the 210 then stays for a bit and then goes to the highest setting. The infared readings aimed at the water pump at the base of the heater hose outlets was with in 5 degrees or matched the guage. The temperature guage is not linear and thus can not be interpollated so that 5 dgrees may be more like 0 degree error.

The above was with running water only in the radiator after flush and driving around for about 20 mins.

What do you think? Running to hot? Or am I fine. From memory it might be a tiny bit higher when in the parking lot but it is not something I do. Other driving temps seem in line before the sludg showed up in his car.

 

Those temps seems ok, all my XJ run at thermo temp while moving at speed, but as soon as they idle, the temp will soon rise to the temp the fan is progrmmed to switch on, which I think is 105C

It will then cycle on and off. If the electric fan does not cycle off, then you possibly have an issue (runs all the time with A/C switched on)

A defective system will overheat with extended idling

I had a new learning experience recently, I disturbed some aftermarket wiring enough for it to be grabbed by the viscous fan, (while I was driving), tearing the wire, and partially wrapping around the VC

This impaired its operation enough that my vehicle OH at idle...spewed coolant...they keep getting hotter after you turn off the engine

 

My electric fan cut in temperature is consistent with the 105C. Thanks for the feedback. ouch on the wiring incident.

 

Hey all,
I’m following up on some older threads I’ve seen here, but I’m still stuck dealing with radiator sludge and haven’t found a real fix yet.

I’ve got a 2021 Jeep XJ. A while ago, I had a mechanic do a coolant flush (or so they said), but I wasn’t present and I’m not sure they actually did a full, proper job. Since then, I’ve still got major sludge and rust buildup under the radiator cap and inside the neck. The coolant is still brown and full of sediment. It looks like iron oxide sludge, not the “milkshake” you’d see with a head gasket issue, so I don’t think it’s that.

Also, I filled the overflow bottle about three months ago, and it’s now almost empty again. So I’m definitely losing coolant somewhere, but there’s no visible leak and no white smoke or cross-contamination with oil.

Main questions:

• Has anyone here actually solved this problem long-term and how did you do it?
  
• Would you recommend something like Thermocure or Blue Devil radiator flush, or is a full radiator removal the only way to go?
  
• Should I be replacing components like the radiator cap, thermostat, or radiator itself at this point?
  
• Could this sludge be clogging my heater core or restricting flow elsewhere?
  

I’m trying to avoid just throwing parts at it unless needed. Any advice from folks who’ve beat this issue would be much appreciated. Photos below for reference.

Thanks in advance!

 

Since it’s running hot and the overflow was empty, start by checking for leaks (hoses, radiator, water pump). If no leaks, test the thermostat might be stuck. Also, check the fan clutch or electric fan operation. If coolant was brown, a flush might help, but if overheating continues, could be a failing head gasket (check for milky oil under the valve cover or white smoke from exhaust). Compression test if unsure.