When the rad was changed 5 mos ago, was straight water used to fill the system? Even if the block/head/heater core were not flushed, there's no way the proper coolant mix and fill could turn that nasty in only 5 mos. Might need another new rad soon.

 

That pic looks like the copper radiator stop leak.

My thermostat stuck closed and I didnt have another one to put in so I'm going thermostat-less

traffic -185-195
highway-170-175

 

FWIW, the only reference to the t-stat in the FSM is what was installed at the factory and DO NOT operate without one.

 

those temperatures will kill your 4.0 early....

 

Well it feels a lot better, not nearly as sluggish. It's only been driven about 20 miles (home from work) and of course something else happened so I havent driven it since. I already have the new thermostat just needs to get put in.


I'm curious why you would say cooler temps would be bad for the engine?

 

I would be interested to see what the FSM has to say about a 3" lift, removing doors, 33" tires, and cutting my fenders to fit

 

I'm running at around 195-200 with a new radiator, 60/40 mix of water and antifreeze, water wetter, and all new hoses.

 

the in town temp wont the freeway temps a little low forcing the motor to run lean which will lower performance, worsen gas mileage and shorten life. no tstat is fine for a drive home but for everyday driving its bad...

 

That brown sludge does resemble stop leak. My guess is that the system was flushed, but the heater core was not. That gunk most likely is settled in your core. You can pull both hoses from the core and flush it separately from the rest of the system. Flush it both ways and you will see things that look like river mud.

Good luck.

 

16 year old XJs will die early runnin' those cool temps.

 

I post "FWIW" and still get a response.

 

Haha I got your back brother

 

Ok so just got my engine back together. Got her running and filled and burped the cooling. While I was first working on getting the air out it got up to 215... now I've been idling about 45 minutes and its staying right around 190 195... wow that's almost scary to me. It used to heat up to at least 210 idling that long... new 195 t-stat.

 

How do you flush the system if you can you a garden hose just trying to learn as much as possible so I can fix this mess b4 something goes wrong with it

 

I've heard that a garden hose works well because you dont want too much pressure, but I've never verified or tried it myself. Maybe someone that's done it can chime in. I was looking into flushing my heater core before I checked the t-stat because I was getting cold air from the vents and though I had a blockage in my heater lines. There are lots of threads on many forums if you google it.

Not to hijack the thread.... but I only have dummy lights in my jeep and I was under the impression that it wasnt a "reading" type temp sensor, just an on/off if it's over/under a certain temp to trigger the light? I have looked into a cluster swap and one of the requirements is a new sending unit from a jeep with gauges in the cluster. I could very well be wrong tho.