I noticed my jeep would rarely, but occasionally heat up a little over halfway on my gauge. I checked my rad fluid and noticed brown gunk on the rad cap. My headgasket should be more than fine at only 100k km, so a coolant flush and replace will be in order. 12' JK .6L. Just wondering if theirs anything else I should check, or if these wranglers have any known issues regarding this. Perhaps someone could identify based on colour. I had an old Montero that had a similar issue, the gunk doesn't feel oily so I don't think theirs oil mixing in, rather, I don't believe the previous owner ever changed the coolant...
You can test the coolant for combustion gasses, that would rule out a headgasket.
You clearly have a leak between you radiator circulation and one or more other systems. If you have an automatic transmission, and it circulates transmission fluid through a cooler housing that transfer heat to the radiator, that could be the problem. If you have an oil cooler that does the same, that could be the problem. A blown head gasket could also be the problem. The quickest checks are looking at the transmission fluid dip stick - if you run an automatic and have a dip stick for it, and also check the oil dip stick. You may also want to check for combustion gases in the coolant. What ever the problem is you want to deal with it as quickly as possible, or the costs of the parts cannon could really shocking. One other problem might be mixing incompatible coolants (HOAT and OAT), which causes the coolant to turn into something nasty.
Was gonna say this appears to be an incompatible coolant mixture. The flush and coolant change should show you the correct and steady temp. If there are still temp fluctuations with the occasional heat increase, I'd start investigating transmission, oil cooler (if you have one) and head gasket.
I don't trust those tests, ive had two different tests done on my old Montero that absolutely (and confirmed after teardown) had a severe leak in the headgasket resulting in exhaust gasses passing through the coolant. I'll probably test it just for peace of mind but I wouldn't rely on it lol
It is a standard, so no atf fluid. It's all OEM but pretty sure the Oil cooler is entirely separate from the Radiator. The rest of the fluid looks fine, bright, vibrant green, not dirty. Oil also isn't milky so I don't think I've got a headgasket issue between the radiator and an Oil passageway. I'm guessing/hoping the dealership I bought it from, or the old lady who owned it prior, made the mistake of mixing coolants not caring. Either way, I'll perform a coolant flush and top it up. Might go as far as pressure checking the cylinders for peace of mind.
I did notice the overflow container is dirtyyyy, no fluid in there tho. So i suppose it's entirely possible there was an issue prior to me buying it, it was fixed, and I'm left with just a little bit of remnants from that job.
Seems reasonable. If your fluids all look good presently, then hopefully what you see around the radiator cap is history.
Speak of the devil, had this happen today on my way home from work.. randomly at that. Turned onto a street, and it rose to there, and slowly went back down