Change the rear diff cover; now my baby is over-heating ...

Knowing my mechanical limitations has help me avoid many a melt downs in the garage. Most times when I work on vehicles, there remains a blue cloud of "my Navy words" hovering close to the ceiling.

Background. Bought an stock '13 JK Unlimited with 25K miles. Took the Jeep to my trusted mechanic and he indicted the Jeep had NEVER been on a dirt road from the looks. Great, there should not be many issues. New 3.5" lift and 315s and I'm beginning to feel like a Jeep guy.

The Bacon8r has always seem to run a little "warm". TrailDash alarm triggers at 235 degrees (no sure why I choose that). Norm running temp is around 210. Long highway grades and mountain passes, easily push it towards this temperature. I did the Rubicon Trail in August and while there were times it reached 240 degrees, it did not stay there long and cool down reasonably fast.

Last weekend. Biffed my rear diff cover during the Rubicon Trail ride. Replaced the diff (near the top of my mechanical expertise) and to my surprise, IT DIDN'T LEAK! Headed for a road test and within a quarter mile, temp hits 240 and I go into panic mode. WHAT THE HELL DID I DO? I slowly make my way back home. I checked the radiator reservoir and it was empty. Next, I checked the radiator itself. Can't see any fluid. I spent a half hour reading a JK write-up concerning coolants; great info and background.

I go to the local parts store and get some antifreeze (Zerex G-05). I mixed it 50-50 and added it to the radiator. Much to my surprise, it only took 3/4 of a quart. I added some to the over-flow for good measure (1/4 fill). I'm thinking, what good is that little amount going to do for me? Apparently that did the trick. First surprise!!! I have not had it out on the rocks yet but driving around town, things are much better. I still have to address the the cooling issue but at least I can get to work.

Second Surprise! My flipping heated is blowing hot air. For weeks, while camping in the mountains of central Utah, I couldn't get the heater to blow hot air; only warm and VERY inconsistent. Tada! My heater is working as advertised for the first time in memory and with no hot/cool fluctuations.

Diff cover and heating problem: Coincident but threw me for a loop.

Bottom line: Still need to investigate cooling issues.

What a noob!

Glad you got some issues worked out. Rent or buy a cooling system pressure tester. You likely have a leak somewhere. It is possible that when the temps were 240, some of the coolant blew out of the reservoir which can happen when engine is running warmer than normal. I would start there. Also make sure fan is working and radiator/condensor fins aren't plugged up.

WJCO said:

Glad you got some issues worked out. Rent or buy a cooling system pressure tester. You likely have a leak somewhere. It is possible that when the temps were 240, some of the coolant blew out of the reservoir which can happen when engine is running warmer than normal. I would start there. Also make sure fan is working and radiator/condensor fins aren't plugged up.

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This.
You'd be surprised how much mud can be hiding between your radiator and fan.
Pulled mine apart awhile ago as I was overheating, must have been a half inch wall of mud stuck there.

WJCO said:

Glad you got some issues worked out. Rent or buy a cooling system pressure tester. You likely have a leak somewhere. It is possible that when the temps were 240, some of the coolant blew out of the reservoir which can happen when engine is running warmer than normal. I would start there. Also make sure fan is working and radiator/condensor fins aren't plugged up.

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Thanks for the suggestions. I have an infrared thermometer so I thought I would check the radiator input/output hoses for temperature. Just to ensure the radiator is cooling.

do you get an antifreeze smell in the interior?

if the radiator and overflow were that low, sounds like you may have a pinhole leak in the radiator or in the heater core.

If it's the heater core you'll likely smell it in the interior. sometimes I've seen them leak at the hose to the heater core so I'd check the connections at the firewall.

As mentioned a pressure test will confirm a leak - then you just need to find it. Get a black light and do your inspection in the dark, antifreeze will glow under a black light, don't forget to check the interior

jeeeep said:

do you get an antifreeze smell in the interior?

if the radiator and overflow were that low, sounds like you may have a pinhole leak in the radiator or in the heater core.

If it's the heater core you'll likely smell it in the interior. sometimes I've seen them leak at the hose to the heater core so I'd check the connections at the firewall.

As mentioned a pressure test will confirm a leak - then you just need to find it. Get a black light and do your inspection in the dark, antifreeze will glow under a black light, don't forget to check the interior

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No antifreeze smell that I can tell. Pressure test to follow ...

BillTheCat said:

No antifreeze smell that I can tell. Pressure test to follow ...

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Also, if you don't visually see a leak, watch the gauge. If it drops at all, there is a leak somewhere. Also replacing the radiator cap every 30k-50k isn't a bad idea either, cheap insurance.