Two mysteries

[03CanadaTJ]

Hi all, first I want to say thank you to everyone who posts. I've lurked these forums before, mainly for smaller things like clockspring or hvac blower resistor, and have now signed up.

Yesterday and two I've run into two issues that have me stumped (more 1st than 2nd) with my 2003 TJ.

1. Last night, I was driving home (highway), and my check gauges light came on, with the battery gauge reading somewhere around 12. I managed to make it home, and when checking the battery with a multimeter, the battery was ~12.3V with the car off, and <12V with the car on. Checking between negative battery post and alternator I was getting <12V too. Today on the way to dropping it off to a shop, the alternator seemed to jump back to life, with gauge going back up to normal (14). Checking battery (off and idle) I had regular readings. Is this an alternator on its way out? Battery too?
2. Next thing is my coolant reservoir. Topped it up, drove 10 min, and found it low again. I haven't had any temp issues and couldn't see any leaking. Only thing I did spot was what appeared to be a hose/tube that isn't attached to anything that's near the bottom of the radiator, and I saw when looking down at the space between where the coolant reservoir tank and front of the jeep.

Any thoughts? Thanks in advance

 

[macleanflood]

1. Clean battery terminals and grounds. Check for loose or corroded connections on the alternator. If all of those look good check the PCM connectors for corrosion.

2. Could be entirely normal. Just burping out air pockets. Most like scenario. Could be a head gasket. Could be a leaking water pump. Keep monitoring the level.

-Mac

 

[03CanadaTJ]

1. Clean battery terminals and grounds. Check for loose or corroded connections on the alternator. If all of those look good check the PCM connectors for corrosion.

2. Could be entirely normal. Just burping out air pockets. Most like scenario. Could be a head gasket. Could be a leaking water pump. Keep monitoring the level.

-Mac

Thanks Mac. For the battery terminals/grounds, and connections on alternator, why would that impact what the alternator is throwing out?

Any idea what the hanging hose/tube could be? I'll try to get a photo or better understanding of what it is tomorrow.

 

[John Cooper]

Thanks Mac. For the battery terminals/grounds, and connections on alternator, why would that impact what the alternator is throwing out?

Any idea what the hanging hose/tube could be? I'll try to get a photo or better understanding of what it is tomorrow.

Get a photo of the hose.

If you aren't getting a good positive or negative connection it can and will throw off the alternator.

I would check all grounds, even at the starter. Check every body ground also.

 

[macleanflood]

The PCM controls the voltage output on the alternator. Any loose or corroded connections could affect that relationship. Often as not folks throw a new alternator at the problem and solve nothing.

I'd guess the hanging hose is your front diff vent line. But it's just a guess without pictures or more info.

-Mac

 

[L J]

@wranglertjforum.com

 

[Zorba]

1. Clean battery terminals and grounds. Check for loose or corroded connections on the alternator. If all of those look good check the PCM connectors for corrosion.

2. Could be entirely normal. Just burping out air pockets. Most like scenario. Could be a head gasket. Could be a leaking water pump. Keep monitoring the level.

-Mac

Could even be a pinhole leak in the puke bottle - I had that happen on mine.

As for the alternator - do follow @macleanflood 's advice. If it continues, it could be the alternator. I don't know if TJ alternators have brushes that can wear out - I had to replace the brushes in the old MBZ alternator at about 330K miles. Had to do similar to an old 240D years back.

 

[03CanadaTJ]

In no particular order, haha, thanks Mac, John, and Zorba. LJ, hope I am not doing something idiotic (though I may be an idiot).

Here are the images. It does kinda look like the breather hose. In my best attempt to follow it, did seem to feed into the front diff

 

[John Cooper]

In no particular order, haha, thanks Mac, John, and Zorba. LJ, hope I am not doing something idiotic (though I may be an idiot).

Here are the images. It does kinda look like the breather hose. In my best attempt to follow it, did seem to feed into the front diff

View attachment 660869

View attachment 660868

Yep that's probably the front diff breather hose. See the vent on top of it.

I would do what I could to get the hose up as high as you can.

 

[03CanadaTJ]

Will do. I definitely had it mounted higher... many moons ago.

As for coolant levels, they dropped sitting overnight, but my parking spot is bone dry... could it be air bubbles making their way out of the system and refilling the rad? I haven't been able to open the rad up yet.

 

[John Cooper]

Could be. You don't see any sign of coolant lose anywhere?

 

[macleanflood]

I'd get the hose to a point where you can blow through it and verify it's not clogged up.

And yeah get that radiator cap off and start monitoring coolant levels.

If you can park it nose up...that tends to burp out more air.

-Mac

 

[Strizzo]

Will do. I definitely had it mounted higher... many moons ago.

As for coolant levels, they dropped sitting overnight, but my parking spot is bone dry... could it be air bubbles making their way out of the system and refilling the rad? I haven't been able to open the rad up yet.

rent/borrow a cooling system pressure tester from the parts store and check your radiator cap. If it isn't holding pressure, you'll boil off coolant without any leaks.

if your rad cap is good, you might need to do an exhaust gas check in the cooling system. sometimes a bad head gasket will burn off coolant while running, then the overflow gets pulled down when the system cools.