Problem with charging/cooling... linked?

Asked by Jan 24, 2016 at 04:02 PM about the 1988 Jeep Comanche

Question type: Maintenance & Repair

I have a 1988 Comanche that I bought well used back in '07. Soon after, I
had to replace the water pump and thermostat. After that, it would never
get up to full temperature. Even on a 90 degree day the temp gauge would
just barely register any temp at all. I didn't worry about it since it was
running fine and was not my daily driver. But just the other day as I was
coming home from work I noticed that the temp gauge was showing almost
full operating temperature. Since it was 17 degrees outside, it seemed
really unusual. I also noticed the voltmeter was very low... about 9 or so.
Not good. Anyway, after just a couple minutes, both the temp dropped to
the usual non existent, and the volt meter returned to normal 14v. I felt my
chances of getting home were better but still, something is wrong. Later, as
I kept an eye on the gauges, the temp started climbing... at the same time
the voltage dropped. It eventually overheated and I had to get towed home.  

I'm at a loss to guess what the problem might be. The water pump may
have gone (the heater was blasting cold air, the reservoir was full).. with
possibly an alternator issue. But both at the exact same time? Only
connection I can make is the serpentine belt. But it isn't broken, and seems
to be in good shape. I'm lost with this, any help out there?


9 Answers


If you did not have this issue before changing the water pump and t-stat sounds like air was not completely removed from cooling system. Does your vehicle have the over flow tank with cap to add anti freeze ?


Do not think you have to separate issues just vehicle shut down from over heating.

Ok, I guess I should have included one detail. I replaced the pump way back in '07. Never had any issue with it til about a week ago. And that's one thing that is puzzling me, I don't know if they are related or separate issues. I just know they both happened at the same time.


You did say in your question that after replacing those items would not get up to full temperature. It is strange that you went this long before having this problem but I would try removing all air from cooling system. Will the vehicle start now since it has cooled down ?

Oh yeah.. it seems to be running normal right now, it's charging the battery and everything. When all this stupid snow clears out I'm thinking of taking it out for a drive and see what happens. Right now it's got a huge pile of snow blocking it in so it'll be a while.


Understand that just finished digging my vehicles out. Like I said do not believe you have a problem with charging system because when a vehicle over heats it shuts the vehicle off and dash lights will come on when vehicle shuts off before turning off the key.

I really don't think the discharging was a result of the overheating. Let me describe the scenario in detail... It was about 9:30 pm, I'm leaving work. It's 17 degrees outside, I have an hour drive to get home and no heat. Yay. About ten minutes into the drive I happened to notice the voltage was down around 9, in the red. At the same time I looked at the temp gauge, which is normally showing the needle just barely above the 100 degree mark is now around 150 or so and climbing. Just a few seconds later, the temp dropped to 'normal' and the volts went back to 14. Everything seemed ok, but I was still worried. Twenty minutes later, I'm about halfway home, keeping an eye on the gauges, when the temp begins climbing again. At the same instant the volts drop to 9. Before it ever got a chance to overheat. But this time the temp kept on climbing. I managed to find a place to pull over and stop before the temp gauge hit the ceiling, although it did overheat. There was a puddle of coolant on the ground after I stopped. So I'm wondering if these are two separate events that happened at the same time, if so.... how? Or is there something going on that could have caused both to happen simultaneously? I really don't think the discharge was a result of the overheating.


Did you find out where the anti freeze leak was coming form ?


I believe once you fix the anti freeze leak you will be good to go. I still believe it was from the vehicle over heating because when a vehicle over heats does not do it instantly as vehicle is getting to that point of over heating the vehicle is starting to shut down.

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