Background information:

  1. I was driving a 2008 Jeep Wrangler 3.8 L.
  2. Before I noticed the gauge, I first noticed the A/C on cold stopped working. Then the temperature gauge needle hovered a little over 3/4's of the way but never touched the maxed out line. I shut it off two blocks after the sudden increase but let's go with about 5 minutes from noticing going about 35-40 MPH at less than 2,500 RPM's. Once parked, I shut it off then restarted to see if I could replicate the problem.
  3. When I looked at the coolant reservoir to refill it, the reservoir had about a cup or less left.
  4. I refilled the reservoir while the engine was still hot about a tenth under the max line (I overfilled it last year and had to get a new radiator from the manufacturer). I used the designated Mopar coolant but didn't realize I had to dilute it to 70 % (I plan on having the whole thing flushed properly tomorrow as at most it's diluted at 90-95%).
  5. Then I let the engine idle while putting the heater on max hoping this would help alleviate the heat in the engine. The temperature gauge needle almost dropped back to the normal middle immediately. The temperature gauge light disappeared.
  6. When I drove it back to work, within 5 miles from where I stopped in a 35 MPH zone, the temperature gauge needle jumped between the middle to less than 3/4's of the way. Once I parked it, I saw it leaking coolant from what looks like near/behind the idler belt pulley. The temperature gauge needle during those conditions stayed near the middle, then jumped to about 5/8ths.
  7. When I drove it to AutoZone and then back home, the temperature gauge needle stayed near the middle or a two lines above it. The OBD scanner print out from AutoZone is reading only one code - my same old Code P0420 Catalyst system efficiency below threshold but nothing else.
  8. I placed a rag under the leak to monitor the progress as the engine cools down. I hope to see if the conditions in line 7 won't come back once the engine is completely cooled in the morning but I got a feeling I cracked something.


Did I set up my engine for future failure? Did I destroy my water pump? Will I have to change the head gaskets? How can I go about finding the leaks I probably caused? What other horrible things did I do to my Jeep because I drove it without enough coolant?

Thank you all for any and all help!

  • If the engine got too hot, it might have warped the heads, causing the head gasket to leak. However, if you never got it too hot, it might be okay. You should fix the coolant leak and keep driving it. Check for drops of water in the oil (or chocolate milk oil if there is a bad leak), or white sweet-smelling exhaust, which will indicate a head-gasket leak. You might also want to change the oil, as it will loose some part of its lubricative ability if it gets too hot. Sep 26, 2019 at 2:43

1 Answer 1


It doesn't sound like it's likely you have any lasting damage as you didn't run out of coolant, it just got low and you caught it fairly early. It could be a straightforward coolant leak from a hose or a lose connection, however, since you said it's near the idler pulley it's very possible it's the water pump. The pump may have failed or it may be the gasket, either way it needs attention. The repair procedure is to drain, remove the serpentine belt, replace the water pump and gasket, replace the belt, and fill.

The diagram below shows how close the idler is to the water pump. enter image description here

As for the AC not working it may be unrelated, I'd fix the water leak first and then see if the AC issue is still there.

  • It is quite possible the ECM shut off the a/c when the temperature went beyond the normal range.
    – mikes
    Sep 26, 2019 at 20:10

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