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Unread 09-07-2011, 11:25 AM   #1
mrgriscom
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new owner, diagnosing an overheat

My dad just gave me his '02 Wrangler SE and I drove it from his house in FL to NJ. We drove straight through and the engine overheated after about 1,000 miles and 18 hours on the road.

The car was running fine for all of the trip and the driver at the time said the overheat happened quickly (temp needle did not creep up slowly). Under the hood I found the radiator overflow hose detached and coolant spewed out everywhere. Small amounts of coolant were burning and steaming, but not enough to see "smoke from under the hood". The overflow reservoir was full (I did not know at the time that the overflow hose was the only connection to the reservoir). I re-attached the hose, let the engine cool, and started driving again. After about a half-mile, the temperature gauge went off again.

This time we surveyed more closely. I heard a gurgling/percolating sound for some time. Then, after a while, I heard a sudden 'rush' of liquid and noticed the coolant reservoir was now empty. Eventually I added ~1.5L of water and drove again. It did not overheat. After stopping, I felt the radiator intake hose and radiator cap and both were hot to the touch (indicating coolant was circulating?). The reservoir was nearly depleted of the added water. I topped off with 100% ethylene glycol and have driven ~200 miles since and it has been OK -- the temperature gauge centered on 210°.

The coolant is quite brown. When the reservoir was empty, there was a brown sludge at the bottom. I opened the radiator cap, and the water inside appeared very rusty.

I did some basic diagnostics for blown head gasket (examine motor oil, film around oil cap, bubbles visible through radiator cap when running engine), and they were all negative.

Questions:

1) Was the overflow hose coming off the cause of the problem, or a symptom of a larger problem? Should coolant be exiting through the overflow during normal engine operation? And if there is no reservoir to catch it, would it continue to exit until a low-coolant situation is reached?

2) Is the dash temperature gauge an accurate assessment of whether engine overheating is actually taking place? Can it be trusted? During the half-mile drive it indicated OK then suddenly shot up to red.

3) What caused the sudden 'rush' sound? Were there voids in the cooling system due do venting/boiling coolant that suddenly collapsed?

4) Recommended service from a mechanic? I'm thinking a coolant flush at minimum.

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Unread 09-07-2011, 11:32 AM   #2
GOLENJEEPTJ
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I would definitely start out with a complete flush,even a new thermostat and rad cap would be in order.Do the radiator fins appear to be clear not clogged with dirt?
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Unread 09-07-2011, 11:41 AM   #3
Best4x4
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Yeah I'd flush that puppy ASAP. If it's got clogged fins I'd replace the radiator.

I would also switch over to the green coolant found everywhere in the USA vs the Jeep/Chrysler HOAT which is very hard to find except at a dealership. Everyone on here swears the green coolant is bad for your engine, but it now last up to 100-150K and with a full coolant flush you shouldn't have any problems. My 05 with less than 20k on it had nasty crude in the overflow reservoir and it was nasty when I flushed it (I bought my 05 with less than 3k on it and I never added any coolant). I went to every auto parts store Auto Zone, Advanced, and Oreilly's and not a one of them carried HOAT and would have to special order it.

I now have 52k on my Jeep and the coolant is very clean with no "sludge" in the overflow reservoir!
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Unread 09-07-2011, 03:05 PM   #4
mrgriscom
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no dirt in the radiator, just a lot of bugs. is there a certain kind of "green" coolant or are you literally referring to coolants that are green? i just bought some PEAK-brand antifreeze that is fluorescent green. thanks for the assistance.
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Unread 09-07-2011, 03:15 PM   #5
j_niko
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I would definately change your thermostat. It's a $3 part and pretty easy to do and it could be sticking from all the crud built up from the dirty antifreeze.
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Unread 09-07-2011, 08:51 PM   #6
Best4x4
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All the new "green" coolant should be the same. I'd flush that radiator, replace the thermostat, and while you're at it the radiator cap.
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Unread 09-07-2011, 10:07 PM   #7
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Do a good flush not just a drain and refill. Might even use some super flush being you have brown sludge.
When done be sure to use the correct antifreeze and burp out all the air out of the system.

If you want to be more preventative, change the thermo (195 Deg Stant) and radiator cap (18psi Stant). Plus be sure the overflow bottle is not cracked filled properly and the hose is connected properly.

The cause could be as simple as dirt on the outside blocking the radiator fins to a cracked head. Being your overheating hasn't happened again it is likely something simple. Your temp gauge should hover between 200 and 210 while driving.

Does your heater work and blow hot air? If not directly flush the heater core by removing the heater hoses from the engine and use a garden hose to force water through.
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Unread 09-07-2011, 10:16 PM   #8
mike_tx
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Like others said....sounds like a malfunctioning thermostat, coupled with a dirty system. I just flushed my system and changed the thermostat two days ago. My "new to me" '98 also had sludge in the bottom of the overflow tank. I washed it out during the process. I was running a consistent 210+ before the flush......now it's definitely running cooler (only by ~5 degrees, but it's noticeable on the temp gauge).
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Unread 09-07-2011, 10:25 PM   #9
Best4x4
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If you break down out in the middle of no where good luck finding some of that HOAT. Stick with the green stuff which after a complete flush will work just fine and it's available everywhere.

The main reason Jeep/Chrysler used HOAT was for it's long life which the green stuff now goes to 150,000 miles or 5 years as well.
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Unread 09-07-2011, 11:21 PM   #10
joe108
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I have only been able to find the HOAT stuff at NAPA, no where else, of course I stopped there.
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Unread 09-08-2011, 12:06 AM   #11
JPNinPA
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You could substitute G05 for the HOAT. Plus there are many different types of antifreeze out there and available at most auto stores. Yes HOAT is difficult to locate. But if you were out there in a bind you would be adding water until you could replenish otherwise.

Be aware some engines components react with different antifreeze types. The results could be corrosion, component breakdown or deposits. all bad for the engine and cooling system
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Unread 09-08-2011, 01:25 AM   #12
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Anything but Dex Cool!!
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Unread 09-09-2011, 11:43 AM   #13
mike_tx
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Quote:
Originally Posted by Best4x4 View Post
Anything but Dex Cool!!
Agree....DexCool should be avoided. When I just flushed my coolant system, I first ran some RMI-25 in the system for two weeks, then flushed it completely and used the "any color" antifreeze from Walmart. Works great....have it in all my vehicles. Once my vehicles hit the magic "replace coolant" mark, I switch them over to generic 100k stuff. This way I never have to hunt for coolant.
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