Radiator mystery - JeepForum.com
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post #1 of 3 Old 02-12-2020, 09:59 PM Thread Starter
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Radiator mystery

This issue boggles me and my Mechanic.

I have a 2008 Jeep Wrangler Unlimited. 90k miles. This summer I noticed that as I sat idling in the pick-up line at my son's school, my Jeep would "surge" a bit. The RPMs would rise a tad, and the temperature gauge would go from 1/2 to 3/4 in a matter of seconds. It would idle like this for around 30 seconds or so. While it's still idling high, the temperature would stabilize again back to 1/2. This would repeat every few minutes. It is not limited to idling. Happens while driving as well, but not as noticeable due to external noises and such.

So in August my radiator cracked. My mechanic replaced the radiator, pump, thermo, and hoses. The high idling was still happening. At one point in this high idle episode, the thermo gauge went into the red. Took it back to the mechanic and he fixed a hose that was leaking, which was a hose they just replaced. The surges kept happening.

I notices coolant on my driveway when I parked at home. Took it back and they replaced another hose.

Then at the pick-up line, it surged into the red and steam poured out from under the front passenger side of the hood. Drove right to the shop. They replaced the radiator cap, said it failed.

Got the Jeep back and surging kept happening. Driving home today, steam starts pouring out from under the hood. Went right to the shop. The upper radiator hose completely blew off. The hose clamp was still tight.

So they did a block test to see if there is a head gasket leak. It passed. So this is still a mystery.

Any idea what can cause surges in RPM, Temperature, and enough pressure to blow radiator hoses off? I'm guessing the radiator cracked due to pressure surges, but that's my uneducated guess.

Thanks in advance. Let me know if more details are needed!

phatsajak is offline  
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post #2 of 3 Old 02-13-2020, 04:48 AM
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Any idea what can cause surges in RPM
Failing iac comes to mind. Could be mass air sensor, This can be checked with a scanner that reads live data. I think the shop should do or have done a pressure test on the cooling system. Also could be the t stat or trapped air air in the system. This should have been checked before returning it to you.
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post #3 of 3 Old 02-13-2020, 08:23 AM Thread Starter
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Gotcha. One other symptom that I forgot to mention... Before all this surging started to happen, there would be a water trickling sound in my dash whenever I would start my Jeep. That has since disappeared. I'm guessing that was right before the crack in my radiator was fixed, and the trickling sound was low coolant level, but not sure if that also points to air pockets...

Last edited by phatsajak; 02-13-2020 at 08:34 AM.
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cooling systems , radiator , surge

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