I recently bought a 2006 LJ. It does not run hot but when I shut it off it starts gurgling into the overflow tank. I have done the following, I pressure tested the radiator cap to 18 pounds and it is good (new cap). Tested the coolant for exhaust gas and it stayed blue. Pressure tested the radiator and no leaks. Used the radiator burp funnel kit with the jeep front elevated, I did this more than a half dozen times. No oil in coolant or coolant in oil. I pulled the spark plugs and they all look good and the same. Put in a new thermostat. That fan seems to engage well when hot. The jeep does not overheat while running, the temperature gauge is straight up. Is there something that I have not done yet. I have searched many forums and cannot find anything new. I appreciate your help.
Radiator gurgling after shutting off
- Thread starter georgekob
- Start date
When mine did that, it was a bad fan clutch. YMMV and all that...
Mine also did that once upon a time and it was a bad fan clutch.
I am curious, if my fan clutch was bad, wouldn't it run hot? I was told that it was air in the system but I have burped it with the front elevated on ramps and using the burp funnel kit.
KennethS
TJ Expert
I was under the impression that is typical for hot (summer) operation. When the engine shuts off, the coolant temperature in the block rises since the water pump is not turning and circulating the fluid. That hotter coolant increases the pressure and pushes into the overflow tank, as it’s designed to do.
thank you, I understand the hot coolant expands into the overflow, but this is steam and coolant bubbling into the overflow.
If you don't know the age of the radiator I would advise buying a new one for your safety while working around it .
https://wranglertjforum.com/threads/radiator-exploded.85438/
https://wranglertjforum.com/threads/radiator-exploded.85438/
When mine was boiling into the overflow, it was a bad radiator cap not holding pressure. Same as you, it wasn't overheating while driving.
Pressure test your radiator, you may a pressure leak somewhere else.
Be sure your radiator isn't starting to crack right where the top hose comes in.
Assuming you have reasonably fresh coolant of the proper mixture.
Pressure test your radiator, you may a pressure leak somewhere else.
Be sure your radiator isn't starting to crack right where the top hose comes in.
Assuming you have reasonably fresh coolant of the proper mixture.
Try shutting the AC off about a minute before you arrive at your destination. I know this is just a Band Aid but I had to do that to prevent the boiling in the overflow on mine. I have all new stuff now but I still do it to alleviate heat soak.
I missed that you tested the rad.
Some overflow is normal upon shutoff, but if it sounds like you're brewing coffee, that's not.
Some overflow is normal upon shutoff, but if it sounds like you're brewing coffee, that's not.
DirtDawg
TJ Enthusiast
Here's my experience within the last week, noting my engine had been running too cold since purchased 6 weeks ago, thus I (wrongly) suspected a 180* t-stat previously had previously been installed;
> Drained enough old coolant and added a quart Thermocure in prep for full flush
> Drove off-pavement and on-pavement prox 150 miles
> Drained, flushed with tap water, drained, blew-out, then 2 cycles distilled water likewise drained / blown-out
> Replaced new hoses, new CTCs, new RobertShaw 195* t-stat and new Mopar t-stat gasket
> Filled engine through heater hose and radiator with Zerex G-05
> Ran engine and topped-off after t-stat opened plus filled reservoir to cold level
No leaks, so thought I was golden - until driving off-pavement next day with same boiling in reservoir as the OP described. Manually burped out some air, then another drive with same boiling phenomenon. I did not drill 1/8" bleed hole in the t-stat, figuring no need with that brand being highly regarded. At that point, still using old Moto Rad radiator cap, so replaced that with the new Mopar cap purchased but hadn't installed. Problem now completely gone with no boiling nor abnormal behavior in the reservoir.
Here's what I think had been happening; the old t-stat (despite being marked 195*) wasn't opening fully, thus never got to 212* boiling temp. With the new RobertShaw 195* t-stat, normal engine temps but the old Moto Rad radiator cap didn't hold 18 psi pressure, thus allowed coolant escape to the reservoir. With the combo of new quality brand t-stat and Mopar cap now in play, problem fixed!
> Drained enough old coolant and added a quart Thermocure in prep for full flush
> Drove off-pavement and on-pavement prox 150 miles
> Drained, flushed with tap water, drained, blew-out, then 2 cycles distilled water likewise drained / blown-out
> Replaced new hoses, new CTCs, new RobertShaw 195* t-stat and new Mopar t-stat gasket
> Filled engine through heater hose and radiator with Zerex G-05
> Ran engine and topped-off after t-stat opened plus filled reservoir to cold level
No leaks, so thought I was golden - until driving off-pavement next day with same boiling in reservoir as the OP described. Manually burped out some air, then another drive with same boiling phenomenon. I did not drill 1/8" bleed hole in the t-stat, figuring no need with that brand being highly regarded. At that point, still using old Moto Rad radiator cap, so replaced that with the new Mopar cap purchased but hadn't installed. Problem now completely gone with no boiling nor abnormal behavior in the reservoir.
Here's what I think had been happening; the old t-stat (despite being marked 195*) wasn't opening fully, thus never got to 212* boiling temp. With the new RobertShaw 195* t-stat, normal engine temps but the old Moto Rad radiator cap didn't hold 18 psi pressure, thus allowed coolant escape to the reservoir. With the combo of new quality brand t-stat and Mopar cap now in play, problem fixed!
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The Robertshaw stat has a bleed hole already in it. It's the bump.
KennethS
TJ Expert
Is there really a problem? The coolant gurgles into the overflow reservoir when hot, then siphons back into the radiator as the system cools. So if the colant doesn’t puke out of the reservoir, and the engine doesn’t overheat while driving, is there actually an issue?
When it does it violently it makes a mess out the vent and each time you loose a little. The OEM reservoir had a pipe in it to prevent that but the replacements don't.
fourpointzero
TJ Addict
This has happened to me when offroading in very hot weather. Hasn't happened in a long time. The only thing since then that Ive done was in terms of "big work" was replace my AC compressor, and other AC accessories in the process. Never had it happen again...least not that Ive noticed.
KennethS
TJ Expert
My original doesn’t have a pipe. Are you referring to the connection that goes to the bottom of the reservoir?
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