Ok so on my Jeeps 5.9 magnum i have noticed that occasionally when i turn the engine off after driving around I can here the overflow tank gurgling. It makes bluup bluup bluup bluup noises and when i pop the hood i can see the big bubbles coming up.

I cant figure this out, for one I have had the Jeep for almost a year and I have put on 6k miles almost. I have done 1 oil change on it, and that oil looked perfectly normal (black). Im about 2600 miles in on that change and from the dipstick the oil looks pretty darn clean actually. Still has that honey color pretty much. I dont see any signs of milkshake, oil cap is clean, from what i can see in the valve cover hole it looks clean.

I also recently like 2 weeks ago, replaced a blown timing cover gasket which was leaking coolant outside the engine onto the ground. While i did that we replaced the timing chain and i looked into the oil pan and the oil was fine. I also had a compression test done, all the cylinder averaged 162psi dry, and 166 psi with oil. 1 cylinder tho was like 150psi dry and 155 with oil. My coolant was very clean also, no oil, or oily substance..

All the spark plugs were clean and normal looking, and smell fine. I dont have white smoke coming outa the tailpipe and honestly since i've never smelt what burned coolant is suppose to smell like i cant tell you if it smells sweat like coolant or not.. It just smells like exhaust from a stinky V8 to me lol.

I replaced the radiator cap, thinking my old one was bad (and it did have some crusty stuff on the spring and it pretty much lost its springyness i didnt even have to push down on it to take it off. I could just twist it. So i got the new one and the newo ne i have to push down to twist it on like you should.


One thing i noticed when we fixed the timing cover problem, was after we filled the system back up and turned the engine on and reved it to check the timing i noticed the hose that goes into the thermostat was making a suction action. Like a suction action any hose would make it you hold one end with your palm and breath in on the other end sucking the air out. Is this normal ? My friend was concerned that something is wrong with the thermostat. Im not convicned tho because if you feal the hose and wait till 200f itll get hot as the thermostat opens up.. I dunno.. I dont have overheating issues.. never have, temps always 200-205f, and it never gurgles when its on, just after it gets turned off sometimes. I think the hose was making a suction action because the water pump when you revv the engine was trying to suck coolant in and since the thermostat was closed it was just making that movement (like the hose on your palm thing i mentioned)


Sorry i wrote so much but i want to get all the info out i can to help.. PPL on the Jeep forums are telling me its probably a cracked head, they said pretty much every magnum has cracked heads, and when i turn the engine off the pressure is escaping into the coolant. How could that be tho if it doesnt do it when the engine is on ? Im thinking the gurgling is from the coolant getting hotter in the actual engine after you turn the engine off (since the coolant isnt moving its absorbing all the heat, and then it starts to boil or something and boils into the overflow tank)

 

Maybe i wrote to much and scared everyone ?

 

Have you checked how much coolant is in the system or changed your thermostat?

 

Havent changed the thermostat. Coolant level stays the same

 

i have a freeze plug leak....i know my collant is getting low when i hear the coolant "surge" thru the heater core....if u shut off the radio and listen when u stomp on it.....do u have leaks present????

 

No i dont, i did on the timing cover but its fixed. Nothing is leaking on my Jeep cept the rear main seal, valve covers and my transfercase.

 

It's probably just trapped air. If it still continues to do it after another week.... you may have issues.

 

Well its been doing it for a lot longer then a week thats for sure probably months or the year i've owned it. I just never noticed it until a month ago when i poped the hood and saw it bubbling in there

This is something i dug up on google.

http://wiki.answers.com/Q/What_does_...s_not_overheat

One guy says the gurgling after long trips is normal. Read answer number 2. He is saying after long trips, the reservoir is near the natural boiling point , and after the engine shuts off the coolant in the engine isnt flowing anymore so it gets warmer as pressue builds it releases into the reservoir and since the reservoir isnt pressurized the coolant boils. Im wondering if this could be what it is, cause I asked this on yahoo answers and this was the response i got from someone telling me the same thing as the #2 answer on that link.

Cause it never gurgling on short trips, but on long trips after its shut off (sometimes) it will gurgle. When i shut the engine off and let it sit for like say 2-5 minutes and then turn the power on and check the engine temp, it will be 210 or a little over, the engine temp actually goes up about 10-15f after its shut off. Since water boils at 212f, im thinking maybe it really could just be boiling in the reservoir (coolant or not the reservoir isnt pressurized so it will boil).. Who knows maybe im wrong but could this theory be possible ?

I checked the charts, for a 30-40% coolant mixture the boiling point is 220f. 30-40% freezing point is around -15-23c. I checked my coolant just now and its actually more water the coolant, the temp was only good up to -20c or so. Which is a 30-40% mixture, if that unpressurized is 220f boiling. Then maybe the coolant was actually boiling in the reservoir due to the engine being shut off and the coolant getting hotter in the engine getting pushed into the reservoir.

Kinda makes sense to me.. sorta

 

Actually, the dynamics you describe there, are sound. Would not surprise me a bit if that were correct. (it does make really good sense.....)

 

i mean if your not loosing coolant then you should be ok.