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Frango100 02-03-2011 05:05 AM

Coolant loss
A couple of months ago i noticed a strange noise coming from the radiator cap a few minutes after switching off the engine. It was like as if air bubbles where passing by the radiator cap. Didnīt see any bubbles in the expansion reservoir nor any level changes, so didnīt pay much attention to it. Few days ago when driving on the highway, i saw a slightly higher cooling liquid temp then then i was used to see. At least normally the temperature was just below 100š C and this time it was just slightly above it. Changed the waterpump and thermostat some weeks ago, so thought it had maybe to do with the new thermostat. But when looking under the hood, i saw the level in the expansion reservoir low and some liquid around the reservoir. Filled it up again, but yesterday the same story. looked at the reservoir with engine running, but no air bubbles. This morning just ran the engine with radiator cap off, but also no bubbles. There is a slight residue floating on top of the liquid, which i never saw before. Cooling system was flushed and filled with fresh liquid some weeks ago as well.
No strange smell from the exhaust. I probably have to go for a cooling system leak check (but no time this week), but iīm afraid of some problems with head gasket or worse. Anybody had the same syptoms?

JeepMe 02-03-2011 06:19 AM

Re: Coolant loss
Have you changed your oil recently? Any signs of coolant in the oil?

TJXJWJ 02-03-2011 07:52 AM

Re: Coolant loss
It's possible you have/had a big, fat air bubble in your cooling system from the work you did and it's working it's way out.

01grand 02-03-2011 08:11 AM

Re: Coolant loss
Did you make sure to bleed the cooling system like the manual shows when you filled it after the flush?

Frango100 02-03-2011 09:54 AM

Re: Coolant loss
I did indeed remove the bleed screw when filling the system and also squised the upper radiator hose to remove as much air out of the system as possible. The first 2 days i had to refill the expansion reservoir after cooling, but thereafter the level didn't change anymore. Now i'm seeing the liquid disappear from the expansion reservoir fill opening, at least, its wet overthere. I never saw the liquid pooring out when i was standing next to it. I reved it up to 5000 rpm for a while, but didn't see any bubble in the reservoir. What i was thinking, is it possible that the radiator cap is not holding the pressure, which will lower the boiling point of the liquid and make it boil during higher loads, causing the overflow in the reservoir? At least i will give this a try and buy a new cap to start with.
Didn't change the oil very recently, but if there is coolant in the oil, it should normally give a creamy look in the oil filler neck. All normal overthere.

TJXJWJ 02-03-2011 10:06 AM

Re: Coolant loss
You're probably right....I always change my cap when I do a flush and refill. It's cheap insurance and they go bad...people don't realize. I shouldn't assume everyone replaces their cap when they do a flush. I've had good luck with OEM and Stant caps.

Also, just for a double check, make sure the overflow hose is attached tight with no pinholes. If your finding water around the overflow tank, that would be the first thing I would look for.

Me Fix 02-03-2011 01:16 PM

Re: Coolant loss
Hi Frank

I appreciated all the ideas given to my Dimming Mirror issue and so now it's my turn to respond to your question.

When I traded my old 1996 Grand Cherokee for this newer 2004 Overland I noticed that the top radiator hose would collapse after the system cooled. The hose collapsed because the check valve in the cap was not opening to allow the vacuum from the cooling engine to draw back coolant from the overflow tank. A new cap solved the problem. Maybe you have a bad cap or like someone else suggested a hole in either the tank or the line running from the tank to the radiator fill neck at the cap. My experience with water in the oil is milky oil and water droplets on the oil fill cap or worse. Even a steamy appearance to the exhaust. Lets hope it's nothing serious like that.

Frango100 02-03-2011 01:32 PM

Re: Coolant loss
Thanks everybody for your ideas. I will try to find the cap (probably with the stealer) and will keep you informed about the result.

Frango100 02-09-2011 08:13 PM

Re: Coolant loss
Good news guys, picked up the new radiator cap this morning and just installed it for the return trip and temperature stays at 98/99š C again as it was used to be before. Ofcourse i normally never do this, but just to check the cooling system to be ok, drove it to 170 Km/h and all stayed ok:D. Now the upper radiator hose is hard as a rock with engine at operating temp, as before you could just squeeze it as easy as if the engine was cold,
I can only advise to those of you who never changed the radiator cap before (as me until now) to do this at least once every 2 years. It can safe you a leaking head gasket or warped head in the worst case, or several stops during a trip due to boiling cooling liquid.

FredoinSF 02-09-2011 08:55 PM

Re: Coolant loss
Well done. Glad you solved the problem and it did not break the bank.

Frango100 02-14-2011 08:04 AM

Re: Coolant loss
Well, seems that my problem isnīt solved yet. After putting the new radiator cap on it seemed to be ok for a while, the system was pressurizing and temp stayed normal. Now again the temp rizes a few šC above the normal reading and there is no pressure in the system again. After comparing the old radiator cap P/N 55116897AA with the new one, P/N 55116901AA i saw that the new cap doesnīt have the small spring to keep the vacuum valve closed anymore. (if you keep the cap in the normal mounted position, the vacuum valve opens by gravity on the new cap)Anyone knows if this is normal?
So strange that directly after installing the new cap everything seemed to be ok, and now it starts again.
Removed the radiator cap this morning and removed the serpentine belt and let the engine run shortly to check for air bubbles, but non observed. (this according the jeep service manual instructions, only didnīt remove the thermostat) Only the liquid level rose rapidly, what could have been combustion air entering the system, but no bubbles observed. I think that i have to go for a cooling system pressure test now. Any more ideas from your side?

Frango100 02-19-2011 07:28 AM

Re: Coolant loss
Ok, an update. Did the cooling system pressure test today. Left the radiator cap in place and mounted the pump/indicator in the place where normally the bleed plug is. Unfortunately my indicator only goes until 15 PSI, but with this pressure it was steady for more then 10 minutes. Also when warming up the engine, there where no pressure fluctuations and the pressure was building up slowly. I will have to look for an other indicator which can handle at least 25 PSI to see if that will make any difference.
But if the head gasket is bad, i would have thought that there would be a leak at all times, cold or hot. Iīm now more thinking in the direction of a crack in the head or block, which would let high pressure combustion gasses pass by, even probably only when driving at higher speeds or when higher power from the engine is needed. When not under load, i can rev up the engine and there is no fluctuation in the cooling pressure and no bubbles in the liquid. Am i thinking right, or do i oversee something? Would any stopleak stuff do any good in case of a crack in head or block?

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