I know I should do a post in the new guy forum but I am on the road with a little problem.
I have a 2004 grand Cherokee Laredo 4wd with the 4.7 and auto transmission.
After running 65 - 75 on the interstate and then slowing down on an exit ramp, the fan is making a lot of noise. I can shut off the engine and restart approximately 5 seconds later (waiting on fan to wind down) and the noise is gone.
I can drive around town for 45 minutes or more with no problems!
What can try to further troubleshoot this problem and what is your best guess as to what I am going to have to fix?
Thanks so much for your help!
FYI: I replaced the water pump and thermostat and belt about 6 weeks ago? Possibly the fan/shroud is loose or moving from wind load at high speed?
It developed a small leak. I replaced the thermostat because I thought most people did it at the same time. The old one looked perfect though. At the time temperature was a non issue.
Currently on the interstate, the temp is a little over the 210 mark. Maybe a little higher than I consider normal. Outside temp was in the 45 f range so with interstate airflow and outside temperature, overheating should not be possible as long as water is flowing.
After filling the coolant system, did you bleed all air out of it? Will the fan slow down by itself after leaving the highway, or do you have to switch off the engine? I have never heard my hydraulic cooling fan in high speed mode after leaving the highway, also with 35 ºC outside and airco in full. My Jeep runs a little below 100 ºC normally, not sure how much that is in degrees F. Are you sure they sold you the right thermostat?
I meant to get back on the forum sooner but...Hopefully this will help some others...
Anyway, before leaving Ky to head back home to SC, I bought a gallon of Dexcool and topped off the overflow tank. I didn't even bleed it again. It took almost a half gallon in the tank but I did not have a "coolant low light" illuminated.
Anyway, the problem has gone away and not returned. It was due an oil change when I got home so I did an oil change and checked all the fluids. It did not use any more coolant on the way home.
All I can think is that it had an air bubble near the temperature sensor and it was making it the fan go into high speed mode. When I installed the water pump, I did bleed the system and operated the heater as well. It just seems funny that it only happened on the interstate.? I could drive around town for an hour at temperature and it never spooled up into high speed mode.
Now at 70,000 miles, I think I should be replacing some other fluids... Differentials, Transmission and transfer case so I'll be reading up on that.
I'm not sure about your jeep, but on mine there is no sensor anymore on the cooling expansion reservoir to show low level. But half a gallon low is quite some. Is the temperature now back to normal level as well? Glad that your problem is solved.
Well, It has been almost 2 months since this original post and problem. The jeep worked great on the way home from KY and has since driving around town in SC. I've done some more Preventative maintenance changing some fluids. Full transmission flush with filters and front differential fluid change and new front brake pads with rotors turned and new air filter.
Well my wife drove to KY again yesterday and the problem came back exactly like last time. Driving much over 60 on the interstate with the outside temperature just above freezing, the coolant temperature would get above the 210F mark (boiling) and the fan would cycle on. It was pretty hard to drive that slow on the interstate with the speed limit at 70 and cars zoomimg past but she did make it to KY.
Left it at the Jeep dealership in KY and hope to know more on Monday. Initial observation at jeep showed it hard to repeat w/out driving above 70 and all they have done so far is to rebleed the cooling system to see if that helps. They are going to check more on Monday.
I would really like to find out what is going on!
Facts:
It never did this until after I changed the water pump, thermostat and belt. Water pump was changed due to small coolant leak from pump shaft. Thermostat and belt were changed because I thought I should do them while I had it apart.
I don't understand how it would run hotter on the interstate with near freezing temperatures when it doesn't run hot around town with temperature in the 70's...
Maybe it is a faulty temperature sensor or an air bubble in the system near the temperature sensor? The only other things I can think of are:
Transmission temp causing coolant temp to rise?
higher RPM's on interstate at 75mph?
Hi Planenut, i´m having some problems with a little higher coolant temperature at highway speeds around 120 Km/h ( approx 4 ºC) and coolant coming out via the expansion reservoir. My biggest bet at the moment is the radiator cap. The cap has 3 functions: 1 - to seal off the cooling system from the outside, 2- to pressurize the cooling system (and by doing this, to increase the boiling point of the cooling liquid) and 3- to let the cooling liquid flow back from the expansion reservoir to the radiator when cooling down.
If the radiator cap will not let the system pressurize (enough), the boiling of the cooling liquid can start as low as 100ºC, very close to the normal operating temperature of the engine (mine normally runs around 98/99ºC). So when driving on highways, the produced heat by the engine can let the liquid start boiling, resulting in higher cooling liquid temperatures. Will not say this is your problem, but could be a cheap fix. Surfing around on the web, i found out that the radiator cap should be changed every year, because of the important function it has and the relatively low price.
Also you did mention your cooling fan never behaved like this before you changed pump, thermostat etc. When you did this change, you removed the radiator cap.............
One thing to look at the cap is for indents in the rubber seals. As soon as you see that, its a good time to change the cap. Never knew this before and i never changed any cap on my cars before.
That is a great point and a cheap thing to try. I'll be calling the shop in KY tomorrow and make the suggestion to them and make sure they at least consider it..
The shop in KY had it from Saturday til Tuesday.. Really found nothing to speak of. They checked with Chrysler who reported problems with aftermarket thermostats so I went along with the change for lack of anything else to try. They never were able to duplicate the problem. They drove it over 20 miles and left it running for hours.
I asked them about the radiator cap and also if the Dexcool I used was an acceptable coolant. Prestone Dexcool was said to be as good or better then the required coolant.
They did say that they checked the temp sensor and it was spot on.
They also said something to the effect that the radiator showed different temperatures at differernt sides and that supported the thermostat potential. I don't really see how that supports the thermostat as a problem.
Anyway, my wife picked it up and paid the 180ish bill for troubleshooting and thermostat replacement. She is not driving home until Friday so I won't know anything else before then..
Thanks for checking back.. I will update as I know more.
I installed the Stant thermostat on mine and was also thinking in this direction. But yesterday changed my radiator cap and bingo, problem solved. Did you try to squeeze the upper radiator hose with engine at operating temp? (use a glove or some rag to not burn your hand), the hose should be rock hard and you should not be able to deform it. On mine i could just deform it warm as easy as i could do it when cold, showing that there was no pressure buildup in the system. When not changed yet or in the last few years, i would advise to do so. I had in fact the same problem as you had, just a little higher then normal temp when driving at highway and the cooling fan at higher then normal speeds.
My manual says to remove the plug and burp 4 times, of course after driving in-between each burp. I have no idea where the air hides. I'd change my fluid but who wants to do the burping. Fan shouldn't come on at highway speeds. You may still have trapped air pockets even after miles of driving.
The hydraulic cooling fan is always on, only it should rev at approx. 600 rpm when no extra cooling is needed. Normally all air should go to the highest point in the system, underneath the radiator cap, and should be drawn to the expansion reservoir when heating up. Normally you only should remove the bleed screw only once when filling the system.
Well my wife drove it home (10 hours) and didn't experience any difficulty so MAYBE it is fixed.. I'm away on the West coast until Monday or Tuesday. I'll try a few more things when I get home including the squeeze the radiator hose (while hot) test and might just change out the cap for good measure..
Hey guys I know this is an older post but I just ran into a issue with my 05 jeep Cherokee limited 5.7L... My issue I'm having is that as soon as start the jeep and put the jeep in reverse to get out of drive way my cooling fans starts kicking on right away and will stay on, So far I've had the following items replaced! New Radiator, New AC condenser, New water pump, new temp sensor, New thermostat, Today I'm having some AC work done such as putting in new AC discharge line and a Liquid line installed as well with Drier, I'm trying to figure out what is causing my stupid Hydraulic cooling fan to kick on right away, There are times when I start the jeep and idel and fan doesn't kick on but as soon as I put into drive the fan starts kicking right away... ANY IDEA'S what might be causing fan to kick on right away? Any Help will be appreciated
Do you mean that the fan goes to high speed? The fan should always run as long as the engine runs, only with low speed (500-600 rpm). There are some inputs which cause the fan to go into high speed. A missing coolant temperature info for example will bring it to max rpm. The AC pressure signal can also rise the rpm, but that normally goes gradually. Transmission oil temperature is an other input which can rise the fan rpm. The signal for the cooling fan to change speed, comes from the PCM. So a faulty PCM can also change the fan rpm.