so now mine is overheating.......whats the next step?

[90eliminator]

Ok, the coolant bottle blew up, so I replaced it with one from Napa, but now the new coolant bottle is pushing coolant out the cap through the blow out valving built in. I noticed that the aux fan is not operational, need to fix that...but that should not it to overheat sitting at idle...should it. Also I guess I need to know what the next step is. Radiator, thermostat? thanks in advance

[jpnjim]

Check your clutch fan too, make sure it's working effectively.

The temp in my XJ has been creeping up lately (had to run the heat yesterday to keep it ~210),

when I stopped, I spun the clutch fan by hand, and it spun very freely (= I don't think it's locking up as well as it should when warm).

 

A plugged/clogged radiator could do it as well, as could a bad impeller in the waterpump (tho a with a bad impeller will usually show as a temp drop when you increase RPM's, as would low water level).

[Drahcir495]

I replaced everything. Thermostat, water pump, temp sending unit, aluminum coolant bottle, clutch fan, & Radiator. At a stop light at idle the temperature will climb until I put my aux fan on a dash switch. I kick it on when needed - no problems. I would fix the aux fan first. If you still have a problem, get a new radiator and burp the system correctly. I think mine would have been fine with just the new rad & fan fix - HTH Rich

[Eagle]

First things first: How far are you filling the coolant bottle, and did you get the system fully bled when you installed the new bottle?

 

The bottle on the closed system is an expansion/surge tank. With the system cold, it should be filled halfway ... NOT full. You have to allow for expansion of the coolant when it gets hot. If you have any residual air trapped in the system, there will be hot pockets where the coolant doesn't remove heat and that can cause overheating.

 

Lastly, if the system was properly "burped" and the bottle is only half filled when cold -- a bad fan clutch causes overheating at idle. The symptom is overheating when stopped, but as soon as the vehicle starts moving the temperature goes back to normal (because the vehicle motion pushes more air through the radiator).

[jpnjim]

First things first: How far are you filling the coolant bottle, and did you get the system fully bled when you installed the new bottle?

 

The bottle on the closed system is an expansion/surge tank. With the system cold, it should be filled halfway ... NOT full. You have to allow for expansion of the coolant when it gets hot. If you have any residual air trapped in the system, there will be hot pockets where the coolant doesn't remove heat and that can cause overheating.

 

Lastly, if the system was properly "burped" and the bottle is only half filled when cold -- a bad fan clutch causes overheating at idle. The symptom is overheating when stopped, but as soon as the vehicle starts moving the temperature goes back to normal (because the vehicle motion pushes more air through the radiator).

 

 

It's been a while since I had a closed system 4.0L,

Eagle's right, the single biggest problem I had with that setup in the past was air pockets.

I would always pull the radiator hose off at the thermostat housing to fill it up,

and still keep refilling it for the next couple days.

 

 

My issue may be a plugged radiator (even thou it's only 6-7 years old),

since it was running warm (past 210, with a known good temp sender) on the highway as well as in traffic.

[mythreesons]

Ok, the coolant bottle blew up, so I replaced it with one from Napa, ............

 

Besides, other's suggestions, I would make sure that the hood is not sitting on top of the coolant bottle cap when closed. Learned that the hard way with a replacement bottle from NAPA. The NAPA replacement unit has a taller cap than original. Repeated banging on the cap by the hood closing is not a good thing!

 

Scott

[mnkyboy]

My XJ had a new aftermarket bottle on it when i bought it. the cap never fit correctly and it would overheat at idle, i replaced the bottle with an OEM and it went away.