Weird coolant temp readings

[Drdan524]

I have just started running my girlfriends 92 Yj around since she is coming home from college for Thanksgiving.  As I was driving, I noticed that it doesn't stay at normal operating temperature.  As it runs it will go up to about 210 degrees like normal, then once it hits about 210, it drops quick to about 150ish.  Once it drops, it slowly works its way back up to 210 and it repeats.  If I let it idle in place, it will do the same thing except much slower.  It does this all the time, whether the heat is on or off.  But you can notice the temperature difference coming through the heater.  When it is at 210 the heat works good, but after it drops, the heat gets cold again.  Any ideas what this could be?  It is a 92 YJ with 2.5L and manual transmission.  Somebody put a 2 inch body lift on it so there is no fan shroud on it.  Any ideas would be greatly appreciated.

Thanks
Dan

 

[NomadJeep]

well first thing is get a fan shroud, or switch to an electric fan... even though it has a BL, it can still have a shroud. (I do :wink

This will direct the air where it needs to be... esp with the 4cyl which is so far away from the motor anyway... that means that the fan is doing nothing with no shroud in there...

as for the rapid changes...  My first thought is coolant level... have you checked it?  That is one of the most common things I have seen when a vehicle is low... it will fluctuate strangely... but my gut feeling tells me you have no thermostat in there...

if she is not the original owner, I would not be surprised if it has no thermo in it being they left the shroud off.  They probably took the thermo out thinking it would help it run cooler... well it wont...  it will fluctuate strangle being it will be far more sensitive to RPM with water pump flow / RPM. 

If you need a hand swapping it out or checking it over give me a shout.

 

[CJKarl]

Thermo....and Dude, you're on before ME! (Detour)

 

[NomadJeep]

gremlins

Ron what kind of Gremlin, mean or nice or metal?   :rotflmao: :rotflmao: