4L heating issue

[JackstandJohnny]

jeep was running at normal temperature last week..... running at 1/4 of the guage;  did the valve cover gasket and ended up breaking the temperature sending unit wire on the back of the block.  on the 93 ZJ they use two different units; one for the guage and one for the computer.
anyways, it was running cool. then i broke it, installed a new one, and now it reads overheating;  (runs at about 3/4 of the gauge now)

so, is it possible theres an airpocket in there or something?  there is no antifreeze coming out of the overflow bottle either; 

probbably just being paranoid?

[TL-Iguana]

"What is the correct term for a pack of unibody jeeps anyway?'
'A Junkyard?'

 


If you had to take out the sensor from the back of the block it could be an air pocket as air would be introduced into the system. Im not a mechanic by trade, nor do I claim to know what im talking about, but in theory I would think you could perhaps jack the front of the jeep up, to make the rad cap the highest point, and when cool, remove the cap and then start the engine. Turn on the heat to high to open the thermostat and the air should then bleed up to the highest point. This approach worked for a friends 4.2l eagle that never heated up. It might be worth a shot?

[halfcRoOk]

you might not have the same gauges as my xj, I have the big fuel gauge insted of the tach, but my oil light comes on when the engine is nice and warm, flashes only at idle, checked the oil level and fine! it looks like oil pressure, I'm thinking it's my sending unit! or my oil pump, I haven't done anything yet.

So your saying your temp gauge is indicating 3/4 warm insted of 1/4?? so the engine is overheating?
Have you checked if your engine was actually hot? maybe ur gauge isn't wrong. I'm just saying!

[JackstandJohnny]

yup pretty sure the gauge is wrong.  rad cap isn't even hot.  and it got to that running temperature aweful quick. 

when i have a few minutes tomorow i'll burp the system; i think theres air in the system.

[vantagetes]

There are a couple other possibilities, I think there were two sensors depending on which dash/year split but you probably got that one right. The other is that your old one was reading wrong (low) and the new one is finally reading correctly.  Do you have numbers on that beasty or just a h/c? 3/4 is where it should be it's when you're in the red or not heating up at all that you should be worried.

[hps4evr]

when it gets to 3/4 spot on gauge you figure its at operating temperature right? grab all the hoses and see if all are hot or cold. upper and lower rad hoses, inlet and outlet on heater core. if all hoses are hot enough that you cant hold onto them for long then you should be at operating temp. if you had the system open then my first guess would be air in the system. correct me if im wrong but i thought i gave you my old themrostat housing with both sensors in it? or did you plug the hole and install the little sensor at the back of the head? the little sensor is for the gauge. i dont think the gauge would be pooched just yet. ive never changed a gauge before, maybe someone else has but they are so simple they dont seem to malfunction, even those little sensors are pretty basic. if all these thing check out then maybe a clog in the system or the thermostat isnt as happy as it was.   

[JackstandJohnny]

its on the ZJ hps

the Yj was running good with the new tstat. but i found out yesterday the upper rad hose decided to call it quits and i gets a nice big puddle o' green stuff under it this morning.  but, i found the leak; its not sealing on that tstat housing you gave me   time for new hoses methink as it sealed just fine before.....


on the ZJ, i'm gonna burp it tonight.  its not hot under there;  when its 'hot' i can grab the upper rad hose and its not very hot.  i can literally grab it;  the rad cap is also not very hot.  and there is no coolant bubbling out of the overflow. if its running that hot, it should bubble....... 

gonna burp the system tonight, because when i pulled that sensor yesterday, it spit out a bunch of fluid, probably more than enough to get some air in the system. 

after driving today i'm on the side of the air pocket;  it got up to operating temperature 2x as fast as it normally does.......

or the thermostat is stuck

[JackstandJohnny]

 Burped the system and its runnin good again. Runs just under 100 and stays in that area. Must be a jeep thing

[halfcRoOk]

I ran my buddy's hyundai in a hill with the radiator cap off but before that, blew air in the heater core, and put the hose back on, once it was running, I just squeezed all the lines to pop the air bubbles out of the hoses and everything and his heating came back on!

[Tinkerer]

Burped the system and its runnin good again. Must be a jeep thing

Just like babies... lots of TLC, things from the store and burping after feeding!