Ok so I just did some minor work to my XJ (RENIX 4.0L)within the last few days, so ill start from the top...

Did an oil change 2 days ago, used Castrol GTX High Mileage Synthetic 5W-30, changed the oil and let the engine run while I was cleaning up for about 20-25 mins. When I go to turn off the engine, it is already overheating and boiling over out of the reserve tank, so I allow it to cool.

SAME DAY, I take it in to get smogged (which it failed) on the first run, it wasnt warm enough so the dumba** tech ran the engine at high idle for 5 mins before running the test again. I SPECIFICALLY TOLD HIM to put the fan in front of the grille, explaining my incident earlier, but he didnt, and while running the 25 mph test, the engine starts overheating like crazy...(OH I WAS HOT!!!!!) I had coolant leaking from the reserve, and somewhere near the front of the engine (which I could not find the source of).

YESTERDAY, I replace the O2 sensor like the smog tech suggested (stupid moron) and after that, the engine is acting kinda funny. When I start it up from sitting cold, it will stall almost immediately, and on the second start, it will rev up for a couple seconds, and sounds like the timing is off or its misfiring, plus the idle itself will be at the normal RPM, drop for a second like it wants to stall, then normal until the engine warms up.

When I drive it, the temp gauge is sitting right below 210, then drop a couple lines, then back to under 210, over a course of a minute or so. It kinda seems like when it reaches normal operating temp, it will drop a little then go back.... and at a standstill for over 5-7 minutes it will creep over 210 and start to overheat....

I am PRAYING the shop didnt blow my head gasket (I blew a gasket when it overheated) but from the symptoms, I think so... I am going to try to burp the system when I get home, but other than that I am clueless, never dealt with this kind of problem before. IF (knock on wood) it is a gasket, can I hold the shop responsible???

ANY OPINIONS???

 

hows your coolant lookin? are you missing any?

is your aux fan coming on when its supposed to? in the summer months i toggle mine on whenever I take long trips or 4x4 cause mine likes to jump a little over 210 at idle or beach 4x4.

but i also have burnt crappy (possibly oily) coolant, but not overheating in these winter months.

I suspect a blown HG on my own and will confirm this once it gets warmer out and i can get access to a garden hose..

 

Coolant looks okay, no signs of leaking or oil mess. I checked it before and after I drove and I had more when the engine was warm

 

And the aux fan never comes on at all as a matter of fact but it does work. Is there any way to hard wire it or find out what triggers it?

 

you can hook it up to the battery with a switch as if it was a light, but alot of people do it through the relay

 

there should be a temp sensor to tell it to come on, but idk where that might be on your 89

 

How would I do it through the relay

 

Chances are the problem is A) your efan not working, fix that immediately, B) your clutch fan may be a little weak, spin in by hand and see how quick it turns, fast=replace slow or none=good make sure the engine is off when performing this test. C) Possible blockage in the cooling system, bad water pump, bad T-stat, even tho the thermostat is new it can still be bad as any of us have the horror stories to prove it. D) take your jeep to a shop and have them do a leakdown test, compression test, and a block test to verify you do or do not have a blown head gasket. No coolant in the oil is not always an indicator that you do not have a blown head gasket. I have seen many vehicles with no coolant in the oil blowin the coolant out the tail pipe.

 

howdy;

question....

how old is the radiator?

I ask, because similar occurence was mine. some time ago,

so being mr wrenchy,,,,i order new radiator, hose, belt, thermostat, coolant and go to it on a saturday to replace.........

see a CRAPPY radiator will weigh a TON (relatively) cuz of all the crap in it over time. and the new one will be oh so very lightweight!

once I put it in (always good to have changed out the stat and hoses and belt), i have had no more problems and that was 80 thousand miles ago.

just a thought sir!!!!



cpnwrench

 

no the shop cannt be held responsible lol if it over heated when you where working on it the problem already existed and should of been fixed before taking it to them

i agree with the others check your fans check or replace the t-stat

make sure when changing the oil you didnt bump some wiring and unplug something

as for holding the shop responsible they are just doing there job and its there job to do it as quickly as possible it isnt there problem if your vehicle isnt working properly

 

I hate reading threads like these. I just replaced my t-stat from a 180 to 195 and have yet to test it out. Working on my column.

Boy I hope I am in the clear.

 

I would most certainly make sure none of your spark plug wires are crossed and or arcing. Is the connection on the O2 sensor secure and fully connected? Is it a universal O2 sensor or the correct, specific O2 for your Jeep? T-Stat could be stuck open, or closed... when they fail, they fail in an instant. If this is the cause, replace with a fail safe T-State, they fail in the open position only.

Things known to me to cause overheating:

Clutch fan
Secondary fan
Blocked Radiator
Waterpump
Coolant leak
Overheating automatic tranny
Crossed spark plug wires
Thermostat
Low oil
Air pockets in the coolant system
Radiator Cap
Collapsed Radiator hoses
Airflow blocked from passing through the front of the radiator or A/C radiator
Slipping fan belt (or broken fan belt)
Blocked exhaust

One or any combination of the above can cause overheating.... won't hurt to run through and double check this list if you can.

 

i used to have overheating problems. all i did was unbolt the thermostat housing(while the engine was cool) took the t-stat out, ran water through the radiator and out the t-stat hole in the block. then replaced t-stat and coolant, ran great ever since with no overheating problems

 

Aux. fan sensor needs to be replaced.

 

Not sure, only owned the XJ for about 3 weeks now, BUT it does look in good shape. I'm gonna flush it out later today