Coolant Check Engine Light??

First of all, yes, i have searched this subject and I think I MIGHT know what to do tomorrow, but just wanted to just post this to get some second opinions/feedback on this and to see whether or not others have come across the same issue...

Jeep 2000 XJ Classic
91k miles
Purchased a month ago

No issues whats so ever since I bought but I had a leaky radiator. Today I replaced the radiator with a CSF from radiatorbarn.com 3 core, also replaced the upper/lower hoses and t-stat with a SuperStant one(drilled a little bleeding hole).

Put the heater all the way on hot and fired her up. Bled the system of any air, but for the 20 or so minutes that I had her idling the lower radiator hose never got hot. Is this normal? Temperature climbed nicely to about 190 and stayed there for a bit. Heater worked well, all is ok, but noticed, however, the check engine light was on.

WTF!

No idiot light on before, so why now? Could this be the coolant temp connector not on tight enough?

Any and all feedback greatly appreciated, THANKS

It must be A mopar thing.....

My 94 T&C will throw the coolant temp sensor code if I let it warm up in the driveway without driving it.....

If i just get in and drive, it doesn't throw the code.....

just my $0.02

I am begining to love Renix more and more.....

No mystery lights, just oddball behavior.....

and nothing a DVOM can't diagnose...

DId I mention I am ASE certified (P2 and A/C recycle and service), AND have several years of Automotive work under my belt, plus I worked for Detroit Diesel?

probably the light for "coolent temp not up to high enough temperature"

what degree T-stat did you get? 180? 195?

UPDATE********** This morning(now 5AM) Started up fine and NO CEL!!!

I'm sorry I didnt mention before -- the T-stat is a Stant Superstant 195*

Question is, though, do I still have to go in and clear this tripped code now that the CEL came on once, will it come on again, or no?

Thanks all

it should clear itself. I dont think that code actually hurts anything, its more of the ECU thinking that there's a problem b/c the engine doesnt get to "running" temp (IE, thermostat stuck open). The only thing it might do is dump more fuel into the combustion chambers in order to get it to burn hotter and get the temp up higher - so watch your gas mileage.

when i did my new waterpump/hoses/radiator/t-stat, i had the same problems for a little bit, it ran a little on the cool side for a week or two...once the weather warmed up a little, it was fine

Oh ya, did you replace the radiator cap when you did all this?

Is it possible the fluid level was low, and the temp sensor was uncovered from liquid, thus giving incorrect readings? As well, the air in the system after first start from fully draining the cooling system, can cause big spikes in temp as the air works it way out, maybe you just had a spike that set off a light for overheating.

As far as people getting temp lights under certain conditions, could it be air in the system as well. Very little Jeep experience here, but I never had a problem with the coolant recovery system keeping all air out of the system for any of my Chrysler's or other vehicles except my Jeep with the AMC motor. No matter what I do, there is always a little air left in the motor/radiator.

The Chrysler Speed Density System works just great on Chrysler motors. Never having experienced a Renix system, perhaps the complaints come from Chrysler adapting their system to AMC motors that they still kept around for Jeeps.

Did you do the key dance, ignition key on/off/on/off/on and watch the CEL light or the odometer (if you have a digital odometer). A digital odometer will display the fault codes. No digital odometer, then the CEL will Blink Out your fault codes. Any manual will have a list of the codes under the emissions section, probably find them with a Google search as well.

If you want to clear codes, just disconnect the battery for 20 minutes, the PCM (Power Control Module) will dump all its stored codes. Of course it will set a code 12, "Power to PCM disconnected within the last 50 key on cycles", but that code will clear itself within "50 key on cycles".

Stored codes will do nothing to the system, they do NOT need to be cleared, besides, like I said above, if you want to clear them, just disconnect the battery.

A code, indicating a problem that may need attention can be stored without ever lighting a CEL.

The first trouble-shooting step for any drivetrain problem for Chrysler owners is too always do that key dance to get the PCM codes to spit out. Fix the stored fault code, will usually fix the problem 85% of the time.

If your CEL goes out, it means your problem is NOT bad enough to need service. A code, indicating a possible problem may still be stored.

If your CEL stays on constant, it means your problem is BAD enough to need service soon. A code will be stored.

If your CEL is blinking, it means your problem is BAD enough you need immediate service and should NOT continue to drive the car because it may do further damage.

I have a lot of Chrysler experience, very little Jeep experience. I suspect any problem with the Chrysler system on Jeeps is because Chrysler adapted the system to AMC motors they kept from buying out AMC/JEEP.

Thanks for everybody's input here.

This board has been a great help since I first got my Jeep.

I will drive the Jeep again (Leaving work in an hour or so) and see what happens...

Again, thanks for all your responses to this issue.

By the way, that damn lower transmission line that feeds into the bottom of the radiator was a biotch to get off, and biotch to get back on. My whole left arm is sore because of that thing! :hang:

NewToJeeps said:

Thanks for everybody's input here.

This board has been a great help since I first got my Jeep.

I will drive the Jeep again (Leaving work in an hour or so) and see what happens...

Again, thanks for all your responses to this issue.

By the way, that damn lower transmission line that feeds into the bottom of the radiator was a biotch to get off, and biotch to get back on. My whole left arm is sore because of that thing! :hang:

Click to expand...

Could not have been too bad if it didn't draw blood....