Running too cold

[OkieXJ]

Thanks for the suggestion. I'll likely try another cheapie if my temp sender is working properly.

 

[OkieXJ]

For reference, here is a pic of where my temp gauge normally resides:

I haven't been able to work on the Jeep much because it got really cold and started snowing. I did change my oil (there is about to be another thread about my oil pressure gauge btw) but haven't had a chance to test my temp sender.

I did pick up a cheapie thermostat and gasket from autozone. My thermostat housing was leaking so I have to replace that anyway. I'll try to test the temp sender first though. I usually try to test one thing at a time so I can tell which step fixes it (hopefully).

 

[orange]

That is where my 96 temp gauge reads. Warms up till it touches the 210 mark then drops and holds as per your photo.
---------------
Be a good idea to check if it is going into closed loop with a scanner. Open loop gobbles fuel. (Have you done the battery disconnect reset so it relearns?)
Any codes?

Also if the O2 sensor is weak/old it can mess with fuel milage, as can other FI parts.

Good Luck,
Orange

 

[OkieXJ]

That is where my 96 temp gauge reads. Warms up till it touches the 210 mark then drops and holds as per your photo.
---------------
Be a good idea to check if it is going into closed loop with a scanner. Open loop gobbles fuel. (Have you done the battery disconnect reset so it relearns?)
Any codes?

Also if the O2 sensor is weak/old it can mess with fuel milage, as can other FI parts.

Good Luck,
Orange

What kind of scanner can you use to check open loop and where do you find one?

The O2 sensor has been replaces to no avail. I have an embarassingly long list of parts I've replaces that have not fixed this issue. Although, most of the parts replaces were 20 years old and probably needed it anyway I suppose.

What mileage do you get on your 96 and is it running in open loop?

I have reset the battery. I need to do the key trick I suppose to get any codes. I can go try that.

Edit: the key trick doesn't appear to throw any codes but I might not have done it right or something. on, off, on, off, on within 5 seconds. The check engine light comes on then goes off after a few seconds.

 

[87manche]

Ouch, 5 t-stats to get one that works? That would piss me off to no end.
Autozone t-stats are made in Israel (surprisingly not China)... have never seen one come back.
I have looked at the AZ Valu-craft, the Duralast, and the FailSafe... no noticeable/visual difference. But I went with the failsafe, as I know when the temps are back to 100+ this summer, I will likely get too hot again.

So far so good, went from running too cold in the winter to holding right at 205-210.

This was about 4 years ago, I don't think they were Israeli made at the time. I replaced it when I went open cooling system last year ad the Israeli one worked OK first try.

For reference, here is a pic of where my temp gauge normally resides:

I haven't been able to work on the Jeep much because it got really cold and started snowing. I did change my oil (there is about to be another thread about my oil pressure gauge btw) but haven't had a chance to test my temp sender.

I did pick up a cheapie thermostat and gasket from autozone. My thermostat housing was leaking so I have to replace that anyway. I'll try to test the temp sender first though. I usually try to test one thing at a time so I can tell which step fixes it (hopefully).

Mine hit's 210, and then stays a needle width below that, unless I'm bagging on it, then it hits 230ish and stays put.

This is all with a new pump/rad/hoses. Basically everything but the heater core, I do not have an electric aux fan, just the mechanical one. I also did not bother with the heater control valve.

Prior to the new cooling system I have seen the temp gauge at the 3 o'clock position. My motor hates me.

 

[OkieXJ]

Every part of my cooling system but the overflot bottle, heater hoses and core and thermostat housing has been replaced within the last year. Radiator was replaced about in '02 I suppose. Should have left something crappy in there, maybe it would have run the right temp then.

 

[orange]

Don't know about the scanner for a 91, I was thinking 96. Apologies!
Might call the az or other parts places and ask about scan on 91.

The key trick is s-l-o-w reading normally, say 1/2 minute or longer on mine, Just have to wait for it to plod thru. Starts with '12' and ends with '55'.

I get about 16 mpg, mostly around town. A little better hwy.

 

[OkieXJ]

I was able to find the MIL indicator section in my FSM. I'm pretty sure the codes I got were 12 and 76 then I could see the 55 meaning it was done.

There is no "12" listed in the FSM. It goes from 11 to 13. and 76 supposedly means:
FUEL PUMP RESISTOR BY-PASS RELAY CIRCUIT.
Condition is: open or shorted condition detected in ballast resistor
by-pass relay circuit.

but I haven't messed with the ballast resistor. And I thought that you could eliminate it altogether with no ill effects. I guess that isn't very helpful. I'll check it again later, its pretty difficult to watch the light and remember the numbers or write them down at the same time. I could have been wrong.

 

[87manche]

I think 12 is normal, because the motor isn't running.

It could be that the ballast resistor is already bad and the ECU bypassed it.

I don't know, you're out of my depth on the OBD system.

 

[kastein]

the code you got about the bypass relay is the ECU saying that it sees a short or open in the relay coil drive circuit, not the ballast resistor circuit itself.

I do not think it is relevant to your issue.

 

[Mike Mike]

Keeping an eye on this thread.
put a new ECU in the wifes 89 Renix and now runs 170 and I guess in open loop because dropped 2-3 mpg.

 

[ehall]

Code 12 means battery was disconnected recently and can be ignored

Does the heater hose get hot to the touch? You might have air in the heater core, which could cause the thermostat housing to block up.

 

[OkieXJ]

Code 12 means battery was disconnected recently and can be ignored

Does the heater hose get hot to the touch? You might have air in the heater core, which could cause the thermostat housing to block up.

The hose that goes to the heater core definitely gets warm, the temp from my IR thermometer is posted in here somewhere. I suppose there could be air in the heater core. How would one go about bleeding out?

Thanks for the tip on code 12.

 

[87manche]

The hose that goes to the heater core definitely gets warm, the temp from my IR thermometer is posted in here somewhere. I suppose there could be air in the heater core. How would one go about bleeding out?

Thanks for the tip on code 12.

Turn heat to highest setting.

Run motor until heat is hot.

that's about it for bleeding a heater core, the thermostat (if working properly) will force the coolant into those lines.

I like to run it with the radiator cap off for a few minutes and watch for air bubbles that make it to the radiator when the thermostat opens. Use caution. When it starts to overflow when the thremostat opens stick the cap back on after no more air bubbles, fill up the overflow bottle and turn it off.

 

[OkieXJ]

OK, that's pretty much how I do it everytime I have to refill the coolant.

 

[OkieXJ]

I tested my temp sender and I was feeling extra nerdy so I made a graph.

The orange line is a log curve fitted to the values I got by boiling the temp sensor and measuring the temp and resistance. The green curve is fitted to the values Joe posted. They are pretty much the same so Ill have to say my temp sensor is working properly. Now to change out the thermostat yet again and hopefully seal the leak at the same time. I think I'll also test the gauge. Thanks for the tip about buying some resistors, I have a pot that I think I'll use instead though.
My wife was making fun of me so I bet this ends up on fb too.

 

[kastein]

:cheers:

First time I've ever seen someone post an excel graph of their measurements here :thumbup:

 

[OkieXJ]

Found a 2k pot to use while testing my gauge. I can use it to get all 3 of the resistances Joe posted to test my gauge. Hopefully I can do that tonight. I haven't driven the Jeep long enough to find out if my new thermostat makes a difference.

I used to be in charge of quality control for a product line of a fairly large place so it seems normal for me to including a graph whenever applicable... Takes me back.

 

[87manche]

it could also be added resistance in the harness.

Might be worth a gander to pull the cluster and check out the conections back there. and refresh the grounds in the dashboard harness.

 

[OkieXJ]

Thats a good idea, my speedometer has been flakey. I had planned to pull it and switch it out but it could be the ground for the whole thing behinf both issues.