'96 XJ running too cold - even with Robert shaw tstat
- Thread starter 90Pioneer
- Start date
Speed_racer
NAXJA Forum User
- Location
- Ft Myers, Florida
I learned the hard way that its not always the sensor.. and sometimes the gauge itself 
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Ditto on the pressure cap havoc. For that matter any kind of small intermittent leak can cause the similar headaches (changing problems while trying to diagnose the first problem). Be sure and check everywhere for any signs of small old or fresh coolant leaks and check the seal area on the bottle itself where the cap seals.
Straight water will transfer more heat faster than a 50/50 mix of antifreeze and water.
Perhaps the running too cold right after the Wynns flush was unrelated to the cooling system?
By the time you go from from winter to summer something else could change causing the summer overheating, like a fan clutch failing (or becoming marginal) 6 months later.
Shouldn't the electric fan come on and keep it from overheating in the summer even if the fan clutch is week?
Small hidden radiator leaks that come and go can cause or contribute to some of your problems. Perhaps it is several things like a small intermittent leak (coolant ingredients are designed to be self sealing so small leaks can come and go) combined with one or more other intermittent issues or problems. One problem can sometimes hide another problem for a while.
Mike McGinness
South Houston, TX
Straight water will transfer more heat faster than a 50/50 mix of antifreeze and water.
Perhaps the running too cold right after the Wynns flush was unrelated to the cooling system?
By the time you go from from winter to summer something else could change causing the summer overheating, like a fan clutch failing (or becoming marginal) 6 months later.
Shouldn't the electric fan come on and keep it from overheating in the summer even if the fan clutch is week?
Small hidden radiator leaks that come and go can cause or contribute to some of your problems. Perhaps it is several things like a small intermittent leak (coolant ingredients are designed to be self sealing so small leaks can come and go) combined with one or more other intermittent issues or problems. One problem can sometimes hide another problem for a while.
Mike McGinness
South Houston, TX
So I just looked at my radiator cap. I had my mechanic install the radiator for me, and apparently he replaced it. So it has a new cap, doesnt look factory, says "made in Mexico." On the cap it also says "vented 16lbs." So I should be OK radiator cap wise. Or do you think swapping this new cap with a new factory cap would make a difference?
Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
I run a 16 PSI Stand radiator cap, with the pressure relief valve. I believe it says Made in Mexico too, and it works just fine.
Not the same system, but, Mexico makes good crap
That has nothing to really do with running too cold though......I don't have any idea what your problem is, I believe you are a first timer here for a "too cold" problem!
I still recommend you buy a Prestone antifreeze mixture checker/gauge and check the ratio of your coolant/water.....
Not the same system, but, Mexico makes good crap
That has nothing to really do with running too cold though......I don't have any idea what your problem is, I believe you are a first timer here for a "too cold" problem!
I still recommend you buy a Prestone antifreeze mixture checker/gauge and check the ratio of your coolant/water.....
My ratio should be 50/50, as only premixed coolant has been put in this Jeep. But I will get one of those checker gauges and see for sure what it is tomorrow.
Tonight I tried installing a mud flap under the engine bay, similar to a factory splash guard. Didn't make a difference.
My temp gauge swings between 195 and 160, usually running just a tad over the first white mark after the 100* line.
I checked over the motor today looking for signs of any coolant leaks, and saw none.
Running out of ideas, any other suggestions on how to keep my temp steady???
Would it be possible that the actual gauge in the cluster is malfunctioning in the way I have described? Only I don't think it is because the temp will rise if say it's at 160 and I park the jeep in the garage and let her idle...temp will slowly climb.
Tonight I tried installing a mud flap under the engine bay, similar to a factory splash guard. Didn't make a difference.
My temp gauge swings between 195 and 160, usually running just a tad over the first white mark after the 100* line.
I checked over the motor today looking for signs of any coolant leaks, and saw none.
Running out of ideas, any other suggestions on how to keep my temp steady???
Would it be possible that the actual gauge in the cluster is malfunctioning in the way I have described? Only I don't think it is because the temp will rise if say it's at 160 and I park the jeep in the garage and let her idle...temp will slowly climb.
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HilltopXJ
NAXJA Member #950
- Location
- Eagle Point, OR
I think its the guage sender or the guage itself. Leaning more twards the sender. IMO
Speed_racer
NAXJA Forum User
- Location
- Ft Myers, Florida
90Pioneer said:
Absolutely.. my xj factory gauge was giving me all kinds of hell.
At first, it would start at the bottom, like normal, and slowly work up to 180.. never topped 180... til it started boiling over overheating...
So I changed the temp sender, and the thermo, and the fan clutch, gauge read 240-250*! and acted normal on its slow climb to get there... this was on a road trip, id stop every 20 miles to smell the motor and check for excessive heat... but nothing....
After that I threw in an aftermarket gauge.. and realized that even idling for an hour the jeep wasnt topping 190*!!!!
Now Im left to get a thermo back in so it can actually WARM UP!
Also.. if you have a 195* thermostat in your jeep, it is not physically possible for it to run below that for more than 20-30 minutes.. think of the fire thats going on inside your motor... if it never breaks 195,,, and the thermo stays cold.. that coolant sitting in your block would be so superheated its not even funny...
Unless you have an xj that defies the laws of a cooling system.. my vote is for the gauge itself!
OK, I will look into the gauge.
But still think it's possible it's the gauge since the aux fan kicks on when the gauge reads 220, everytime? And that it climbs when parked in my gauge (less air flow).
What is the easiest way to hook up an aftermarket temp gauge up? Figure I will test it before I swap the factory gauge, as that will be a PINA.
But still think it's possible it's the gauge since the aux fan kicks on when the gauge reads 220, everytime? And that it climbs when parked in my gauge (less air flow).
What is the easiest way to hook up an aftermarket temp gauge up? Figure I will test it before I swap the factory gauge, as that will be a PINA.
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Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
You never know what water is left in the block, even if you park at an incline and drain it all out......
I'd get another external temp reader too, or have a shop check actual temp. I suppose they have those on hand and you wouldn't need to buy one then.
I'd get another external temp reader too, or have a shop check actual temp. I suppose they have those on hand and you wouldn't need to buy one then.
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
Speaking of temperature measurements, gauges and sensors, I went to Harbour Tools today and bought a small, key chain size portable, infrared temperature tester for $9.95, on sale. It has a range limit of -27 F to 230 F, but the price was right and it is real easy and super fast to use. Don't know how accurate it really is (claims +/- 2% or 2 C at an ambient of 23 C) but I was pretty impressed after using it. The readings were very repeatable.
I tested my Gauge Temperature Sender (GTS) and Coolant Temperature Sender with an ohm meter and they read, 280 ohms on the CTS and 252 ohms on the GTS. The FSM says that 160 F is 450 ohms, and 212 F is 185 ohms, and 100 F is 1,600 ohms.
Both sensors (the CTS and GTS) use the same variable resistance temperature device and have the same resitance at the same temperatures. Unfortunately, after plotting the temperatures from the FSM in Excel they do not appear to be linear (so it is not a typical thermistor, which as I recall is linear, so it might be a thermocouple(?), so I am not sure exactly what temperature 252 or 280 ohms is. If I had to guess I would say about 180 to 190 F. I have a 165 F thermostat currently in this jeep (as best as I recall).
The gauge indicator was just barely below the second notch or line above the 100 F mark and just a bit more that 2 notches below the fourth mark which is labeled 212 F. Therefore, it seems clear that not only is the Thermocouple(?) non-linear but so is the gauge!
Has anyone ever mapped out the intermediate marked values on the water temperature guage between 100 and 212 F or from there to 260 F? My 1987 gauge has three notches between 100 and 212 F. I know now that they are not linear and that the first knotch is about 160 F, based on the infrared temperature readings I got today, and the second notch is about 190 F, at least with my current sensor, gauge and infrared meter combo.
Do these numbers and readings corelate with your alls readings?
Based on todays tests I now realise that my engine has been running at 160 to 190 F and not at 130 to 160 F as I previously thought.
I took a variety of temperature readings all over the engine bay. The upper radiator hose was typically 20 F cooler than the thermostat housing. I took readings all over the engine block, top right, left and middle of the radiator, intake manifold, valve cover, etc. It was quite enlightening to see the temperature variations all over the engine.
I think the $9.95 was well worth it.
I tested my Gauge Temperature Sender (GTS) and Coolant Temperature Sender with an ohm meter and they read, 280 ohms on the CTS and 252 ohms on the GTS. The FSM says that 160 F is 450 ohms, and 212 F is 185 ohms, and 100 F is 1,600 ohms.
Both sensors (the CTS and GTS) use the same variable resistance temperature device and have the same resitance at the same temperatures. Unfortunately, after plotting the temperatures from the FSM in Excel they do not appear to be linear (so it is not a typical thermistor, which as I recall is linear, so it might be a thermocouple(?), so I am not sure exactly what temperature 252 or 280 ohms is. If I had to guess I would say about 180 to 190 F. I have a 165 F thermostat currently in this jeep (as best as I recall).
The gauge indicator was just barely below the second notch or line above the 100 F mark and just a bit more that 2 notches below the fourth mark which is labeled 212 F. Therefore, it seems clear that not only is the Thermocouple(?) non-linear but so is the gauge!
Has anyone ever mapped out the intermediate marked values on the water temperature guage between 100 and 212 F or from there to 260 F? My 1987 gauge has three notches between 100 and 212 F. I know now that they are not linear and that the first knotch is about 160 F, based on the infrared temperature readings I got today, and the second notch is about 190 F, at least with my current sensor, gauge and infrared meter combo.
Do these numbers and readings corelate with your alls readings?
Based on todays tests I now realise that my engine has been running at 160 to 190 F and not at 130 to 160 F as I previously thought.
I took a variety of temperature readings all over the engine bay. The upper radiator hose was typically 20 F cooler than the thermostat housing. I took readings all over the engine block, top right, left and middle of the radiator, intake manifold, valve cover, etc. It was quite enlightening to see the temperature variations all over the engine.
I think the $9.95 was well worth it.
Went on a night run in the snow last night. It was about 15 or 20* outside. On the way out there it was running at 170ish. While crawling on the trail in 4lo, or idling, the engine would heat up to 220 and kick the aux fan on. The engine was staying pretty warm, almost too warm. If it was summer time and 100* out I think it would of gotten too hot.
Back in 2wd drive again and moving about 35-40mph the temp will drop again to 160-170
I assume the gauge is accurate because the aux fan is supposed to kick on at 220*, which is what my gauge was reading. But I still want to double check it. I'm just trying to figure out a real simple way to install an aftermarket gauge. Ideas?
Back in 2wd drive again and moving about 35-40mph the temp will drop again to 160-170
I assume the gauge is accurate because the aux fan is supposed to kick on at 220*, which is what my gauge was reading. But I still want to double check it. I'm just trying to figure out a real simple way to install an aftermarket gauge. Ideas?
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
After re-reading this entire thread and reviewing my own recent experiences the last few weeks (discussed in other threads here recently) and overheating experiences inpast years and vehicles, I have a few new suggestions. One is that part of your problem may have to do with the system randomly switching from a lean to a rich fuel mixture and back again.
I have noticed that now that I have several things fixed that were forcing my Renix to run in the rich, open loop mode all the time, that it is starting to run much hotter, like 200F, inspite of a 165 F thermostat, in cool weather (60 F).
You might be fighting a failing (intermittent sensor) or even more likely a loose sensor/ECU electrical connection that is throwing the system in and out of Rich and Lean fuel mixture operating modes. I would start looking into all the wiring, sensor and ECU connections and the grounds for loose or poor connections.
Also, Your latest data seemed to indicate a possible weak fan clutch (this does happen with new fan clutches!) inspite of the fact that it is new.
Mike McGinness
South Houston, TX
I have noticed that now that I have several things fixed that were forcing my Renix to run in the rich, open loop mode all the time, that it is starting to run much hotter, like 200F, inspite of a 165 F thermostat, in cool weather (60 F).
You might be fighting a failing (intermittent sensor) or even more likely a loose sensor/ECU electrical connection that is throwing the system in and out of Rich and Lean fuel mixture operating modes. I would start looking into all the wiring, sensor and ECU connections and the grounds for loose or poor connections.
Also, Your latest data seemed to indicate a possible weak fan clutch (this does happen with new fan clutches!) inspite of the fact that it is new.
Mike McGinness
South Houston, TX
Is there any specific way to tell if my XJ is switching between lean and rich modes?
This would make since because my jeep only gets 10 mpg city or 11 mpg highway. Granted it's lifted with 33s, I'm running 4:56 gears so I should have at least somewhat better mileage.
This would make since because my jeep only gets 10 mpg city or 11 mpg highway. Granted it's lifted with 33s, I'm running 4:56 gears so I should have at least somewhat better mileage.
- Location
- Maurertown,Va.
Let me jump in on this.I too have a 96,and was happy with the way it ran,never overheated or blew out any water.Replaced the Idiot light Inst panel with the guage panel and found the temp readings were way too high.
Had dealer check readings thru scan tool and found all readings to be correct,Guage sender,ECU temp sensor and aux fan start point were fine.Guage was not saying correct temp.
Went to aftermarket (Autometer) temp guage,plumbed into the t-stat housing with a Tee.Also included in this fitting is a sensor for the aux fan over-ride switch.
Temps now run in the 210* range with a factory t-stat or 195* with a Robertshaw balanced flow stat.
As you know the sensors are located in two different parts of the motor,so the gauge sender ,being in the back of the head,fartherst from the radiator should be the hottest part of the engine.While the ECU temp sensor is in the coolest area.
With the MPG your getting it could be the engine is not in the closed loop,therefore running too rich,--may be time for that new coolant temp sensor.
Wayne
Had dealer check readings thru scan tool and found all readings to be correct,Guage sender,ECU temp sensor and aux fan start point were fine.Guage was not saying correct temp.
Went to aftermarket (Autometer) temp guage,plumbed into the t-stat housing with a Tee.Also included in this fitting is a sensor for the aux fan over-ride switch.
Temps now run in the 210* range with a factory t-stat or 195* with a Robertshaw balanced flow stat.
As you know the sensors are located in two different parts of the motor,so the gauge sender ,being in the back of the head,fartherst from the radiator should be the hottest part of the engine.While the ECU temp sensor is in the coolest area.
With the MPG your getting it could be the engine is not in the closed loop,therefore running too rich,--may be time for that new coolant temp sensor.
Wayne
Ecomike
NAXJA# 2091
- Location
- MilkyWay Galaxy
I posted my temperature sensor ohm meter (resistance) readings in another thread here a few days ago. There was a 28 ohm difference between the coolant temperature and the gauge (coolant) temperature sensor readings on my 87, 4.0 L, with the gauge being the hotter, lower resistance reading of the two as Wayne just suggested!
Good question on the how do we tell when it switches between running rich or lean. I would like to know that as well, as well as what the magic temperature(s) (actually ohm meter/resistance readings) are for the coolant sensor that it uses to make that decision!!!!
Also, does the Renix switch back to the rich mode if the coolant sensor senses a too hot (and therefore too lean) conditon????
I just noticed something interesting in my Renix FSM!!!!
If the wires from the ECU (D-3 and C-10) to the coolant temp sensor have a large enough resistance (due to poor contact, corrosion....) it will add to the resistance of the coolant sensor thus telling the ECU that the engine is cold even if it is warmed up with a good sensor!!!!! Thus keeping it in the open loop gas hogging mode!!!!! Check those wires people!!!!!
Mike McGinness
South Houston, Tx
Good question on the how do we tell when it switches between running rich or lean. I would like to know that as well, as well as what the magic temperature(s) (actually ohm meter/resistance readings) are for the coolant sensor that it uses to make that decision!!!!
Also, does the Renix switch back to the rich mode if the coolant sensor senses a too hot (and therefore too lean) conditon????
I just noticed something interesting in my Renix FSM!!!!
If the wires from the ECU (D-3 and C-10) to the coolant temp sensor have a large enough resistance (due to poor contact, corrosion....) it will add to the resistance of the coolant sensor thus telling the ECU that the engine is cold even if it is warmed up with a good sensor!!!!! Thus keeping it in the open loop gas hogging mode!!!!! Check those wires people!!!!!
Mike McGinness
South Houston, Tx
Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
The coolant temp sensor at the end of the block by the firewall is the one wire, white plug sensor right?
- Location
- Maurertown,Va.
Blaine B. said:
Depends on what year. Up until 96 that was the sender for the guage or idiot light.
In 97 or 98 the sender was removed.All temp info comes from the sensor in the thermostat housing and is routed thru the ECU.
Wayne
Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
Ok, so the sensor at the end of the block is for the gauge, and the sensor on the thermostat housing is for the electric fan, and for the computer to change the fuel mixture?
