I have a 90 Cherokee with the 4.0 engine and i recently replaced the engine. It had a previous overheating problem and the previous owner had let the engine freeze over the winter and but the block. Any way I replace the motor new water pump and thermostat and new radiator. For the first few days no problem then it starts trying to overheat so I pull the thermostat out completely. That's only a temporary fix because a few days later same problem again the system has been burped and I'm positive there are no air bubbles. I have no idea what else it could be I'm stumped. Any ideas????? It's the only transportation we have. :banghead:
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overheating problems
- Thread starter rkbonds
- Start date
scottmcneal
NAXJA Forum User
- Location
- not here
where did you get t-stat from? I went to dealer for stock.. You need t-stat to slow the water down
avnsteve
NAXJA Forum User
- Location
- South Austin or North San Antone
this topic has been discussed ad nauseum, below is a link for a search of "overheating"
http://www.naxja.org/forum/search.php?searchid=1706374
now, on to your question, have you considered the fan clutch? how about collapsing lower radiator hose? when does it get hot, at highway speeds, or low speeds? does it overheat immediately, or gradually? are you running plain water or do you have antifreeze mix? when you install water, once this problem is fixed, be sure to use distilled water and avoid tap water for any duration because it has minerals in it which will eventual clog your radiator new or not. waiting for answers
http://www.naxja.org/forum/search.php?searchid=1706374
now, on to your question, have you considered the fan clutch? how about collapsing lower radiator hose? when does it get hot, at highway speeds, or low speeds? does it overheat immediately, or gradually? are you running plain water or do you have antifreeze mix? when you install water, once this problem is fixed, be sure to use distilled water and avoid tap water for any duration because it has minerals in it which will eventual clog your radiator new or not. waiting for answers
WildernessJeep
NAXJA Forum User
- Location
- Houston, TX & Weston, CO
The t-stat was from Advance Auto parts and was a 160 degree and that didn't help it made it worse seems like. After I pulled out the t-stat it ran good for a few days and today I'm out riding around and get out of the truck and turn it off and I hear it bubbling and notice it's at 210 with no t-stat. As long as I'm driving it seems ok it's when I idle or turn it off that's the problem. It gradually overheats not quickly and if I start driving it helps it cool down some. For the time being plain water until I get this problem fixed. Fan clutch seems to be working properly I have even purchased a new fan shroud for it as well to try and help keep it cool. The lower radiator hose I'm not sure of I'll have to check on that but, what would cause it to boil overwhen I turn the engine off? Even if it's only showing to be 210 degrees. I'm afraid to install a new t-stat because it's already overheating driving it, with the t-stat in it would overheat in 10 mins doing anything.
AZRockRunner
Nobody
- Location
- Tucson, Az
Stick a factory 195 in there. If the water dont sit in the radiator long enough to cool, YOUR SCREWED!!!!!!!!
Lower T-stats are a waste of time. Take it from me, I swapped a engine, put on a new hesco high flow water pump, new upper and lower ( with spring ) hose and accidnetly grabbed the wrong T-stat and installed a 180. OVERHEATED STILL. Popped in a good 195 and it now runs at 205 with AC, without AC stompin it or idle. Also added a bottle of redline water wetter and used less anti-freeze. I dont need to much anti-freeze living in the desert.
Hasta
Lower T-stats are a waste of time. Take it from me, I swapped a engine, put on a new hesco high flow water pump, new upper and lower ( with spring ) hose and accidnetly grabbed the wrong T-stat and installed a 180. OVERHEATED STILL. Popped in a good 195 and it now runs at 205 with AC, without AC stompin it or idle. Also added a bottle of redline water wetter and used less anti-freeze. I dont need to much anti-freeze living in the desert.
Hasta
Onkover
NAXJA Forum User
- Location
- Red Bluff CA.
The 4.0s are prone to over heating. First mistake you made is installing a 160. This not only will make the computer think to put it into warm up mode but allows the water to flow to fast. This doesn't allow the coolant to stay in the radiator long enough.. as said before. Then taking it out completely was another NO NO. Go get a 195 and install it. Also pick yourself up some water wetter. As long as your fan clutch is good you shouldn't have any other issues. The Aux fan normally kicks on with the AC and when it reaches about 230 I think. Without a tstate the computer isn't getting the right reading to control the fan.
- Location
- MilkyWay Galaxy
Some of the comments below are not correct for your year model. You have a Renix era (1990) jeep. The electric fan comes on at 185 F (and off at 165 F) and always turns on (and off) via that other relay mentioned by others that comes on with the AC clutch regardless of coolant temp.
It is controlled by a thermal SWITCH (185 on/165 off) which is located in the cooler, return side of the radiator just above the tranny cooler line connections to the radiator (asuming you do not have a modified system or external tranny cooler...). It has two wires and connector on the end of the switch.
I have been running a 165 F thermostat in my 87 Renix for 3 years with no problems. 5-90 runs a 180 F thermostat in his Renix jeep too, with no problems.
The Jeeps including 1991 and after are a different matter entirely.
Oh, and get some antifreeze in that Jeep's water right away. It's not just antifreeze, it also protects the engine and radiator from corrosion which is a big problem with hot water and disimilar metals in contact with hot water. And it protects from boil over to higher temperatures than just tap water.
It is controlled by a thermal SWITCH (185 on/165 off) which is located in the cooler, return side of the radiator just above the tranny cooler line connections to the radiator (asuming you do not have a modified system or external tranny cooler...). It has two wires and connector on the end of the switch.
I have been running a 165 F thermostat in my 87 Renix for 3 years with no problems. 5-90 runs a 180 F thermostat in his Renix jeep too, with no problems.
The Jeeps including 1991 and after are a different matter entirely.
Oh, and get some antifreeze in that Jeep's water right away. It's not just antifreeze, it also protects the engine and radiator from corrosion which is a big problem with hot water and disimilar metals in contact with hot water. And it protects from boil over to higher temperatures than just tap water.
rkbonds said:
Last edited:
Bored400
NAXJA Forum User
- Location
- Grand Junction, CO
bro, do a search. type in Aux fan bypass switch or something. All of us Noobs gotta work the database. Every answer to every question is in there, man.
scottmcneal
NAXJA Forum User
- Location
- not here
Ecomike, if i put a anything lower than stock on my 89 it get like 6 miles to the gal, then when on open road not freeway, it will over heat.. I did some reading about t-stats an went with a oem 195 an now it runs good an doesn't over heat...open desert out here
- Location
- MilkyWay Galaxy
Just install a local bypass toggle switch right at the radiator switch wiring.
rkbonds said:
- Location
- MilkyWay Galaxy
6 mpg, wow, I was getting at least 8 mpg with mine just parked in the driveway idling for hours, LOL, while I ran tests.
I think the problems many others have had with different non-oem thermostats has had more to do with a wide range of different flow rates through the different thermostats (different maximum opening sizes), than it has to do with the opening temperature. As I recall the Renix has a 180 F OEM, dealer optional, thermosat available.
In the summer mine gets up to 190 F with the AC running and never over 200 F on a 100 F day with the AC on. In the winter it runs right at 172 F. I have seen no mileage difference between the winter & summer or between the 200 F summer and 172 F winter operation on mine. But I suspect I have the right size throat, opening, on my non-oem 165 F thermostat.
I have verified my temperatures with multiple (3) external temperature measurement devices including infrared and a thermocouple style probe & meter. For whatever its worth, I installed a new plastic pressure bottle and cap, fan clutch, fan shroud, and all copper/brass radiator (2 or 3 row, I forget which) and the notorious, much malined, 165 F non-oem thermostat shortly after buying my jeep (87, 4x4, wagoneer), and it has never overheated, and I got 16 mpg peak mileage during a winter trip to the hills in Austin from Houston, and that was with a defective TPS sensor keeping the tranny from ever getting into its peak efficiency, peak torque range (Note TPS was just replaced, and I am working an AC upgrade, so I do not have the new mileage yet, but I am expecting to see it finally hit 20 mpg.
I have a suggestion on your mileage problem. Check the third, larger diameter wire going to the O2 sensor and see if it is getting the proper 12 to 14 volts it needs to heat the O2 sensor. IF it is not, it might explain why your mileage and overheating problem came and went with a hotter thermostat. Also check the resistance on that third wire to ground on the disconected O2 sensor itself. If the O2 sensor internal heater goes bad (near zero ohms, or infinate resistance) it will give out O2 data, but it is slow, bad data (biased) and can cause overheating and poor mileage under different operating conditions making it look like a thermostat issue!
I think the problems many others have had with different non-oem thermostats has had more to do with a wide range of different flow rates through the different thermostats (different maximum opening sizes), than it has to do with the opening temperature. As I recall the Renix has a 180 F OEM, dealer optional, thermosat available.
In the summer mine gets up to 190 F with the AC running and never over 200 F on a 100 F day with the AC on. In the winter it runs right at 172 F. I have seen no mileage difference between the winter & summer or between the 200 F summer and 172 F winter operation on mine. But I suspect I have the right size throat, opening, on my non-oem 165 F thermostat.
I have verified my temperatures with multiple (3) external temperature measurement devices including infrared and a thermocouple style probe & meter. For whatever its worth, I installed a new plastic pressure bottle and cap, fan clutch, fan shroud, and all copper/brass radiator (2 or 3 row, I forget which) and the notorious, much malined, 165 F non-oem thermostat shortly after buying my jeep (87, 4x4, wagoneer), and it has never overheated, and I got 16 mpg peak mileage during a winter trip to the hills in Austin from Houston, and that was with a defective TPS sensor keeping the tranny from ever getting into its peak efficiency, peak torque range (Note TPS was just replaced, and I am working an AC upgrade, so I do not have the new mileage yet, but I am expecting to see it finally hit 20 mpg.
I have a suggestion on your mileage problem. Check the third, larger diameter wire going to the O2 sensor and see if it is getting the proper 12 to 14 volts it needs to heat the O2 sensor. IF it is not, it might explain why your mileage and overheating problem came and went with a hotter thermostat. Also check the resistance on that third wire to ground on the disconected O2 sensor itself. If the O2 sensor internal heater goes bad (near zero ohms, or infinate resistance) it will give out O2 data, but it is slow, bad data (biased) and can cause overheating and poor mileage under different operating conditions making it look like a thermostat issue!
scottmcneal said:
scottmcneal
NAXJA Forum User
- Location
- not here
thank you sir, i'll check that stuff too. I just got the 02 put in because of my mileage, i had black crap dripping from the exj pipe, that help get up to what i'm at now, so time to get working on it i guess
Ok I replaced the t-stat and temporarily straight wired the electric fan it did a lot better than before. The only time it tried to overheat was sitting and letting it idle while waiting in line to pick the kids up from school. That's the only time it got past 210 F and it went up to probably 235 F the mechanical fan pulls full all the time ( no clutch ) and the electric fan as well so now what? Any other ideas it's also now 50/50 anti-freeze.
AZRockRunner
Nobody
- Location
- Tucson, Az
well, if your saying that the clutch fan is locked and therefore always cranking 100% of the time, and the electric fan is on high, then either the fluid is not staying in the radiator long enough to cool, meaning non-functioning T-stat, or a clogged radiator not allowing the fluid to enter the engine fast enough.
I had replace my engine in mine also, new high flow water pump, the works, from top to bottom new except the 9 month old radiator and it still over heated. I took out the radiator and had it tested and sure enough, it was 15% clogged. Replaced with a new single core all brass/copper and no more problems. I live in the desert and regularly wheel in the 110 degree heat and it never goes above 210 now.
Cooling systems are basic systems when you think about it, air cools the water through the fins in the rad, flows the coler water into the motor, it heats up again and continues this cycle.
Also, check the heater core, if its clogged it can screw things up for you also.
Good luck man, I know how frustrating these things are.
I had replace my engine in mine also, new high flow water pump, the works, from top to bottom new except the 9 month old radiator and it still over heated. I took out the radiator and had it tested and sure enough, it was 15% clogged. Replaced with a new single core all brass/copper and no more problems. I live in the desert and regularly wheel in the 110 degree heat and it never goes above 210 now.
Cooling systems are basic systems when you think about it, air cools the water through the fins in the rad, flows the coler water into the motor, it heats up again and continues this cycle.
Also, check the heater core, if its clogged it can screw things up for you also.
Good luck man, I know how frustrating these things are.