MJfan94 Posted November 26, 2014 Share Posted November 26, 2014 My 89 Mj keeps overheating. I can drive about a mile before the needle is in the red even with the electric fan on. I've replaced the theromstat, water pump, fan relay and fan switch sensor. I can't figure out what might be causeing this, feed back or ideas would be great. Link to comment Share on other sites More sharing options...
88whitemanche Posted November 26, 2014 Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? Link to comment Share on other sites More sharing options...
willi2ds Posted November 26, 2014 Share Posted November 26, 2014 Could be the cap on your bottle Link to comment Share on other sites More sharing options...
MJfan94 Posted November 26, 2014 Author Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? 1.whats a spal controller? 2.i've not tried a pressure test yet, ill try that in the morning. 3.my coolant tank lid is in good condition. Link to comment Share on other sites More sharing options...
az comanches Posted November 26, 2014 Share Posted November 26, 2014 Try flushing your radiator it did wonders for mine. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 26, 2014 Share Posted November 26, 2014 bad thermostat Link to comment Share on other sites More sharing options...
cruiser54 Posted November 26, 2014 Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? 1.whats a spal controller? 2.i've not tried a pressure test yet, ill try that in the morning. 3.my coolant tank lid is in good condition. Where is the coolant leaving the system when it overheats? Not the coolant bottle cap? Link to comment Share on other sites More sharing options...
MJfan94 Posted November 26, 2014 Author Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? 1.whats a spal controller? 2.i've not tried a pressure test yet, ill try that in the morning. 3.my coolant tank lid is in good condition. Where is the coolant leaving the system when it overheats? Not the coolant bottle cap? The coolant forces its self from the bottom of the coolant tank Link to comment Share on other sites More sharing options...
cruiser54 Posted November 26, 2014 Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? 1.whats a spal controller? 2.i've not tried a pressure test yet, ill try that in the morning. 3.my coolant tank lid is in good condition. Where is the coolant leaving the system when it overheats? Not the coolant bottle cap? The coolant forces its self from the bottom of the coolant tank Then the tank is bad...... Replace the tank and install a 703-1396 cap on it and go from there. Link to comment Share on other sites More sharing options...
MJfan94 Posted November 26, 2014 Author Share Posted November 26, 2014 1. Your electric fan...is it installed with a spal controller? It mAy not be putting the correct output to spin the Fan fast enough to cool your system.... 2. You may have a blown head gasket...do a pressure to make sure it's not a blown gasket.... 3. How is your coolant tank lid? 1.whats a spal controller? 2.i've not tried a pressure test yet, ill try that in the morning. 3.my coolant tank lid is in good condition. Where is the coolant leaving the system when it overheats? Not the coolant bottle cap? The coolant forces its self from the bottom of the coolant tank Then the tank is bad...... Replace the tank and install a 703-1396 cap on it and go from there. I'll try that. Link to comment Share on other sites More sharing options...
MJfan94 Posted November 26, 2014 Author Share Posted November 26, 2014 Ok i've done a compression test and each cylinder reads the same psi and i have changed the tank and cap with the 703-1396 cap and its still overheating, is there anything else I'm over looking. Link to comment Share on other sites More sharing options...
willi2ds Posted November 26, 2014 Share Posted November 26, 2014 My friend had a similar problem and it ended up being an air bubble. We put on a newer T-Stat housing with the sensor in it and used it to let the air out. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 26, 2014 Share Posted November 26, 2014 Yeah Reread my post Link to comment Share on other sites More sharing options...
nitroxsteve Posted November 26, 2014 Share Posted November 26, 2014 Describe it a little more. When is it overheating? Driving at speed? Setting in traffic? Idling in the driveway? How do you know it's overheating? Is it boiling over or is the gage telling you? When did the problem start? Link to comment Share on other sites More sharing options...
MJfan94 Posted November 27, 2014 Author Share Posted November 27, 2014 Describe it a little more. When is it overheating? Driving at speed? Setting in traffic? Idling in the driveway? How do you know it's overheating? Is it boiling over or is the gage telling you? When did the problem start? I first notice it about a week ago driving at highway speeds, so i had it towed home and it sat in my driveway, after replacing the thermostat in , let the air out of the system and it stated to overheat at city driving speeds. How i know its overheating because coolant was forcing its way out of where the line attachs to the coolant tankon the bottom and the gauge needle was in the red. Link to comment Share on other sites More sharing options...
sloride Posted November 27, 2014 Share Posted November 27, 2014 You replaced the fan relay and switch, but do you know for certain your fan kicks on? I'm asking if you've got the engine up to temp while parked to see the fan kick on..... And just because you replaced old with new, doesn't necessarily mean they're good. I check relays before I replace them with new ones. I don't normally check thermostats before installing them, but you could have a new one that's faulty. It happens. Get a pan of boiling water and a thermometer and see if yours is functioning as it should. And before I install thermostats, I like to drill an 1/8" hole at the thermostats flange 12 o'clock for any air bubbles that might form. That trick goes back to my working at the gas station days. Link to comment Share on other sites More sharing options...
hillbilly51 Posted November 27, 2014 Share Posted November 27, 2014 And before I install thermostats, I like to drill an 1/8" hole at the thermostats flange 12 o'clock for any air bubbles that might form. That trick goes back to my working at the gas station days. Me too. I just installed a new thermostat on my 88 Comanche 4.0L the other day, and that is exactly what I did. I didn't have any problem at all burping the system. On the 80's models 4.0 engines, the closed loop cooling system with the pressurized expansion tank can be a real pain in the a** when trying to get air out of the cooling system. This simple modification helps a lot. Link to comment Share on other sites More sharing options...
nitroxsteve Posted November 27, 2014 Share Posted November 27, 2014 Describe it a little more. When is it overheating? Driving at speed? Setting in traffic? Idling in the driveway? How do you know it's overheating? Is it boiling over or is the gage telling you? When did the problem start? I first notice it about a week ago driving at highway speeds, so i had it towed home and it sat in my driveway, after replacing the thermostat in , let the air out of the system and it stated to overheat at city driving speeds. How i know its overheating because coolant was forcing its way out of where the line attachs to the coolant tankon the bottom and the gauge needle was in the red. Is it still forcing coolant out of the tank? If you are loosing any pressure the coolant will boil and cause overheating. With the temp all the way in the red it should never spill coolant. Link to comment Share on other sites More sharing options...
Jeep Driver Posted November 27, 2014 Share Posted November 27, 2014 For $#!&s and giggles- Image Not Found Yesterday while reading this thread and posting that you reread my post, I took this pic with my phone. Ambient temp was 49 degrees, truck was at idle for better than 20 minutes with heater on as I was taking a break from work. The E-fan NEVER came on. I do NOT have a mechanical fan. If you have an air pocket in your head you would get an overheat after about 3 minutes at idle, you would never make it to 'city driving'. You have a no-flow condition. Either your rad is completely clogged, your water pump is the wrong rotation, or you T-stat is bad. It's that freakn' simple. If you had a blow head gasket it would show itself in other ways, miss, white steam/smoke, loss of power.....etc..... I have gone through several....4 or 5 stats that failed, ran hot or temp fluctuated wildly. Stant absolutely SUCK!!!!!! Either your rad is clogged or your stat SUCKS, change it. Link to comment Share on other sites More sharing options...
MJfan94 Posted November 27, 2014 Author Share Posted November 27, 2014 For $#!&s and giggles- Image Not Found Yesterday while reading this thread and posting that you reread my post, I took this pic with my phone. Ambient temp was 49 degrees, truck was at idle for better than 20 minutes with heater on as I was taking a break from work. The E-fan NEVER came on. I do NOT have a mechanical fan. If you have an air pocket in your head you would get an overheat after about 3 minutes at idle, you would never make it to 'city driving'. You have a no-flow condition. Either your rad is completely clogged, your water pump is the wrong rotation, or you T-stat is bad. It's that freakn' simple. If you had a blow head gasket it would show itself in other ways, miss, white steam/smoke, loss of power.....etc..... I have gone through several....4 or 5 stats that failed, ran hot or temp fluctuated wildly. Stant absolutely SUCK!!!!!! Either your rad is clogged or your stat SUCKS, change it. I've now tried different t-stats and drilling a hole in one of them. After touching some of the hoses, ive notice the top radiator hose is really hot but the radiator was cold. So I'm guessing that my radiator is clogged. Now knowing that i might have to replace the radiator, would it be possible to create a hybrid system using a open cooling system radiator in a closed system or does that not really work. Link to comment Share on other sites More sharing options...
gogmorgo Posted November 28, 2014 Share Posted November 28, 2014 http://comancheclub.com/topic/44535-closed-to-open-cooling-diy/ It's been done. You'll also need an open system overflow bottle, but that's pointed out in the linked thread. Link to comment Share on other sites More sharing options...
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