TheSiLvAPython Posted June 10, 2022 Share Posted June 10, 2022 I have an 89 comanche with 4.0 and a closed cooling system and I have air bubbles stuck in my cooling system. I would loosen the temp gauge sender bolt on the back of the engine but it is stripped really badly to the point i can't get it open because the socket can't grab. Are there any other ways of getting the air out?.. or do i need to just rip this thing out. Are there replacement temp gauge sender bolts or am I screwed? I have many other questions about lots of other things but this one is my first post so far. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 10, 2022 Share Posted June 10, 2022 I have NEVER needed to bleed one of those cooling systems. Been working on them since 1987. Perhaps describe your issue in more detail. Symptoms? Link to comment Share on other sites More sharing options...
Eagle Posted June 11, 2022 Share Posted June 11, 2022 There is no temp gauge sender bolt. Are you referring to the actual coolant temperature sensor? https://shop.advanceautoparts.com/p/crown-auto-jeep-replacmnt-coolant-temperature-sensor-53005056/11740438-P?searchTerm=Coolant+Temperature+Sensor I've also never had to remove that to get air out of the system. Any air should purge itself -- just keep adding coolant until the level doesn't do down any more. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted June 11, 2022 Author Share Posted June 11, 2022 When My truck is Idle i will start to "over heat" with the temp gauge reaching 210 or higher if I don't move, but once I start to drive the temperature will drop pretty drastically from 210+ down to about halfway between the 210 and the start of the temp gauge. So I assumed I had trapped air in the cooling system causing hot spots. Could this just be my radiator not dissipating the heat? Maybe I do need to just add more coolant. I will give it a try. So Really you haven't ever had to purge the air out of the sealed cooling system. This definitely is starting to seem like user error. Sorry this is my first Jeep ever and I don't know much about vehicles but this Truck is definitely teaching me some things. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted June 11, 2022 Author Share Posted June 11, 2022 Yes that is what I am talking about I think the temperature sensor and it is on the back of the valve cover on the driverside. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 11, 2022 Share Posted June 11, 2022 That sounds like a cheapy thermostat and a bad fan clutch to me. Link to comment Share on other sites More sharing options...
AZJeff Posted June 11, 2022 Share Posted June 11, 2022 When temperature drops dramatically when the vehicle starts to move, it's because air is now flowing over the radiator at a much higher rate than when the vehicle was stationary. The cooling fan(s) are supposed to cause air to flow when the vehicle is stationary. If they do NOT, then coolant temperature will rise dramatically. All MJ's have one mechanical cooling fan with a viscous clutch. Most MJ's also have an electric fan that acts as a booster, and is present if the vehicle has AC or a heavy duty cooling system. We will ignore this for purposes of this discussion. When this mehcanical clutch/fan (and associated fan shroud) are properly functioning, the fan should be able to keep the engine within normal operating range when the engine is idling and stationary. It sounds like your clutch is not engaging properly, and allowing the fan to "slip" on it's shaft even when the temperature would call for the clutch to "lock up" and allow the fan to spin at high speed. In addition, when an MJ is running down the road at a speed of 45mph or more, the fan no longer becomes a factor in keeping the engine cool. There is enough air entering the radiator through the grille to keep the temperature at the normal level, whcih should be about 210*, give or take 5-10 degrees. If your temperature is dropping to much lower than 210, it means your thermostat is opening WAY too far, and allowing too much coolant flow through the radiator, and thus OVERCOOLING the engine. A new, high quality/brand name thermostat should fix this. Be sure to get a thermostat set for 195*, and NOT one that is set to open at lower values like 160* or 180* Link to comment Share on other sites More sharing options...
cruiser54 Posted June 11, 2022 Share Posted June 11, 2022 This^^ Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted June 21, 2022 Author Share Posted June 21, 2022 Good to know thank you so then my truck is been running under temperature of the whole time I did follow eagles advice in just filling until coolant level doesn't go down anymore that seemed to help. I have a new thermostat to install. Will do that along with my radiator because it is damaged now. Thank you for your inputs I appreciate the helpful knowledge. Link to comment Share on other sites More sharing options...
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