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Hi all, I need some desperate help because I’m about to turn to the sledge soon. I’ve had the Jeep 6 months and it has 176k miles. I’ve completely replaced the brake system, a bulk of the a/c system, and now the cooling system. I’ll back up.... 6 weeks ago I had my ac system fixed and the mechanic (lifelong friend) told me my fan clutch was starting to go. 2 days later he changed it out with a brand new one. 2 weeks ago I did my oil change but changed from 10w30 to 10w40 (since I’m in south fla I’m hoping to help with overheating). The next day I took a 1:15 hour drive and it overheated in the last 5 mins. When I looked the top radiator hose blew off. Fun fun. Over the next few days I ended up replacing the thermostat, water pump, radiator (and safety cap @18lbs), and hoses. I also changed the power steering pump bc it was leaking, only to find out the steering box is leaking.... next project I guess. The temp before overheating always stayed right infer the 210 mark. Never went above. Over the past few days I’ve driven it around to test it and after about 45 mins of driving and idling it holds steady around 225 and then elevates another 10 until I turn it off. Today when I did it, when I turned off the engine the radiator and overflow tank were shaking a lot and seemed to be boiling and then all of the sudden it completely stopped.... so it couldn’t have been boiling stopping suddenly. I did a block test with the blue fluid in the radiator cap and after 2 mins it did not change showing that I dont have a leaking gasket. Also did the ol’ smell test for gas in the fluid and nothing. I’m at a loss. Anyone have any ideas??
 

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You most probably have residual air in the system - get the front of the jeep as high up in the air as you can safely, open the rad cap and burp it - run the engine with the heater on full hot with the cap off. CAREFULLY squeeze the upper rad hose to release any bubbles - watch out for the FAN - it will take a finger off easily. Make sure the thermostat opens properly - you should see the coolant level drop in the radiator as the air is bled out - top off with the engine running til it wont take any more and level stays pretty constant and normal operating temp. Re-fit the cap and fill the overflow tank to it’s full mark. Let it sit overnight then in the morning, check the radiator level again - if there’s more air, rinse and repeat.
If the overflow tube is worn out, it’s possible to get air drawn back into the system as the coolant contracts so make sure the hose to the overflow seals on the radiator nipple as well as the plastic overflow tank (I use hose clamps but you can use zipties too)

BTW; what coolant are you using? Make sure the concentration is no more than 50/50 water-coolant/antifreeze as this can cause issues with cooling also.

Have you verified the fan clutch is operating correctly?

Sent from my iPhone using Tapatalk
 

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Could be unrelated, but maybe not...

Do you have a new(er) Stant 18 lb. radiator cap on there by any chance?
My entire cooling system is only 2 months old. My upper hose blew off the thermostat housing after driving around town a little and parking in the driveway. I think mine was likely the Stant cap not relieving pressure, causing the hose to blow off the top of the housing.

Coincidence, your top hose blew off this week too. Figured it was worth seeing if there were any common threads here... I put my old radiator cap back on. Fine so far.
 

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Discussion Starter #5
You most probably have residual air in the system - get the front of the jeep as high up in the air as you can safely, open the rad cap and burp it - run the engine with the heater on full hot with the cap off. CAREFULLY squeeze the upper rad hose to release any bubbles - watch out for the FAN - it will take a finger off easily. Make sure the thermostat opens properly - you should see the coolant level drop in the radiator as the air is bled out - top off with the engine running til it wont take any more and level stays pretty constant and normal operating temp. Re-fit the cap and fill the overflow tank to it’s full mark. Let it sit overnight then in the morning, check the radiator level again - if there’s more air, rinse and repeat.
If the overflow tube is worn out, it’s possible to get air drawn back into the system as the coolant contracts so make sure the hose to the overflow seals on the radiator nipple as well as the plastic overflow tank (I use hose clamps but you can use zipties too)

BTW; what coolant are you using? Make sure the concentration is no more than 50/50 water-coolant/antifreeze as this can cause issues with cooling also.

Have you verified the fan clutch is operating correctly?

Sent from my iPhone using Tapatalk
thank you for the detailed response. I’ll do that first thing tomorrow. Yes I can verify the fan clutch is working and good to go based on forum searches for testing. The coolant is 50/50 but not sure of the brand.May be a dumb question but does brand make a huge difference? Also... my overflow tank hose is NOT clamped on, it just slips over the nipple. I haven’t noticed any leaking from it though but I’ll still clamp it down. I’ll let you know how it goes!!
 

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Discussion Starter #6
Could be unrelated, but maybe not...

Do you have a new(er) Stant 18 lb. radiator cap on there by any chance?
My entire cooling system is only 2 months old. My upper hose blew off the thermostat housing after driving around town a little and parking in the driveway. I think mine was likely the Stant cap not relieving pressure, causing the hose to blow off the top of the housing.

Coincidence, your top hose blew off this week too. Figured it was worth seeing if there were any common threads here... I put my old radiator cap back on. Fine so far.
yes I do have a new slant 18lb cap, but still the same results. I was really hoping it would be a $6 fix but I can’t be so lucky. Lol
 

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Discussion Starter #8
thank you for the detailed response. I’ll do that first thing tomorrow. Yes I can verify the fan clutch is working and good to go based on forum searches for testing. The coolant is 50/50 but not sure of the brand.May be a dumb question but does brand make a huge difference? Also... my overflow tank hose is NOT clamped on, it just slips over the nipple. I haven’t noticed any leaking from it though but I’ll still clamp it down. I’ll let you know how it goes!!
You most probably have residual air in the system - get the front of the jeep as high up in the air as you can safely, open the rad cap and burp it - run the engine with the heater on full hot with the cap off. CAREFULLY squeeze the upper rad hose to release any bubbles - watch out for the FAN - it will take a finger off easily. Make sure the thermostat opens properly - you should see the coolant level drop in the radiator as the air is bled out - top off with the engine running til it wont take any more and level stays pretty constant and normal operating temp. Re-fit the cap and fill the overflow tank to it’s full mark. Let it sit overnight then in the morning, check the radiator level again - if there’s more air, rinse and repeat.
If the overflow tube is worn out, it’s possible to get air drawn back into the system as the coolant contracts so make sure the hose to the overflow seals on the radiator nipple as well as the plastic overflow tank (I use hose clamps but you can use zipties too)

BTW; what coolant are you using? Make sure the concentration is no more than 50/50 water-coolant/antifreeze as this can cause issues with cooling also.

Have you verified the fan clutch is operating correctly?

Sent from my iPhone using Tapatalk
Ok so I did as you told me and it’s still holding steady around 215-220. It’s not going above it though. Driving me crazy. One thing that may be something, a week before it started overheating I changed oil from 10w-30 to 10w-40. Could that be stressing system causing overheating?
 

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I don't think the engine oil causes overheating. Engine oil is there for lubrication, not cooling.

Somebody already recommended above checking the thermocoupling on the fan is working properly.

Then I would do a swap of the cooling fluid, you said you are not sure what you have in there. The brand is not the main thing, but having the right type of antifreeze is critical. Normally it will increase the boiling the point above 100 degrees Celsius. Having a lower boiling point might turn the liquid into steam and thus leading to improper flow -> overheating.

If you changed all the main parts of the cooling system and it is still like that, my next bet would be some kind of garbage in the cooling system. Most likely in the engine block if radiator, hoses and the water pump were changed. That could explain running fine for a time and then clogging up the system and causing the overheating. But I think this is the least likely, a blocked engine would act up all the time.

LE: forgot about the in-dash heater. Do you see any leaks in the passenger foot well? If the in-dash heater is leaking, it could allow air to get into the system and again cause issues with the flow. You can also try, when you see the needle going up, to turn the heating to max, see if that helps. It won't fix it, but it might bring the temp down a bit, in order to not boil the engine.
 

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Discussion Starter #11
Thank you for your reply. I’ll change out the fluid today. I have a generic 50/50 in there and I’ll swap it for the good stuff.
negative on the water on the floorboards, the heater core seems to be working properly and I have driven it and had to turn the heater on (awesome in south Florida heat btw lol) and it does bring it down from the middle of the “0” to just under the 210 mark where it should be.
 

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You most probably have residual air in the system - get the front of the jeep as high up in the air as you can safely, open the rad cap and burp it - run the engine with the heater on full hot with the cap off. CAREFULLY squeeze the upper rad hose to release any bubbles - watch out for the FAN - it will take a finger off easily. Make sure the thermostat opens properly - you should see the coolant level drop in the radiator as the air is bled out - top off with the engine running til it wont take any more and level stays pretty constant and normal operating temp. Re-fit the cap and fill the overflow tank to it’s full mark. Let it sit overnight then in the morning, check the radiator level again - if there’s more air, rinse and repeat.
If the overflow tube is worn out, it’s possible to get air drawn back into the system as the coolant contracts so make sure the hose to the overflow seals on the radiator nipple as well as the plastic overflow tank (I use hose clamps but you can use zipties too)
If you remove the heater hose from the thermostat housing when filling the radiator, you will give trapped air an easy escape route and can avoid the above procedure entirely. (Keep in mind that the heater flow bypasses the thermostat entirely, so the technique works perfectly well on a cold engine.)
 

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Discussion Starter #15
I used an aftermarket. I know I should have gone with the oem but at the time I didn’t have the funds. Just got full custody of my daughter and she’s more expensive than the Jeep. 😂
 
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