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Jeep Wrangler keeps blowing radiator hoses

Discussion in 'Wrangler JK (2007-2017)' started by phatsajak, Feb 18, 2020.

  1. Feb 18, 2020 at 7:03 AM
    #1
    phatsajak

    phatsajak [OP] Member

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    I have a 2008 Jeep Wrangler Unlimited. 90k miles. This summer I noticed that as I sat idling in the pick-up line at my son's school, my Jeep would "surge" a bit. The RPMs would rise a tad, and the temperature gauge would go from 1/2 to 3/4 in a matter of seconds. It would idle like this for around 30 seconds or so. While it's still idling high, the temperature would stabilize again back to 1/2. This would repeat every few minutes. It is not limited to idling. Happens while driving as well, but not as noticeable due to external noises and such. Also, when I started my Jeep, I would hear a water trickling sound in my dash.

    So in August my radiator cracked. I'm guessing the crack was there and the coolant was low, hence the water trickling sound in my dash. My mechanic replaced the radiator, pump, thermo, and hoses. The high idling was still happening. At one point in this high idle episode, the thermo gauge went into the red. Took it back to the mechanic and he fixed a hose that was leaking, which was a hose they just replaced. The surges kept happening.

    I notices coolant on my driveway when I parked at home. Took it back and they replaced another hose.

    Then at the pick-up line, it surged into the red and steam poured out from under the front passenger side of the hood. Drove right to the shop. They replaced the radiator cap, said it failed.

    Got the Jeep back and surging kept happening. Driving home today, steam starts pouring out from under the hood. Went right to the shop. The upper radiator hose completely blew off. The hose clamp was still tight.

    So they did a block test to see if there is a head gasket leak. It passed. So this is still a mystery.

    Any idea what can cause surges in RPM, Temperature, and enough pressure to blow radiator hoses off? I'm guessing the radiator cracked due to pressure surges, but that's my uneducated guess.

    Thanks in advance. Let me know if more details are needed!
     
  2. Feb 18, 2020 at 7:53 AM
    #2
    aggrex

    aggrex Well-Known Member

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    Welcome @phatsajak ...after all that cooling system work the heater core should be suspect.
     
  3. Feb 18, 2020 at 8:38 AM
    #3
    kowdog

    kowdog Member

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    Sounds like an air bubble in the cooling side. I had that issue with a Subaru Outback with the boxer engine, (4 cyl ).The Subaru forum said it was a known issue with the 2.5 subbie engine.They said air becomes trapped after any time the system is worked on.Not sure if that is your problem, but worth a try maybe.
    I put it on the ramps so the front would be higher, then using the radiator cap, let the pressure release, opened the cap, and let it run for a few minutes. I saw air bubbles at the radiator cap hole, so turned it off and let it cool down completely, 2 hours later, I topped it off and put the cap back on. Took it for a ride, no more issues.
    As Aggrex said, the heater core could be part of the issue as well. The gurgling you heard under the dash is most likely air trapped in the system trying to move through the core, but any blockage in the core will cause back pressure, hence the sounds. Remember, the water pump will bypass some but not all of the pressure in the system through the bypass hose. Not sure if a partially blocked core would be the cause of ALL of the pressure, I have had new pumps fail too, any warranty from the shop that replaced it? You didn't say which engine you have, but, cooling is cooling. Do you have AC? Have you checked air flow through the condenser if equipped? Also, did the mech do a pressure test on the system after the replacement?
     
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  4. Feb 18, 2020 at 8:44 AM
    #4
    kowdog

    kowdog Member

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    One more thing, If you have the 3.6, try loosing the bleed screw located on the thermostat housing near the hose. Jeep says to bleed the system after replacing the t-stat.......
     
  5. Feb 18, 2020 at 12:04 PM
    #5
    phatsajak

    phatsajak [OP] Member

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    It's a 3.8L V6. The mechanic ruled out a bad heater core. I will get his reasoning or get a second opinion on that. I will also find the bleed screw. They did a block test, and it passed. I assume they did a pressure test and bled the system after all this work, but you never know.

    Yes, there is AC, and I have not checked the air flow. There are a couple more symptoms... At one point at the beginning of Fall, the AC would not blow. This only lasted a few minutes, and has worked since. Not sure if there is any correlation there.

    A symptom I noticed just this morning... When the engine starts to heat up, and before the surge in RPMs when idling, the coolant overflow hose starts to rapidly shake coupled with a higher pitched "motor" sound coming from near the air intake (I did not get too close to the engine because this is usually when a hose pops off and sprays hot coolant). Then, when the engine/temperature surge finally happens, the upper radiator hose collapses. As soon as I shut off the engine, the hose returns to normal. The cap is brand new, so I'm wondering if the resovior hose is plugged? Any thoughts?
     
  6. Feb 18, 2020 at 1:54 PM
    #6
    kowdog

    kowdog Member

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    Have you checked for codes? Sounds silly maybe, but if you have an OBD II code reader, check for any saved codes related to cooling. The system has more than one sensor/sending unit for the coolant, one is for the efi system for fuel management. The surging is most likely related to a sensor. Also check any and all electrical connectors in the engine area for corroded or looseness at all of the connectors. Also check all of the associated grounds, a bad or loose ground can cause a plethora of issues. A failed or failing sensor can cause some strange symptoms as well.
    I didn't see where you replaced the t-stat. I know some shops will do it as part of any coolant systems issues, some not so much. I am thinking the issue is related to the flow path through the system, so.....The hose collapsing is a symptom of vacuum/pressure in the system after shutting down the pump.
    1. If you aren't sure the t-stat has been changed, do so.
    2. If it has, you might think about removing it and bench test in a pan of cold heated to hot water while watching for it to open. Helps to have a temp probe for accuracy, opening temp is stamped on the flat of the t-stat.
    3. Noises; The symptom today sounds like coolant flowing through the overflow line, (hence the vibrating/shaking), into the overflow tank. More info on the sound is required tho, exact location is critical, and when you say motor sound, I am unclear as to that. Do you mean a wirring or maybe winning?
    The overflow tank hose is easy to check, just loosen or squeeze the clamp and remove it from the radiator fill neck, carefully wipe the end off and open the tank lid. Blow a little air into the hose, you should see or hear bubbles in the tank. That's not an issue i don't think, as that 1/4 " hose won't cause any of the engine surging issues you have.
    The AC not blowing was most likely just a switch not connecting for a few seconds, happens from dust, or just wear.
     
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  7. Feb 18, 2020 at 9:20 PM
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    phatsajak

    phatsajak [OP] Member

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    Yes, I have a Fix'd app and sensor that did not detect any codes. Also had the free auto parts store scan for codes. I think a deeper diagnostic is in order.

    Yes, thermostat is new.Tested the overflow line and it did just as you said, so that seems fine. The noise i think we should disregard. There is an orchestra of different noises coming from different areas in inconsistent patterns.

    The overflow tank is roughly 1/3 full. I could not replicate any condition tonight that would cause the radiator to dump into the reservoir, and the hose did not collapse. My guess is that the upper hose collapses only when the radiator is trying to dump into the reservoir. But if the cap is new, and the overflow line is not obstructed, what could cause that vacuum?

    Checking hoses and connections tonight, I noticed the air intake hose that connects to the throttle body was not tight. The hose clamp was there, but not tightened down at all. A slight tug pulled the entire hose easily from the throttle body. I clamped that down.

    Thanks for your help so far, Kowdog!
     
  8. Feb 19, 2020 at 2:03 PM
    #8
    Jim Beam

    Jim Beam Well-Known Member

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    Are you using a high coolant content with the water in your cooling system? As coolant expands when it gets hot and if the radiator cap does not release the pressure, something has to give. I would suggest checking the coolant/water ratio with one of those cheap gauges at the parts store and making sure that new radiator cap is good and not to strong of a release pressure. Too light of a pressure release will cause an engine overheat though. You could try a cooling system leak repair additive for at least a temporary repair if you have a heater core leak.
     
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  9. Feb 19, 2020 at 4:06 PM
    #9
    aggrex

    aggrex Well-Known Member

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    The collapsed upper radiator hose needs to be looked at..... pressure rating of the new cap has to match the rating on the old cap or oem spec. Radiator caps are inexpensive so order another online. Make sure the thermostat is the correct one for your jeep. Perhaps they installed it upside down or it's defective or it's the wrong one. I've seen thermostats clogged with the sealant used to make the installation water-tight. If it fails in the closed position the WP will pull coolant from the radiator resulting in a collapsed hose and could cause the motor to overheat.
     
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  10. Feb 20, 2020 at 7:32 AM
    #10
    kowdog

    kowdog Member

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    Aggrex and Jim Beam are both onto something, I've had new parts fail outta the box, t-stat issues are among the most frustrating. I had a shop install the t-stat backwards in the Subaru I mentioned, after a head gasket R/R, and it had the exact symptoms as you are having. It took me three tries to finally figure it out!!Took the bench test to confirm that it was installed backwards, hence the surging.It is a pain, but checking EVERY component in the system is important.
    You didn't say how long this issues has been going on, did it just happen overnight? Were there any indications of an issue prior to the surging, (overheating, loss of coolant from a leak/hose failure,ect.)?
    Also as JB said, the right mixture of coolant/water is more critical with today's engine controls, as well as heat displacement.The surging might be caused by a lack of coolant passing the sensor,(temp gauge rising & falling) and also causing the hose to collapse after the t-stat opens, or the air is displaced by some of the coolant movement.Remember, the hot side is the upper hose,(inlet), the bottom is the cooled,(outlet) side.When the upper hose collapsed,it was caused by the sudden opening of the t-stat, or the movement of the air in the system.
    Here's a suggestion, put the jeep on ramps, or jack it up and use jack stands to elevate it a couple feet, then, drain the system,and if you are sure the t-stat is installed correctly, and functions correctly, (I can't emphasize enough the importance of bench testing it), put it back together, then add the correct amount of 50/50 coolant/water. I've attached a link for a funnel that will attach to the radiator fill port, it is the surest way to get all the air outta the system, as it keeps a small amount of coolant in it, and allows the air to rise to the top as you run the engine. Allow the engine to come up to operating temp. and watch for air in the funnel. You could most likely find one at Auto Zone or Advanced Auto Parts, maybe even Walmart.shopping_5c1c789ecc244369c6f8224a4c2c5571582ee141.pngGotta love this Forum!!!!
     
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  11. Feb 22, 2020 at 10:42 AM
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    phatsajak

    phatsajak [OP] Member

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    So the issue with surging has been happening since last summer. Right now the Jeep is at an offload center with someone who knows Jeeps and their cooling systems. The surging is the fan kicking into high gear due to a spike in temperature. They are suspecting something as simple as an air bubble at the thermostat.

    The cap is a good question, they replaced it twice since the radiator cracked. The second time might not have been the correct rated cap. But the Jeep stayed in the shop an extra night because they supposedly had to order the correct cap. So you would think it's the proper oem spec, but i didn't get this far in life by thinking...

    It would make sense that the T-stat originally failed, and was replaced with either a bad or incorrectly installed T-stat. That might be the next investigation.

    Not sure on the coolant mixture. That radiator has been drained a few times since this. I will inquire their methods.

    Thanks all! I'll update once these matters are looked in to...
     
  12. Feb 22, 2020 at 3:09 PM
    #12
    Jim Beam

    Jim Beam Well-Known Member

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    Drilling a tiny hole, of about a 1/16" inch or so in the thermostat will help get rid of any air in the cooling system, look it up online. Along with driving up and down steep hills. This will get the air to the top of the radiator.
     
  13. Feb 22, 2020 at 10:15 PM
    #13
    phatsajak

    phatsajak [OP] Member

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    Wow, never heard of that one. But I'm sure it works! But here's my latest very interesting revelations...

    Got it back from the mechanic (suspension work, but since it was an off-road shop, the mechanic knows Jeeps inside and out). Pressure test passed, so no detectable leaks. But, when I got home, I sat in the driveway and let it idle for about 10 minutes. The fan kicked in to high gear at one point, the temp gauge reached 3/4 hot, then stabilized while the fan was still running high speed. The fan shut off about a minute after the temp gauge returned to the center mark. I still let it idle, then after around 5 minutes later, the fan kicked on high again, but the temp gauge went in the red. I shut the Jeep off at this point. About 5 minutes later, I started the Jeep again and let it idle. The temp gauge never read above the center mark, BUT... about 10 minutes in, the radiator started dumping boiling coolant into the overflow tank, and the fan wasn't running at all and the temp gauge was still at center mark. So, if I'm not mistaken, if the radiator is dumping boiling coolant into the overflow tank, the temp gauge should show it, and the radiator fan should be running. What I'm thinking is the radiator fan or the gauge are not always getting the message that the engine is hot. So we tested the radiator fan wiring with a meter, and we got an inconsistent reading. It was stronger when i hit the fan relay with a wrench while my buddy was taking a reading with his meter. So there are three things I will try... Replacing the radiator fan relay, replacing the fan motor wiring, and replacing the temperature sending unit. Another thought I had with my limited knowledge of mechanics, the Jeep fan has two speeds, perhaps the lower fan speed is controlled by a different relay that the high speed fan mode and the fan only gets a message to cool the radiator down at high speed, but at this point it is sometimes too much to ask for the high speed fan to do without the first speed of the fan to do it's job in the first place?

    FYI, I'm not a mechanic, obviously. I'm a graphic designer who am not very good with engines, but good at problem solving! That's what these forums are for, you experts teaching us novices. And us novices with the eagerness to learn appreciate it!!

    Thanks in advance! I believe this will be a case study fore a lot of Jeep owners with mysterious cooling system problems with your help!
     
  14. Feb 24, 2020 at 9:02 AM
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    kowdog

    kowdog Member

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    After re-reading all of the posting on this issue, it becomes clearer, the issue is air in the cooling system. As JB said, drilling a small hole in the t-stat will help the trapped air rise and go to the top of the radiator. The temp sensor will only read temp if it has liquid surrounding it, hence the surging is a direct result of little to no fluid, and/or, fluid being suddenly released by the t-stat. and the fan coming on as a result of the sudden hi temp. reading at the sensor. I found this on another forum, might give you some info related to your issue.

    The e-rad fan only comes on at certain conditions.

    OPERATION
    The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relay. The PCM regulates fan operation based on input from the engine coolant temperature sensor, battery temperature sensor,air conditioning select switch and vehicle speed. The fan is not energized during engine cranking regardless of the electrical input from the temperature sensors and ,air conditioning switch. However, if engine operation conditions warrant fan engagement, the fan will run once engine starts.

    Vehicles Equipped with AC:
    In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the ,air conditioning system is activated. The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).


    Interesting to know the fan has so many inputs to control it's operation. I also saw a few videos on youtube on testing the 2 spd. fan.
     
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  15. Feb 25, 2020 at 5:40 AM
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    phatsajak

    phatsajak [OP] Member

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    Right now they are replacing Fan relay, fan motor wiring, and temp sending unit. They are also gonna remove and bench test the t-stat. I'm fairly certain they will not install a new t-stat that I modify, so that's one that I will have to do on my own. But wouldn't there be a manufactured t-stat with a bleed hole certified for Jeeps? And does it make a difference is the t-stats on a 2008 wrangler JKs are installed to take on a vertical flow of coolant, as opposed to horizontal? Meaning that the t-stat flange sits horizontal against the housing. Pic attached of how it sits installed. This is not my Jeep, looks like a 2011 image I found online. And this t-stat has a manufactured bleed hole. That bleed hole is starting to sound pretty essential...

    Screen Shot 2020-02-25 at 6.55.43 AM.jpg
     
    Last edited: Feb 25, 2020
  16. Feb 25, 2020 at 4:41 PM
    #16
    Jim Beam

    Jim Beam Well-Known Member

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    Interesting that you spotted a thermostat with a air bleed hole in it. So now I wonder if it is an aftermarket only item or an oem part. The manufacturer of that item does have to spend money to put that hole in, and sometimes the bean counters just won't allow it. I would not consider it essential, but it does help. If the thermostat is mounted vertical, place the hole at the 12:00 position. Too big of a hole can affect how long it takes the engine to warm up.
     
    Last edited: Feb 25, 2020
  17. Feb 26, 2020 at 4:52 AM
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    kowdog

    kowdog Member

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    I found this at Carquest on-line. Notice the brass tab in the middle of pic. It's an air bleed.....
    CARQUEST Engine Coolant Thermostat
    [​IMG]




    45 Reviews


    1 YR REPLACEMENT IF DEFECTIVE
    Part # 14209

    Exact Fit for your 2008 Jeep Wrangler Unlimited X
    OE Type Thermostat; Temperature: 195 Degrees; OE Temperature
     
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  18. Feb 26, 2020 at 4:59 AM
    #18
    kowdog

    kowdog Member

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    I hope you have deep pockets.... sounds like you are spending a lot of time in the shop, @ $100-125.00 per hour, it adds up! Steep learning curve....but essential at this point. Did the shop discount any of the labor? I would suggest you ask em, as my ex Mother-in-law always said, "Nothing ventured, nothing gained"......
     
  19. Feb 26, 2020 at 8:23 AM
    #19
    phatsajak

    phatsajak [OP] Member

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    They are replacing with a t-stat that has a bleed hole. They are working with me financially. I believe the t-stat will be of no charge. I guess it wouldn't be a Jeep if it was easy and cheap! Hopefully it comes back today and I can update with some good news. Thanks all!!
     
  20. Mar 3, 2020 at 6:23 AM
    #20
    phatsajak

    phatsajak [OP] Member

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    I'm proud to report that the problem seems to be resolved! The last round of repairs included as I stated above (t-state with the bleed hole), but also included the entire fan assembly and the low speed fan relay. I'm guessing the low speed fan relay was the culprit. Now when I sit and idle to investigate, the fan kicks on more at low speed, which did not happen frequently enough before. The high speed fan would kick on usually too late to cool the engine on its own. So while we enjoy our 70 degree Arizona winters, the engine is staying put at normal operating range. We'll see once our temps reach 45 degrees hotter in a few months. Thanks for all the advice!
     
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