Thread: Coolant Mystery

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    BTaylor34's Avatar
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    Coolant Mystery

    Hey all, wanted to see if anyone could give me some ideas I might have overlooked.

    I have a 2000 TJ 2.5. The other day I was changing the oil, and noticed the coolant reservoir was empty. Filled it to the full line, and after the change, drove it about 20 min then came back. Coolant reservoir was empty again, so I filled it again to the fill line.
    --This kinda bugged me, so I started looking around. I don't see any coolant on the ground, and when I run the heat sometimes there is the feint smell of coolant, but I mean really feint, not very strong at all. I have checked for symptoms of a head gasket leak. No white smoke, oil is good, coolant is bright green, no hard idle, temp good, power about the same.

    After each drive, I have been trying to find something but still come up short. So far, the radiator is full, and there is still coolant in the reservoir, but that is going down little bit by little bit. Checked this morning and have about 5 inches in the reservoir. Does it sound like maybe a pinhole leak or something? Any ideas would be great!

    Thanks!

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    Re: Coolant Mystery

    It sounds to me that the heater core is leaking . Usually when they leak , there is fogging on the inside of the windshield but if you are not seeing this , you should still check for leaks in the cooling system. You will need a pressure tester that pumps pressure through the radiator filler neck. Perform this test with the engine off and cool enough to remove the radiator cap. If there is a leak , the added pressure will force out coolant when it is leaking.

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    Re: Coolant Mystery

    I haven't had any fogging, but I will def check that heater core. Thanks for the direction. If said heater core turns out to be the problem, is it pretty much a replacement issue, or is there an additive that will plug up small leaks? (like radiator stop leak) There hasn't been any coolant in the floorboards, so it may be evaporating, but worth the look.

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    Re: Coolant Mystery

    I'd steer clear of miracle in a jar juices , they are famous for plugging up cooling passages like radiators and heater cores and don't help water pumps and thermostats much either .
    People will beg to differ but every time I take apart something in the cooling system that someone added Barsleak or something else , I find a gooey mess , more clean up,work and a part that still has to be changed anyway. The only true fix for something is to repair it or replace it .
    I try to live by that .

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    Re: Coolant Mystery

    Sounds like good advice. I'm an intermediate with mechanical and upgrades, so I take in all advice. On a different subject now, hijacking my own post...I am looking to snorkel my TJ soon. Nearly all I've seen that are in my price range say they are for the 4.0. Will these fit the 2.5?
    I didn't know if the 2.5 and 4.0 use the same air box.

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    JPNinPA's Avatar
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    Based on your initial description.

    What to does your engine run when at temp for 10 min? Does it run hotter when idling than when driving 35 mph or greater? Any overheating?

    Based on what you mentioned there are a few things to check. First if you are filling the recovery tank to the top you are overfilling it and the fluid will be pushed out as the engine comes up to temp.

    There is a line on the recovery tank, marked half way up as full when cold. Only fill to there. Any more will spill out as the temp rises and fluid expands into the tank.
    Fill at night and check in the am to be sure your tank is not cracked.
    Second inspect the hose connections at the tank and at the radiator near the cap. Be sure they are fitting tight and are not rotted or loose. Also check the top of the radiator where plastic meets metal for leaks.
    Third check your radiator cap. It should be an 18lb cap. Any lower and you will have issues.

    From under the vehicle look up at the water pump weep hole for wetness.


    After verifying all above them with the engine cold and either parked on an incline or lift the front of the vehicle, open the radiator cap and start the vehicle. As it comes to temp and the thermo opens watch for bubbles. App 25 or so large bubbles may come out then stop. Fill the radiator and replace the cap. If bubbles keep coming there is other issues.
    While it is open look for oil in the fluid.

    My bet is on radiator cap fail.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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    Re: Coolant Mystery

    Quote Originally Posted by JPNinPA View Post
    My bet is on radiator cap fail.
    Give the man a cigar. Replace your rad cap, and make sure its a 18lb cap.

    blatant jokessubliminal sarcasmsexual innuendo

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    Re: Coolant Mystery

    i had the same issue. mine was the radiator cap.
    no more jeeps at this time. next time it will be a cj with a v8

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    Re: Coolant Mystery

    Thanks for the suggestions all!

    Engine temp runs between 190-210 at full warm up. On the reservoir, I have only filled it to the full line, never all the way up. I haven't thought about burping it though, that's a good idea and will def give that a run. I will check the water pump, however, the engine and water pump are both new, with only about 4k on them, so I wouldn't think that is the problem, but you never know, right? :S

    I'll update what I find out. Thanks again ya'll.

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    Re: Coolant Mystery

    Well, I finally had to bite the bullet and take it in. Luckily I have a friend with a mechanic shop close by. After checking anything I was at a loss, just could not find that leak. Then at the parts store when I was picking up the new rad cap, I noticed a slow leak coming from under the bell housing. When I put the new rad cap on and cranked her up and let it run a bit, I noticed it was a considerable fast paced drip coming from the same spot. Perhaps better pressure from a new cap made the leak stronger, idk...but anyhow, with a ride coming up tomorrow, I didn't want to chance it. Thanks to all of ya'll for the suggestions, there was a lot on there I didn't even think about. I'll let ya'll know what the final verdict is!

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    Oh... Sorry to hear that.



    First be sure it is coolant and not the cowl drain or AC drips from defrost.

    If it is coolant:
    There are radiator hoses going to the heater core on the passenger side firewall. One of those hoses may be leaking.

    Also There are two freeze plugs above the bell housing. I don't know how hard it is to get to but read a post or two (not many) of this leaking.
    http://www.jeepz.com/forum/cj-yj-tj-...lant-leak.html


    Something I didn't mention. First be sure you only put recommended coolant in the jeep. Do not mix!!!

    Second a black light will illuminate coolant so leaks are a bit easier to trace back.
    Last edited by JPNinPA; 01-18-2014 at 04:45 AM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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    Re: Coolant Mystery

    Well, have the final verdict....NEW ENGINE!! Yup, we thought it was the front freeze plug, so went about getting that changed, and when we pressurized the system after the new plug, we noticed it was still leaking. Son of a..... lol. Turns out, there was about a 1/16" hole in the block directly above the freeze plug. I couldn't find the leak when looking cause when she was hot it was just coming straight out and vaporizing. Luckily, the new motor only had 3k on her, and was totally covered by warranty. Dodged a bullet this time. I wanna say thanks again to everyone for their help and the info!

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    Glad you figured it out. That's a bit more than a radiator cap, but hopefully you didn't spend a lot to find the issue.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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