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Thread: Smell coolant and oil on inside of windshield?

  1. #1

    Default Smell coolant and oil on inside of windshield?

    Hey guys I'm new to the forum. Haven't owned a jeep in a few years and just bought a 1985 XJ Pioneer with the 2.1L renault diesel. It's a strong runner but I'm having a weird issue.

    Lots of moisture on inside of windshield when running the heater and when I wipe it off it's sorta brown. It smells like coolant as well. Does this mean I need to do the heater core? Based on what I've read through searching it's looking that way. Also I noticed that the diesel has an air/oil separator... would replacing that help??? I haven't done a thorough check under the dash yet but did notice some oil when I brushed my hand under the passenger side. Any help or suggestions would be appreciated!

  2. #2
    Join Date
    Jul 2009
    Oakhurst Oklahoma


    sounds like you do a coolant leak under the dash,,,,,

  3. #3


    If it is sweet smelling, it is probably coolant. Oil doesn't smell anything like coolant. The brown color is probably because the coolant is dirty.

    I'm not familiar with the diesel, (you should verify that oil separator unit is not a cause) but I imagine that the heater core setup is probably the same and that sounds like it may be the primary suspect here.....
    99 XJ Sport, 4.0, A.T. NP242 "Daily Driver"
    Past Jeeps: 49 Willys, 81 Scrambler, 88 Cherokee

  4. #4


    Hmmmm. Yeah I guess the wording on my post was awkward. It smells sweet for sure so it must be coolant leaking, I was just curious about thoughts on the brown residue being left on the windshield. I did do a little reading and after getting confirmation I was suspecting the oil separator and heater core together. The coolant was NASTY when I checked it yesterday. I'll have to drain and flush that garbage out. Any other thoughts? Anyone know of a write-up on the heater core in the diesel model?

  5. #5


    OK so I have been working on this project for HOURS and am getting stuck at every step. Every bolt wants to strip or spin on me. I emptied the coolant system to find it FILLED with rust. The Jeep must have been sitting for a while somewhere. The original steel radiator was the culprit. I flushed the mother like 20 times before it ran clean. (This explains the brown/red deposit on the windshield when the moisture forms).

    Still trying to figure out the AC system discharge & heater core removal since all the retaining bolts on the firewall have spun? I have taken a couple of pics along the way and will TRY to get them up when I figure this thing out (so fewer others will have to suffer with this nonsense). Luckily I didn't sell my other rig so I can take my time with this one... man I love projects!

  6. #6
    Join Date
    Apr 1999
    Pacific Northwest


    I had one of the 85 2.1L turbo charged renaults at one time- it was a love hate relationship- get a factory service manual if you can find one-

    I remember mileage was pretty good- but parts like starters and alternators sucked.

    Heater core on the newer years isn't too bad- but I can't help you with this one.


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