preemptive head gasket replacement?

Discussion in 'KJ General Discussion' started by Aloicious, Apr 12, 2019.

  1. Aloicious

    Aloicious New Member

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    *Long post warning*

    So I've got a '05 KJ, 3.7L, 6 speed manual, 4wd, 265k miles, pretty well maintained for the most part, wife's Daily Driver. pretty much stock except for a aftermarket headunit.

    Prepping it for a 3000+ mile round trip that the family will be taking in it in about a month an a half, and doing some preventative maintenance and chasing a few small leaks that I've been monitoring through the winter.

    So I've got a symptom of a rough idle (never cleaned the TB, IAC, or intake manifold so hoping that is the issue here) and a very slight vibration at 2.5K+ rpm which is only dependent on engine rpm, not related to trans or drivetrain (this might be considered "normal", this is my wife's vehicle so I am not in it super frequently). There is also a good amount of white vapor out the exhaust on startup which tends to go away once warmed (no loss of coolant that I can tell, coolant appears clean, oil is clean, plugs look consistent between cylinders and normal color, none wet or fouled upon inspection, never overheated since I got it at 80k miles about 10 years ago) I have only noticed the vapor during this winter, so I am *hoping* it's only vapor related to the goofy weather (still below freezing up in the mornings here in the Wisconsin northwoods,) and not a head gasket considering everything else seems OK.

    only 1 code gets pulled P0155 from a known pinched wire on the harness, will be replacing the harness connector with a new pigtail.

    I am currently prepping to pull the intake manifold to do a good cleaning of it and the TB, and going to do intake gaskets, replace the IAC, plugs, and a few other things while I'm in there trying to clear up the rough idle issue and just prep it all for the trip and beyond. While I'm getting the intake off, now would be the time for me to do head gaskets as well, but I'm not 100% sure it *needs* them. I still need to do a compression test also, which I'm planning on doing.

    I definitely do not want to do head gaskets but I'm on the fence as to rolling the dice and hoping the vapor is weather related only, or sucking it up and just doing the head gaskets to be on the safe side. Anyone have thoughts on that?

    What it comes down to is we also need to keep this vehicle for a good long while as finances won't allow a new vehicle purchase for a number of years, so this may seem excessive work for 1 trip, but really it is also for the long haul down the road. I will rebuild the engine when/if I need to, but want to delay that until its actually needed.

    Some recent history (beyond regular fluid/filter changes which have been regularly done):

    2 yrs ago:
    -Water pump replaced
    -PS pump replaced
    -New fuel pump
    -Fuel 'burp' issue fix modification documented on this site (worked great!)

    1 yr ago:
    -new clutch/PP set
    -New U joints
    -New slave/master assembly
    -O2 sensors
    -New battery and ground cable
    -PCV
    -Brakes pads/shoes, rebuilt rear E-brakes

    within 3 months:
    -new motor/trans mounts
    -new oil pan gasket (inspected bottom end while it was off, looks very good from what could be seen, no issues noted)
    -New valve cover gaskets (inspected top end/valvetrain while they were off, again looks good, not issues noted)
    -New Cam & Crank sensors (both leaking a little, just replaced 'em altogether)
    -New radiator (had a small end tank leak, no overheating, kept coolant levels up)
    -New Harmonic balancer (probably not needed, but was trying to chase that slight vibration, new balancer made no difference)
    -new front main seal (while balancer was off, went ahead and did this too)
    -new injectors (old ones were really dirty, just put new ones in while the old ones are sent off to be cleaned and tested)
    -new coils (I accidentally broke one while doing plugs, so I figured 250K+ miles on original ones, might as well do 'em all)
    -new thermostat and upper/lower rad hoses
    -Front strut assemblies
    -rear shocks


    Prepping to do before trip:
    -Intake manifold gaskets
    -deep clean the intake manifold while off, and the TB
    -Plugs
    -IAC valve
    -Update PCV system to the '07+ style (already have all the factory parts from the TSB)
    -O2 sensor harness repair as noted above

    Sorry for the long post, but any thoughts are appreciated
     
    Last edited: Apr 12, 2019
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  2. renegade 04

    renegade 04 Full Access Member

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    I would do a compression check and see if you are starting to lose compression, but it sounds like you will need to do head gaskets soon due to the white smoke.
     
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  3. HoosierJeeper

    HoosierJeeper Gold Supporter/Admin Staff Member Administrator

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    If the coolant level is staying good, I wouldn't say you need to do it. Is it steam or white smoke coming out?
     
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  4. Aceofspades

    Aceofspades Full Access Member

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    What does the underside of the oil cap look like?
    Let it sit a long time and use / rent a cylinder borscrope and take a peak see if coolant builds up over night.
     
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  5. artfull dodger

    artfull dodger New Member

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    A cooling system pressure test can also give an indication of any leaks in the cooling system, while not specific to a headgasket issue, it can tell you if you need to look at it further. Some white smoke on start up on these cool and damp mornings is normal, even brand new cars do this if are watching them right after start up and the first few min of driving as the catalitic converter and exhaust system warms up. The exhuast needs to clear the condensation out of it that is the by product of the Cat. Just watch how much water comes out of the exhaust when following people. With not coolant loss, clean coolant, if the compression test comes back decent, I would be inclined to leave it alone for now.
     
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  6. Aloicious

    Aloicious New Member

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    Thanks all, its definite steam on cold startup (nothing from warm startup).

    Underside of the oil cap looks normal, ive never had the nasty condensation build up under the cap.

    I did just notice yesterday that there is a very slight puff of blue smoke when revving in neutral while warm which is not noticable from inside the cab. So im thinking valve seals may need replacing as long as compression test comes back normal.

    I haven't noticed coolant or oil loss since the recent radiator leak and various gasket leaks were repaired, but that has only been completed within the past 2-3 months, so it definitely could have a very slow leak internally somewhere, nothing is leaking externally.
     
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  7. Charlesthe2nd

    Charlesthe2nd Full Access Member

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    Seems to me with all the work you've done on it that you now have a new Jeep! Long trip with an old vehicle just means you'll need to be monitoring everything a bit more.

    White smoke is normal. I had a similar heart drop moment when I the Jeep getting started from inside the house. White smoke for the first couple minutes after it started, as well as black soot on the pavement after idling. Freaked me out, but that was 20k miles ago.
     
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  8. HoosierJeeper

    HoosierJeeper Gold Supporter/Admin Staff Member Administrator

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    That's normal....all of my rigs do that.
     
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  9. Aloicious

    Aloicious New Member

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    For sure, I expect it to run another ~300k with all this work on it haha.

    I'm not too worried about the trip, but I come from a SBC/LS engine background, so just looking for quirks on the 3.7L I need to be aware of. If i end up not doing the head gaskets I might do valve seals with the heads on to try and address the slight blue smoke I've noted above. I'm too OCD...

    I've read a bunch about valve seats dropping/valve springs breaking on the 3.7, but I suspect if I haven't had that happen by this point, it's either a non-issue with my specific engine, or the instances reported might be mostly due to neglect or abuse?

    I'm going to try and do the compression test tonight or tomorrow and I'll post up the numbers I get
     
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  10. HoosierJeeper

    HoosierJeeper Gold Supporter/Admin Staff Member Administrator

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    x2, I think if it's made it 265k it's a good one and healthy. It seems like the valve issues were on 02s and on neglected ones, usually rears its head between 100-150k miles it seems like.
     
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  11. ltd02

    ltd02 Active Member KJ Supporting Member

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    Yeah, valve seat dropping was an early issue. Allegedly solved although I still wouldn't want to ever overheat one of these. That's good to hear that an 05 is running so well with high mileage. I hope to put another 200k on mine!
     
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  12. Aloicious

    Aloicious New Member

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    Thanks everyone for the assistance.

    Yeah she's been a good little 3.7 so far, but probably 75%+ of her miles are highway, so that probably helps account for some of the longevity.

    Im doing the compression test today after work and going to do a cooling system pressure test and block test for CO gasses in the coolant just to verify before i commit to doing the head gaskets or not. Ill post results tonight.
     
  13. Aloicious

    Aloicious New Member

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    Tests were promising.

    Coolant system pressure test was done cold and at operating temp. Cold it held pressure without any drop for over 10 mins, at temp it held pressure fairly well but did drop about 1 psi slowly over 10 mins, possibly just due to the engine cooling down? Not sure what rate of pressure drop is "normal".

    CO gas block test was negative for CO gas in the coolant.

    Compression test was done dry and results were:
    1 - 150
    2 - 155
    3 - 150
    4 - 150
    5 - 160
    6 - 160

    Compression test done wet with 6ml clean oil in each cylinder, results were:
    1 - 160
    2 - 170
    3 - 160
    4 - 175
    5 - 180
    6 - 180

    So those are all promising, especially given the high mileage. I think at this point I'm comfortable that there aren't any head gasket leaks and leaving those alone. The slight occasional puff of blue smoke is most likely from valve seals so ill probably do those while im pulling the intake.
     
  14. HoosierJeeper

    HoosierJeeper Gold Supporter/Admin Staff Member Administrator

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    Does it burn or leak oil?
     
  15. Aloicious

    Aloicious New Member

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    no external leaks that I can find since doing the various gaskets (oil pan, front main, valve covers, pressure sensor)

    Just currently getting a slight puff of blue smoke out the tailpipe while revving at idle at temp. Judging from the dipstick, oil loss is very minimal, it's dropped from roughly 3/4 up the hatched area on the dipstick immediately after oil change, and it's just over 1/2 of the way up the hatched area (over the course of 700-1000 miles, about 2 months of time) running 5w-30 conventional. oil loss seems in the 'normal' range, but judging from the little bit of smoke, it might be burning some.

    previous to the gasket changes I was running 10w40 and had to add 1-1.5 quarts per month to keep the level adequate during the winter. so there has been a large improvement in that area.

    I may do the intake and PCV TSB update before working on the valve seals and see if it improves the smoke at all (the current PCV is fairly new, about 1 yr, but I hate the original design and I want to get rid of the excessive breather/PCV hoses running over the engine compartment, both of which have been broken in the past and cobbled back together)