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New 4Runner, bad exhaust Valve, what to do

Discussion in '3rd Gen 4Runners (1996-2002)' started by 504Runner, Jan 31, 2021.

  1. Jan 31, 2021 at 12:58 PM
    #1
    504Runner

    504Runner [OP] New Member

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    Hi I just bought my first 4Runner. A 1999 white 3rz standard. Got it for really cheap because of engine problems. Did a compression test and 1 cylinder is at 75 psi, the rest are around 175 psi. I did a leak down test and it's flying out the exhaust pipe. My question is should i just replace the one shot valve or rebuild the whole head. If I do, what do i need replace and what doesn't. Not sitting on bags of moneys but if i need to I'll pull out of saving to do the work i will. Thanks for the help?
     
  2. Jan 31, 2021 at 2:54 PM
    #2
    Ahdofu

    Ahdofu New Member

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    Well you're going to pull the head anyway to replace that bad valve. Once you've done so, you can check the condition of the rest to make the go no-go decision. Had this been my vehicle, I'd opt for a complete rebuilt head assuming of course that the rest of the vehicle is OK
     
    Moon Landing and Toy4X4 like this.
  3. Jan 31, 2021 at 2:57 PM
    #3
    504Runner

    504Runner [OP] New Member

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    While I have the head out, is there anything else I should be replacing besides the valves? The rest of the car is tip top.
     
  4. Jan 31, 2021 at 3:12 PM
    #4
    Toy4X4

    Toy4X4 New Member

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    If it were mine I would do a complete valve job, perhaps the good valves just need a touching up.
     
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  5. Jan 31, 2021 at 3:17 PM
    #5
    504Runner

    504Runner [OP] New Member

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    Sounds like a plan! I'll replace what I need to and clean up what i can. Any other recommendations while I have the head out? Thanks for the input!
     
  6. Jan 31, 2021 at 3:21 PM
    #6
    Toy4X4

    Toy4X4 New Member

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    I'm not up on the 3rz, but have done a bunch of valve jobs, I'm not to much help on this engine. Sorry. Some one here knows.
     
  7. Jan 31, 2021 at 3:35 PM
    #7
    Ahdofu

    Ahdofu New Member

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    Of course replacing the valves is not sufficient. You'll need to to re-seat them. And if I am replacing the valves, I'll be replacing the guides as well the cam followers. Given this I'm more inclined to buy a rebuilt head from a reputable place just because I don't trust myself in rebuilding a head.
     
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  8. Jan 31, 2021 at 4:43 PM
    #8
    504Runner

    504Runner [OP] New Member

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    Thanks Matt!
     
  9. Feb 5, 2021 at 11:21 PM
    #9
    504Runner

    504Runner [OP] New Member

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    Here's that bad valve..

    My intake manifold is very wet and dirty. Does anyone know the cause?

    20210206_011350.jpg
    20210206_011919.jpg
     
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  10. Feb 6, 2021 at 1:12 AM
    #10
    Ahdofu

    Ahdofu New Member

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    Thanks for posting this picture. Since you have a cracked intake valve, you were either not getting any combustion or perhaps a incomplete one in that cylinder. Every time the cylinder came up, I surmise it forced some of the fuel/air/exhaust mixture back into the intake. My curiosity is more on the valve. Why would the intake valve crack? Worn valve guide? We also do not know about the rest of the head so this is where a shop can test it out for you.
     
    Last edited: Feb 6, 2021
  11. Feb 6, 2021 at 4:30 AM
    #11
    504Runner

    504Runner [OP] New Member

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    The cracked one is the exhaust valve. I know there is a crack in the exhaust manifold. Not sure if that can cause a valve to go bad. I have no experience in that issue.

    The rest of the valves look good, just a little dirty. I cleaned them up a bit. Need a special tool to take the valves out and lap. Need to find our rent the adaptor.

    20210206_012812.jpg
    20210206_042854.jpg
     
  12. Feb 6, 2021 at 6:26 AM
    #12
    Ahdofu

    Ahdofu New Member

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    My mistake. Should have noted it is exhaust by its color and smaller size. Now I am on the same page as you were. Why would intake be so affected? Perhaps there is another damage that we're seeing and that is where a shop can help. Nice cleaning job by the way.

    An after thought. During the intake cycle as the cylinder moves down, it creates suction which then brings in fresh air/fuel through the intake valve. Given the crack in the exhaust valve the suction capability would be impacted and perhaps only a fraction of the mixture made it in and the rest remained in the intake
     
    Last edited: Feb 6, 2021
  13. Feb 6, 2021 at 1:31 PM
    #13
    504Runner

    504Runner [OP] New Member

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    I was don't some research and a lot of 4Runner owners talk about installing an oil catch can. Is that something I need to do in the future? Maybe that's why the intake is so wet.:notsure:
     
  14. Feb 7, 2021 at 2:36 AM
    #14
    Toy4X4

    Toy4X4 New Member

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    Maybe your EGR valve is bad, that may or may not be another reason for the 'wet' in the intake. That exhaust valve just didn't decide to go bad, I would suspect getting 'rode hard and put away wet' was the start of the problem. If you were stuck or in a situation where the vehicle temp was on the verge of overheating or the like, then shut off the engine without a cool down period that could have cracked that valve and started this process of 'burning the valve, you mentioned cracked exhaust manifold, same process except cool air seeps in upon shut off and cracks the valve. One other thing that could have burned that valve would be improper valve lash, then over a period of time it cracked. So it doesn't really matter "what came first ? the burn or the crack." Just giving you some 'suggestions' on why this may have happened. How's it going fixing it? P.S.- don't forget to check valve guides, if they are sloppy, get "em changed!
     
    504Runner[QUOTED][OP] likes this.
  15. Feb 7, 2021 at 8:38 AM
    #15
    Ahdofu

    Ahdofu New Member

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    Should not hurt having one. However if there is a underlying issue with the engine, you want to fix that as opposed to treating the symptoms with an oil catch can.
     
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  16. Feb 7, 2021 at 2:44 PM
    #16
    Moon Landing

    Moon Landing AFFTC 1967/68 Eddies Air Patch

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    "My intake manifold is very wet and dirty. Does anyone know the cause?"

    The crack in the exhaust manifold would cause rapid cool down and was most likely the culprit of the cracked valve. imo

    The cracked exhaust valve is not allowing complete cylinder combustion. Hence the build up in the head and perhaps, back stream too(intake).

    You should have the head die tested for cracks and checked to see if it needs to be resurfaced(milled). Over the long haul damage like this can have numerous reasons. One is, shutting the engine down when it's in the high range of it's heat cycle(or a cracked header). The pro's say it's best to let an engine idle for a minute or so before turning it off. Like we have time for that. :)
     
    Last edited: Feb 7, 2021
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  17. Feb 7, 2021 at 2:50 PM
    #17
    SR5 Limited

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    Answer is simple= cracked exhaust manifold created a lean condition on that cylinder and burnt the valve...,
    Sounds funny but exhaust gases actually cool the combustion chamber.
     
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  18. Feb 8, 2021 at 10:26 AM
    #18
    504Runner

    504Runner [OP] New Member

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    Thanks for all the advice! I'm in the process of removing the valves to replace or lap. But the spring compressor I have wont work with the bucket shims. So I bought one off Amazon that says it works for my car but it doesn't. Dose anyone know how to go about this? Did I miss a step or is it just the wrong tool?

    20210206_003152_HDR.jpg
     
  19. Feb 8, 2021 at 1:29 PM
    #19
    504Runner

    504Runner [OP] New Member

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    Excuse my ignorance... They just pull out. Sorry.. I'll update when on the next step.
     
  20. Feb 8, 2021 at 2:49 PM
    #20
    504Runner

    504Runner [OP] New Member

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    I rigged my old spring compressor to fit the attachment from this cheap Amazon compressor (it sucks). Also put duck tape around it so i don't damage the aluminum. So far it's working perfectly.
    20210208_163827_HDR.jpg
    20210208_163839_HDR.jpg
    20210208_163853.jpg
    Besides the crack in the valve everything looks good. I am a noob at this so any tips and advise is appreciate. Thanks 4Runner gang, back to work!
     
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  21. Feb 8, 2021 at 2:51 PM
    #21
    SR5 Limited

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    Titanium replacements would be nice...
     
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  22. Feb 9, 2021 at 4:23 AM
    #22
    Toy4X4

    Toy4X4 New Member

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    They are available. Probably about $1,000 - $1200 for the set, then there's the lead time on making them.
     
  23. Feb 9, 2021 at 7:47 AM
    #23
    alittleoff

    alittleoff New Member

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    Kinda off topic but, my Wife was walking behind me and noticed that you’re using a fabric cutting mat. And she said that for your sake and well being that you are using an old one.
    Is your partner a quilter?
     
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  24. Feb 9, 2021 at 10:26 AM
    #24
    504Runner

    504Runner [OP] New Member

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    I bought that from a auction. I thought it was just a regular cutting mat lol thanks for letting me know!
     
  25. Feb 9, 2021 at 10:27 AM
    #25
    504Runner

    504Runner [OP] New Member

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    That's too rich for my blood, thanks though!
     
  26. Feb 9, 2021 at 11:33 AM
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    treyus30

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    Why would that lean out 1 chamber? Doesn't make sense at all
     
  27. Feb 9, 2021 at 11:41 AM
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    negusm

    negusm New Member

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    So logically thinking out loud...

    A cracked exhaust manifold would allow gas to escape before the downstream sensors?

    Which would cause the ECU to compensate?

    Which would cause richening of the fuel mix?

    Discuss?
     
  28. Feb 9, 2021 at 11:42 AM
    #28
    504Runner

    504Runner [OP] New Member

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    I was thinking that as well. The crack was right in the middle of the manifold. You would think cylinders 2 and 3 would be most affected from the "cooling".
     
  29. Feb 9, 2021 at 11:43 AM
    #29
    504Runner

    504Runner [OP] New Member

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    Would that explain the wetness in the intake manifold as well?
     
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  30. Feb 9, 2021 at 12:55 PM
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    SR5 Limited

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    You would think that naturally I know. It’s OK. Actually any escaping exhaust creates a lean condition...
     

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