94 mtx top engine knock? With video link

Discussion in 'Gen 1 & 2 - Emergency Issues - Help & Maintenance' started by Cole maclachlan, Apr 19, 2019.

  1. Cole maclachlan

    Cole maclachlan New Member

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    I think this can be possible. I am going to put it all back together and do some running tests.
    Once I’ve done that I will disassemble again and dig deeper.
    Thank you
     
  2. zoomlater

    zoomlater SHO Member Supporting Member

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    I will say for an engine with 300K miles, the cams and inside surfaces looks pretty clean. The previous owner must have done regular oil changes.
     
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  3. Dirty Harry

    Dirty Harry New Member

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    I wouldn't think a cracked piston, as suggested earlier, would cause exhaust to blow back out of the throttle body. Although this is not the cause of the knock, it should be addressed. Do a compression and leakdown test. Could be cracked or worn valves.

    As a side note. Yes it's a clean engine. I can recall as a kid in the sixties (1960's for the young crowd) pulling a valve cover off an engine that still used non-detergent oil. You had to scrape off an inch of mud & gunk to even see the top of the head. Thank God for additives.
     
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  4. Cole maclachlan

    Cole maclachlan New Member

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    Yes it has been well kept for sure.
     
  5. Cole maclachlan

    Cole maclachlan New Member

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    4738CEC0-E92A-4D98-9222-5FA0B96FDBA8.jpeg D73BAD12-0613-41CD-A063-825BFA4545BC.jpeg 4738CEC0-E92A-4D98-9222-5FA0B96FDBA8.jpeg Ok so I have found the culprit
    Cylinder 6 crank bearing/ Babbitt bearing?

    It was super loose I could move it with my fingers

    The main nuts are off in this but it would do this before I took them off.


    Now I am in search of new bearings which I haven’t looked to hard for yet as I have been super busy with work.

    I don’t think my local parts store can get them but I will check soon.
    I will also new dfront and rear main seals.

    There weren’t too many shavings in the oil pan but the oil stank pretty bad

    So here’s a question
    The oil pan drain plug I couldn’t get off because the exhaust pipe cerise’s over and was right in the way.
    Does the y pipe “upgrade” cross in front of the opdp? There is a rod shifter and the pipes go around it to accommodate. I just want to know if the y pipe is the reason why it crosses in front of the opdp.

    Asides from that next step is
    bearing (single) or all 6 replaced
    Torqued
    Gasket set/seals
    Clean all the parts thoroughly
    Back together
    Pan
    Exhaust
    Starter
    New oil
    Filter

    Then give her a run

    Once that’s done and out of the way I will return to the top end and re do everything

    Valve cover gaskets
    Intake manifold gaskets
    New plugs

    Etc...

    Also want to thank everyone for their input
    It has helped tremendously in the search for what was wrong.

    Much appreciated
     

    Attached Files:

  6. blk\blk90

    blk\blk90 SHO Member Supporting Member

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  7. zoomlater

    zoomlater SHO Member Supporting Member

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    Replace all the rod bearings.
    Do you have an equal length Y-pipe (take a look at the picture on the Shosource website). That can get close to the oil drain plug and make it difficult to remove.
     
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  8. luigisho

    luigisho SHO Member

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    If it's open replace them all. As mentioned above I would look a the rod and crankshaft mating surfaces. If they are mucked up the chances of replacement bearing failure in short mileage in that spot goes waaay up. If you can see and feel damage on the crankshaft journals or connecting rod bearing mating surfaces then you should replace those items or swap in a replacement motor

    Don't chase your butt on this. You are talking about alot of maintenance work on an engine that may need to go. Assess that first.
     
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  9. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    unfortunately, replacing bearings does not solve that problem - since the bearing spun, it wallowed out the rod end and likely messed up the crank journal too. I would be looking for a new short block.
     
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  10. NoSlo

    NoSlo GoldMember

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    Updates?

    For bearings, rockauto.com - Clevite CB1435P x 6, with forum discount code.

    Looks like they spun, from the radial wear on the connecting rod. There's not much edge keeping bearings on the correct side any more...

    See that replacements bearings are flush with connecting rod cap top and bottom. If they don't line up perfectly flush with the finished mating surfaces and a machinist level or glass, that's a surefire sign that the connecting rod bore has been worn and dished from spinning.

    An industrious person would get at least a replacement connecting rod cap. A shadetree mechanic might score or mar the old cap's surfaces across the spinning marks; scratches might keep the bottom bearing in place and distribute the scoring. Even lap fractions off the cap mating surfaces until plastigauge crankshaft clearance can be brought near max allowable.

    Really up to you if you want a new connecting rod, (+ piston or pin with tool, rings and lip bore, ring compressor, etc) and head gasket now or later.

    Clean up crank with a band of 600 grit paper. Assemble; connecting rod cap is first 26, then 36 ft-lb. Plastigauge with new bearings. Cross fingers. Use assembly pre-lube on the crankshaft.

    (This thread is remarkable for such casual-ness opening up the top, front, and bottom, usually even exhaust studs are an annoyance.)

    Connecting rod crankshaft journal - 51.976-52.000mm
    Connecting rod bearing bore diameter - 55.000-55.016mm

    Connecting rod bearing - clearance to crankshaft:
    Desired: 0.024-0.056mm; Allowable: 0.08mm
    (bearing wall thickness 1.484-1.496mm)
     
    Last edited: May 25, 2019
  11. Cole maclachlan

    Cole maclachlan New Member

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    2222FE5A-749A-480E-88EE-9992D0FCF5DC.jpeg
    Thank you NoSlo
    This I really appreciated
    Updates coming soon guys
    Sry have been slammed super busy working
     
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  12. zak

    zak SHO Member

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    rod bearings. Has it been like that for a while? If not new bearings might save it. Depends on what the crank looks like.
     
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  13. Cole maclachlan

    Cole maclachlan New Member

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    Alrighty guys

    Sorry for the late update but have been working like a dog

    I have cleaned out everything on the bottom end pretty good for inspection.
    Nothing seems to be out of order in terms of cracks and excessive wear or damage. A092EDE4-9528-40FD-BD35-8D53912848F3.jpeg

    I cleaned and inspected all the pan bolts and inner pan bolts as well as the oil pick up and the mains stabilizer pan and wrack with bolts. 89B90212-0CF4-4A00-9333-35E3DF8055DA.jpeg A28DA3B5-238A-4609-986D-67B60AE8F9C2.jpeg D4404E25-6D1E-45FD-866C-6D8B8F776D94.jpeg 66B99D5D-714B-454F-A363-EAB762C64124.jpeg
    Also cleaned and inspected the removed bearings (haven’t removed all of them yet) connecting rod caps and the starter. I don’t have a picture but I have found that the starter power connection post is stripped. Right into the base of the starter.
    3015E672-06A2-42F4-A77E-123B89C1580A.jpeg
    Thanks for the tip NoSlo Totally didn’t use the promo code as I’m new and didn’t know where to find it lol

    18CDEAF1-0A68-40BA-BC3A-71DDCD8E1142.jpeg
    Don’t pay no attention to the oil as I’m only going to use this cheap stuff to give the engine a thorough clean with some cleaner and then dump it for some good stuff.

    I haven’t pulled the trigger on putting everything back together as I am still waiting for a couple gaskets ( oil pickup/ front and rear oil pan rubber gaskets) plastigauge pre-lube and some 600+ sandpaper for the journals.
    Oh and an oil filter can’t forget that

    Once I have everything I need I will be preforming most of what @NoSlo has posted
    (Thanks a bunch )
    I have never used plastigauge but I will do some research before hand. Any tips will help.

    I will be attempting to do all of this from underneath the car (bottom end) while the crank and pistons are still in the engine.
    From my guestimations it is doable.

    My shifts at work have turned into nights which makes me a zombie ‍♂️ and it is hard to set the body back to days which puts me all over the schedule map.

    It will be done sooner than later.

    Thanks again for everything.
    much appreciated
     
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  14. Irish Pride

    Irish Pride Irish Inside Staff Member Super Moderators

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    Can you feel any damage on that rod journal? If so, you are going thru all this for nothing. If the journal is messed up the crank is toast. Run your thumb nail across it. If you feel ridges, it's done.
     
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  15. NoSlo

    NoSlo GoldMember

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    Not toast, the crank journal(s) would just need to be turned for .25mm undersized bearings. You can verify you got undersize bearings, because they will have black paint on the side instead of orange. Still available here: https://www.amazon.com/Clevite-CB-1435P-25MM-Engine-Connecting-Bearing/dp/B000C06ENA

    Toast from a financial standpoint, maybe.

    If the plastigauge on the inside of the bearing of both top and bottom squish to within clearance, even closely examining for low width areas from scoring, chances are good it shall run fine, (or spins again, no loss). Check bearing wear pattern & replace bearing 10K later after it has broken in the crank.

    Maximum allowable 0.0031 on SHO - plastigauge squished to at least the .003 width:
    [​IMG]
     
    Last edited: Jun 5, 2019
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  16. Cole maclachlan

    Cole maclachlan New Member

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    Thank you @Irish Pride i will keep attention to each journal.
     
  17. Cole maclachlan

    Cole maclachlan New Member

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    This is great
    I have gotten these exact bearings.
    I will have to pick up some plastigauge for sure
    Thank you @NoSlo
     
  18. NoSlo

    NoSlo GoldMember

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    --- Luckily, you didn't, you got the correct ones from RockAuto. The last link, in my reply just to Irish Pride, is for undersized bearings - the -.25mm in the part number. They would destroy your crankshaft.

    If the crankshaft has been quite damaged, as revealed by the plastigage showing too big a gap, then the only option is to have it turned in a machine shop. Only then would you use the undersized bearings

    If the plastigauge shows the gap is too big, it is up to you if you still want to re-assemble anyway and drive until it goes sho-boom.
     
    Last edited: Jun 6, 2019
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  19. NoSlo

    NoSlo GoldMember

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    This can be fixed by replacing just the starter solenoid, which is available at Advance Auto with at least a 20% discount code anytime ("PS20" is the discount code they give when their website doesn't work), when you order for store pickup, for under $15.

    Here's a thread where I describe how to work on the starter: https://shoforum.com/index.php?threads/howto-starter-motor-rebuild-and-replace-brushes.134666/
     

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