Failed compression test

Discussion in 'How To' started by Dannyboy745, Jun 18, 2015.

  1. Dannyboy745

    Dannyboy745 New Member

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    Okay so my girlfriend bought a 2002 Jeep liberty from a dealership back in March. Last week it wouldn't start. After I replaced the spark plugs it started but was idling poorly. I decided to have it towed to a shop. They did a compression test and cylinder 2 has 0 compression. They pretty much told me I was probably going to need a new motor. I'm gonna have it towed back here so I can work on it myself. Is there any chance of saving it? I already have a $300 shop bill for the little bit of testing that they did.
     
  2. dude1116

    dude1116 Full Access Member

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    Dropped a valve seat probably?? :(
     
  3. Jbergun

    Jbergun Full Access Member

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    Isnt there some kind of lemon clause on that you bought this thing from a dealership less than 4months ago
     
  4. Dannyboy745

    Dannyboy745 New Member

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    Seal or seat? I know what the valve seal is. Do you have a diagram of what where exactly the valve seat sits?
     
  5. Dannyboy745

    Dannyboy745 New Member

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    She bought it as is with no warranty so I really don't know
     
  6. ftaa

    ftaa Full Access Member

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    dropped a valve it happens on them eventually ... just like the rad leak ... and the saggy front suspension .... you either need a new motor or get the whole top end done.
     
  7. CactusJacked

    CactusJacked Full Access Member

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    That was my first thought too. In layman's terms, the seat is a hardened ring pressed into the head that the valve sits down to. They have a tendency to work loose and "drop", which could wedge the valve open. A stuck open valve will give you zero compression. Even a terribly worn engine has some sort of compression, unless the cylinder wall is blown out. Ask them if they have a scope where they can go in through the spark plug hole for an exploratory. I think they're jumping the gun trying to tell you you need a whole new engine.
     
  8. ftaa

    ftaa Full Access Member

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    agreed on the whole new engine.. but at least while in there may as well do the whole top end ... if funds are an issue a new to him motor may be in order .
     
  9. Dannyboy745

    Dannyboy745 New Member

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    I got the jeep back from the shop. I'm going to pull the heads off myself and check out the damage. Trying to cut down on the cost of fixing it since we just got it. It the heads are bad I will the them machined. I got the time so I'm hoping I can do this myself. Any tips are greatly appreciated.
     
  10. ftaa

    ftaa Full Access Member

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    its not the heads its the sleve that the valves sit in ... heads will be fine. its the valve train you will need to replace. they have a habbit on some to come loose drop down and cause the valve to be stuck open giving no compression the other thing could be a lifter off under the rocker cover you will need a lash adjuster to fix that the plastic rockers can come loose. ..... thats the minor problem they normally fall off because of the dropped valve and thats the sleeve ..
     
    Last edited: Jun 18, 2015
  11. dude1116

    dude1116 Full Access Member

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    Yep should do no damage to the bottom end of the engine.
     
  12. Dannyboy745

    Dannyboy745 New Member

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    How the hell do you get those stupid plastic clips that hold the heater hoses off?
     
  13. TwoBobsKJ

    TwoBobsKJ Full Access Member

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    Don't bother with them. Instead take off the oil filler neck - there are 2 small bolts that hold it to the block. Remove them and the filler neck with the heater hose clips (and therefore heater hoses) can be moved out of the way.

    Bob
     
  14. Jbergun

    Jbergun Full Access Member

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    Yea after reading into it some states cover used cars under the lemon law for a month or two after purchase but not florida only cover new or new lease cars so yea no that wont work
     
  15. Dannyboy745

    Dannyboy745 New Member

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    So this job has turned to big a pain. Didn't know I was going to need special tools just to get the engine apart. Now I have to spend like $130 bucks on tools I will almost never use.:emotions34:
     
  16. profdlp

    profdlp Grouchy Old Cuss

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    Rent them or buy them and sell them off afterwards.
     
  17. M38 Bob

    M38 Bob Full Access Member

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    How many miles does this engine have on it? It's been a given since T model days that doing the head(s) will cause increased oil consumption. How much is usually in proportion to mileage/wear on the lower end.

    Someone mentioned a used engine transplant. Good luck with that! the 2002-03 3.7 is very model specific. ALL of em are 12+ years in service, and most are well over100K miles. When I had to re-engine mine a few weeks ago, these engines were going for 1,500.-1,800. bucks with a 30day warranty. New reman from O'Reilly with unlimited mileage, 2 year, labor inclusive warranty was $3k That didn't take long to ponder.

    As far as a back yard valve/head job? Not for the faint hearted, but well within most mechanically inclined, industrious individuals scope. IF you're sweating a couple plastic hose clamps,,,,,,,,,,,, might not work out too well.

    Bob
     
  18. TwoBobsKJ

    TwoBobsKJ Full Access Member

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    You can use a 3.7 from up to at least a 2012 Chrysler product. It requires some internal work to swap over the crankshaft ring and the cam sprocket but it saves a LOT of money. The reason original '02 and '03 Liberty engines are expensive is because most folks aren't willing to dive into the engine a little bit so they want a direct replacement. It's not a technically difficult project, just takes a little time and patience.

    From one Bob to another :cheers:
     
  19. cnull

    cnull New Member

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    So looking at a very similar issue.
    Just got back from a mechanic who told the wife that cylinder 2 had 5lbs compression. Same engine 2002 3.7 Jeep Liberty.

    Does the compression indicate the problem is with the valve seat or does it require more diagnosis?

    He quoted me $4800 to replace the engine. That seems very high to me. Also if you cant get a new engine then maybe not worth the effort?

    I just don't have the money to put out right now and wondering if I can be the next expert youtube trained mechanic or I could at least find someone who can do it for much much less.
    TKS,
    Chris
     
  20. tjkj2002

    tjkj2002 Full Access Member

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    Being a 2002 your screwed with pricing since they changed the cam/crank tone rings for later model years.Your going to pay twice the price for '02's then newer models.

    You can drop in a used newer engine but you will have to swap the older cam/crank tone rings in to work.

    There is a "how to" somewhere on this sit on what is needed and how to do it.Not saving much if any over paying for the correct remaned engine from the start.