Thread: Engine Issues

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    Default Engine Issues

    I am looking for some insite from any mechanics that maybe able to provide it.

    I have a 1981 Thibault cab over aerial. It has recently started to leak oil pretty severly from around the valve covers. It also appears to be blowing half burnt oil through the exhaust. Any where there is a joint you can see a wipe off black sticky oil where it has blown out through the seam. This concerns me enough that I have put the truck out of service. You can see the smoke from it burning off the exhaust as well as if the ground is wet you can see the oil on the ground where it is leaking.

    It has a Detroit Diesel series 92 engine in it.

    Any thoughts on what might be my issues would be greatly apperciated.

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    Typically, the saying for Detroit Diesels is: "If it ain't leaking, it ain't running." However sounds like you have a bit of a bigger problem than typical DD leaks. There could be a whole myriad of problems here, ranging from bad valve cover gaskets to bad piston rings.

    When I worked in a major truck shop and a unit came in presenting these symptoms (which was rare as we were very Preventive Maintenance-Intense) the first thing we would do is give the engine a serious steam cleaning. Top to bottom. Clean that puppy until she shines. Then we would stick it under a loaded trailer and run it up and down the main drag a few times or out on I295, then bring her back to the barn, and see if it was one leak (which I suspect is the case here) causing the whole thing to get dirty and nasty, or if it truly was several leaks.

    Do you have any trucking companies locally with their own maintenance shop that would steam it for you, or allow you to use their steamer? That's where I would start. You need to get a better grip on where it is coming from.
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    I can clean it here in house actually I have the gear to do that. And I am quite familar with teh old saying....and quite used to it out of all the trucks that sit in my bay tehy are all DD's. LOL

    This one concerns me though she has always leaked a bit but never anythign this serious. Valve cover seals I'm not as concerned with as what might be wrong internaly. My first thought was piston rings due to the burnt oil coming out through the exhaust.

    My Other fear is cost. We are none profit here and a large engine job is going to cost. Other than the truck being old it is in great shape and I would hate to see it sacrificed over something that may or may not be serious.

    I want to try and get some input before I call in a mechainc to look at her.

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    Possible turbo issues?

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    The 71 series leaked when they wern't running. lol The 92's were better, and the last few years of the 92's were a lot better.

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    Quote Originally Posted by donethat View Post
    The 71 series leaked when they wern't running. lol The 92's were better, and the last few years of the 92's were a lot better.
    You dont understand the saying....."If it ain't leaking, it ain't running" as in the blown engine kind of "ain't running."
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    Quote Originally Posted by MColley View Post
    I want to try and get some input before I call in a mechainc to look at her.
    You have the gear to steam clean her in-house.....I would do that first. There are just so many variables as to what the problem could be, you need a starting point to center on and go from there. Steam her and run her hard for an hour and see what happens......
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    Quote Originally Posted by FWDbuff View Post
    You have the gear to steam clean her in-house.....I would do that first. There are just so many variables as to what the problem could be, you need a starting point to center on and go from there. Steam her and run her hard for an hour and see what happens......
    After you steam clean it get a vial of fluorescent leak check dye and put it in the oil. Then while it's running you'll be able to determine whether it's internal or external.

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    I'd be checking blower seals or possible broken rings. See if it's pushing up the dipstick tube. Sounds like some pressure going where it doesn't belong. On a Tibo,this ain't gonna be a fun job. T.c.

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    I agree with TC, too much crankcase pressure could the be the culprit, but I'd start by looking for a stuck CCV valve. A stuck CCV would cause the excessive pressure, especially on an older engine like this that's got a bunch of blow-by, and its the cheapest item to fix. TC you've probably got a lot more DD experience than I do, any guidance on checking for this (if it even exists on this old of an engine)?
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    Quote Originally Posted by Rescue101 View Post
    I'd be checking blower seals or possible broken rings. See if it's pushing up the dipstick tube. Sounds like some pressure going where it doesn't belong. On a Tibo,this ain't gonna be a fun job. T.c.
    I don't seem to be getting oil pushing back up the dip stick rod. Thats probably the only part of the motor that doesn't have oil all over it actually....suprisingly LOL.

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    Question Clean

    Well I cleaned her off this morning and took her for a good run and ran the motor hard for a bit and here is what I have come up with.

    First of all it burned dirty for the first 25 minutes or so. Dark blue smoke. Then it cleared up and hasn't even puffed a bit of smoke since. And the motor still seems clean.

    So here is my thoughts on what may be going on. The truck is used at a school facility where it's farthest drive is a 2 minute walk. It rarely sees any kind of rpm's due to the fact the onsite hydrant system provides an unlimted source of water and pressure. (typicaly 80PSI) So the pump is usually just a "manifold" for differnt lines. Aside from using the stick once in a blue moon it probably never goes past a 1000rpm. I'm wondering if this lack of rpm's could cause a build up of unused oil causeing the truck to run rich (so to speak) and throw the half burnt/used oil out through the exhaust.

    Any thoughts on that secnario????

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    Quote Originally Posted by MColley View Post
    Well I cleaned her off this morning and took her for a good run and ran the motor hard for a bit and here is what I have come up with.

    First of all it burned dirty for the first 25 minutes or so. Dark blue smoke. Then it cleared up and hasn't even puffed a bit of smoke since. And the motor still seems clean.

    So here is my thoughts on what may be going on. The truck is used at a school facility where it's farthest drive is a 2 minute walk. It rarely sees any kind of rpm's due to the fact the onsite hydrant system provides an unlimted source of water and pressure. (typicaly 80PSI) So the pump is usually just a "manifold" for differnt lines. Aside from using the stick once in a blue moon it probably never goes past a 1000rpm. I'm wondering if this lack of rpm's could cause a build up of unused oil causeing the truck to run rich (so to speak) and throw the half burnt/used oil out through the exhaust.

    Any thoughts on that secnario????
    Absolutely. I think you have it right there. Get it out periodically and run it hard. Drive comfortably - both feet flat on the floor!

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    Agreed that lack of use can cause all sorts of issues.

    Now let it sit overnight or longer, roll it outside and gently (2-5 seconds) bring it up to upper range RPMs. White smoke and you've got tired injectors, no big deal on an engine this old. Blue smoke however can be either valve stem seals or scavenger seals...

    Scavenger seals are a concern, on older DD's they eventually leak bad enough that enough engine oil gets into the pistons that the engine will actually run on it. Most older Detroits had an "emergency shut off" somewhere in the cab which would close a butterfly in the intake to starve the engine of air, if you have one make sure its working and that all your operators know how to use it.

    Watch the oil level, keep an accurate log of how many hours between needing an extra gallon of oil, watch for a steady increase in oil consumption. If the engine does not seem to want to stop (you have to hold the shut down for more than a couple of seconds) keep a close eye on it.

    Good luck!
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    Default Thanks

    Thanks for all the info from everyone. It's been really helpfull in starting points and what to look for

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    I ran the engine up nice and slow and let her run high for a bit then brought her down nice and slow. Tried that a couple of times and she's not smoking at all. So I'm thinking the lack of any real rpm's and a build up were my problems. I'll keep an eye on it for now and see if she is using any oil.

    Thanks again for all the input

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