Buying a 6.9l
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Thread: Buying a 6.9l

  1. #1
    Join Date
    Jan 2016
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    Buying a 6.9l

    About to buy an $800 f250 with a 6.9l non turbo and a manual. Needs clutch and brakes. Anything under the hood to look for that would be a deal breaker?

    First diesel so not %100 on what to look for.

  2. #2
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    Re: Buying a 6.9l

    Those are mechanically injected. They are slugs, but generally a reliable engine. Aftermarket turbo kits make them drivable though.

    I drove a bunch of ambulances with that engine. Top speed of about 65 mph. The lights and siren didn't make them go any faster...
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  3. #3
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    Re: Buying a 6.9l

    Other than the obvious fuel, oil and water leaks that any engine might have you should verify when the injector pump was changed/rebuilt.
    They are almost like clockwork needing to be repaired at 100,000 mile intervals. They are easy to change and most
    diesel injection shops will rebuild them for about $400.
    The other regular issue that some people had(but I never did) is the glow plug timer/relay. Easy to change and relatively cheap.
    If when you turn the key to the run position the "wait" light stays on for about 10 seconds it is working properly.
    The 6.9/7.3 non power stroke series are dead reliable.
    Regular maintenance should get them to 500,000 miles easy.

  4. #4
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    Re: Buying a 6.9l

    Ad says 280k so I'll expect it to be needing done soon. Thanks for the info.
    I test drove one once and it shook pretty bad. Should I expect a decent amount of that?

  5. #5
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    Re: Buying a 6.9l

    No they should be smooth, actually a v 8 should be smoother than an inline 6.

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  6. #6
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    Re: Buying a 6.9l

    Southpaw is correct. A 6.9 that is running correctly is smoother than some gasoline engines.
    If it runs smooth and moves you can't hardly go wrong for $800. Around here a good engine by itself goes for $1200 to $1500.
    I was going to say as long as it is not a rust bucket but then I noticed you are in Indiana!

  7. #7
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    Re: Buying a 6.9l

    [QUOTE=Max Zubrenic;8634535]Ad says 280k so I'll expect it to be needing done soon."


    Or it may have been done recently!

  8. #8
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    Re: Buying a 6.9l

    1. The connector on top of the glow plug controller likes to lose contact, a small bungee will take care of that. 2. If the rubber seal is bad on the back of the hood rain water can run onto the top of the air cleaner and drip into the engine thru the hole where the stud protrudes and cause a hydro-lock. An upside down oil drain pan takes care of that. 3. The factory valve guides/seals didn't last too long resulting in big time oil consumption and blue smoke. Better ones came out later to fix that. 4. Like mentioned the Roosa Master injection pumps don't last forever and there were non metal parts in them that would begin to disintegrate and clog everything up. 5. The glow plugs are 6 volts and cannot stay on more than about 10 seconds or they will break up and drop into the cylinders, a glow plug LED on the dash will warn you if the relay gets stuck in time to shut down. 6. The water separator on the fire wall likes to suck air and cause rough running, bypass it and install a Racor instead to take care of that.

    All in all my N/A 6.9 2WD 4 speed posi was one of the best trucks I ever had, easy to keep running (If it won't run, it's not getting fuel-simple as that), dependable, good MPG. The manual will even start and run with dead batteries with a push. Won't win any speed races although mine could cruise at 80 easily and get 18MPG (empty). AC was ice cold and never quit. Oil consumption became a problem toward the end, I was burning a quart every 200 miles or so. Got my 7.3 now and love it, 14 years old and 175K still feels like a new truck.
    Last edited by bigb; 08-12-2018 at 12:16 AM.
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  9. #9
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    Re: Buying a 6.9l

    I remember Reading in one of my do you diesel truck magazines that the six.9 was that susceptible to the cylinder walls rusting out in-between the cyclynder walls and eating the parallel cylinder wall only on the 6.9 if the anti-freeze wasn't changed often enough might want to check that out. You could check that out with the compression tester.
    Last edited by duramax-rob; 08-12-2018 at 08:02 AM.
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  10. #10
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    Re: Buying a 6.9l

    These are great trucks to use for a straight vegetable oil conversion (SVO) too.
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  11. #11
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    Re: Buying a 6.9l

    Well I own her now.
    We didn't have good enough batteries to get it primed but the compression sounded good and even. Ran on a sniff of ether. No coolant but the radiator didn't smell oily.

    Hopefully I can get it home. Friend has a truck and trailer but no winch. Would a 2 ton come-along pull it onto a trailer?

    Between brakes and a clutch issue it isn't driving home and no brakes I'd rather not flat tow....

    Pic tonight, cuz I can't get a Pic to upload on mobile.
    Last edited by Max Zubrenic; 08-12-2018 at 03:41 PM.

  12. #12
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    Re: Buying a 6.9l

    Early ones into the 1984 model year liked to pop head gaskets and crack cylinder heads. Both problems fixed with newer carbon graphite impregnated head gaskets. As mentioned the plastic distributor ring in the Roosa-Master style injection pump liked to break usually around 60k from my experience(s). Glow plug relay or controller was usually replaced with a firewall mounted contactor and push button on the dash eliminating the original problematic one. Many starved for fuel when the owners would eject the water separator completely which was mounted by the brake master cylinder and then start the engine. If you have one of these eject about two to three seconds as the water if present will be in the bottom of this separator. It will replenish with engine start but not if completely drained fast enough to starve the engine out. Then you have to reprime the fuel filter. When you change filters fill them up fully before mounting onto the engine as they didn't like to crank a long time before the starters were very hot in the early ones. Seen a couple including one I owned have the oil pressure relief valve jam open in the oil/water cooler dumping oil pressure back into the oil pan. It washed the bearings out in the lower end of mine but I caught it without damage to hard parts. Oil pressure went very low and I drove the truck home 30 miles thinking the gauge or oil pressure sending unit failed. Good engines and an AST, or Bank's turbocharger system will really bring it to life just about doubling the output power with minor adjustments to timing and fuel delivery.
    Slob

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  13. #13
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    Re: Buying a 6.9l

    Name:  37904717_2608236259201934_3900828304843735040_o.jpg
Views: 170
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    Not too rusty considering it is Indiana, 32 years old and got it for 750. Only non advertised issue I noticed was the rear u-joint had about an 1/8 inch of slop in it. Sat for 8 years so going to drain all the fluids and do all the filters. Get some batteries and check all the rubber lines.

  14. #14
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    Re: Buying a 6.9l

    Quote Originally Posted by Max Zubrenic View Post
    Name:  37904717_2608236259201934_3900828304843735040_o.jpg
Views: 170
Size:  119.6 KB

    Not too rusty considering it is Indiana, 32 years old and got it for 750. Only non advertised issue I noticed was the rear u-joint had about an 1/8 inch of slop in it. Sat for 8 years so going to drain all the fluids and do all the filters. Get some batteries and check all the rubber lines.
    Looks very close to my old truck down to the bumper guards. I sold it to a gent whom gave it to his son in Indiana? If it's the same truck I always was right at 20mpg as it had a 3.08 rear and was a pooch starting off but would really roll down the road. I sold mine in 1990.
    Slob

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    Oh yeah, also an unabashed internet "Troll" too.....

  15. #15
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    Re: Buying a 6.9l

    Quote Originally Posted by Slob View Post
    Looks very close to my old truck down to the bumper guards. I sold it to a gent whom gave it to his son in Indiana? If it's the same truck I always was right at 20mpg as it had a 3.08 rear and was a pooch starting off but would really roll down the road. I sold mine in 1990.
    If it is the same truck that would be awsome. I love stuff like that. Its in white county Indiana. I think they said the previous owner pulled horse trailers with it? I can message you the vin if you know what it was to see if it matches once I get it back to the house.

  16. #16
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    Re: Buying a 6.9l

    I wouldn't remember or have any paperwork on that truck remaining. It certainly would have been a struggle to pull a heavy horse trailer given the rear axle ratio. I did however purchase it from a cattle farmer in Nokomis, IL back in 1988 whom hauled feed/grain with it.

    It is possibly the same truck as the son worked for Caterpillar in Layfayette, IN. Sure looks close if not the same.
    Slob

    Purveyor of intimate unparalleled knowledge of nothing about everything.

    Oh yeah, also an unabashed internet "Troll" too.....

  17. #17
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    Re: Buying a 6.9l

    They did make a lotta those trucks and that was a popular color scheme, also the flip side with the brown on top/bottom and the creme in the middle. Mine was those colors as well and had the bumper guards just like that cept mine was a Supercab, 1983.
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  18. #18
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    Re: Buying a 6.9l

    Max, there's an additive for the cooling system to help prevent the head/head gasket issues, I think it needs to be added every 15000 miles. They may have finally modified coolant specs to eliminate this need but I'm not sure. I worked on those terds in the late 90's till about 2006 or so, so I've forgotten some. the roosa master pump and fuel return lines and injector hats were a problem too.
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  19. #19
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    Re: Buying a 6.9l

    I heard about the anti cavitation additive for them and that it wasn't a huge deal like the 7.3l
    I'm going to go through all the soft lines and replace any that are suspicious

  20. #20
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    Re: Buying a 6.9l

    Quote Originally Posted by Max Zubrenic View Post
    I heard about the anti cavitation additive for them and that it wasn't a huge deal like the 7.3l
    I'm going to go through all the soft lines and replace any that are suspicious
    Yes there is an additive that needs to be put in the radiator that stops the cavitation. You can buy some antifreeze that already has it in it. The stuff I used to use was fleetguard antifreeze. It was available at Fleet Farm and some local heavy truck shops carried it. There are test strips you use to test the coolant with. The additive needs to be replenished from time to time. I had the glow plug relay problems with mine . The worst thing about my old 6.9 was it was always had to be plugged it to start if it was below 20 degrees. I hatted that and always had to be aware so that electric power was available if it had to sit more that a few hrs.

  21. #21
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    Re: Buying a 6.9l

    She lives!!!

    Good batteries and filled the fuel filter with fresh fuel.

    Clutch is stuck disengaged though. Pedal springs either all the way up or all the way down. I think I'm going to replace the slave cylinder. I took it off and it was super sloppy.


    Tommorow I'm going to see if pulling that out engaged the clutch. Hopefully it did as that means I won't have to pull the trans and do a clutch.

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