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96 gm 6.5 diesel

Discussion in 'Chevy Trucks' started by eastcoastjava, Jan 24, 2014.

  1. eastcoastjava

    eastcoastjava Senior Member
    from Boston
    Messages: 165

    Looking at a 96 gmc 3500 dump it has 114 k miles and has a 6.5 diesel on. Looking to see if any of you guys have any info on problems or what to look for on a truck like this. Break lines and tranny were replaced
  2. jrs.landscaping

    jrs.landscaping Senior Member
    from Maine
    Messages: 722

    Fuel pump, injectors, glow plugs, relays I know there's more I just can't think of them
  3. eastcoastjava

    eastcoastjava Senior Member
    from Boston
    Messages: 165

    Are they a total headache? I Haven't owned a diesel, only gassers
  4. jrs.landscaping

    jrs.landscaping Senior Member
    from Maine
    Messages: 722

    Not a total headache, I've never owned a 6.5 only a 6.2, its absolutely gutless but is the most reliable engine I've seen.
  5. maxwellp

    maxwellp PlowSite.com Addict
    Messages: 1,123

    I would drive one if the price is good and it is not a rust bucket, but read this about the 6.5.

    Is the 6.5 a "good" engine?

    Simple answer: no.

    It is an affordable rig for that was built for mileage but it is not considered overbuilt or durable.


    Lift pumps die regularly. result - rough running/power loss/ip strain
    IP dies. result - no start/doesn't run right
    oil pressure switch burns out. result - no start
    Harmonic balance deteriorates. result - broken crank
    Crank pulley deteriorates. result - broken crank
    Weak block casting. result - cracked main webs/cracked head bolt holes/cracked cylinder bores/broken starter mounts
    Heat issues in the heads. result - cracked valve bridges/water in combustion chamber
    Poor head gasket clamping. result - blown head gaskets
    Injectors - only good for around 100,000 before replacement. Result - everything from rough running to a holed piston.
    Failing vacuum turbo control system. result- low power, rolling black smoke, overheating, burnt up engine.
    Electronics - PMD overheat issues. Result - all kinds of whacky troubles from no start to engine run aways.....

    Then there's just the simple fact that even the "newest" one is old. Mileage, rust, etc all take their toll over the years.

    The 6.5 is good for about 300,000 miles and then it's looking for a rebuild/replace. It can go longer, but very few break 400,000. And that's if they've been lightly used and taken care of. There's always going to be someone spark up "I've towed 20,000 CGVWR every day for the last 20 years and haven't done a thing to it, i got well over 400,000 on mine" to that last comment, but they're very rare if true and even then they've been very lucky....take those claims with a grain of salt

    Plus all the other common problems in an older GMT400 chassis (ie: front end components, ignition switches, windshield leaks, rotted cab corners, etc)

    Now, the good stuff;

    Because of these problems (which your truck may or may not have) they are perceived as "turds". This means they are an affordable diesel to purchase.

    They are still also relatively "simple" diesels so you don't need a PHD in electro-mechanical engineering to work on them.

    Emissionsare nearly non existent.

    Fuel MPG is good for such and old hack. 13-15 mpg combined is normal, some can get slightly over 20 mpg highway running (depending on condition, speed, gearing, etc).

    Parts are relatively cheap compared to modern diesels.

    As long as the block is still sound (IE: not cracked and there's no way to know other than tear it down so you're taking a chance) most issues are also affordable fixes.

    For example:

    500 bucks relocated your PMD outside the engine bay and you can get 10 odd years out of it. A full set of injectors only costs around 400-500 bucks (price out a duramax and you'll see why thats good!). The OPS can be fixed with a bit of wiring and a relay. Glow plugs can be had for around 8-10 bucks a piece (good duraterms, not cheap ones).

    A 6.5 can be a good truck, if you do some work and accept it's limitations. It's a light duty diesel made for MPG. You can work it (towing) but it's not intended for full time commercial use. It will do it, but you're taking life off it every time.

    It's never going to make much more than 250-300 hp. It's going to take mucho buckos to cross 500 lb/ft.

    If you're looking for a truck you can pick up cheap, put a little money in ot, drive it lightly or tow a bit, it can be a good choice.

    Just make sure you get one in decent shape to start with.

    Things to look for:

    Hows it start? smokey? smoke color? Blue=bad, Whitish grey = unburnt fuel (can be ok if it clears in short order), white = coolant in combustion chamber.

    Does it roll black smoke on acceleration? if so, the Vacuum system for the turbo wastegate is toast. A properly running 6.5 has almost no black smoke. Good news it's usually and easy fix. 50 bucks for the solenoid valve, 150 bucks for a vacuum pump, 100 bucks for a vacuum actuator or simple vacuum line replacement.

    Pull the intake boot off the turbo. Check for play in the wheel (with the engine off!!!). Side to side movement is acceptable as long as the wheel doesn't touch the housing. It floats on oil on plain bearing so no oil pressure side to side movement is normal (but no touchy the side walls!). If the wheel moves in and out a lot that's a different story, the turbo is getting ready for replacement. looking at around 800-1200 for a replacement GM turbo. Around 800 for an aftermarket "upgrade". When something spins 150,000 odd rpm, it deteriorates fast once it starts to go. Worst case scenario; the wheel comes apart and sprays metal into the engine....

    Pull the filler cap. Does it chuff smoke? Can indicate worn rings or cylinder bores. Some will say it's a bad CDR, but if it's a higher milage engien 99% of the time is cylinder/ring wear. If it's puffing smoke from the dipstick tube and the dipstick is still in, turn around and walk away. It's ready to die on you.

    If it's got a small amount of smoke from the filler, it's probably OK. Take it for a test drive with a friend and pull over in a parking lot. Take a long piece of clear tubing with you that fits over the dipstick tube and a bottel of water. Slip the tube over the dip stick tube and the other end in the water. Hold the bottle down by the tire and get your buddy to rev the engine to about 2000rpm. If the water rises a couple inches, the engine is in decent health, if it rises 4-6 (or more inches) it's probably got a bad CDR valve, if it pushes the water down a couple inches or it blows bubbles in the water, drive back to the owner and hand him back the keys. It's about to die.

    Also look veeery closely at the starter mounting area. These blocks have been known to crack off in this area and owners "buck shee" the starter back on to sell them. This is always a temporary fix and once it lets go again the only fix is to replace the entire block!

    Good luck, take your time and check it over thoroughly.