lifespan of 6.5td

Hi,
What's the lifespan of a 6.5TD?
Geert

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My '95 6.5L turbo diesel was at 156,000 miles before I sold it, but not because of the motor. The issue with the 6.5's is that you need to do a lot of learning about diesels in general and 6.5's in particular in order to get the best service out of it. It is definitely not a 'gas and go' motor. On the positive side, it has been around long enough that either GM or the aftermarket has managed to work through all of it's major problems, specifically head gasket burn-through (a cooling issue) and fuel injection pump reliability (by relocating the FSD). I loved my former truck, and would be driving it still today except that I got such a great deal on my current 2004 2500HD with the 6.6L Duramax and the Allison tranny.
Although I didn't keep mine long enough, I have heard of these motors going easily to 250-300k miles.
Cheers - Jonathan

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A friend of mine bought one a few months ago(94 one ton dually),, and it has been doing fine except when it is hot,, and shut off (lunch time)then restarts it to leave and it will sputter and usually die, and then has to crank as if it ran out of fuel or something. He changed the pump on the frame rail with no change. what are you referring to about relocating the FSD?? and would this cause the motor to die like this? It will also will sputter on heavy accelleration. Any info about his truck I will pass on to him. THanks in advance Philc
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A friend of mine bought one a few months ago(94 one ton dually),, and it has been doing fine except when it is hot,, and shut off (lunch time)then restarts it to leave and it will sputter and usually die, and then has to crank as if it ran out of fuel or something. He changed the pump on the frame rail with no change. what are you referring to about relocating the FSD?? and would this cause the motor to die like this? It will also will sputter on heavy accelleration. Any info about his truck I will pass on to him. THanks in advance Philc
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What your friend is experiencing is very classic with these motors, especially the pre-'97 models (I had a '95). What is most likely happening is that the Fuel Solenoid Driver on the fuel injection pump is dying, but let me step back for just a moment. These trucks have two fuel pumps - a lift pump on the frame rail under the driver's door and a fuel injection pump mounted on the top of the motor in the V (under the front of the "Turbo Power" plastic cover. The lift pump draws fuel from the tank and sends it to the motor (via the fuel filter and water separator), and the fuel injection pump pressurizes the fuel and sends it to the fuel injectors.
In the '94 and later 6.5's, the fuel injection pump was an electronic unit call the DS4. Prior models had an all-mechanical unit called the DB2. The DS4 is actually a very good pump except for one fatal flaw. The FSD (also called the PMD for Pump Mounted Driver) is the small black box mounted to the driver's side of the fuel injection pump and contains two high powered transistors that activate the fuel solenoid inside the pump. It works very, very hard (it runs at 4x engine speed) and generates a great deal of heat. The theory behind the DS4's FSD is that the heat it generates will be absorbed by the fuel injection pump itself which in turn will be cooled by the fuel flowing through it. This worked great on the test bench, but mount the fuel injection pump and FSD in the V of the motor and cover it with a large plastic cover and that is where reality breaks from theory. What happens is that the FSD generates much more heat than the FI pump can absorb and the fuel flow can carry off, the the FSD eventually overheats and dies. There is also a domino effect, as the excessive heat can thin out the fuel, making it lose its lubricating properties for the FI pump, and also cause the optical sensor inside the pump to fail. If caught early enough, only a new FSD will be required (about $225 + labor). But if not, the entire pump will have to be replaced and/or rebuiilt (about $1700.00+). Typically, an FSD in the stock mounting position will last around 75,000 miles.
The easy solution is to remove the FSD from the side of the FI pump (actually installing a new one is easier as you have to remove the intake manifold to gain access to the pump and FSD). There are several products available that you mount the FSD to which are nothing more than finned heat sinks which allow the heat generated by the FSD to be bled off to the atmosphere instead of into the FI pump. Search for "FSD Cooler" and you should find it readily available from any one of several diesel supply houses. In its most common mounting location it doesn't even require an extension for the wiring harness, which makes installation a snap provided that you are installing a new FSD at the same time.
Good luck - Jonathan

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I am driving a 95 GMC 2500 with a 6.5L diesel. The truck has over 423,000 miles and is in good shape but the original "non spray cooled pistons" engine was replaced at about 170,000. The current engine is a 98 model 6.5 and has the piston oil spray cooling. It has lasted over 253,000 miles and has not been babied. As Jonothan says, it is not a "gas and go" motor but doesn't require constant baby sitting either. Just become knowledgable and treat it with respect and it will do it's job very reliably.
I have some blow by now and expect to do a total rebuild before the odometer gets to 470,000 miles. I just have to remember that it is not a Power Stroke, Cummins, or a DuraMax. As long as my expectations are reasonable the truck will fulfill my needs. Last year I pulled a 29 foot fifth wheel (9,000 lbs.) over 4,000 miles including over several passes around 10,000 feet in height. And no troubles. I am happy with it.
Best of luck.
Jonathan Race wrote:

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