Re: '95 GMC 6.5TD engine

Posted by jdemaris on September 07, 2006 at 06:09:52 from (66.218.13.15):

In Reply to: '95 GMC 6.5TD engine posted by JCSinGA on September 06, 2006 at 14:23:21:

Detroit Diesel designed the 6.2-6.5 engine series for General Motors - from the ground up, and I suspect - at least at the outset - fuel economy was the goal - and not durable and heavy-duty pulling power. 6.2s and 6.5s use the same cranks, heads, basic blocks, etc. But, for the most part, the 6.2 blocks were better than the 6.5s. There were minor updates as power was increased - with the cooling systems, rear main seal, etc. When GM starting using electronic controls ca. 1994, fuel mileage went down - not up, and reliabilty went WAY down. The electronically controlled system on the 6.5 went through three major changes - the last (third) was pretty reliable. Most of the new system parts are retrofitted to the older 6.5s. The 1993 turbo-charged 6.5 diesel with mechanical injection and thick-casting block is probably the best of the series ever built - in regard to reliability and fuel mileage.
General Motors Corp. claimed that it was too difficult to meet the newer emmissions standards for diesels with the 6.5 - and that is why they changed over to the Japanese Isuzu Powermax engine. G.M. owns most of Isuzu anyway - so I guess, why not? Most people I know that have diesel Chevys with the Isuzu V-8 are disappointed with the fuel mileage.
The military 6.5s ALL retain mechanical injection.
In regard to a changeover- from electronic to mechanical - there is small book published with the info needed.
After 1993 or 94 (depending on the casting #), the 6.5 block got cheapened and lightened. Subsequently, there are cracking issues. The 6.5s being built now (mostly for the military and marine use) are thick castings again, just at all the 6.2s and first year 6.5s were.
One of my 6.2s recently blew up with over 500,000 miles on it. So, I can look at it two ways. 500,000 miles with NO teardown is pretty good. But, what upsets me is - it blew with absolutely NO warning. Engine started and ran great. Good oil pressure, never ran hot, etc. I was going down the highway at 70 MPH - and the engine set-up. In fact, it happened so fast, the fan belts flew off the engine. I pulled the engine out and took it apart. The crankshaft broke into three pieces and tore the main-bearing webs clear out of the block with the bolts still intact. The rod and main bearing journals, and bearings, all look pretty much like new with very little wear evident. So - it appears the weak link is the crank and this engine could of easily went more miles if not for that.
I have read that 6.2s and 6.5s break cranks when the harmonic balancers get worn. I checked my balancer on my blown engine and it looks fine.

Replies:

• Re: '95 GMC 6.5TD engine billpa 08:10:02 09/07/06 (2)
  • Re: '95 GMC 6.5TD engine Bob 08:44:25 09/07/06 (1)
    • Re: '95 GMC 6.5TD engine jdemaris 12:10:57 09/07/06 (0)

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