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I just returned from a large construction trade show out west. An LBZ display model was there as well as a couple GM engineers. I was refered to the "expert". He has asked me not to use his name and was supposed to have been involve with the development of the medium duty truck as well as the Duramax down to every nut and bolt. When I questioned him about the over heating problems with the LLY he didn't seem suprised at all. He told me that the impeller on the LLY was a redesign and moved more water at a faster rate through the block and was not allowing the coolant properly cool the block and that it was wreaking havock with the thermostats making them constantly cycle. It seems to make sense. He then said if I had been to the dealer with over heating issues to have an LB7 water pump installed. I remember reading at one time that the part # was the same for the LLY and LB7 water pump. Has anyone verified this or is this guy blowing smoke up my a** to get rid of me? Has anyone tried this?
 

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I have yet to see a difference in the pumps myself. I've looked closely after reading about supposed differences here on the board and I must be blind
 

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I thought that it was Killer Bee that said the LB7 had a bigger pulley than the LLY. But I'm not sure if it was him or that I remember correctly.
 

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They are the exact same, have been inspected and measured to be the exact same, have the same gearing, and have been verified to be the same on the engineering drawing by sources with the inside ability to make sure.

They are the same.

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Water pump isn't belt driven. No pullys.
 

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I thought that it was Killer Bee that said the LB7 had a bigger pulley than the LLY. But I'm not sure if it was him or that I remember correctly.
The FAN pulley is differently sized. Thats really old info, we knew that last year. The water pump is gear driven, not pulley driven, and are identical parts between the LLY and the LB7.

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Sorry guys!!! My mistake. I do remember about the fan now that you mentioned it TxC.
 

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I thought that it was Killer Bee that said the LB7 had a bigger pulley than the LLY. But I'm not sure if it was him or that I remember correctly.
The fan pulley is different size. It is old information that has never been tested. Mitchagain and myself found this out in a side-side comparison. There is maybe a little effort underway to test the theory that the LLY fan clutch is overdriven, behind a very resistive stack, leading to overheated silicone viscous clutch fluid.
 

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I just returned from a large construction trade show out west. An LBZ display model was there as well as a couple GM engineers. I was refered to the "expert".
Could you please PM me his name?
 

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I just returned from a large construction trade show out west. An LBZ display model was there as well as a couple GM engineers. I was refered to the "expert". He has asked me not to use his name and was supposed to have been involve with the development of the medium duty truck as well as the Duramax down to every nut and bolt. When I questioned him about the over heating problems with the LLY he didn't seem suprised at all. He told me that the impeller on the LLY was a redesign and moved more water at a faster rate through the block and was not allowing the coolant properly cool the block and that it was wreaking havock with the thermostats making them constantly cycle. It seems to make sense. He then said if I had been to the dealer with over heating issues to have an LB7 water pump installed. I remember reading at one time that the part # was the same for the LLY and LB7 water pump. Has anyone verified this or is this guy blowing smoke up my a** to get rid of me? Has anyone tried this?
BART, the guy was blowing smoke up your azz, they overheat due to faulty piston/head design combination.

Are ya watching GM? The secret is out because I know what you did........can't hide it no more!

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Are ya watching GM? The secret is out because I know what you did........can't hide it no more!

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That's the first time I've heard you state it that way, but then I remembered wrong a couple of posts ago too:eek::
 

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That's the first time I've heard you state it that way, but then I remembered wrong a couple of posts ago too:eek::
I never stated it that way before because I never knew exactly why we overheat.

Now I do. Thats no BS either. The fix is truly coming down the pipeline with its lights glaring, and it isn't ANY of the stuff we previously tried or did or thought.

I have some design/custom stuff to do, and at this exact moment I am on hold for parts. I expect proof runs mid February.

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That sounds great TxC!!! And when you say "parts" I'm hoping that means just add ons and not tearing the engine apart. The recent talk about the heads was scaring me.
 

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try the lbz pump and take a look at the new fan/shroud on the new lbz model all was changed for the overheat problem the lbz pump is different as i have 1 on the bench from each the lbz impeller is diff. the new fan rocks and per gm the reason for the change is the overheating problem. after looking at the parts the new fan and shroud could be mounted on prior models its just a matter of cost.
 

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try the lbz pump and take a look at the new fan/shroud on the new lbz model all was changed for the overheat problem the lbz pump is different as i have 1 on the bench from each the lbz impeller is diff. the new fan rocks and per gm the reason for the change is the overheating problem. after looking at the parts the new fan and shroud could be mounted on prior models its just a matter of cost.
Those are great ideas, thanks!

:D

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You guys need to listen to TxChristopher. Got to ride and look at his engine. Until you see all his monitoring tools and sensors going everywhere; this guy kinda has an idea what he's talking about. Its not the water pump either. I've had the water pump, radiator, and thermostats changed. The truck doesn't overheat anymore, but it still spits coolant once a day. I've got compression coming from something b/c my upper radiator hose is solid even when the engine is ice cold.
 

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We laid some tracks didn't we Beau? :)

Actually we already had the LBZ fan on at PUSU, it made an impact but not enough.

I haven't verified the fix, but I will, its just parts waiting and some parts to make.

We shall see.

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Laid more than some tracks.):h Drove my truck this evening and guess what? I don't really need to tell you, do I? -:t Thats what. Oh well, dealer round 3 with only 33,500 or so on the clock.
 
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