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Waterless Coolant

WarWagon said:
I never noticed a problem with HO water pumps and single T-Stats. The original concern I read about, aside of reduced GPM, was extra block pressure pushing out the freeze plugs. The only temp excursions I would get to 210 was sneaking up on a hill in OD, but, not enough throttle to drop to 3rd. Better turbo reduced ECT's for me so I may have room now to run it without concern. The setup also had 180 T-Stats and a KD low temp fan clutch with the 21" steel or Duramax fan. Funny, but my 95 dual heat suburban always ran hotter than the pickup even with different turbo's. Maybe because the AC was always on...
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Interesting, I wonder what in your mix is preventing the pressure surge with the high output pump heater hose always flows or?
 
bowtiebutler956 said:
I too am running a 97+ HO pump with a single stat, and my cooling system works very well. The single stats on our 6.5's are much larger than a standard stat, like the duals used in the later models. While the one large stat may not flow as much as two standard ones, its still a high volume stat. I'm running a Delco 190 in mine.
Its funny, after going through my engine awhile back, I installed a Robert Shaw stat in it, and it continually ran about 210, and I didn't know why. Thats when I got to reading about the bypass blocker used on these 6.5 truck engine. The stat I installed was for a 6.5 Van engine that didn't use a bypass blocker, so the stat didn't have one. I swapped it for an OEM 190 with the blocker, and now my truck almost never leaves 190, even on hot 100* days. Now when I'm towing I sometimes see 200.

Matt
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As I mentioned in reply to WW I am surprised no pressure surge w/high output pump and single thermostat are your heater lines flowing always or?
 
Those of you w/HMMWV knowledge know if the P400 has dual thermostats or on earlier 6.5 if the single thermostat crossover is higher flow than say any GM 6.5 crossover, or?
 
I think the difference is the redesigned single thermostat crossovers. My hummer has the one where a block off tstat can not be used. These were the ones that had all the water pump damage as well. The difference in 130gpm water pump and 97-98gpm(iirc) single stat caused the cavitation on pumps- hence dead pumps and heads.

WarWagon, and everyone else that is ok with the ho pump and single stat: Which crossover and stat are you running? If it is in the 110 gpm range, that could be enough to eliminate the cavitation, and boiling off is gone as well due to less airiation of coolant.
 
Will L. said:
I think the difference is the redesigned single thermostat crossovers. My hummer has the one where a block off tstat can not be used. These were the ones that had all the water pump damage as well. The difference in 130gpm water pump and 97-98gpm(iirc) single stat caused the cavitation on pumps- hence dead pumps and heads.

WarWagon, and everyone else that is ok with the ho pump and single stat: Which crossover and stat are you running? If it is in the 110 gpm range, that could be enough to eliminate the cavitation, and boiling off is gone as well due to less airiation of coolant.
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Thanks for the input I'm trying to get a handle on how many versions of cross-over t-stat housings for the 6.5 and their good/bad difference. I've seen images of the P400 full dress w/dual stats and was curious it this is the configuration run on them to enhance cooling flow.

The remote accumulator on my Burb has a coolant input from radiator then a hot coolant feed to lower radiator intake hose and a vent I'm sure this increases coolant flow capacity as well.
 
Admittedly, I went from a 1985 GMC Jimmy w/6.2 diesel never had any cooling problems whatsoever to this 1999 GM that was borderline as cooling goes after mods.
 
FellowTraveler said:
Admittedly, I went from a 1985 GMC Jimmy w/6.2 diesel never had any cooling problems whatsoever to this 1999 GM that was borderline as cooling goes after mods.
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1985 had standard rotation fans, perfected water pumps, lower set point for fan lockup, and better airflow through the stack from ram air. Nevermind the additional heat load of the restrictive turbo, dual "good" exhaust w/o the mess the turbo manifold is, and doubling of the engine's rated HP. Reversing the water pump rotation somewhere screwed them up for balanced flow and had to be fixed later.

I did remove the restriction in the heater core fitting on the 1993 t-stat crossover. However I run a block off valve and completely block heater core flow for every degree of AC performance. I run a Murry or whatever the local parts store has blocking thermostat and yes, it wanders the temps more than AC-Delco. The blocking flow design is one advantage to the single t-stat setup. You put a high load on the dual t-stat setup with a restrictor in the bypass and you could boil coolant in the heads before the t-stat warms up. The 1993 does dump heater core return into the cold side of the radiator and another reason to block the heater core when not needed.

IMO the HO aftermarket 4 bolt water pump may still have a small balance flow issue as the driver side #1 piston scuffed from what I think was shock cooling due to flow imbalance. Otherwise both front pistons would have scuffed. Maybe it was so close that a little bit is all that mattered.
 
I think you'll be ok running either one. Duals are said to flow more, but if they do its negligible. Its the water pump that dictates the gpm if nothing else changes. I prefer the single because of the bypass block.
FYI in early 1996 only they ran a single tstat, but in a housing that fit like a dual application. They are rare as they only came on 1996 for a few months.
 
WarWagon said:
1985 had standard rotation fans, perfected water pumps, lower set point for fan lockup, and better airflow through the stack from ram air. Nevermind the additional heat load of the restrictive turbo, dual "good" exhaust w/o the mess the turbo manifold is, and doubling of the engine's rated HP. Reversing the water pump rotation somewhere screwed them up for balanced flow and had to be fixed later.

I did remove the restriction in the heater core fitting on the 1993 t-stat crossover. However I run a block off valve and completely block heater core flow for every degree of AC performance. I run a Murry or whatever the local parts store has blocking thermostat and yes, it wanders the temps more than AC-Delco. The blocking flow design is one advantage to the single t-stat setup. You put a high load on the dual t-stat setup with a restrictor in the bypass and you could boil coolant in the heads before the t-stat warms up. The 1993 does dump heater core return into the cold side of the radiator and another reason to block the heater core when not needed.

IMO the HO aftermarket 4 bolt water pump may still have a small balance flow issue as the driver side #1 piston scuffed from what I think was shock cooling due to flow imbalance. Otherwise both front pistons would have scuffed. Maybe it was so close that a little bit is all that mattered.
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I've been a little suspect w/the bypass restrictor also and GM designed the bypass into the HO dual stat system to increase the flow through the 6.5.

Because I had a pinhole in my front heater core air got into the cooling system some years ago and the OATS coolant became more and acid that a coolant so I stay clear of it. I'm considering the wider core radiator and removing the bypass restrictor sooner than later.
 
Need to know, if only the HO pumps equipped diesels have the extra line attached to the lower radiator hose pulling coolant from the surge tank into the water pump.
 
FellowTraveler said:
Need to know, if only the HO pumps equipped diesels have the extra line attached to the lower radiator hose pulling coolant from the surge tank into the water pump.
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I looked up a lower radiator hose for a 2000 K2500 and it had the small extra hose teeing on the big hose.

Also I just got a 2000 water pump for my build that is supposed to be the one Heath recommends. I took some pics of it next to the HO pump that came on my Optimizer if you want to see. I don't want to pollute/hijack your post so I'll only post them if you want me to.
 
Oops, I just reread your post. I looked at it wrong. I went backwards in the catalog and it looks like 94 is the first year of the small hose, which I don't think coincides with the HO pump.
 
Yes my 1995 had the "T" in the lower radiator hose. Real PIA to eliminate the surge tank and go back to a 1993 cooling system - to clear the spool valve.
 
n8in8or said:
I looked up a lower radiator hose for a 2000 K2500 and it had the small extra hose teeing on the big hose.

Also I just got a 2000 water pump for my build that is supposed to be the one Heath recommends. I took some pics of it next to the HO pump that came on my Optimizer if you want to see. I don't want to pollute/hijack your post so I'll only post them if you want me to.
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Post away this way others can see what it is too.
 
WarWagon said:
Yes my 1995 had the "T" in the lower radiator hose. Real PIA to eliminate the surge tank and go back to a 1993 cooling system - to clear the spool valve.
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So this is not just an HO pump thing, I see lots of flow from this smaller hose on surge tank into lower radiator hose to water pump and wonder if it is an attempt to keep the coolant warmer, or just add to the flow capacity.
 
n8in8or said:
I looked up a lower radiator hose for a 2000 K2500 and it had the small extra hose teeing on the big hose.

Also I just got a 2000 water pump for my build that is supposed to be the one Heath recommends. I took some pics of it next to the HO pump that came on my Optimizer if you want to see. I don't want to pollute/hijack your post so I'll only post them if you want me to.
Click to expand...

I'd like to know what if any difference there is w/pumps, my Burb came with all the cooling mods Heath mentioned to include the HO pump I just added the bypass restrictor which I'm trying to figure was the right thing, or?
 
Ok here ya go. Let me know if there are any other pics or dimensions you want and I'll get those for you too.

00WP1.jpg 00WP2.jpg 00WP3.jpg 00WP4.jpg 00WP5.jpg 00WP6.jpg 00WP7.jpg 04WP1.jpg 04WP2.jpg 04WP3.jpg
 
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