New HO waterpump without dual therms upgrade..

**rameye** · 05-05-2007, 16:34

I have the front of the engine part..trying to get it and running up for this week. Running outta dough and patience.

Found a new HO waterpump for 20 or 30 bucks more than the standard pump...thinking I might go this way. I'm sure I wont get the benefit of the full upgrade but its gotta be better than the original pump....right?

Your thoughts..

**Robyn** · 05-05-2007, 17:15

Cant hurt at all.

**ronniejoe** · 05-05-2007, 19:00

Do a search on this subject. There has been much discussion about it. I posted some pictures once that show there is a significant increase in flow area both through the thermostats and through the bypass with the new housing. GM reported popping freeze plugs when running the new pump with the old crossover. There's been lot's of argument both ways.

**Mark Rinker** · 05-05-2007, 19:51

I ran an HO pump with a single thermostat system in a 1994 K3500. We later removed the thermostat completely and it ran much cooler all summer, and still made good heat in the winter while plowing.

**Chicago TDP** · 05-06-2007, 14:59

I think the radiator cap will burst before a freeze plug, right? Is' that suppose to be the first place of pressure release?

And the HO pump is just a larger dia impeller I think, which helps the flow more then increase pressure, the better the flow, the less pressure you have, they are an inverse of eachother. I am almost certain too that it is a 37 gpm pump instead of a high 20's gpm.

I also know there is a second revision offered. When I purchased my new 05 Pen motor, I came with an extra water pump that was a little beefier then my 1998 hi-flo pump. I put then on the truck and it seems to always stay cool, I have pulled 12k and had no overheating issues at all.

**Kennedy** · 05-07-2007, 11:55

I've seen confirmed reports of block heaters vacating the block with this setup. I guess simply put it just makes sense to do it right the first time...

**john8662** · 05-07-2007, 13:09

For a temp fix, you can install the HO pump w/o the dual stats.

The recommended practice is to complete the upgrade when you can.

I can't find THE thread, but here is a good one..

Why Are Dual Stats Part Of The Upgrade

**dieseldummy** · 05-07-2007, 19:19

I'd still like to see all these blown freeze plugs and block heaters... I put over 15K miles on with the HO pump and single stat. No issues here. When I had the motor out the freeze plugs and heater were just fine. The dual stats will help cooling, but aren't exactly necesary.

**rameye** · 05-08-2007, 06:58

Wow...I know a little about centrifugal pumps..(20 yrs in the FD) I never figured that little of an impeller change would build that much pressure!

I figure the pump would "slip" instead of build great amount of pressure as opposed to a positive displacement pump.

I agree with JK that its best to do it right, but I'm at the bottom of the money barrel right now. Couple that with the fact that this engine @ 157K probably has a less than a 40K life expectancy before it grenades.

Just afraid to dump more money into it...would rather pay it forward towards a new power plant.

As always your comments are much appreciated..

**oilburnertoo** · 05-08-2007, 07:13

I installed a take off HO water pump on a '91 6.2L PU [was off a crate motor & not aware at the time it was an HO pump] the issues I had were the side tank blew off at the seam twice on a brand new Harrison OEM radiator. After the second time I looked a little closer at the pump and saw the "HO" on the casting. I replaced the radiator again with one for a '94 6.5L aluminum w/plastic tanks and no problems since, BUT looking back I would put the whole package on at the same time and be done with it. The money I spent on the radiators alone would have paid the labor to install the pump and dual T-Stat manifold the first time around. Coincidence, I don't know?

**More Power** · 05-08-2007, 10:28

Way back in 1997, I had an email conversation with a GM cooling system engineer about the then new 1997 cooling upgrades. He told me that one or more test engines loosened/blew softplugs as a result of using the 130-gpm water pump without dual t-stats - under some unspecified operating conditions. That is the primary reason for the dual t-stats.

Now, I have also heard that many 130-gpm water pumps have been sold as an upgrade item to lots of 6.5 folks who didn't also install the dual t-stats. Did any of them experience a problem? Maybe. Maybe not. I don't know.

If someone wants to run an HO pump w/o twin stats, I'd say go for it. I wouldn't run a 130-gpm pump without dual stats, but you can let us know how it turns out for you.

Jim

**rameye** · 05-08-2007, 15:13

Well I guess I can be a test case...in the Mean time I'll cruise the junk yards for the dual stat setup....gotta be a few out there...

regards

Tom

**Kennedy** · 05-09-2007, 07:59

If I were to run the HO pump w/o the rest of the upgrade I might be inclined to eliminate the bypass block off part of the OE single stat or try the older 6.2 stat w/o this feature. This should give the coolant somewhere else to go...

**rameye** · 05-09-2007, 09:27

JK can you elaborate on that?? Whats the difference for the lay person??

**ronniejoe** · 05-09-2007, 09:48

http://www.schoolcraftpowertrain.com...a/IM001290.JPG

http://www.schoolcraftpowertrain.com...a/IM001291.JPG

http://www.schoolcraftpowertrain.com...a/IM001292.JPG

http://www.schoolcraftpowertrain.com...a/IM001293.JPG

http://www.schoolcraftpowertrain.com...a/IM001294.JPG

http://www.schoolcraftpowertrain.com...a/IM001295.JPG

DmaxMaverick, why did these show up as links instead of as embedded images?

**DmaxMaverick** · 05-09-2007, 15:58

Originally Posted by ronniejoe

http://www.schoolcraftpowertrain.com...a/IM001290.JPG

http://www.schoolcraftpowertrain.com...a/IM001291.JPG

http://www.schoolcraftpowertrain.com...a/IM001292.JPG

http://www.schoolcraftpowertrain.com...a/IM001293.JPG

http://www.schoolcraftpowertrain.com...a/IM001294.JPG

http://www.schoolcraftpowertrain.com...a/IM001295.JPG

DmaxMaverick, why did these show up as links instead of as embedded images?

Not sure. I'll reply to your PM.

**Kennedy** · 05-09-2007, 20:20

Originally Posted by rameye

JK can you elaborate on that?? Whats the difference for the lay person??

When the single stat with the bypass blocker (92-95 I believe) it blocks off the bypass hose so the only place flow can go is through the stat and radiator as well as the heater core. The dual stat config has no block off so there is a lot of area for the coolant to flow through.

I've recently heard of a Dmax that has been pushing out plugs after overhaul so yes it can be done...

**daustin** · 05-10-2007, 06:00

Originally Posted by rameye

Well I guess I can be a test case...in the Mean time I'll cruise the junk yards for the dual stat setup....gotta be a few out there...

regards

Tom

I know a friend that got a new dual thermo crossover from NAPA for about $80. I'd go that route unless there's a deal ot be found in the boneyard. The 6.5 is rare in the yards around here.
Don

**rameye** · 05-10-2007, 18:27

Hmmm Napa ...only 80 bucks sign me up!

Thanks for the insight...coming up empty in junk so far.

tom

**daustin** · 05-11-2007, 05:58

I looked for several months at the boneyards, not one to be found around here. I figured it would be pretty easy to find a used dual thermo housing BUT NOOOO.. LOL I was griping about it to a friend who has a 6.5, and he told me about the NAPA deal. The $80 was for the main housing, didn't include the thermo's, outlet ...etc but it sill sounded good to me. Next payday i think i'll see if i can get one at my local NAPA.
Don

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