New HO waterpump without dual therms upgrade..

[john8662]

JK's idea above is how I figured those that were not having problems were getting by with the upgrade.

I don't think it'll hurt, afterall the new 2-stat one has no bypass block-off.

J

[Shikaroka]

If anyone can get the part number for NAPA, please post it or send it my way.
My local guys can't find it.

[dieseldummy]

I've been running with the OEM single stat w/bypass blocker this whole time... I'm not saying it can't happen, but blown out freeze plugs and heaters are really stretching the worst case scenerio thing. I'm still waiting for the proof...

[rameye]

dieseldummy...

how long have you had this set-up????...

BTW I totally chickened out and pulled the thermostat...I will reinstall without the bypass blocker...

After working on this thing on and off for months on end...I started to freak when I thought about what it would take to pull the heads to get to a rear freeze out...

With advice from JK and pics from RJ and seeing the new set-up I've pretty much made up my mind that with the bypass blocked I am tempting fate..

sign me

Big Chicken

[GSE2SCHMIDT]

OK I gotta throw out the BS flag on the loosening freeze plug thing.

Let's say one morning it's 40 degrees outside. You start up your truck and get on the freeway before the thermostats open.....

....so lets see there are 2 thermostats, but they are closed

....somehow having 1 thermostat closed builds more pressure?

....so everyone with 2 thermostats, they must never close, and the radiatior can never have more than 9% restriction or POW no more freeze plugs

Also if the dual stat flows no more than 9% to the radiator, the dual stat setup would not have an effect until the single stat ran out of range at 100 percent open which would be 91% open for the dual....

...so how often is everyone running at or above 91% cooling?

....9% more flow to the radiatior wouldn't a single flow stat have better block flow?....flow has to go somewhere?

[rameye]

I'm guessing what JK and RJ were demonstrating that (as far as I can tell) is that with the single stat setup, with an OEM thermostat that has the blocker, is that when the thermostat is closed it will build pressure. Apparently with the significantly larger size impeller in the HO pump, it builds quite a bit more pressure than the small impeller. With the dual set-up, the bypass never gets blocked so it dumps pressure via the heater circuit.

What JK was offering as a compromise, was to remove the bypass blocker off the OEM thermostat, to allow any pressure to dump into the heating circuit in the same way the the dual set-up does.

Truth is the blown out freeze outs might never happen (Diesel Dummy is running that setup)...however my luck sucks, and I'm not in the mood to tempt fate to prove a point. JIm has pointed out that GM engineering has verified that the HO pump/single stat in the stock setup may cause a freeze out/blow out situation. This time of year this truck is the vacation mobile, and she needs to be up, running and stout..not leaking antifreeze on the side of the highway.

My $.02

[dieseldummy]

I've ran w/single stat and HO pump for 15K miles w/no problems. The last 10K was with dual stats and HO pump, also no problems. That was all on the origional motor w/148K ish miles. For the last 5K I've wen't back to the single stat/HO pump combo and still have no problems. I run a stock stat w/blockoff intact.

The only advantage I see to the dual stats is slightly better cooling ability.

[ronniejoe]

OK I gotta throw out the BS flag on the loosening freeze plug thing.

Your BS flag needs to be recalibrated...

[dieseldummy]

Lets recalibrate it with some proof then...

[rameye]

I guess we could screw a pressure test gage into the block where the sender unit goes and check it out...single stat, dual stat, single without blocker..

anybody game??

[robscarab]

Anyone get that part # from NAPA for the dual T-Stat deal? I called and they told me that they have never stocked anything like that. It took him about 4 seconds of "research" to respond, so I asked him if anyone else had asked for this piece? He said..no...Alrighty then, I think I will call back when the afternoon shift comes on. Perhaps I will get someone whom will at least try and look it up.... By the way, I said my truck was a 98 to avoid a lecture about how it wouldnt fit on my 93,but we never got that far... I hope I can just call back with a part number later, unless he's right ?

Also there are thousands of 6.5TD's in my part of Canada so I'll check the boneyards and let everyone know if there are some around town.

Rob

[rameye]

That would be great!!

$250 for a new one!!!

[gherrell]

That would be great!!

$250 for a new one!!!

Don't have the NAPA number, but Rock Auto (.com) has the AC Delco parts for the dual thermostat crossover:

AC Delco #1580782; Engine coolant thermostat housing (lower part of crossover): $104.79

AC Delco #151753; Water Outlet: $51.79

Get these parts and (2) AC Delco #131103; thermostats ($17.83ea) and you are set!!!

Regards,

Gary

[rameye]

Thank you for those numbers...I checked them out..those are Good numbers!!

much appreciated

[GSE2SCHMIDT]

Well the BS flag thing.....

My 1999 chassis engine(non-turbo) has the screw on fan style waterpump, all the part cross over lists show there is only 1 part number for many applications including the single thermostat that my engine came with. The pressure of the pump is basically going to be determined by how tall the impeller is and how fast it spins.

If the pump outlet is fully blocked the pressure will only increase so far and the power it takes to spin the pump will decrease. Pumps mostly use horsepower to pump the liquid, not pressurize it so much.

So lets say that a small impeller pump is good for 10psi and a large capacity pump is good for 15psi.

At upper RPM the pump will pressurise to max pressure from the inlet to the outlet. The inlet is coming from the radiator and that does not change.

The other end is to the radiator. So if the thermostat(s) is/are closed. Pressure will increase to 10/15psi repectively. Does not really matter if the bypass valve is installed because it is wide open pressure will increase to the whole block in seconds with or without restriction and it will sit there recirculating the coolant at the engine at 10/15psi at whatever gpm can flow thru the block. At this time if the freeze plugs are going to blow they will now.

As the engine warms up the thermostat opens and bypass closes but even with a totally open single thermostat and totally blocked bypass the block pressure will not increase and will actually decrease if the radiator cannot flow quick enough.

I think your right someone might have to do the pressure gauge test and yes the bigger pump will have more pressure, but with a totally closed thermostat(s) pressure has no where to go

[joescj5]

Great stuff here guys. I'm also looking at the best bang for my buck to help my chevy tow better. Reading through this thread I have come to believe if I were to install just the HO pump would run the risk of blowing out freeze plugs.

Now what would happen if I were to instal the HO pump, and then drill a modest bypass hole in the single thermostat? The engine would take a bit longer to warm up, but the T-stat should still function mainly normally. Now in my mind this should decrease the pressure through the block before the T-stat opens, and reduce the chance of popping freeze plugs. This should also allow a bit more coolant to flow through the block without resulting in cavitation.

I apologise if the bypass hole idea has already been discussed, but I thought it was a good fit in this thread. If anybody's done this then post up, let us know how it works. I've halfway convinced myself to pick up a new HO pump, drill a small hole in my T-stat and see what happens Somebody needs to stop me soon if this is a really bad idea

[tommac95]

>157K probably has a less than a 40K life expectancy before it grenades.
Possible , but I'm expecting 300K . Headgaskets may be in order , though....

The block freezeout plugs won't go anywhere [i removed a couple], the heater , maybe so.

Glad you raised the issue !

[j_k_auto]

I guess the single 180 stat,marine pump,cooler clutch with the dmax fan must be the ticket on keeping it cool. As We now when he comes out with a setup it must be great.

[j_k_auto]

Also I think if you would run a single stat an remove the bypass it would take care of the pressure build. that is my opinion.

[joescj5]

Well I just did it. Drilled four 7/64th holes in the flange of my stock thermostat, and installed a HO water pump. Just took it for a spin around the block and up a small grade. Put it into drive and kicked the RPM to just under 3k and cruised up the grade for about 2-3 miles. Temp made it up to 190, but I ran out of grade. As soon as I slowed down the temp dropped to 170.

Tommorrow, or later today actually My wife and I are going for a Sunday drive to look at some land. This will give me a chance to try out our local 6% grade for 7 miles right after the first 6% and 4 miles section of highway nearby