Cooling Upgrades Techie Question

[Robyn]

As was mentioned earlier, "to eliminate hot spots"
The factory heads have some areas that the coolant can stagnate in and the extra flow will cause more turbulence and result in the mixing of cooler water being routed into these "Dead zones"
The bottom line is less head problems such as cracking.
My personal opinion is that GM did this as a stop gap measure to redesigning the heads.
Retooling is costly any way you cut it and when an engine design is slated for termination (production end) they are not going to spend the $$$
The addition of the dual stats and different pump was a cheap fix and it seems to have helped for sure.
It would be interesting to see if the heads coming from Navistar and also the ones from the after market (clear water) are the same inside as far as flow asd the GM heads or if the flow issue was fixed as well as the thickness of the head in the crack prone areas.

Just some thoughts

Robyn

[MTTwister]

Any opinions of use of "Water Wetter" or Dawn dish soap?

[GMC Hauler]

Any opinions of use of "Water Wetter" or Dawn dish soap?

I used Water Wetter, but didn't notice any difference. The principles it's based on are sound.

It will leak out unless your system is absolutely tight (someone here told me that and I subsequently found that out.)

If i had to make the decision again, I wouldnt bother.

[rustyk]

As was mentioned earlier, "to eliminate hot spots"
The factory heads have some areas that the coolant can stagnate in and the extra flow will cause more turbulence and result in the mixing of cooler water being routed into these "Dead zones"
The bottom line is less head problems such as cracking.
My personal opinion is that GM did this as a stop gap measure to redesigning the heads.
Retooling is costly any way you cut it and when an engine design is slated for termination (production end) they are not going to spend the $$$
The addition of the dual stats and different pump was a cheap fix and it seems to have helped for sure.
It would be interesting to see if the heads coming from Navistar and also the ones from the after market (clear water) are the same inside as far as flow asd the GM heads or if the flow issue was fixed as well as the thickness of the head in the crack prone areas.

Just some thoughts

Robyn

Now, Robyn, youreally know the answer don't you? When I was an oil peddler in the late 60'/early 70's, Detroit Diesel 6-71's with the 65 injectors (rated at 318 HP) had overheating problems. GM's solution? Bigger cooling passages? Higher capacity water pump and radiator?

Three guesses:




Nope, wrong!





Wrong again!




Solution: Advertise it as, "The Cool One"! (I came to this conclusion in collaboration with one of my customers who was an OEM DD dealer - we examined things pretty much in detail...)

[moondoggie]

Good Day!

rustyk: Could you interpret your last post for me? I have no idea what you're talking about.

Thanks & Blessings!

(signature in previous post)

[rustyk]

Sure, you mentioned the GM instituting the dual thermostat/higher cap pump as a stop-gap measure.

Stop-gap measures tend to be signature solutions for GM.

I agree with you that they probably tried it to avoid a redesign/retooling of the heads. The problems with the 6-71/318 (which go back to the early '70s) I mentioned to show a trend...

In that case, they basically did nothing except refer the issue to the marketing department for a solution.

[Tim Pringle]

A thought ... only a thought - I can see wisdom in running the high out water pump to help cool the heads, but I too am a little curious about the dual t-stat. In the past, I have oft been known to modify water pumps on some engines, gassers to be more precise, by removing half the blades to reduce cavitation & drag on the engine, = more available power. I have done a number with only running slightly warmer at idle. What's this got to do with a dual t-stat diesel setup? Nothing. But, wouldnt shoving the coolant through the radiator faster allow less time for cooling? I have always been of the mindset that letting the coolant move slower through the radiator allows more time for the temp to drop before returning to the engine. Ever remove a t-stat from your engine & find it actually runs hotter than with?

Tim

[Robyn]

Moving water through too fast can cause an overheat issue in hot weather as the radiator does not have time to dissipate the heat.
The dual stats allow each side of the engine to open the stat when the temp is optimum.

To answer another post.
The 318 was actually the small horse power 8V71 the larger ones went up to
475 in the 8V92 silver
The 6V71'a were available in Hp's down to around 265 in the coach applications and up to 360 in the turboed version. I had a city bus once that I converted to a motor home, it had a small hp 6V 71.
I got rid of that unit and bought a big "Hound" and converted it.
GM has always been good about sugar coating things and side stepping issues untill the time that they could phase the design out and start into some other debacle.
Funny
They got it right with the small block's (mouse motor) 265-350
we wont mention the 400 SB
And the MK IV 396-454 (Rat Motor)
Great designs that lasted decades and served well with minimal troubles over the long haul.
Starting with the 5.7 Olds diesel and on to present they just cant seem to get it together. Once they get it figued out they scrap the design and go build another mess to sort out.
We won't even mention the 4 cyl vega.
I think all the big manufactures have placed all controls now on design with the bean counters and none with engineering.
Ford has had their share of crap too as has MOPAR.
One thing the factories dont do any longer is "road test" they dont give the prototype to "BUBBA" and have him beat it to death on the test track as in the past. Most all testing is done in a computer program. WRONG answer. It takes a crazy to beat the stuff to death to really find issues that will come into play when you hand it over to the general public..
If the factory had taken only a small number of rigs and set them up with folks to beat them every day under the worst possible conditions for a year prior to production runs most of the stuff you and I have seen could have been fixed.
The issues with the PMD and IP's
overheating
Cracked heads, Blocks, cranks
All these little gremlins would have come to light and could have been addressed prior to ever building a truck for the general public.
The overall picture in the motoring publics eye would have been a great one instead of how it turned out.
I rest my case
Robyn

[More Power]

GM introduced a higher capacity water pump primarily to increase flow through the cylinder heads, which was intended to sweep away the thin vapor boundary layer formed on the hottest portions of the heads - thus allowing cyl head heat to be transferred to the coolant, which reduces the incidence of head cracking.

Dual t-stats add redundancy and increase maximum flow capacity. Flow through the radiator is not necessarily increased by the same amount as the increase in water pump flow rate. This is because the earlier 87-gpm systems used a blocking bypass thermostat, that forced all coolant through the radiator when the t-stat was fully open. The 97+ t-stats do not block water pump bypass coolant flow.

Jim

[moondoggie]

Good Day!

"What's this got to do with a dual t-stat diesel setup? Nothing. But, wouldnt shoving the coolant through the radiator faster allow less time for cooling? I have always been of the mindset that letting the coolant move slower through the radiator allows more time for the temp to drop before returning to the engine."

(From my initial post) "Again from memory, this upgrade increased flow through the block ~ 75%, & flow through the radiator ~ 9%." If this is so, they're NOT increasing flow through the radiator much at all, but LOTS through the block, reasons being explained (THANK YOU!) in previous posts by others, which is why I started this topic in the 1st place. :

Blessings!

(signature in previous post)

[GMC Hauler]

Moving water through too fast can cause an overheat issue in hot weather as the radiator does not have time to dissipate the heat.
The dual stats allow each side of the engine to open the stat when the temp is optimum.

Be careful, it is not true that increasing the flow speed (or flow rate) causes overheat issues. This is contrary to the laws of thermodynamnics. The faster the flow rate, the more heat that can be dissipated.

[DmaxMaverick]

Be careful, it is not true that increasing the flow speed (or flow rate) causes overheat issues. This is contrary to the laws of thermodynamnics. The faster the flow rate, the more heat that can be dissipated.

True. Removing the stat removes the restriciton necessary for the bypass to work. Without the stat, unheated coolant get recycled through the radiator. This does not apply to all engines. Some are uneffected, others can be catastrophic. Depends on the cooling system design.

[Robyn]

D max
It has been proven many times that in automotive scenarios that the radiators, depending on their construction and "condition" will not respond to the faster is better theory. Many times with automotive radiators you cant get the heat to transfer from the water fast enough to be able to get rid of it.
I agree that if the heat is in the radiator fins you can blow it off, however due to the marginal sizes of vehicle radiators so many times you will very often surpass the optimum heat transfer time needed and the water will carry more latent heat back into the engine than if you run the flow a little slower to allow for better transfer.
This also does not even consider the condition of the core (Skunked up with crud that is insullating it)
** Under idea thermal conditions** but we dont ever have ideal in the truck world.

Robyn

[DmaxMaverick]

I disagree, and so does thermodynamic law. I thought the same as you for a long time, and the results of my experience pointed to it. However, there is more to exchanging heat than just the radiator. The coolant has to pass through the radiator to be cooled. In many cases, including the 6.5, removing the stat prevents the bypass coolant from ever getting to the radiator. Also, there are other demons at play. Improper dynamic properties can also cause pump cavitation. Automotive water pumps are a very weak centrifical design. Their function is simple, but easily foiled.