6.5 dual stat cooling upgrades back in stock!

[Robyn]

A flux capacitor....that's the ticket

Once installed between the two wires on the CTS everything is just sweet...


I'm with ya RJ
ANSWERS TO THOSE QUESTIONS are "Unobtainable"

[phantom309]

On the bright side I think we are past the rear head bypass BS that a certain vendor has at a Rendezvous a decade plus ago touting as the latest.

I'm almost afraid to ask why the four corner cooling mod is no good,?
I ran two coolant lines from the back into the themostat housing,.i drilled and tapped etc,.. inmho it made a difference,.
I read quite a bit from the aussie forums and their conclusions and their mods were different than north american mods. Drilling extra steam holes in the fire deck etc,. Australia has some very hot country ,.
The gist of their idea was the extended soak time of the coolant in the heads from the long trek from front to back to front again, caused steam bubbles leading to water pump cavitation. I am definitely not as smart or as innovative as Some people on this forum,. But for me the extra lines helped my old dually

Nick

[ronniejoe]

I ran two coolant lines from the back into the themostat housing,.i drilled and tapped etc,.. inmho it made a difference,.

Please take no offense to any of this because none is intended.

If you did as you say here and allowed coolant from the block off plates at the back of the heads to go directly back to the front crossover, then you removed cooling flow from your cylinder heads.

The coolant leaves the pump outlets and enters the front of the engine block on both sides. It is pushed to the back of the engine while absorbing heat from the cylinder walls. At the back of the engine, it flows up through the kidney shaped core passages into the heads and is pushed forward absorbing heat from the combustion chambers along the way to the exits into the crossover/thermostat housing. There are core passages in both the heads and the block decks between and around each of the cylinders which could allow coolant to short cut the circuit. Some does, but it is limited by the head gaskets, which have very small metering holes in them which line up with the larger core passages. These holes are necessary to keep air pockets from forming during initial fill of the engine with coolant. Without these small holes, air could be trapped between cylinders near the deck surface. With them, air is displaced through the holes, into the heads and out the bleed port on the thermostat housing allowing a complete fill of the system. Once full and in operation, these holes are no longer necessary, but they cannot be removed or closed without significantly increasing the complexity of the machine, so they allow a very small percentage of the coolant to short cut the circuit.

The cylinder heads are obviously where the most of the combustion heat energy is concentrated, therefore, this is where the coolant picks up most of its heat energy in the flow circuit. By allowing a significant portion to bypass the heads and return to the thermostat housing, you have reduced the flow through the heads where it is needed most.

I can see the potential for lower coolant temperature readings at the gage sender location, however, that are not indicative of the actual coolant temperature at other places in the engine. The gage sender is located near the front of the driver side cylinder head. Theoretically, with the as engineered cooling circuit, this is where the coolant temperature should be highest as it is near the end of the loop after passing by all of the heat transfer surfaces in the engine. There should be no higher temperature any where else if there are no blockages or other flow problems. Since you have bypassed a significant portion of the coolant flow which should pass through the heads and routed it to the front of the engine, the gage sender will likely see a lower temperature because of heat transfer through the fluid to the cooler fluid entering the crossover from your bypass set up. The head loss in your bypass lines is likely much lower than the head loss through the passages in the cylinder heads, so you might even be seeing partial backwards flow of bypass coolant into the front of the cylinder heads. This likely means that some coolant is dead headed around the middle cylinders of each head. If you could put your sender between the number 5 and number 7 cylinders (or the number 6 and number 8 cylinders), you would see significantly higher temperatures which would likely scare you.

If you want to improve your cooling system, figure out a way to take the pump discharge and push it through the heads first and return it from the block. This is the "reverse flow" approach that is common on newer engine systems. This is a difficult task with the existing architecture of the 6.5.

I recommend that you remove your bypass lines and plug the holes that you made and let your cooling system work as it was engineered to work.

[ronniejoe]

Poor crank

The cast cranks in the 6.5 get a bad rap that they really don't deserve. They're actually pretty good. The crank that I used in my Suburban until right before it was totaled was from the warranty engine that was installed at about 65,000 miles right after I got the truck. I ran it in that engine almost 100,000 miles until it broke the number 6 piston. I had that crank index ground (.010" under) and balanced and installed it in the new engine that I wrote the articles about. It ran another 125,000 miles and would still be running if a catastrophic oil leak had not caused a spun #7 rod bearing.

During that time, the truck was towing something, usually heavy, for at least 50% of the time. With the new engine, I had boosted power to a level not seen in any other on-road 6.5 L Diesel, and I used it.

I have replaced it with a new forged crank from GEP which is now in my K3500 Dually.

Kennedy has said this and I have come to the same conclusion: broken crankshafts in these engines are secondary failures that are the result of main web cracking which allows excessive deflection of the crank. If the main webs don't crack (splayed mains), the factory cast crank can take a lot of abuse with no issues.

[sctrailrider]

I see Walt has a single stat that supposedly outflows the dual stats. How a conventional reverse flow even comes close to the flow area of a balanced sleeve is beyond me.

On the bright side I think we are past the rear head bypass BS that a certain vendor has at a Rendezvous a decade plus ago touting as the latest. I also hope we are past the 70% flow bias in the OE water pump BS, but I do see Leroy has a "balanced flow" water pump

Sad thing is uniformed people are buying it.. I think it's high time someone with the data speaks up on the various other forums...

[Kennedy]

On the single stats how about removing the bypass closing disc from the thermostat altogether? Only the early 90's trucks had them and they had the most issues albeit at higher power levels than their predecessors. The water pump can easily move may times more water than the bypass circuit can flow.

Still not a substitute for the dual stats but...

[phantom309]

The water pump can easily move may times more water than the bypass circuit can flow..

Ronnie this is where, in my opinion i think that the water pump has plenty of flow, when the stats are closed you are allowing for a quicker route time thru the engine,.cold water water from the rear of the heads mixes together with hotter water from the front of the heads right at the tStats, keeping the stats closed untill a more even temp of water (i.e even after mixing the stats open at set temps) what is attained in the use of a water pump that flows a lot more volume if you choke the flow? proper proof of either theory would come down to measurements.
flow from front of heads with no rear head bypass lines and water exit temps
flow from head of heads with rear bypass lines and water exit temps
time to achieve working temps
engine would need to be on a water dyno to simulate steady load.

jmho
nick

[ronniejoe]

Did you read my post?

You can do whatever you want with your truck. I'm just offering you some sound advice. When you overheat the center two cylinders on each bank and gall a piston or two, then maybe you will appreciate the engineering behind the cooling system.

I've explained very clearly why you might be seeing lower temperatures on the gauge with this setup. I've also explained why the temperatures at the longitudinal center of each head are likely significantly higher than what your gauge is reading. For this reason, the "bypass cooling" is a bad idea and I recommend that you remove it. It is your truck, though. You do what you want.

[phantom309]

Did you read my post?

You can do whatever you want with your truck. I'm just offering you some sound advice. When you overheat the center two cylinders on each bank and gall a piston or two, then maybe you will appreciate the engineering behind the cooling system.

I've explained very clearly why you might be seeing lower temperatures on the gauge with this setup. I've also explained why the temperatures at the longitudinal center of each head are likely significantly higher than what your gauge is reading. For this reason, the "bypass cooling" is a bad idea and I recommend that you remove it. It is your truck, though. You do what you want.

Yes i did read your post,. I also sense your lack of patience regarding someone else's view point that does not correspond to your own,.

No malice intended.

Your view point of the 4 corner coolant flow, gives the impression that the block will be starving for coolant due to added coolant flow paths
Basic hydraulics , liquid will always choose the easier path. Do you think the two lines from the back of the heads carry more flow than what is passing to the front of the heads thru the head castings? Do you believe that the water pump will not produce enough pressure/volume to support two extra paths of flow? The extra flow paths are being re-introduced to the t stat housing thereby keeping pressure up and keeping exit volume the same. If the rear lines dumped into the rad i could see your point.
Would the water pump rated at X flow, flow more or less depending on its restrictions?
The idea of drilling the fire deck for better flow volume of coolant has merits too ImHO. According to the author in australia that wrote about it, it was a necessary mod to finally cure his overheating problems. Head gaskets already had the holes but the block didn't. He increased volume by decreasing restriction
Factory engineers work within time and cost restraints. Improvements have been made to numerous systems on vehicles to address engineering shortcomings.
Small oil capacity, small turbo, small water pump, inadequate air flow across the rad etc etc , all things that have been addressed and are now common place upgrades and improvements.
Yes it is my truck,. Yes i will do as i want,. With or without your respect.
I respect your knowledge and pioneering accomplishments,. But unless you have documented measurments of temps and flow volumes your theory has as much merit as mine inmo.
Carry on, i'm finished here,. I'm off to re read why the back two pistons had to have more clearance due to excessive heat or something like that.

[More Power]

More info on bypass cooling:
https://www.thedieselpageforums.com/tdpforum/showthread.php?t=25230