How hot is too hot?

[CBRF3]

I've seen that. Certain engines can have localized hot spots that would cause the flash boiling scenario. I don't think our IDI's are one of them though.

In my experience, most engines that appear to be flash boiling actually have cracked heads/blocks or a failing head gasket. All of those will all put air in a cooling system, and since air doesn't transmit heat as well as water, the thermostat closes, vapor locking the cooling system, causing an overheat. Or it causes the radiator cap to open, lowering system pressure, causing more boiling.

You can plug it, I don't really care, but drill a small hole in the plug to vent the air trapped behind it when you do so.

when you crank up the fuel on our motors and go into mountains under hard load aka low air density our EGT's spike fast causing coolant to boil ( because alot of coolant in the head is used to cool the exhaust ports ) very often risking the thermal runaway. I have had this happen to 10 motors of mine and these were studded and built properly motors that pretty much no cost was spared AKA done right and built to the hilt and overkill. So saying a faulty head gasket was issue when it was built overkill running a stock 7.3 turbo injection pump turned up and a HX40 turbo with intercooler power stroke rods the 10thousandths raised wrist pin pistons and no more than 18psi boost and these were decompressed motors mind you so 18psi was not the issue and these motors could hold around 25psi+ literally all day long but I dialed them back and I didn't have the fuel to push above around 18psi.

I believe i need to help explain this I had a fleet of farm trucks and logging trucks built around these 6.9 / 7.3 IDI's for simplicity and reliability over the first gen powerstroke and Dmax's of the day I wanted to keep it analog with as little electronics as a issue considering the ones of that time that were electronic were a nightmare to keep going the cummins 12 valve was a option but the parts availability at that time was slim yet our old IDI's we could go into pretty much any autoparts store and get anything we needed anywhere in the country and not have to find a rare cummins dealer of that time we could be in the back woods find a napa or oriely's / IKT and such and get our parts literally same day or over nighted not so much with the cummins 12 valve at that time.

 

[Clb]

So 5 pages later...

Ok has anyone done a 3 valve bypass on the heater core?
I don't see proof positive on blocking the bypass EITHER way....
@CBRF3
Perhaps I missed it?
Did you block the bypass or not?
$3k in dyno time should have given a solid answer.
Gunna go reread the thread as I'm fighting heat issue's on a 60k original mile truck/eng.

 

[CBRF3]

yes I blocked the bypass behind thermostat and removed the check ball in the thermostat neck so always have a steady amount of fluid bypassing to the radiator so no air can build up once our engines are warmed up the thermostat never fully closes it always stays partially open. So pressure restriction on the coolant really is not a issue and only effects things when motor is cold and at that time you really don't want coolant to bypass in the block thru the port behind the thermostat which bypass's straight to the water pump you want it to run thru your heater core then back to the water pump by doing this I have found my coolant temps and oil temps stay much more stable and much lower under heavy load / towing. I pull a fairly large / heavy fifth wheel camper and tow vehicles / equipment and such nearly daily and have for years this mod has greatly reduce my engine oil temps because the coolant being fed to the oil cooler is cooler to start with and not nearly boiling recirculated coolant that is bypassed behind the thermostat.

I have tested coolant temps before and after the oil cooler and oil temps also while working the engine real world testing also tested multiple areas of the block realtime for long hauls also have tested my oil temps in multiple areas including oil pan itself yes i welded a bung there and inserted thermal probes and added one to my oil bypass filter system that runs off the ear of the block near bell housing on drivers side of motor in short tested it thoroughly for thousands upon thousands of miles daily under heavy load. My old work truck is ugly as sin but its my test platform I have been hammering for a very longtime and is my main tow pig i use and trust I just hauled my fifth wheel camper loaded with tools and equipment and such weighing around 17,000+lb's not including my 7,500lb truck from Tampa Florida to southern Illinois and pushed it hard and had no issues and it pulled it like a champ.

 

[CBRF3]

I forgot to mention I drill out the hole where the check ball goes in the thermostat upper housing and drill the spot on block to match I just remembered this it allows more bypass to occur and eleviates alot of issues I say this because i just did the mod to my other 6.9l and didn't drill that out and it would try to overheat not actually overheat but would try under hard load high RPM's with that drilled out it no longer does this.

 

[laserjock]

Just to catch this thread up, I did fit the 6.4 fan and fan clutch with adapter bushing. I have one trip on it and that combination seems to work pretty well. I haven’t put it to the max stress yet (I-68 with the AC on) but on the trip to Michigan last fall, kicking the fan on kept it cool enough to actually drive it. The PA turnpike is not as steep as I-68 but there are a few decent pulls. I do need to go to a progressive controller for better results.

 

[JPM4]

I know with your extensive effort, it's not this, but just to add to the conversation... What ratio antifreeze/water are you at? I had similar issues on a Perkins diesel in my tractor. The float/ball type indicators are worthless. I had way too much antifreeze. I got a refractometer type indicator and ran a correct 50/50, and it helped my overheat problems. With the higher antifreeze ratio, the coolant liquid temps were running normal, but actual block temps were hitting 240 in certain areas. The coolant wasn't pulling heat out of the engine efficiently due to incorrect ratio. Has anyone tried (at least during summer months) running higher water content?

I also converted over to Chevron ELC, no more checking SCAs.

 

[Booyah45828]

We did that dirt racing years ago. Actually ran straight water with a corrosion/lubricant additive. Cars were always in a heated shop though so we could get away with it. Cooling is way better with water, but I honestly wouldn't change from a 50/50 ratio. At least run enough of a mix to protect you for your coldest weather. I wouldn't run a summer and winter mix, it'd only cause trouble if you'd forget or get late on swapping it out.

 

[Old Goat]

This remind me of a Mechanic we had at work back in 1968 when I started working for the Division of Highways which later became Cal-Trans in Ca.
He would drain out the Coolant in the spring and run Water Soluable Oil, then in the Fall drain and switch back to Anti-Freeze.

Goat