1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

How hot is too hot?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by laserjock, Apr 26, 2021.

  1. laserjock

    laserjock Almost there... Supporting Member

    Posts:
    8,805
    Likes Received:
    3,071
    Joined:
    Nov 20, 2012
    Location:
    Maryland
    Good thoughts guys.

    Most of the answers are in my build thread.

    Down shifting to 3rd really does not help that much. I think it’s pretty much hosed by then. I made it to the top but the water temp really did not drop.

    Top of the list is timing. My meter is a dti tech time. It has worked well in the past but the last couple times I’ve used it, I have not seen the pump timing behavior I’d expect. I see less timing at low rpm rather than the advance coming out at 2k. I saw that once before with my other pump too. If someone has any thoughts on that, I’d love to hear them.

    I am currently pulling the turbo water from the back of the drivers side head. I did put a restrictor in that line because it seemed possible I was robbing too much water from the head. I am running a coolant filter as well.

    I know my heat load is more than stock but my camper is not that heavy. I weighed the whole rig first time out and truck and trailer with enough tools for a full engine swap and rebuild (those who remember that rally will know why I did that) was only ~12,500. I might be 13000 gross now with the generator and the extra battery but I doubt it.
     
  2. 03wr250f

    03wr250f Full Access Member

    Age:
    32
    Posts:
    482
    Likes Received:
    193
    Joined:
    Jan 13, 2014
    Location:
    Hamilton/Montana
    Seeing everything I think you are on the right track.

    I wouldnt worry about what timing does below 2k. You will chase your tail on mystery numbers below 2k is my experience. So I just run it to 2k and time it, drive it, readjust and repeat.

    My thought was pull in 3rd gear (closer to 45 mph up the hill the whole way and see how it behaves. It certainly isnt the cool or fun way to do it, but I may work/ bandaid the issue.

    I truly think your biggest issue is the fan clutch. I would try swapping to a new one, heck maybe even find a used oem. I know mine locks at like 210 or 215 with would be huge in helping you stay cool since it would be activating likely at mile 1.5 of a grade vs mile 4 (or whatever the case may be)

    Sent from my SM-A015V using Tapatalk
     
  3. laserjock

    laserjock Almost there... Supporting Member

    Posts:
    8,805
    Likes Received:
    3,071
    Joined:
    Nov 20, 2012
    Location:
    Maryland
    I think the fan clutch is fine. It is a new motorcraft unit and it is coming on. I think the heat is not getting to the radiator fast enough to bring it on when I need it to. Remember it’s the radiator temp that brings the fan in not the temp in the block. At least for now....
     
    Cubey likes this.
  4. CBRF3

    CBRF3 Full Access Member

    Posts:
    142
    Likes Received:
    108
    Joined:
    Mar 22, 2020
    Location:
    Riverview Florida

    I would add a oil bypass filter using the ear on the side of the block on drivers side as the feed then add a restrictor on the feed into the bypass filter mounting base. I like to slightly drill my fittings and insert a small motorcycle carb jet as the restrictor then on exit of the bypass run it into a large trans cooler and mount this in front of the radiator believe it or not it makes a huge difference on temps as the oil is used to cool the pistons hince piston squirters. So your oil is taking a massive amount of heat with it thru the system ( and often overloading the factory oil cooler ) and this is a easy mod to really help get your temps down where you want them 205f-225f anything above is bad and running into massive oil breakdown territory which leads to more friction and more heat and with this mod your oil is filtered better meaning less engine wear and tear also another piece of advice run the motorcraft FL1995 powerstroke oil filter it helps also by adding capacity and better filtration over the regular normal filter.

    I want to also point out the port behind the thermostat use a small freeze plug there and sink it as deep as can so thermostat opens all the way still and remove the check ball in the thermostat upper radiator hose neck and this will divert all coolant thru rad and keep it from going directly back to the water pump. The reason I say this is when your loading the coolant hard and get near boiling you will get air pockets these pockets go back into the water pump and cavitate and flash to steam and can make our cooling system go into thermal runaway.

    I want to point out ford pushed international not to invest to heavily into the cooling of our motors and instead opted them to detune our motors 160hp-190hp don't take alot to cool LOL and they didn't want to spend the money or time in R&D to go much above this as at the time they didn't have alot of competition or incentive in the pickup market for a diesel engine but when they did they came out with the powerstroke to raise the power and torgue and efficiency.

    These mods I have used for years and it gets my temps down in a very safe range no matter how hard I push these motors I also advise a coolant filter in the heater core circuit to filter out foreign contaminants and such and help reduce risk of block / cylinder wall cavitation.
     
    Last edited: May 4, 2021 at 11:49 PM
    tjsea and steve phillips like this.
  5. Cubey

    Cubey Full timer RVer

    Posts:
    2,479
    Likes Received:
    804
    Joined:
    Oct 18, 2017
    Location:
    USA
    Higher gear = lower rpm, lower water temp, higher EGT

    Lower gear = higher rpm, higher water temp, lower EGT

    So, yeah down shifting is just going to make the water even hotter. If you're in third (C6), fourth (E4OD), or fifth (M/T) and overheating, or nearly so, pull over. That's your only option really. Letting off throttle some might help a little but the last thing you want to do is downshift and keep driving.
     
    CBRF3 likes this.
  6. CBRF3

    CBRF3 Full Access Member

    Posts:
    142
    Likes Received:
    108
    Joined:
    Mar 22, 2020
    Location:
    Riverview Florida

    Exactly right
     
  7. Cubey

    Cubey Full timer RVer

    Posts:
    2,479
    Likes Received:
    804
    Joined:
    Oct 18, 2017
    Location:
    USA
    Unless... You have a Triton gas engine. They are odd. If they overheat hard, they shut down the fuel and spark to half of the cylinders and continue to run, abeit at high rpms with poor power. The idea is that it uses air to cool it so you can continue to drive to a safe location to stop. I'm not sure if it alternates which it turns on and off or what. I had it happen on a 97 E150 that sprung a coolant leak on a hard line and ran out of coolant. I limped home that way about 1/2 mile. Once it cooled overnight, I refilled it with tap water from the garden hose and it was fine. Didn't blow the engine. I had the hard line replaced and had 50/50 put back in. Yeah that's off topic but still an interesting tidbit.
     
  8. jwsfarrier

    jwsfarrier Full Access Member

    Age:
    51
    Posts:
    168
    Likes Received:
    23
    Joined:
    Sep 21, 2014
    Location:
    Wilsonville,OR
    What about the cooling mod Wes does. Im sure the last thing you want to do is pull the heads. Mostly just curious if that would make make any difference .
     
  9. IH-GM IDI

    IH-GM IDI Registered User

    Posts:
    22
    Likes Received:
    10
    Joined:
    May 6, 2020
    Location:
    La pine oregon
    Do you have a steam line for your turbo?

    Totally different animal but I had a GM 6.5 service truck turned up on fuel and boost packing 14,000lbs around for 350,000 miles. On long pulls I'd get gas pockets in the head that would cause the Tstat to close up and REALLY get things cooking.
    After I did the dmax fan mod and aluminum radiator things were better but could still get thermal run away on long climbs the cure ended up being steam lines (3/16) that bypassed from the heads into the pressure tank, basically a de-gas setup.

    Also as far as the matter of to hot. When international started casting the 6.5 for GEP in 2000-2001 the spec for a out of service motor was bumped up from 215F for the GM castings to 250F on the improved "optimizer" Navistar castings.

    Again totally different animal, but if there's a diesel that's hated for overheating it's a turbo'd 6.5
     
    CBRF3 likes this.
  10. CBRF3

    CBRF3 Full Access Member

    Posts:
    142
    Likes Received:
    108
    Joined:
    Mar 22, 2020
    Location:
    Riverview Florida
    True but our compression is much higher than the 6.5L and our motors have a thinner cylinder wall so we have less surface area to transfer the heat to the coolant and less buffer and our heads are a totally different beast to the 6.5L. The 6.5 had a issue due to lack of coolant passage size and a more compact cooling jacket which was a perfect storm for a steam generator our 6.9 / 7.3 IDI's were built well in the cylinder head department ( 6.9 has a better design ) as far as cooling passages and such but the bypass to the water pump behind the thermostat was a issue that caused the steam runaway issue similar to the 6.5L. The point is once you hit that point it goes into thermal runaway and there is no simple way of knowing when it was starting hince my mod to block that passage with a freeze plug sunk as deep as can to allow the factory thermostat to work properly and eliminate the issue at its source.

    I explain it all in this post hopefully its understandable along with offers some very worth while info and advice https://www.oilburners.net/posts/1081415/
     
    Last edited: May 4, 2021 at 11:50 PM
    tjsea and IH-GM IDI like this.
  11. IH-GM IDI

    IH-GM IDI Registered User

    Posts:
    22
    Likes Received:
    10
    Joined:
    May 6, 2020
    Location:
    La pine oregon
    The bypass 'delete' does make good sense for a all out performance application and I do believe it has been proven in the gasser V8 world to be effective for such. I however disagree with a total diversion to the radiator for something that gets driven on the road like a normal vehicle would be as it doesn't allow the coolant to cycle within the engine and promote proper warm up and heat retention.
     
    Booyah45828 likes this.
  12. tjsea

    tjsea Full Access Member

    Age:
    33
    Posts:
    649
    Likes Received:
    374
    Joined:
    Jan 8, 2007
    Location:
    Lickdale, PA
    I've actually wondered about this myself. I know the psd uses a bypass blocker on their thermostat and I've always read that if someone installed a thermostat without it in a psd they would overheat under load. I've often wondered that the lack of it in our engines may be the root of the issue, but had never really come up with a way to test the theory before. This sounds like a good way to test that idea.



    Sent from my SAMSUNG-SM-G890A using Tapatalk
     
    IH-GM IDI likes this.
  13. Booyah45828

    Booyah45828 Full Access Member

    Posts:
    380
    Likes Received:
    206
    Joined:
    May 2, 2017
    Location:
    Ohio
    I don't like plugging the hole under the thermostat on any vehicle. That hole serves as a bypass when the thermostat is closed, allowing the coolant to recirculate through the engine heating the entire thing up. Plugging that hole stops flow back to the water pump, and forces all of the bypass coolant through the heater core. If you have valves to shut the heater core off, you'll deadhead the system.

    If you have the proper thermostat installed, and it's functioning correctly the bottom of the thermostat should effectively close that hole off when it is fully opened.
     
  14. CBRF3

    CBRF3 Full Access Member

    Posts:
    142
    Likes Received:
    108
    Joined:
    Mar 22, 2020
    Location:
    Riverview Florida
    The problem is under extreme load aka towing along with upgrades for power and then you get a overheat. The flash steam will cause thermostat to close and then steam is sent directly into water pump thru the bypass because thermostat closed from steam flash cooling. This causes a thermal run away turning the engine into a steam generator and well steam won't remove the heat and then we have seconds to shut it down or well we have a ruined motor because our piston design ( cast aluminum and no steal top ) and fact our compression is so high we end up in the red and then beyond well pistons swell pinch a ring in the ring land and well crack rings and then they gouge our cylinder walls killing our motors or piston tries to seize from swelling and well our inner rods become outer rods and we get a ugly window into side of our block LOL.

    the reason the flash steam will cool the thermostat is because the coolant on other side of thermostat is cooler than the steam and steam when it recondenses it flash cools tricking the thermostat to close causing that bypass hole to be open meaning thermal runaway steam is a crazy thing when it flash cools it rapidly takes heat away so much so its pretty amazing to be honest.

    The key thing here is when people use a shut off in the heater loop theyre doing same thing theyre dead heading all the water pump pressure. I suggest a ball valve bypass for a heater core not a full on shut off ever you want a slight bit of flow thru the heater core at all times otherwise you get sludge and well acidity build up in the heater core asking for a failure when you decide to use the heater. Who wants to have to change a heater core in middle of winter or have that heater core fail while happily towing up a mountain keep flow in the heater core always even if is just a little bit to avoid this.
     
    Last edited: May 5, 2021 at 10:08 AM
  15. CBRF3

    CBRF3 Full Access Member

    Posts:
    142
    Likes Received:
    108
    Joined:
    Mar 22, 2020
    Location:
    Riverview Florida

    The thing is with our 6.9 / 7.3 idi's the bypass plugging I advised doesn't effect normal running temp it still runs the same normal temp range just takes a slight bit longer (1-2 miles further to hit normal operating temps ) to warm up after warmed up it runs in the perfect temp range exactly what your thermostat is regulating it to there really is no downside to this mod only positive and well alot of added safety net for if you do overheat so you don't go into steam generator mode. So long as coolant is in the system and water pump is functioning and well your cooling fan works your set but it will help alot with towing coolant / engine oil temps as your factory engine oil cooler is dependant on your coolant temps if can keep coolant temps in sub 225f your engine oil temp will be around 10f-15f above this and stay under the 250f red zone for engine oil temps.

    The issue is when your coolant temps go over the 225f+ your oil temps can spike above the danger zone and cause oil to thin out making more metal to metal contact meaning more friction and even more heat dumped into the coolant / oil so PLZ understand we are talking about our old engines that were never designed for above 160hp-190hp but we all know we turn them up to the 225-250hp range and above which is far outside of theyre design spec so little hacks like the one I advised can be a engine saver and offer a good amount of safety / security for the added load / heat our setups were never designed for.

    I think you forget about the heater loop its a diversion back into the water pump and the coolant bypass in the upper radiator hose neck above the thermostat so you have a recirc back into water pump and a divert to rad also at all times the one to the rad will allow for burping any air out of system making filling the loop and burping the motor same as normal factory setup again no downsides and not really anything making it more complicated just safer and less prone to thermal runaway.
     
    Last edited: May 5, 2021 at 9:49 AM
    Farmer Rock, IH-GM IDI and laserjock like this.

Share This Page