The problem is that the heat input is NOT a constant. Flow variations around the cylinder liners and cavitations around the liners as a product of fluid flow patterns make hotspots unavoidable. Remember that coolant is introduced into the head at one end; as it moves through the head, it warms, and so one end will ALWAYS be hotter than the other. The Detroit Series 60 introduces coolant into the block between cylinders 3 and 4, at the bottom of the cylinder liners. Guess which liners fail/perforate first?

"Properly" functioning coolant will perform "nucleate boiling" at high temps; it's the most efficient heat transfer into a fluid from a hot surface. As I understand it, what happens when the pressure isn't proper is that the nucleate boiling zones get very large, and the nucleating sites grow larger and somewhat more unpredictable. Larger bubbles form, at a lower temperature, and transfer MORE heat. But since the boiling process doesn't CONTINUE further downstream in the coolant, it never pukes. The result is an increase in transient temps while not showing any other signs of overheating.

Contributing to this is that there's almost NO overhead between the thermostat's opening temperature and the boiling point of unpressured water and/or coolant. The coolant in the block is boiling (or about to boil) by the time the thermostat opens. When the thermostat opens, the hot/almost-boiling coolant mixes with the cold coolant from the radiator, and brings the temps WAY down, and keeps it from puking.

This year is the first year that the Freightliner did not get a new cap as a yearly maintenance item; not because it didn't need it, but because the last one I installed was a 16-PSI cap whereas the "normal" one is a 13-PSI cap. I get a few free months out of the stronger cap. (What I find amazing is that only Detroit dealers have the correct pressure cap; Freightliner dealers do not.) Caps routinely run in the $15 range. And remember that sometimes just because a cap is new, doesn't mean it's good.

You're welcome.

-blaine

 

Great stuff to think about . I think I will try to find some time to look into the boiling points and heat capacities today!

One thing that sticks in my gut though is that he should not be at a high heat load when cruising. Also, for a 50/50 mix, he SHOULD be quite a bit away from the boiling point, the thermostat begins to open at 190 to 195 *F. With the overall temps the op is describing, the thermostat should be fully open.

Eventually the OVERALL return temperatures (not localized) would reflect only the overall heat transfer, not specific to the type of heat transfer (again, unless flow was affected). Specifically, the oil temperature gives a picture of the coolant system - the coolant it sees has not gone through any engine passageways IIRC. If the new oil cooler is not plugged again, then the oil temperatures being elevated along w/ the coolant temps seem to indicate a flow issue or a high initial coolant temp.

 

I'll expound on another point here, the charge cooler. I mentioned earlier that a charge cooler will/may have a "leakdown spec". That means that the cooler can actually leak a little and still be "within spec" for pressure. There's usually enough "overhead" in the fuel injection fueling map to keep up with a slightly leaking charge cooler. Performance isn't usually affected negatively; indeed, improved performance will result since there's extra fuel being applied. However, this extra fuel generates a LOT of extra heat.

The engine isn't SEEING any extra load, but since the charge cooler is "seeping", it's being FUELED like it's loaded, even when it's not.

The Freightliner smacked me around quite hard last month because of this very issue. Driving with an empty deck in 50-70 degree temps on flat, level ground, 60-70 MPH, and the cooling fan was coming on occasionally.

Note that the Detroit ECM is programmed to engage the cooling fan to reduce IAT's when they get high, and the hot turbo (from the extra fuel) was keeping the charge temps high enough to make problems. I replaced the charge cooler and the problems went away almost instantly.

I'd be interested to see what his IAT's are, to see if there was any correllation in the programming. I know that on the EGR-based Series 60's, Detroit uses the cooling fan to reduce IAT's when they get high.

-blaine

 

Very interesting.

Also - on the other topic - it took a drive to work for me to "get" that you are saying at lower coolant pressures, there really is more heat being removed from the engine than at higher coolant pressures (due to increased nucleate boiling) with all other things being constant. I certainly have not heard this perspective before, but I have enjoyed the learning and your posts.

 

and this is were I was headed yesterday. also keep in mind the the eot followed as a result of liquid to liquid cooling. I know it sounds kinda basic.

 

With all the silicates and other additives in coolants these days, I get a little concerned when I hear the term nucleate boiling used. It CAN lead to solids precipitating out and plugging up small passageways. Just something for me to "chew on" for a little bit more.

Anyways ...........

Here is a basic troubleshooting procedure that I found on another site (comments are welcome!):

A good way to check for a weak water pump:

1. Monitor your EOT and ECT.
2. On a cold start both of them will be pretty close together.
3. Go out for a drive, both the EOT and ECT should stay pretty close together, usually the EOT will lag behind 10-15 degrees if everything is normal.
4. As the engine gets closer to operating temp the EOT will catch and pass the ECT, but should stay within 15 degrees of the ECT.
5. If you are running down the road after a cold start and your ECT takes off rapidly up to 200 degrees, say within a mile or 2, and your EOT is lagging way behind, say like 120 degrees, you have a lack of coolant flow, probably a bad water pump.

 

wow you guys no your S#!%! you lost me awhile back...but I am starting to understand what your talking about.

I cleaned out the radiator stack a couple of months ago after reading a post about a truck running warm...didn't notice any temp change.

I have a few degaus bottle caps laying around and I have tried them both and no change...I had bought and replaced those a few times before the HG's went...(thinking that was my problem) I had thought about going and getting a new one but I haven't yet...they also replaced my cap with a new one when they did my HG's...it could be bad even if new I guess...

bismic- I have noticed when driving to work in the morning (12 miles mostly flat) that my ect will go up to 195-196 then drop to about 188-190 about half way there and the eot will lag behind for quite a while only getting up to even with the ect by about the time I pull into work...I regularly see my ect up to 190ish and my eot is only about 170, but that is only for a few minutes till the eot catches up...

 

jlmotox -

What you described, does not really sound like what was described in the troubleshooting procedure. I wonder if you might consider cleaning your coolant system out w/ VC9 ..... Also, be sure that the radiator fins are all clean and clear AND make sure your coolant strength is sufficient.

Back to theory:

Here is a link to an article that describes nucleate boiling in radiator applications. It states that nucleate boiling actually REDUCES the heat transferred.

Joe Guilbeau's Radiator Theory page

I pulled the paragraphs below from the article.

Here is a quick experiment so that the reader can visualize the principals of Nucleate Heat Transfer, where the water passages near the exhaust manifolds and exhaust valve surface areas get hot enough so that Nucleate Boiling will take place. Essentially, bubbles form at the surface of the heated metals, and are then swept downstream where they condense in the coolant fluid.

To illustrate this concept, take a pot and put some tap water in it. Set the pot on the stove and bring up the heat until steam bubbles begin to form on the bottom of the pot. Keep the heat steady, so that a pretty good steady stream of very small bubbles are forming on the bottom surface of the pot while keeping the pot not nearly at a full boil.
This will approximate the exhaust water-cooling passages on the AMC motors, and is a pretty good illustrative concept of Nucleate Boiling. Grab a big spoon and stir the water so that it flows in a circular clockwise or counterclockwise rotation very, very slowly.

As you begin to increase the speed of the circular rotation of the tap water, you will notice some trends with experimentation of the rotational speed of the fluid. A faster circulation prevents steam bubbles from forming, and a slower circulation results in increased steam bubble formation. This is Nucleate Boiling on the surface of the pot.
Some conclusions should be forming, namely that increasing the flow rate of water over the surface of the bottom of the pot in contact with the gas flame or electric heating element inhibits steam bubbles from forming.

This is important for quite a few reasons, namely that once steam bubbles begin to form, they isolate the metal surface from contact with the fluid. After all there is a steam pocket (bubble) that is forming. This bubble results in less cooling fluid being in contact with the metal, which in turn gets hotter. Water as strange as it may seem, is a better heat transfer medium than steam. The steam bubbles actually form an insulating barrier to prevent appropriate heat transfer to the liquid coolant and thus the metal surfaces get even hotter, and in turn the coolant eventually gets hotter and perhaps begins to boil and steam.

and one more interesting article -
(I think this one is more accurate as it states that nucleate boiling in the hottest parts of the engine does help heat transfer, but it can quickly "insulate" and reduce heat transfer if the vapor film gets too large)

http://www.4g63turbo.com/tech/tstat.html

 

Frankenbiker, Bismic, and Cheezit. Great information.and great reading. I have heard about the boiling around cylinder walls (from mechanics since I was a kid in school) On wet sleeve engines. International tractors were more prone to this problem than the John Deere motors.It would be interesting to know how the coolant filter on these engines help elimanate this with there water conditoning properties. I wonder does it help break the cohision of the bubbles so they stay smaller or non existant? And isn't this the same analogy as electrolisis being the bubbles eat away at the liners? any insight to this from you guys.? Just trying to understand and learn more about these diesel engines. Sorry for straying from the original thread.

 

MotorMax Cooling System Booster

Here is what I purchased to stop Nucleate Boiling before I knew what Nucleate Boil even was. I learned about it after I purchase Cold Fire for my water based fire extinguishers so I could fight a fuel fire if needed and 6X the effective gallons of water.

I have put one quart of Motor Max in the 236 Perkins in the tractor but not worked it yet. I have four more quarts. The 454 MH is up for radiator flush this coming spring and the 429 in the "new" 1989 F700 looks like pond water in the radiator so come spring I am going to start flushing it and get new antifreeze in it too. Each one will take 2 quarts of Motor Max because they hold 5.5 gallons each.

The Cold Fire is some impressive stuff from what Google will bring back.

Does Motor Max work? I do not know. It was like $20+ a quart and I just wanted to try it. It causing a diesel to reach operating temps faster would be a good thing for the engine and to warm the truck cab on a cold morning.

Hey I just like to step out of the box from time to time and try stuff most call stupid. I convinced myself Motor Max should do not harm which is rule number one. If it does not help I can live with that but if something does harm then that is not cool.

 

I could be wrong on this one because there are more engine types out there than a person can keep track of. But Perkins is known for being a dry cylinder engine. Meaning it is made like a gas engine and does not have the removable wet cylinders. The electrolisis is not as prevelant on these as the wet cylinders. But that dosn't mean they don't make em. Come to think of it these Ford motors are probably a dry cylinder too. Does any one know? I have never heard of any one replacing liners on them so most likely they are dry.

 

ok do not mix up cavation and eletricolisis woth cavation. they are not the same. Cavation happens from steam pockets blowing off small pices of metal removing small chuncks of metal.
elericolisis is the result of electric current causing erosion. this is can be more easly seen as serface pitting vs themore vilant looking cavatation.

now for some very useless infortmation....
What exactly a cooling system is. All a cooling system is, Is a battery. When you mix an acid (coolant/water mix) in metal and you force flow it around metal you have a lead acid battery. Its very low valtage but still a battery. Coolant by nature overtime will become more acidic causing the voltage in the cooling systme to incress as the coolant ages.
so what does this mean to you?
Well you can test your coolant with a dc volt meter. Stick the black probe on the negitive terminal and the tip of the red lead in to the cooling system if its more then .3v you really should have already changed the coolant.

If I want to know at what temp the coolant is good to Ill use a hydrometer if I want to know if the coolant is good all use a volt metere. I tend to use the volt meter much more.

 

Thanks Cheezit, I remember seeing a film at John Deere showing bubbles as a demonstration for the electrolisis. But that was 25 years ago so my memory is not clear on the specifics.. Appreciate the input..Doug.I like the Volt meter idea, what is normal voltage in the coolant? After changing coolant does it start at 0 and go up from there over time?.

 

it depends on the brand and type of coolant but I assure you .3v is bad reguardless of of type

eletctrolisis will also make bubbles but the end damage looks different atleast to me. Next 6.4 cover I have off Ill take a picture of cavation and post it up. Also if pics of certin things are needed LEt me know and If i can Ill grab them as work flows through the shop

 

Cheezit; Thanks I just changed mine a few weeks ago so I guess I will take a reading for a reference, and start monitoring the coolant more often for voltage. And I changed mine with disstilled water and motorcraft gold. Not taking any chances there.