Never overheat again?

[schiker]

I had a custom 15qt pan on my 6.5TD with a temp sensor in it. I can tell you that it runs around 175-200* under hiway driving no load. However you get a load on it and it can go to 275* plus in a big hurry. I had and IC and cold ait intake with a moderate tune and stock injectors. I think the IC makes about as big a difference in performance as well as over all temps go. It was a 95 and I had Evan's with in it with the high output water pump and dual 205* stats.

Greg

I worked with a Deutz air cooled diesel once and it shut down when oil temp reached ~248F (measured going into the cooler believe it pumped from pan to cooler then to filter and oil galleries). There was no ECT as it was air cooled and keyed safety'ed shutdown off the oil temperature. I also measured some Kubota oil in the 265F range in the pan but it did not thermally runaway. I think Dino oil can withstand 275F and upwards of 300F ok as avg oil pan but its life expectancy is reduced exponentially with temp above 250F. Not sure where it would fail and think it would be a combination of all of the above high ie high EGT,ECT, IAT and oil Temp would be bad. Given only one or 2 high some over the limits it will probably live ok for a while but its not good.

 

[TurboTahoe]

Schiker, your post #99 is pretty good reasoning! I agree that oil temp could probably be a 2nd measurement point for thermal management. Again, we don't have a good model for 'what's safe' if we were all running Evans coolant. We've all trained ourselves that with Water/DexCool and/or Water/Green Coolant that 210 is a safe limit. It would seem that a LOT of members have stayed within these limits and had very good results. It would also seem that we need to have more info on Evans under similar conditions - LOTS of member experiences.


What say you?

-Rob

 

[schiker]

Yeah, I think it would be hard to say what the 6.5 thermal limits were with Evans without more data on EGT, oil temp, IAT, and ECT during heavy sustained loading by several users. I would say it can stand 15-30F increase no sweat with Evans just due to increased boiling point. It probably would take 40-50F more in avg ECT and be ok IF other temp heat indicators were ok. But actual limits I don't know.

I have done some heat testing or heat balance testing on small stationary diesel engines Kubota and Yanmar (25-87 HP). And it takes upwards of 45 minutes to an hour to stabalize oil temps for a sustained loading from cold start. You have to look at RPM, EGT, ECT, IAT and oil temp then air temp surrounding engine near the starter alternator and IP. They also measure air temp before and after radiator fuel temp before and after IP and coolant temp at bottom radiator hose. You have to look at all the facts to see if its overloaded.

The oil temps I said are based on normal maintenance schedules dino oil and trying to obtain 10,000 hours of engine life. Are they hard do not exceed oil temp limits no.

I have never done any automotive or truck testing but talking to techs there are some nuances that are hard to pinpoint without a steady state loading. And its hard to steady state load a truck. Just due to some unloading during driving it would be hard to say if you could catch thermal damage with oil temp as it might get too at the piston but avg oil temp be lower (but climbing). For intermittent loading you could spike one or 2 temperature indicators just over a soft limit but it aint good. If 3 or 4 temp indicators go over then you will probably see damage. Probably in this order of importance EGT, ECT, IAT, then OIL. Oil is listed last only because it takes longer to react. I have seen oil temps rise to just above ECT pretty quick then slowly continue to rise for 15 minutes after ECT stabilized. Have heard of some measuring oil temps continue to climb for 30-45 minutes more but during my testing once I was over 266F it was a deal killer and wasn't going to continue testing.

From reading lots on the 6.5 it appears what happens is the heads get really hot once the coolant can't take anymore heat away the oil temp starts to rise faster. Once the oil temp gets too hot the piston will gual when EGT,ECT, and IAT are high. GM keyed on IAT and ECT to know when to defuel. I don't think the oil temp at the sump reacts fast enough to know when the piston is going to gual exactly.

Let me try and say that again a little later with different wording.

X amount of fuel will make X BTU's of heat that has to be dissipated.

Now what temps cause block web cracking etc I am still chewing on it and not sure. I believe there are multiple issues and compounding effects. I don't think anyone knows for sure yet.

 

[schiker]

A few observations:

Heath says he uses hydraulic cement in the block water jacket with great success. So how much heat does the coolant take away from the bottom end???? I guess not a whole lot.

Interesting enough we don't read of a lot of lubrication failures with the 6.5. Most claim really good cylinder bores and bearing clearances even on high milage rebuilds. How hot does the bottom end get???? Even on cracked blocks we don't see coked oil on bearing or blueing or discoloring of bearings etc.

But the rear cylinder do tend to score or guall when worked really hard and ECT goes high 230F? and above. So is that a heat induced lubrication failure. I think so. What oil temperature is when this happens is I don't know. Would cooler oil help yes but may not prevent it dont know and would depend if the engine has piston oil squirters too etc etc. Does the rear of head get that much hotter and coolant locally loose or have a reduced interface and cooling ability I think so. And thus more heat goes into rear piston and it guals. Better flow and turbulation of coolant has helped increase safety and durability. Would a coolant that won't locally boil help yes I think so.

If Greg saw 275F oil temp with extra oil capacity custom pan and intercooler would a otherwise stock truck have even higher oil temp. I think so but haven't read of what really high oil temps have gotten to when towing hard up a grade with other indicators are high (EGT, ECT, IAT) for an appreciable time and importantly how fast it gets there.

EGT is the best indicator of how hot the potential heat on the piston is getting . But I bet if ECT and oil temp are high say if oil temp is already 220-250F and can approach 275-300F pretty fast then I would guess the piston is in danger of gualling when EGT is high (and depending on IAT). That would have to be corelated though.

Is there a super gradient of heat or temp when coolant locally boils in the head proably yes too cause I think that is what causes head cracks but is the heat gradient all the way to the bottom end ?????

---------

Or does the super heated precup ( when the head is really hot and coolant is loosing its interface and the heat gradient is at its steepest) change the time of combustion power pulse and hammer the lower end while the piston is near TDC....... HMMMM that's just one of my latest theories on a contributor.

And with better controlled head temperature (and precup temp) you reduce this TDC hammering of lower end.

The temperature of the combustion chamber has an appreciable effect on the speed of diesel fuel combustion.

 

[ak diesel driver]

Hmmm interesting hot engine would be akin to preigition in a gasser.

 

[TurboTahoe]

Hmmm interesting hot engine would be akin to preigition in a gasser.

I'm not sure I understand this comment. Preignition in a gas engine is caused when conditions in the cylinder exceed the ignition point of the gas-air mix outside of planned spark timing. This can be caused by a number of things - excessive compression, hot spots in cylinder (e.g. from carbon build-up), IAT too high, etc.

The discussion on diesels was currently centered around how hot one can run a 6.5 without engine damage. I don't think that the concern is about preignition at this point...

-Rob

 

[schiker]

It depends on what you mean by engine damage.

In the short term overheat issue I think its a combination of saturating all the heat dissipation modes. EGT, ECT, IAT and oil temperature concurrently. They all are important and influence heat on the piston which is the first failure mode I am suggesting in a thermal overload situation.

------------

Then its often questioned why blocks crack and crank shaft have problems too. Seems if you always keep ECT under 210-215F the 6.5 lives pretty good.

Well, I don't think the head(s) getting so hot extend heat to the crank area.

I am proposing a contributing factor is under heavy loading uneven heat in the heads and uneven temperature and heat in the precups causes harmonic stress and flexure of bottom end during the power stroke at near TDC. It doesn't show up in uneven cylinder balance because it could be just at near TDC and a harmonic not an actual piston stroke speed difference. Furthermore its probably cummulative damage not short term and why its so hard to correlate.

I have seen high speed photography of combusition and combustion temperature has an appreciable effect on combustion and flame probagation.

Its just a theory of mine I have no proof or real evidence. I just don't understand how other than something like that the ECT at the head could affect the crank and main bearing journals significantly without other heat indicators like short oil life, coking, color evidence on bearings etc. Because coolant doesn't seem to cool the bottom end much.

 

[ak diesel driver]

I'm not sure I understand this comment. Preignition in a gas engine is caused when conditions in the cylinder exceed the ignition point of the gas-air mix outside of planned spark timing. This can be caused by a number of things - excessive compression, hot spots in cylinder (e.g. from carbon build-up), IAT too high, etc.

The discussion on diesels was currently centered around how hot one can run a 6.5 without engine damage. I don't think that the concern is about preignition at this point...

-Rob

Well if Schikers theory is correct then a hot engine would fire sooner then it's supposed too. If it gets advanced too far it would be similar and possibly cause engine damage. It's just a theory

 

[packratt]

My oil temp sender is mounted at the input to the oil cooler. The gauge tracks about 10deg above the water temp.

 

[Matt Bachand]

Well if Schikers theory is correct then a hot engine would fire sooner then it's supposed too. If it gets advanced too far it would be similar and possibly cause engine damage. It's just a theory

Good article about timing in MaxxTorque that explained this.

It is also possible that the computerized IP's such as DS4 compensate for this? They are constantly adjusting TDC0 on the the fly to maximize power and efficiency. Something the DB2's can not do.

 

[schiker]

I did not read the article can you paraphrase a bit of it.

I know they cold start advance and PCM monitors IAT and ECT, and RPM to adjust timing. And this is to optimize timing.

I am just saying that with really hot ECT above 220 avg at the water neck there can be some localized hotter temps in the head and maybe some localized boiling (with water/glycol) which can cause even more temperature gradient to the precup and this causes variation of combustion time due to a significantly hotter precup than normal.

With good coolant flow and turbulation its localized and coolant vapors are cooled and condensed quickly why it doesn't just runaway until a little hotter.

 

[dangerousdave]

Update; Evans waterless cooling doesn't work for me. It boiled 2.5 gallons out at the parking lot to the tramway in Palm Springs over 110f outside, a/c both blowing cool. Wifey was driving slowly in the lot, hadn't noticed the gauge, coolant spewed around 220f. Glad the 'burb has a 7 gallon capacity. 2.5 gallons are now H2O! So, I ...
Cleaned the cooling stack; radiator, A/C condenser, oil and trans coolers. Noted the mfg of rad was 11/2002, prev. owner prob. put it in in 2003. Fan clutch therm. was clean, but great gobs of dead bugs and much came out as I sprayed each unit.
THEN, I drilled 17 1 1/2 inch holes in the front of the grille, and some 3/4 inchers in the center brace that the hood latch bolts to. Flat black paint from the inside only painted the edges of the holes, and on the other stuff behind the grille to cover the worn paint fron 220k + miles. Just ran out to the desert over the mountains, 107 degrees outside, cool inside with dual a/c blowing.
Sure wish I had pictures; those holes remind me of a feul alterd dragster from the '70s.

 

[TurboTahoe]

Well, that's a drag. We were all hoping you would say that Evans is the end-all solution for the 6.5.

I thought they make a big deal out of not putting water in with the Evans?

-Rob

 

[LanduytG]

Update; Evans waterless cooling doesn't work for me. It boiled 2.5 gallons out at the parking lot to the tramway in Palm Springs over 110f outside, a/c both blowing cool. Wifey was driving slowly in the lot, hadn't noticed the gauge, coolant spewed around 220f. Glad the 'burb has a 7 gallon capacity. 2.5 gallons are now H2O! So, I ...
Cleaned the cooling stack; radiator, A/C condenser, oil and trans coolers. Noted the mfg of rad was 11/2002, prev. owner prob. put it in in 2003. Fan clutch therm. was clean, but great gobs of dead bugs and much came out as I sprayed each unit.
THEN, I drilled 17 1 1/2 inch holes in the front of the grille, and some 3/4 inchers in the center brace that the hood latch bolts to. Flat black paint from the inside only painted the edges of the holes, and on the other stuff behind the grille to cover the worn paint fron 220k + miles. Just ran out to the desert over the mountains, 107 degrees outside, cool inside with dual a/c blowing.
Sure wish I had pictures; those holes remind me of a feul alterd dragster from the '70s.

How can it boil out at 220*? NPG+ boils at 370*. I think you need to further investigate what really happened. After all regular anti freeze will not boil out at 220*. Just and observation.

Greg

 

[turbovanman]

How can it boil out at 220*? NPG+ boils at 370*. I think you need to further investigate what really happened. After all regular anti freeze will not boil out at 220*. Just and observation.

Greg

+2, they even spec you don't need to run a pressure type rad cap.


I am thinking you boiled out the water left in the system.

 

[dangerousdave]

1. Wife was driving and gave me her "thoughts" on the temp.
2. It's the first time the engine has been that hot since I changed over.
3. Probable there was some H2O left in the system, but I followed Evans directions exactly; didn't just follow the written instructions, but called them for specifics on the Suburban dual heater system.
4. Yeah, you're never supposed to add H2O, but Wife refused to drive it with the low coolant light on.
5. She added 1.5 gal of the spare drinking water we keep in the 'burb, then the light came on about 15 minutes later (after purging air), and she added another gallon.
6. The "damage" is done, $30 / gallon coolant, +/- 7 gallons IIRC, and now I'm a confirmed ex beliver, feeling extremely dissapointed in the product.
7. This chemical, under other names, is sold extensively as a coolant for food processing equipment. Other companies, some with stronger additive packages, sell it at about the same price.
8. I'm going to seek some non toxic coolant that doesn't cost a fortune, one made for Motor vehicle engines.
9. for now, it's working as it is.
10. Any other reccomendations?
11. Thanks, guys

 

[turbovanman]

I would leave the rad cap off, boil off the water, top up with Evan's, repeat until water is gone.

 

[TurboTahoe]

I would leave the rad cap off, boil off the water, top up with Evan's, repeat until water is gone.

This sounds reasonable. Water boils at 212 degrees, the Evans boils at 370 or so.

Of course, this means you need to pop the cap off and run the truck up to 212++, which makes some people nervous.

-Rob

 

[dangerousdave]

I run a zero pressure cap and a breather filter on the overflow hose since I switched to Evans.
I'm steering clear from Evans, at least until the youngest graduates from Lawyer $chool. Seems sometimes that he's a professional student!

2.5 gallons is a lot to boil off, and I'll probably never run it that hot again.
I remember somebody saying they drained theirs and boiled the coolant in a big cooking pot until it tested "clean" with a hydrometer, then they put it back in.