I was hoping someone would bring that up, cause I'm thinking along with bpk that the right foot has more to do with engine heat than the year your truck was manufactured. But to clarify the issue with 2nd gen 24valvers, it is the valve train itself that runs cooler at idle -- so much so that varnish buildup is an issue. hence the &quot;30 minutes at 140 degrees&quot; rule of thumb. Its possible that the idle efficiency on the 24v's, due to the electronic injection pump under ECM control, as well as the new valve train design, may have improved to the point where less energy is dissipated by the engine at idle and that difference manifests itself in the form of a cold valve train when idling at very low ambient temperatures. DC no doubt had some emissions goals to meet as well, so the timing and fuel delivery method for the 24valvers idling system could be part of the difference. <br><br>So without hearing more direct experiences I would question whether or not the 24v engines actaully run any cooler overall than the 12v engines, when working hard. I would wonder about the cooling system itself and whether or not that has changed -- is the older 12v cooling system any higher in capacity than the 24v? I dunno.

 

I'm not sure about the initial HO transition, but D-C and Cummins said the new design for the '03's were to allow for more cooling area for the extra heat generated by the uprating of power to the 555 lb/ft. That was their statement from last year's auto show in Chicago when they were talking about the styling change. It would not surprise me to find that they increased capacity for the initial HO's as well. Just an observation.

 

OK I know your all talking about my statement about HO's running hotter than the other 24v's. I'm surprised no one has backed me up on this either. Yes, the HO's do RUN hotter, not idle hotter! As I said earlier, I and other people are not sure why. I may be because of the higher compression or the way the injector/ injector pump works. As some may think the HO's dont have bigger injectors, they work on a higher injector pressure. This is why they dont respond to box's as well as the other 24v's. As for idling, well I have been round and round with this one. So I am to understand the 24v's idle cooler than the 12v's which means they dont build up enough idle heat in the cylinder to burn an efficient combustion. When the cylinder temps drop enough the fuel washes down the rings and the unburnt fuel builds varnish on the valve guides which can cause them to stick open. Thats why we shouldnt idle for a long time. Supposedly this is aggravated with bigger injectors. ??? Now as for the varnish, I'm not sure what happens to any when you are pulling a load a 1100* or so. Does it burn off? Not sure. The washed fuel will delute your oil though. Hope I made more sense.

 

My 24v HO is the only Cummins-powered truck I've ever owned, so I can't draw any comparisons based on direct experience, but I can say that the thermostat seems to operate oddly compared to any other vehicle I've driven. What I normally see on my temp gauge is the needle steadily rising as the truck warms up, going past the 190 mark and staying past it for a while, then suddenly plunging back down to 190 and staying there. I've never noticed this on any other vehicle.

 

jfpointer: I've noticed the same thing on my truck. I had a Ferd Aerostar that did that -- its bound to be the thermostat behavior. they open late for the first time and then they seem to be ok. only my Aerostar alwasys opened late . Anyway I'm not sure thats a sign of pre-mature failure but it sure catches your attention!<br><br>Katoom: I can't independantly verify that my 02 ETH runs hotter than an 02 ETC at the same HP level so I'll take your're word for it ;D Do you mean at bombed levels or stock? fueling box present or after market injectors? as for responding to fueling boxes, yea its because the VP44 plunger displaces a smaller volume of fuel -- it is smaller in order to accomodate the higher injection pressures. But as others have pointed out, the variability between trucks is sometimes more than the difference between an ETC and an ETH. I forget now who posted this , but it basically they said that sometimes an ETH truck will come out ahead on dyno day and sometimes an ETC truck will. Even the Diesel Dynamics page shows 20 HP or less ifference betweeen the two when similarly equipped. <br><br>on the idle, I think you've about got it. Only I don't think the varnish is caused by un-burned fuel directly. I think (someone correct me here if Ii'm wrong) it has to do with vapor condensation in the valve train below 140*. and the valve guides themselves don't stick open -- the varnish builds up on the valve stems which causes them to bind. The valves stick and you get bent push rods. and yes, the varnish burns off whenever the coolant temp is at least 140. the CTD loves to work hard, so the valves love to pull ;D

 

[quote author=Doug link=board=4;threadid=15192;start=15#145730 date=1054761824]<br>jfpointer: I've noticed the same thing on my truck. I had a Ferd Aerostar that did that -- its bound to be the thermostat behavior. they open late for the first time and then they seem to be ok. only my Aerostar alwasys opened late . Anyway I'm not sure thats a sign of pre-mature failure but it sure catches your attention!<br>[/quote]<br><br>It definitely freaked me out the first time I saw it do that--I was about to pull over when it dropped back down to where it was supposed to be.<br><br>I'm thinking about why they might idle cooler, but I'm not really an expert on the topic. If the 24v engines have valve timing optimized to allow them to work better at higher engine speeds, maybe that particular timing results in the valves being open slightly longer than might be necessary at lower engine speeds, meaning that the increased air from the increased valve area carries heat away more effectively? Then as engine speed (and in general, load) increases, this effect vanishes because it then enters its &quot;optimal&quot; range?

 

<br>I mean at all levels. It would be nice if someone chimed in here that knew what I was talking about. Cause I cant be real informative about it. Sorry.<br><br><br>Interesting. Sounds logical, but I also though that I read the valves could stick open and clash with the piston, too?

 

bpk,<br>Depending on where you drive these radiators will really pull in some trash. Try washing out the rad. and then install screen in front of it. I know that helped mine a lot. You would be surprised to see the debris in there.

 

<br>Well if things bind up to the point of bending a push rod then surely there is the potential for a valve to stick in the open position. so yea, &quot;crashing the valve train&quot; is a term that comes to mind ;D. <br><br>I wonder if the HO's (higher compression ratio) have less clearance from piston to valve. (different head perhaps, and/or piston. how else do you boost compression with the same block?).<br><br>on the HO's running hotter--well, it occured to me that any time you compress a gas you heat it up (not to bring up the exhaust thread again, but remember that expanding gasses get cool -- so compressing gasses get hot). anyway, A 17:1 compression ratio (ETH) will result in a higher temperature gas (when compressed) then a 16.3:1 compression ration (ETC). that will no doubt help the spontaneous ignition of the fuel, affect timing, etc. whether or not the higher compression ratio itself causes the engine to run hotter I dunno, but it was fun talking about it

 

Well thanks for all the opinions on my problem. Yesterday I pulled the stock thermostat (190) and replaced it with the cummins 180 I bought. It looks the same, fits the same and it lowered my water temp about 10 degrees with the outside temp being 107. No leaking housing that was talked about. I still haven't pulled with it yet, but I think I went the right diresction. The new EZ makes it run better to. Thanks

 

Katoom, yes my temps are down all the time. I just pulled my trailer the other day on a 750 mile round trip to NC. I set the cruise on 73 going down and on 65 coming back. My temps got no higher than 180 going down and while coming back the needle even showed about 170 for quite a while. That may have been a fluke though. Now, I did not have to pull any hills and this was all highway driving. <br>I have sat in DC traffic with the trailer and the temps got up to about 190 but if I turn on the AC and the fan kicks in the temp drops right down..<br>I always put cooler stats in my vehicles!!!

 

[quote author=Dodgezilla link=board=4;threadid=15192;start=15#146351 date=1054892565]<br>I always put cooler stats in my vehicles!!!<br>[/quote]<br>why? just curious as to your objective and how that objective differs from the manufacturer.

 

Hey Dodgezilla, glad to see it worked for you! I was thinking of trying the cooler stat but last time I tried one on a pulling ride the temps were lower untill I hit hills or was sitting in the slow traffic heat. So I didnt see the point. Plus I thought the warmer motor ran better in the winter and I dont want to be changing stats for the seasons. <br>What was the outside temps? Do you think you gained anything? Power, fuel mpg, EGT temps? Please let me know. Thanks.