Overheating on long pulls?

[rparlaman]

overheating

The way to check fan clutch is when cold like sitting overnight with air cond left on ,you should here a strong roar for 15 to 20 sec. when you first drive away. Also, your post you have a auto trans big differents them who run 5 and 6 speeds. I had a CTD for over 10yrs,and autos make to much heat,all it is a large pump that pushes fluid. Thats why i would never own a another auto trans for pulling, MY 2 CENTS



Ron











92 CTD auto518a 01 ho 6 speed, banks power pack,jacobs e brake 50 gal trans flow 30 ft forest river 5th

 

[FCecelin]

Think of what has changed since last year . Dirt ,crud ,etc in or inbetween the cores are suspect as is the fan clutch. .

 

[Eric_77]

Here is a link to info that we have found from racing.



http://www.racemotorcycles.com/cgi-bin/board/YaBB.pl?board=tips;action=display;num=1081715345

 

[I-6DZL]

Anybody thought of anything new ??

 

[dcamilleri]

I just completed an 800 mile trip with 7500lb travel trailer in tow. My new fan made a BIG difference. I was still able to get the temp to rise on several occassions, but only after long hard pulls in 5th with a/c on and exhaust temp hovering around 1200. Temp would max out around 220 and I would back out of the throttle. It appears engine oil is also hot at this time since temp would continue to rise for several minutes before it would start to cool. Most pulls I could crest the top without problems and the engine would very quickly cool within minutes. Ambient tempature seems to have a large bearing on coolant temp. With temps below 80 degrees engine would run at thermostat temp unless pulling a grade. At 90 degrees and above engine would run at about 200 constanly (a/c on) turning a/c off would also result in a slight tempature drop. Most of my pulling was done with TST on level 5. Before this trip I also changed my transmission oil and I am now running Redline 85/140 and the transmission seems to like it. transmission seems a lot happier running extended hard pulls in 5th gear. Shifting is also very good. With this new fan the volume on the stereo has to be a little louder but not too bad. Also, fuel economy didn't seem to change much except for a 100 mile stretch that I ran between 75-80mph only returned 8. 5mpg. The rest of the trip running 65-70 returned around 11mpg.

 

[Berrigan]

Just wanted to let everyone know Im still looking into this. Ive contacted TST, Dodge, Cummins, and local radiator shops. Ive been told my rad is the biggest that will fit. Rad shops cant add cores. One idea that everyone seemed to think might have promise is to put a 3way valve in the heater hose going to the heater core. Use over sized hoses and devert the coolant going to the heater core and send it to a new axillery radiator then back to the suction line of the heater core. Then find a place where the new rad could fit. Put a electric fan on it, and be able to control the system from the cab. The hard part will be finding a place thats large enough for a smaller secondary radiator in the cooling air flow without dumping its heat into existing heat removing devices. Then is the area going to be large enough to put in a rad big enough to make a difference in temps. Then do some calculations on heat rejection to see if its worth the time and $. The one thing I did hear is that the Dodge alarm bell for dash gages seems to be conservative and may alarm before an actual bad situation exists. Im thinking of getting another temp gage to compare to the factory one.



Ill keep you posted, Bill

 

[rweis]

I just got back from Smokey Mtn trip, 1100 miles of towing.



I had changed my tstat to the 180* version.



Temps stayed cool the entire time even under 9* up grades for several miles.



Interesting thing though: All I did was change the tstat from 190* to 180*. Fan clutch frequently came on at 190* ie earlier than the usual 205* or so. Fan clutch seemed to be governed by something other than water temperature. Water temps were fine. Fan clutch came on much earlier than with the 190* tstat. Not sure why, but I am VERY happy with the change.



I know the fan clutch is a viscous fluid temperature sensing system, but I thought it sort of odd it functioned differently than before.



Anyway, much better lower temps all the way around.



Bob Weis

 

[Kirwin]

My .02 worth

I have always noted that the engine cooling fan on my 97 locks up a little too late. BUT if you can't here your engine fan roar when it finally locks up, there is something wrong! According to my Cyberdyne gauge the fan locks up under full load coinditions, hill climbing, around 205-210 F with ambient temperature of around 90 F. Normal temperature for my 12 valve is around 180 F empty and 190 F pulling. Normally while pulling up hill engine coolant temperature rises to the fan lock up point and then slowly decreases to the point of fan unlock at these temperatures. Out west I have pulled on a hot South Dakota day with ambient temperatures around 100 F with the A/C crankin and had the fan lock up for 1 to 2 miles then unlock for about the same time with engine temperature hovering around 205-210 F. If you can't hear fan lock up somthing isn't working right! Ken Irwin

 

[Berrigan]

OK, I give. Anyone have an idea for the location of an extra small rad? It is very full at the inlet side of the truck.

 

[RustyJC]

Fan clutch came on much earlier than with the 190* tstat. Not sure why, but I am VERY happy with the change.



I know the fan clutch is a viscous fluid temperature sensing system, but I thought it sort of odd it functioned differently than before.

Bob,



The fan is coming on more often because you've changed the heat balance of the engine. More of the BTUs being generated by that expensive diesel fuel are now being transmitted to the cooling system because of the higher temperature gradient between the combustion zone and the 10 degF cooler water jackets. This additional heat is being rejected by the radiator, which warms the air passing through it more, which engages the fan clutch.



Rusty

 

[damon]

I agree....

Those with autos are the one's overheating. The reason is because of the auto not locking up in second gear, causing heat to build in the transmission. Once the trans temp rises above the engine coolant temp (usually about 210*) the stacked coolers at the front of our trucks work against us. Since the trans cooler is in front of the intercooler in front of the radiator, the hot air from the trans. heats the intake air which makes the EGT's rise, which make the engine run hotter, which is trying to be cooled by the hot air coming from the hot trans cooler. Does that make sense???



That being said, the first thing we with autos need to do is make sure we are getting lock-up in 2nd. As long as the valve body is set up for it, all you need is a lock-up device. most trans builders have one available for about $300, or you could use some sort of mystery switch.



My new trans (with 2nd lock-up) is going in next week. I'll know then if my findings prove true.

I think Blue Thunder hit this one right on the money. The only time I've overheated was in 100+ heat, up a 8-12% 9 mile grade, with about 13000 in tow. I tried to hit the grade hard which kept me in 2nd gear (not locked up), and once the trans temps went up, the coolant temps followed quickly. After a cool down period, I did the rest of the hill in 1st, locked up, and no overheat problems. Higher rpm's and lower speed for less air cooling equaled cooler temps - tells me the heat generated from the fluid coupling in 2nd may have been the culprit.



Blue Thunder, you said you were getting a new transmission with 2nd lockup. Anything to report in this regard ?

 

[rweis]

Rusty,



Thanks, had not thought of it that way.



Bob Weis

 

[RRFinch]

I pull up to 20,000 Lbs gross vehicle weight. My temp NEVER goes more than one needle width above centerline of gauge.

I had an overheat problem sometime back. Replaced the thermostat with aftermarket one and no problem since.



Changeout is easy. Because engine design puts thermo at top of water level you can change in couple minutes without losing very much coolant. You only need a a 7/16" wrench (I think I remember the size correct). Point is, it is easy job.

 

[Mike Ellis]

On my poor old stock truck, it is easy to tell when the fan kicks in - you hear a roar like a cyclone under the hood, and it sucks away enough HP that you notice the performance hit (hey, I've only got 215 to start with).



I haven't had any trouble with mine overheating on the mild grades around TX/OK during summertime, had the truck in CO with camper on last year and went all over the place with no probs either. In fact the fan rarely has to run, usually the only time I hear it is for a minute or so on startup after a heat soak.



Have had one trip though where the fan stayed engaged for at least 50 miles, it was a while back when they had the huge storms in OK that blasted down the trees along I-35 down around the Arbuckles. We were driving into a horrific headwind and the truck was working hard to pull our Sundowner horsetrailer, it has a huge sail area on it. For much of the way I was plugging along at 50-55 mph in 4th gear (not enough HP to maintain speed in 5th gear with fan sucking away in the huge headwind), never did overheat or anything. I was pretty pleased with the performance for a stock truck, our old Chevy gasser would have been crawling the whole way.

 

[Berrigan]

Well I got some news. I guy here in town has a shop that specializes in building hauling trucks. He suggested removing the two black strips of plastic that are on each side of the fan shroud. They are about 6 inches wide and as long as the rad is tall. They seem to tie the shroud to the outside edges of the rad to force all incoming air through the rad. He says this will increase air flow by alot. I do respect his ideas as he was a Dodge mechanic before opening up his own shop.



Looking at my truck it seems that doing this would decrease airflow at idle with the truck not moving, but increase airflow when moving down the road with the ram air effect. Has anyone tried this? What do you all think? Bill

 

[jjdiesel]

clean the radiator

Gonzo2 hit the nail on the head. I had the same problem... . looked clean but was not. Bet 'cha anything the radiator behind the intercooler is funky. Easy to pull them apart, a little Simple Green soaking and you'll be good to go.

 

[Hohn]

Since we don't have any room to increase cooling capacity in the stock location, it would seem to me that non-stock locations are the next step.



I would imagine an additional cooler remotely mounted (perhaps at the aft of the truck?) could be of some benefit. If you had a way of conveniently adding it to the coolant circuit when needed, it might be a big help. There would also be a decent amount of heat rejection in the plumbing just conducting the coolant back to the aux cooler and back up again (maybe use copper plumbing?). I'd say even relatively small cooler like a B&M aux transmission cooler (for 26K GVW) would be perfect.



I'd like to expand on Rusty's comments. The reason that there is a restriction in the cooling system is that it takes TIME for heat to be transferred from the coolant to radiator. If we just pumped a bunch of coolant throught the cooler, we wouldn't really get optimum heat transfer. The specific heat of the coolant is a huge consideration here, as is that of the radiator's material. It's like when you touch something hot only for a plit second-- you don't get burned nearly as bad as if you grabbed and held on!



One other thing to remember-- only USE as high a percentage of coolant as you need for freeze protection. If you need freeze protection only to -20F, don't run 60% coolant and extend that to -60F.



Water is a MUCH better conductor of heat than ethylene glycol coolant. So if you leave someplace where a frost is as rare as a poultry dentist, I'd suggest minimal coolant and run mostly water. I'd personally go as low as 20% coolant, 80% water. I'd also add a substantial amount of Redline water wetter to reduce temperatures, resist corrosion, and lube the water pump.



I REALLY like the idea of the Evans coolant, and I'm considering it for use in my truck.



justin

 

[hammersley]

Bob,



I think the only reasons we get away with it are (1. ) Dodge must have been pretty conservative on their safety margin in designing the cooling system - knowing we're gonna be working the heck out of the Cummins powered trucks and (2. ) we normally don't use maximum BHP long enough to drive coolant temps out of sight. The situation I'm concerned with is the guy with the 450 BHP truck who drags a 20,000 lb 5ver up a 10 mile 8% grade with the throttle floored. I don't see how the stock cooling system would be able to handle that situation! The easiest solution - lift the right foot, but where's the fun in that?



Rusty

You don't have to worry about the water temps - under this condition the EGT's will be through the roof long before the water is!!!!!!!!!!!!

 

[RustyJC]

You don't have to worry about the water temps - under this condition the EGT's will be through the roof long before the water is!!!!!!!!!!!!

Probably, unless they've spent some major $$$$ on replacement turbo(s)!



Rusty

 

[Dallass]

Here are a couple things that can help alot that we have learned from racing.



1. pure distilled H2O it carries heat much easier and transfers it more quickly. downside the boiling point is much less (this is normally not an issue as the coolant remains cooler since it operates more effinceintly) and no corrosion or freeze protection.



2. Add Red Line Water Wetter it breaks down the surface tension and allows better transfer of heat. (also adds some corrsion and water pump lube when used in pure H2O)



3. Evans NPG this is a non water based coolant, pain to change over to but much higher boiling point and non-toxic. Engine runs at higher temp but hot spots and actual overheating are almost non-existent.



Websites

http://www.redlineoil.com/

http://www.evanscooling.com/

What are the problems to change over to Evans NPG?