Am I screwed??

[vandej]

I have a 94 K3500 with 150K and no mods except for a K&N filter. All my camping is in Wisconsin. I have OK power and gas mileage until the fan clutch kicks in. The fan clutch is contantly kicking in and out. I understand why its doing it, however I'm overheating on just tiny little hills. Am I just asking for trouble if I try to tow my 9,000lb fifth wheel to Florida and back? I'll be going through Kentucky and Tennessee. Will the hills in that area kill me and the truck? Can I even get up those hills if I get stuck in limp mode?

thanks,
Jason

[jb carver]

i have heard and tryed that you can get a cardbord box small and put it in to the outside of the blades when running if it stops the fan the clutch is bad if it tears up the cardbord and keeps spinning its ok.it works just be carefull.

[rjschoolcraft]

I've towed through those mountains many times in stock trim. Your truck will run hot (mine ran between 220 and 240) and EGT's will be high. I've recently installed the late model cooling mods and Kennedy fan clutch and 20" steel fan. No more overheating! The Kennedy intercooler and chip has dropped my EGT considerably.

[cruzer]

I'd backflush rad, spray bugs out of rad, condenser and trans/oil coolers. Spray from engine compartment to the front of truck being careful not to bend fins w/ water pressure.

I pull thru KY & TN on I-75 all the time. In stk form, the hills will slow you down. They are not all up. There are only a few that are miles, mostly up & down. You'll cool down some B4
going back up. I'd do some cooling maintance. If you really concerned try to hit it at night.

[ucdavis]

I wouldn't characterize the fan kicking in as "overheating." It is an integral part of cooling, and kicks in (w/OEM calibration & proper radiator airflow) when engine is just a bit over good running temp. The more lag between engine temp & fan kicking in (bugs in radiator, poor water pump flow, collapsing hoses, fan not turning enough) the more that overheating is an issue.
If the fan is "contantly kicking in and out" that would argue that either clutch is not operating properly or that engine is producing much heat & fan is needed. The flush sounds like a good idea, and the bug-blowout couldn't hurt; many folks report build up of bugs between rad. & AC condenser that can't be seen till you unbolt condenser & lean it forward.
Good luck- heat kills.

[JCM5]

Vandej,
Dont get caught up in these fan mods etc.
You never want the fan to fully engage, doing so means power loss. By installing a fan that kicks in sooner will rob power sooner. These engines have enough issues with power. My suggestion would be to install kennedys hi output cooling mods. If cash is an issue as it is, otherwise we would be driving the duramax. I would go slow through the hills. You should have no issues at 55 or 50MPH. One thing that does help, is changing the rearend ratio from 4.11 to 4.56. You loose top end but at least you can climb those hills.
Good luck and drive slow, PS use Kennedys diesel additive, it does help a little.

[MartyB]

o the high flow water pump and dual thermostat cooling mods that folks are talking about, and would wajor most if not all you heating problems will go away.
Since you do have a 94, if the rad has not been flushed and cleaned in awhile, that will help some to.
I droped some 20F after doing the cooling mods on the hills, such that I can now tow uphill with the AC on. I am using two 180F robert shaw t-stats.

[CareyWeber]

Originally posted by JCM5:
Vandej,
Dont get caught up in these fan mods etc.
You never want the fan to fully engage, doing so means power loss. By installing a fan that kicks in sooner will rob power sooner. These engines have enough issues with power. My suggestion would be to install kennedys hi output cooling mods. If cash is an issue as it is, otherwise we would be driving the duramax. I would go slow through the hills. You should have no issues at 55 or 50MPH. One thing that does help, is changing the rearend ratio from 4.11 to 4.56. You loose top end but at least you can climb those hills.
Good luck and drive slow, PS use Kennedys diesel additive, it does help a little. I have never felt any power loss with my Kennedy fan clutch that engages at 180

[Jim P]

I was just wondering if you guys that have cooling problems also have an automatic trans.

My truck has a manual tranny and have had absolutely no trouble keeping it cool. It is a 95 and has not had any cooling system mods done. The only thing that I did do was port out the heads and intake. Also when I rebuilt the engine, the head gaskets had real small holes for the water to pass through. These holes were punched and had alot of burrs and jagged edges. I used a small reamer to ream these holes and make them nice and smooth. I think it was 3/16 in dia. I don't think my truck has ever gotten above 185 degrees.

Jim P.

[rjschoolcraft]

Jim P:

I think you're on to something there. My uncle has a 1996 K2500 extended cab 6.5 TD. He has never had an over heating issue, although he has never towed out west and his trailer wasn't as big and as heavy as mine. His truck is a five speed manual transmission. My Suburban is obviously an automatic. I think that the extra heat from the tranny is definitely one source of problems. I bought my truck used because my uncle had such good luck with his. He has never had the first engine problem. He also has an 84 GMC K2500 6.2 diesel that has over 300,000 miles.

As for the cooling mods without changing the fan clutch, see my post "Late model cooling mods" for the low down on that. I still nearly cooked my engine while towing to California and back. Since installing the Kennedy fan clutch, my overheating problems seem to be over. I won't say for sure until I tow across the Mojave Desert again, though. While the fan is obvously a parasitic loss, you really can't notice it. Besides, the computer pulls fuel and boost if coolant temps climb and you really lose power then. I know first hand. I would have to say that the Kennedy fan clutch has been my single biggest improvement in the cooling department.

[HowieE]

If you are running a 94 truck and have never had the radiator removed and rodded, and have not cleaned thw condenser and oil coolers it is no suprise that you are overheating. I remove my radiator ever 3 or 4 years and have it cleaned and clean the radiator, condenser and oil coolers at least once a year and when ever I return from a buggy area. Remove the grill and loosen one of the oil coolers and look behind it. You will most likely see a complete matting of bugs. If you want to see a picture of what I am saying e mail me howie.braith@verizon.net
Once the cleaning is completed remove the thermostat and check it by putting it in a pot of water and bring it to a boil. The stat should open just as bubbles form in the water and be fully open before you have a full boil.
If after this you still have a problem then you can start to look for a mechanical problem. But don't spend money before you know what shape the foundation is in.

[patrick m.]

I live in Tennessee, any way i go i hit hills. I installed the high flow cooling mods (97 model water pump and dual outlet t-stat housing with 180* t-stats). I still heat up when pulling heavy, just not as much. It will go from 180 to 200, but cools off much more quickly.
With the single stat set up, temp would climb to 225, then slowly cool off down the hill.
I know that 225* is ok, but i sure like it better the way it is now.

[Jim P]

One other thing about my truck. It has an aluminum radiator. Maybe all these trucks have aluminum radiators. I have not looked at enough to have noticed. Also, when I had engine out for rebuilding, I cleaned the radiator and the other coolers very well. I also put some engine flush in the raditor and drove it around a little after I got the engine back in. Then I flushed it out. Some discolored water came out during the flush. I'm just trying to figure out why some have the cooling problem but I don't seem to.

Jim P.

[ucdavis]

JimP,
18:1 might have a lot to do with it, tho the manual tranny IMO is also an advantage.
I've got the automatic, pull 16,000# no matter what and never have heard of tranny temp problems w/my type of rig (and I've been thru all of California's deserts, up the Grapevine...). But, putting 200 degree tranny fluid thru cooler in front of radiator is bound to add to engine cooling load.
I see a lot of posts on heating that sound like bugs in fins of rad. or between rad. & AC condenser.

[cruzer]

You know thinking about it, I did a trip to Colorado 3 yrs ago w/slidein camper and car trailer(8000lbs) and didn't have any major,in the red, cooling problems that I recall. Then last yr did the same trip and it did on certain pulls. I also did several trips that yr down south 3-400 miles round trip w/the same load and the truck ran hotter than the yrs previous. The engine eventually cracked a piston. I was doing research on how to proceed on rebiuld and found TDP and the cooling mods and other stuff to build 4 power. I read 87gpm to 130gpm W/P and the change made sense to me. During rebiuld I found the rad was junk and had to be replaced & the condenser had major bugs. I think this was the major cause of the engine failure. I'm glad I did the mods, it runs cool now & the power is awsome. I do have an auto trans. It had a brass/copper rad w/green A/F, now it is alum/plastic Visteon rad w/dexcool and distilled water.FYI watch out for inferior after market rads, alot of them have generic applications. Shop for # & size of cores & the proper inlet & outlets, and do the math.

[ucdavis]

I'm gunna hazard a guess based on my experience w/a reasonably low mileage rig: I've had dexcool since first coolant change or new, don't recall. But that implies good radiator insides due to proper corrosion protection & low mileage. My temp gauge drops nicely when fan kicks in no matter the grade I'm on, indicating a clean, fresh, stock radiator (even w/orig. LO water pump & single stat) can handle the cooling load.
Overheating is a simple matter of isolating one of the following (rough order of occurence IMO):
1) bugs. yearly water jetting might produce clean look to AC condenser & motor side of rad, but the space between condenser & rad can accumulate debris over the years that can't be seen till you loosen & tilt the condenser. Probably the number one cause of overheating.
2) bad coolant or coolant proportions
3) stats need changing; simple & cheap (except for the stoopid rad. drain location, oh well).
4) radiator corrosion over time = loss of capacity.
5) pinhole coolant leak in hose, collapse of hose, etc.
6) low pump output due to accumulated corrosion or pump vane deterioration
7) overheating due to mods not respecting cooling needs or overstressing stock config w/repeated high GVW.
8) fan clutch failing (can't hear the roar no more)
The basic message from the Cracked Casting Club is "get dirty if you have to, but find that heat problem & solve it, & don't drive it till you do." If you work thru above list every few years (#1 every year) & change all hoses/stats B4 trouble, it'd be cheap.

[cruzer]

UCDavis, I agree with you whole heartedly,
maintenance is the key. That's the reason for the previous post,I believe, a 6.5 in a stk configuration with old cooling and proper maintenace maybe adequate,given the load it has to pull and how fast you want to get there. I did feel the load I am pulling was about max for the truck. I updated my cooling for the anticipation of more power on the rebuild. I needed/wanted more power because I hate slowing down alot on hills. Now loss in mph is minimal and me and the truck stays cool. It feels safer too.

[vandej]

Thank to everyone who posted. I'll take radiator out and get it propoerly inspected, cleaned and flushed. That I can do cheap assuming the rad isn't junk smile.gif I did find out that something is wrong with my turbo. I am blowing code 78. I replaced the wastegate solinoid and vacum pump several months ago when I was blowing that code before, however its doing it again. I have zero vacum at the actuator right now. I have the factory manuals, but how do I tell which side of the solinod is pin A and which is pin B? I'm trying to determine if I have a circuit failure.

Also I found another diesel web site that states their water mist injection system is much better and cheaper than installing the 97 cooling mods.
http://www.duramax.*******ing.com/My_Truck/water_injection.htm. Is there anything to this statement the company makes?

Thanks again to all the contributors.
Jason

[rjschoolcraft]

No. Water injection may work OK for short durations, but will you leave it on for 200 miles at time while towing across the Mojave Desert? I don't think so.

By the way, I was a little skeptical of all the talk here, but have learned otherwise. This last trip to California (early June this year) I set out with what I thought would be good cooling conditions. I had installed the HO water pump and late model dual t-stat cross over. I also cleaned and inspected the radiator. Inside was perfect...like new. The best I'd ever seen (it had over 150,000 miles at that time). There was some debris between the radiator and condensor. I cleaned that out and cleaned the fins in both the radiator and condensor before I re-installed the radiator.

I had severe overheating problems...similar to what I had in 2000 when towing to Yellowstone and back in stock trim. When I got back in late June, I installed the Kennedy fan clutch and Kennedy intercooler. The fan clutch keeps the temperature in check now and I have a lot more power. Prior to the upgrades, I could tow around east of Colorado OK with temps peaking at 240F (which is hot) then the fan clutch would engage and pull the temp back down to around 210. Out west, though, the truck couldn't keep it's cool. I'm anxious to head out that way again now as I expect things will be much better.

For more detail and a "play-by-play" description, see my post "Late model cooling mods" for the scoop.

[ucdavis]

Jason,
Most of these weather resistant connectors have the terminals marked w/tiny letters. Ya have to clean the dirt off to see for sure. Usually on the collar where wires enter the connector. Check both sides, harness & device, and front & back; might be on one but not other. If no luck there, you can look up wire colors on schematic in manual; might have to follow wires into loom a ways to get real color due to fading.

[HowieE]

Almost all GM electrical connector have the letters marked on them. The markings are small but there.
If you are having trouble with the vacumn pump or wastegate selnoid replace the whole thing with one of Bill Heath's manual controller for a lot less money and a lot less trouble.
If you go to Bill's site you can also get information water injection.
http://www.turbo-master.com/
I again sugggest you check out you oil and AC cooler before pulling you radiator. Check my site for the reason why.
http://mysite.verizon.net/vze54tx9/

[Turbine Doc]

Jason,
A remote trans cooler with electric fan kit is a simple and effective mod, I just recently installed mine, the fan comes on at 180F trans fluid temp, I just ran the hills and mountains of VA, KY, TN and AL, with a loaded bed around 1500 lbs as a 98 I have the hi flow cooling system, plus I added Kennedy's clutch, temps were around 190 at 75mph; prior to trans cooler similar load temps would go up to 198. Summit/Jegs have pretty good prices on fan/cooler kits. Your trans clutch pack will last longer also with cooler oil, when you can afford it a deeper aluminum pan is also another good mod for cooling trans/engine by virtue of more trans fluid to heat up and passive cooling from pan fins/ribs.

[vandej]

Well I pulled the radiator out. Holy crap. I could only see light through 1/4 of the rad and there was a a wad of bugs and dirt 3 inches high between the rad and the air conditioning core. I guess the guy I bought it from last year didn't take care of it very well. It took me 2 hours of blowing air and a full power water hose to get the thing cleaned out. The coolant looked good when I drained it. Does off the shelf radiator flush work or would it be a good idea to take it in to get flushed?

thanks,
Jason

[markelectric]

At this point it would not cost much more to take it to a radiator shop. When I pulled mine, the rodding job was only 35 bucks. I am sure I got a more complete job than a can of flush could give me.

[Johnny B.]

Jason, I use my dually primarily to tow a 30' travel trailer about 7000 lbs., wife and two kids and bikes and firewood in the bed. I bought it last year with 211,000 miles and currently has just over 227,000. I towed my TT across I 80 in Wyoming and down I 77 and back through WV, VA, and NC. Several of the grades on I 77 are comparable to the grades out west. Instead of starting at 5000'-7000' and climbing 2000' feet you start at 1500'-2000' and climb to 2500'- 3500'.

Towing in the midwest in the summer heat and humidity my temp runs 210-220, usually closer to 220. On small hills it climbs to about 230, my clutch fan kicks in at about 220 its pretty consistant. On the Mt. grades on I 77 I was able to maintain a consistant engine temp around 230 at about 2200 rpms and also maintain a good trans temp at about 180-190.

Out west I really only had a problem on the eastbound grade east of Laramie. Last year I pegged my temp gauge at 265, a warning light and buzzer sounded. With a half mile to go I crossed my fingers, windows cracked, heater on and all power access. were off.

This year I did the grade at midnight in a thunder/hail storm and my engine temp maxed at 245, but my trans peaked at 235 for a couple of miles.

After hearing about cooling mods having been done on older 6.5's I decided to finally give it a try. Yes I hose down my radiator, a/c condenser, trans cooler and ps cooler after each trip to remove dirt and bugs. My radiator is clean on the inside and is coming up on 3 years of age. Thursday I'm driving three hours north to Peninsular Diesel to pick up their cooling mod kit $346. Hopefully I can get my engine temps in check and not have to cross my fingers. I was really beginning to think 220 was normal.

Thanks to MartyB posting on another forum I am getting the mod kit. His guidance also directed me to the diesel page which I have found to be a wealth of information.

On the interstate I like to run 65-70mph depending upon conditons. Out west I wish I could run 75 with the big boys, but 70 will do. I do notice fuel mileage drops and engine temps increase tremendously over 55-60mph. My shift selector can usually be found in OD.