Why Did I Overheat??
 

Hi all. We took our new 5th wheel toy hauler out for it's maiden voyage - had a ball. Towing on the flats and minor grades / hills was fine, had power to spare but would like a little more. However, once we got to Ice House road and started pulling the 12 mile 25mph grade, the engine temp got really hot. So we pulled over, the temp came back down to safe range but it was scary to say the least. We got to the campgound and let her cool down for a few hours, started it up, drove around and all was fine. Towed it back home with no problems.

So I heard from a guy at the campground that the Dodge trucks run the trans coolant thru a heat exchanger on the side of the block and as the tranny fluid heats up, it heats the engine coolant and thus, the temp guage soars. Anyone heard anything about this? I could hear my fan clutch roar (slightly). I'm wondering what I can do to cure this. I was going to buy a new fan clutch just for the heck of it since mine has about 100k on it. Also, do the '99s come with an auxiluary cooler on the radiator for the trans? If not, can I bypass this heat exhanger thing?

Thanks very much. Mike.

Can't tell you much about your auto tranny but I would so extremely encourage an EGT guage here. EGT's are just as important if not more then the water temp. If the water overheats it just blows a hose or gasket more then likely, if your EGT's over heat you melt the pistons.

I've never heard of the tranny fluid runnin around the motor but could be. I know you can buy auxillary tranny coolers for less then $100 in some cases. I'd also suggest changin the thermostat in case it's stickin and this is just somethin simple. Was their any indication of leakage, as in is you fuid low now. If so I would also change the radiator cap. If it's not holding the right pressure it won't force it's way through the engine block right and doesn't circulate.

Thanks Uncle Bubba, no indication of coolant leakage - radiator was full; overflow bottle to full level, trans fluid was within safe range. I wonder if my fan clutch could be flakey? When I've driven in 106* temps, the engine never went over 190* (even towing). Most of the time it stays well below that.

What temps should it stay at when towing? I only have a timing box on it now... no fuel.

If I was pulling a 12k load up a long grade in 2nd gear at about 2200 rpms, shouldn't my fan clutch pull enough air to cool the engine? Are EGTs an issue with a basically stock engine?

Mike

To check the fan clutch just turn it by hand. It should have tension on it but be able to manually push it.

The fueling boxes will affect the EGT's in a huge way but do very little to nothin for the water temps.

EGT's and your fueling box. If your hauling or towing and have the stock turbo and/or stock exhaust the box needs to be turned way down if it is adjustable and off if it's now adjustable. They will heat up in a hurry with the extra fuel. 1200 degrees is a safe short term max temp on EGT's but personally my truck has never gone above 1000 degrees and only that high on short runs tryin to climb hills with overweight trailers. Normal operating temps just runnin down the road stay around 300-600 degrees with my stock turbo and RV275 injectors.

On the water temps. I'd hate to answer that one becuase I've heard so many different opinions. Some people say these Cummins motors do best when they run a little hot, up around the 210 degree mark and some say they need to run a little cooler and by the 180 degree Thermostats. So once again personally I would pull over if the truck hit the 220 degrees.

Now having said all this these other guys are gonna come on here and tell you they hit over 1400 degree EGT's all the time along with higher water temps. I stay conservative in my truck, it has to last me. I increased the HP and capabilities of my truck so that I never had to push it to the limit, not so that I could push the limit higher. So all this is just opinions here.

Good info, thanks.

The fan clutch is just as you said - it has tension but can be turned by hand. I'm basically stock except the timing box so I'm at a loss. What do you consider an 'overweight' trailer?

On your Auto I think it's around the 16,000 mark stock. I pull trailers pretty regularly during the summer up to 30,000 maybe a little more when you include the trailer itself. I've got a 40 foot flatbed with three 7000 pound axles that I have modified and reinforced.

:humm: Is your blowby bottle still in the factory location? If so, b4 I took the bottle off of my old truck and extended the hose down, the bottle would keep the blowby and oil mist contained by the radiator. After 148k miles the blowby was built up on the engine side of the rad basicly clogging the cooling fins all to hell! :booo: I always wondered y the truck ran warm b4 that.... You can't tell from lookin at the outside of the rad, you have to climb under her with a light and shine it up there. You should be able to tell right away if its clogged up with oil or not... Just an idea :choochoo:

I took that thing off so many years ago I forgot all about it. Yea this blowby residue will clog the backside of the radiator up good if it's allowed to. Me bein the simple minded person I am just used a 2' piece of black PVC and cut it off so it drains just under the axle level. I use the threaded end to twist it up into the rubber hose and just use it as an extension. Don't remember if it's 1/2" or 3/4" pipe I used though.

I had the same thing on my 02. I took the radiator out and it was nearly 2/3rds blocked with some kinda goop. I used degreaser on it with a low pressure hose and it cleaned up pretty well. No problems since.

to answer you question bout the tranny fluid, the answer is no. THe tranny fluid has its own cooler/pump. no tranny fluid every goes near the coolant inside the motor. there is no "heat exchanger". i had my auto tranny out several times in my old 98.5 and i can tell you that the lines run directly to a small cooler in front of the radiator.

also, when was the last time you flushed you cooling system?? if its been a while or you dont know, go do it. old antifreeze can loose its cooling ability over time and it can create the very problem you described, because as antifreeze wears out, it gets clumps of lime in it and those clumps can build up under heat and clog your coolant passage ways inside the motor, not good.

hope this helps:c:

When I first made my long pull with my 99 it started to warm-up a bit as well. Being unfamiliar with diesels, I got off the fuel and tried to give it a break. That didn't work, you've got to keep your revs up and make it work and not lug it. I second that blowby fix and cleaning the rad, it made a huge difference on mine.

that is a NEGATIVE Captain. after the tranny fluid leaves the tranny, it is pumped though a heat exchanger mounted underneath the turbo/exhaust manifold on the passenger side of the block. then it goes into the cooler infront of the radiator. the only reason that someone would bypass the heat exchanger is to put twin turbo's on and need the room on the side of the block.

Thanks all; the blowby bottle is gone (was that way since I bought the truck a few months ago) and all that's there is the drain hose; no oily residue on the inside of the radiator, just a few bugs between the AC condenser and radiator.

Good ideas on flushing the system and cleaning the radiator. I can blast it from the backside with a hose to dislodge bugs and crap and see what happens. Also, will change the thermostat just to be safe. How 'bout the fan clutch - should I just spend the 70 bucks and change it out? Napa has a Four Seasons severe duty unit for 70 and the dealer wants 225.

I found a B&M supercooler with an external fan and am wondering if that would do any good. Is it possible that the trans fluid is heating the engine coolant through the heat exchanger under the turbo? if so, would it do any harm to bypass the heat exchanger?

Mike

hmm, i just went over to my brothers and looked, the lines ran directly from the trans, right to the cooler, no exchanger there??? we have owned that truck since it had 0 miles, maybe a factory glinch or maybe not done of certain truck years??? ill have to get you guys a pictures.

:humm: I was gonna say, I don't remember my 2000 havin that....

Had the same thing happen to me, when I got up and over the Big Horn mountains to Buffalo wy. to the inlaws I jumped on the computer and hit the forums and they told me to check and then clean the radiator. This can't be done while in the truck very efficiently but only takes about 30 minutes to pull it. Took it to the local car wash to clean it and holy crap it didn't look all that dirty but I blew a ton of oily dirt out of it. The next day after I had it all put back together again we hit the road and it made a hell of a difference, no more heating issues at all.pulled an 11% grade and never went over 190*. At the same time I also threw away the blowby bottle and legthened the blowby hose to down behind the front differential.:U: Ive told my story to several others with heating issues, they pulled and cleaned their rads and problem solved. Cheap and easy fix.:c:

yeah, i just went out and double checked, there is no "heat exchanger" on that truck(98.5) ill go over and check out my buddies 99 and see as well. but i can say this, it would not surprise me if for trucks ordered to go to places up north where it is colder then crap out durign the winter, that it was an option put on those trucks to help wram the tranny is those temps. being around dodges my entire life, i can tell you, no two vehicles were ever built identical. theyve all had something different, even though they were optioned alike.

didnt have time to read all this but runnin the A/C will hurt ya bad on EGT's

yes do check the air cooler and rad for pluggage from oil puke bottle spill over............I have seen that bad bad bad b4

im going to be cleaning mine this evening just as a precautionary event and extending my blowby tube

My 02 doesnt have a heat exchanger. I know, I just removed the lines to change the tranny. What is this blowby bottle you guys are talking about? I know I need to move that because my radiator was nearly clogged up with oily crap. I removed it and cleaned and flushed it and havent been above 190 since.

my 2001 does have a heat exchanger. It is on the right side of the engine. It looks like a small cylindrical air tank. When I changed my tranny line to put the inline trans temp sender line in, it was a pain to work on. I also removed the stop ball that is in the hard line to the exchanger.

The blowby bottle is the best mod that you can do yourself I think. I have mentioned that to a few people that have had overheating problems and sure enough when we went and looked, the back of the rad was plugged up with oil and dirt. Simple Green works well and is non toxic.

Thanks all. GB, good stuff - I know what I'll be doing this weekend.

Marine, thanks also. When you say the "back" of the radiator you mean the shroud side, yes? I noticed a bit of gunk on the frontside in between the condenser and radiator - how it gets there I'm not sure. My blowby bottle has been missing since I got the truck - I've never seen one or where it mounts but my blow by hose is hanging right down to about the bottom of the front timing/engine cover.

Mike.

the heat exchanger is on all auto equipped trucks the 12v 2nd gens had them along with the screwy tranny lines. the heat exchanger is where the check ball valve is on these to keep pressure in line so you are able to get in start and drive and not wait for pressure to build up as it will blead off over time... I myself have bypassed mine as it was full of dust etc and ran a bigger cooler up front had to modify the bumper to fit it and added a permacool with built in fan and mounted it directly to the metal cross bar that I would call the bottom of the core support. even the 3rd gen autos have a heat exchanger my dad has an 04 and we did a tranny service and flush the other day and I checked it out looks a lot better than what us 2nd gens have. the hot line running out of your tranny goes directly to the heat exchanger this is where most of us change out the line to a 94-98 auto line that has a built in place for a temp sender to mount or buy one from genos so we can get our temps from there. It doesn't look the lines really run up to the passenger side of the block through the small exchanger then down between motor and tranny up to the factory trans cooler then to back of tranny.

Yes, the shroud side. Crap will get between the condenser and the rad as well.

Heat exchanger
 

Both my '99and my '01 have the heat exchanger. It's below the exhaust manifold, bolted to the pax side of the engine in front, and the backside is bolted to the tans adapter.

Your truck is probably due for a radiator cleaning

my 01's radiator when I pulled it out to clean:
Attachment 51813

my 90 auto, 01 auto, and 06 auto have heat exchangers on them, they are located under the manifold from factory

Ian