Engine/Transmission (1998.5 - 2002) Engine fails to cool down during idle

[ukmuk]

Hello,



I have a stock '99, no bombs (give me time, I'm saving up). Couple months ago while running empty, I noticed my temp gauge stopped surging left indicating the thermostat opened, so I figured it was stuck shut. Being a pretty cheap repair, I replaced the thermostat last month with the Mopar thermostat. That seemed to solve the problem while running empty.



But when I tow my 7,000# travel trailer, it runs on the warm side (200-210), especially up long, steep hills (duh, right??). Sometimes I tow a load and the thermostat never opens, or if it is opening, it's not cooling the engine. And often, unless there is a really long downgrade, the engine runs in the warm-to-hot range and never cools down to 180-190. This sounds somewhat normal, right?



Here's the part I'm not sure about. When I get home from a camping trip, I have to go up one final hill to my house. This usually kicks the temp to 200F when I hit my driveway. I read in my owner's book not to shut a hot engine down, so I let it idle and idle and idle, hoping it will cool down?



Anyway, the gauge stays right at 200-210 range. I let it idle like this for 45 minutes--no change in the guage. So I did a test. I unhooked the RV and drove around empty again. Within 5 minutes of driving empty, viola, the thermostat opens and needle surges left, and again... . normal.



Am I missing something here? Does this all sound normal? Do I need an auxiliary cooler? I just figured it would cool down on its own at idle after sitting for 45 minutes. Maybe the lack of air over the radiator does very little to cool it. Recommendations please?



Thanks.

 

[SRadke]

I'm gunna get flamed for this but..... Sounds like you're worrying too much. It is perfectly safe to shut down an engine at 200-210°. No harm done. What you want to let cool down is the turbo. 3-5 minutes of idle after a hard pull is sufficient to do this then shut'er down. If the engine were hotter than operating temp, say 230-240 then yes additional cool down is a good idea.

 

[John - K5AWO]

I second the previous remark. I think you have confused letting the turbo cool down versus water jacket temperature. The water, is okay.



Just let the turbo cool off 3-5 minutes before you shut down the engine after a hard pull.

 

[ukmuk]

Worrying too much? You're right! I'm a fairly new cummins owner (about six months), so not sure what to expect. And thanks for the reassurance. I just expected it to cool more on idle.



As you can see, I'm a new TDR member too. But very happy to be a part of all this--joining this site was the best thing I've done since buying my truck. TDR diagnosed a problem I was having with my tach..... and took me through detailed steps on how to replace my crankshaft position sensor--solved the problem--it paid for several years of memberships to TDR!



I've been reading the caTCHER post for close to six hours. As compelling as a good book!



Learning at a rapid pace... ...



Thanks for the input SR.

 

[ukmuk]

Ahhh, turbo, gotcha, John. Oh yea, SR said that too.



Knowledge begins with ignorance... .....

 

[fox]

Your water temp is not coming down at idle because the clutch fan is bad and/or the blow-by bottle is causing oil spash onto the radiator.

Check both.

 

[Wooter]

I dont have an answer, but, I had a very similar situation. Went thru Salt Creek Canyon in AZ. Going down wernt bad but coming up; The engine started to get pretty hot. I pulled over, let it idle; It just kept getting hotter!! The temp didnt hit red, but stayed right before the red on gauge. Finally it started to cool off but not very fast. We were near Show Low AZ and they have a dodge dlr. I remembered reading bout the thermostat sticking problem so bought a new one and put it in in the dlrs parking lot. I havnt pulled that kind of a grade since but will find out if the fix was real when we go thru there again.

 

[John - K5AWO]

Went thru Salt Creek Canyon in AZ.

Pretty country isn't it? Nice grade too, but not as long as the ones from Phoenix to Flagstaff.

 

[tractorface]

Your water temp is not coming down at idle because the clutch fan is bad and/or the blow-by bottle is causing oil spash onto the radiator.

Check both.

What Fox said. Sounds like the fanclutch. Pretty common problem. Cheap fix. When you shut it down at that temp spin the fan by hand it should not spin freely

 

[tp0d]

Also check the rad between the intercooler and the front face of the rad for crud. My dad's 99 had crud caked up so bad in there, that just pulling a little hill would spike the needle. ac didnt work for crap either cus of lack of airflow thru the coils. We cleaned it out with a piece of bent 1/4" tubing attached to a garden hose. powerwasher wouldnt touch it.



good luck



-j

 

[RCone]

Get rid of the blowby bottle. Do a search about extending the tubing down below the axle. Clean radiator, bet there is all kinds of gunk on the back side of it.

 

[ukmuk]

does anybody have of a photo of the stock breather blow-by bottle and a pic of exactly where it's located? i've searched the threads and all I see is that it's behind the cooling fan. I don't see any plastic bottles on my '99 at this location... ... the first line on this link reads "The 2000 and up Ram diesel uses a crankcase vent on the front of the engine. " And my DC serviced manual says "The crankcase breather/filter is no longer used with the 3. 9L, 5. 2L or 5. 9L engine. " Maybe their talking gas engines there--it doesn't say on the heading. Or, maybe my '99 doesn't have a bottle??



Anyway, there is no debris on my radiator, either on the back side of it, or between it and the charge air cooler. So from what I'm reading here, my fan clutch is bad. It rotates freely with the engine off and cool. But I am going to drive it to operating temp to see if the clutch will engage, shut it off, and then try to hand spin it before I go buy a new fan clutch (I found a new aftermarket clutch for $115 at an auto parts store). Curious, my DC service manual reads "If the fan assemby free-wheels without drag, replace the fan drive [clutch]. This spin test must be performed when the engine is cool. " But the threads (even my thread above) say that the clutch only engages when the air temp in the engine comparment is at normal operating temp and that the spin test should only be done at that time. These two things seem to contradict one another. I'm going to follow the advice I've read here, take it for a drive, and try doing the test then. If I end up doing the repair, I have a 36mm fan wrench. If that fails, I'll use a drift punch and hammer, cold chisel, etc. to break the nut.

 

[John - K5AWO]

Just use a very large screwdriver locked between the head of the bolts on the hub.

The nut us reverse threaded. If you have the proper size wrench, it will come loose without too much trouble.



The wrenches provided in the KDP repair kits make it a very easy job, but the above will do as well.

 

[WestTN]

How is your fan clutch? It sounds like you aren't getting enough cooling air flow to cool the engine down unless you are moving.

 

[ukmuk]

--problem resolved--

I must’ve had an advanced case of fan clutch failure—boy was it free-wheelin’. I drove the truck up a long hill, gave the turbo a chance to cool down, opened the hood, went back and shut off the ignition. 10 seconds later walked to the front of the truck and the cooling fan was still spinning!! That convinced me it was fried. Went to the parts store and got a new one. The fan nut came loose easier than I had expected. I put some Marvels Mystery Oil on edges of the nut, let it soak for 10 minutes, wedged a screwdriver between two hub bolts, and turned the nut clockwise. It came right off. When I finished, I pressure washed the radiator, hooked up my 7000# trailer for the ultimate test up the long hill. Case closed, it doesn’t run anywhere near 210F anymore. Try 180-190 even at the top of the hill. I’ve only owned it 6 months, and I heard a sound I had never heard before. The louder RUSH of air when the fan clutch engaged.



Oh and one more thing, I found the breather hose. Right behind the fan, but I really don’t see a “bottle”. The hose comes out the top of some kind of housing, makes a 180 straight down, and ends just below the level of the fan shroud. And there is tons of oil/grease caked on the stabilizer bar—but not a drop on the back side of the radiator, so it really doesn’t bother me--looks like it's doing what it's supposed to. I’m thinking this model had the blow-by bottle problem fixed.



I truly appreciate everyone who responded to my thread. Now I feel much better for the big road trip I’m taking next week.



Matthew in Alaska :-laf

 

[Chipstien]

If the hose ended below the radiator then someone already removed the bottle.

 

[SRadke]

Geez, I leave for a day and a half and taaa daaa, problem solved. Good to hear. Yea, you'll know it when that fan kicks on and since I missed it before, welcome to the TDR.



-Scott