Engine/Transmission (1994 - 1998) No Thermostat Still Overheating, Water Pump?

[MMcCallie]

This problem has become so baffling my most reliable mechanic is finally advising I try switching my license plate because we've swapped just about everything else. My Cummins has always run hot with frequent overheating. I ditched the stock engine fan and clutch for a custom fan and Horton electromagnetic fan clutch. This fan setup moves a ton of air, tons of noise, blows dust clouds below the truck and will blow your hat off with the hood open. I also have a pusher fan in front of the intercooler working at the same time.



After overheating to the point of running out of coolant due to another sticking thermostat that boiled almost all of my coolant out and having to be towed I decided to take a drastic step. I pulled the thermostat and cut out all but the metal bridge in the middle. No longer anything opening or closing, just a constant flow with a slight restriction. This is a 180 degree Cummins thermostat from NAPA. Looked just like the one from Auto Zone it replaced, that stuck shut as well. Before that I'd been through a few original style Cummins thermostats with rubber sleeves that crumpled. The last of those stuck open in the winter and I couldn't get up to 50 degrees.



Removing the main restrictions from this thermostat has disappointingly done nothing to help. I'm grossing about 23,000 lbs on my way to Alaska. But even when empty I still get well over 200 degrees even at interstate speeds. What is odd to me is that my coolant got as high as 228 degrees today while towing up a mountain but didn't boil out. Took several minutes after cresting and going downhill to get back to the low 190 degree range. It usually boils around 210.



The radiator is only a couple years old. Been through a few thermostats before and after replacing the radiator. Can't run air conditioning because that seems to make the engine run hotter. I'm running the purple FLEET coolant from NAPA for big trucks with tap water. Running a higher ratio of water this time and that is the only thing I can think of that has kept my coolant from boiling over this time.



The head is my second replacement within just a couple months. When holding a hand over the coolant reservoir and revving the engine, there is no pressure from the coolant so I don't think my head could be cracked again or leaking through the head gasket, no injection compression or engine oil in the coolant.



The only thing I haven't replaced in a few years is the water pump. Does a water pump slowly go bad and allow overheating or does it just lock up and quit all at once? Do I need to look for a Cummins or Dodge dealer or will I be OK trying one from a parts store? I plan to try to find a shop in Bozeman, MT in the morning to put in a new water pump, assuming I can find one in town.



I should add that the truck usually runs a little cooler at night, but still frequently exceeds 205 degrees even when ambient temperatures are in the 40s. Under hot sun in the 90s we can't even run the a/c and keep temps down into the 90s. But at times even with my thermostat gutted we can't keep coolant temps under 210 climbing up a mountain with both fans on but if I keep the fans on for a long time during the downhill side the fans will sometimes bring the coolant down into the 160 something degree range. Takes a long downhill to get that cool. Thoughts? I've got a lot more towing to do and sure would like to have this problem solved unless it is fine and normal for my engine to not be able to stay under 230 degrees.

 

[Skydiver]

boiled almost all of my coolant out and having to be towed I decided to take a drastic step.

-So how hot did it get? Have you double checked your factory temp gauge?



It usually boils around 210.

-Not possible if system is sealed completly, Compression of something is pushing the coolant out. Water boils at 212 F sea level. You can boil water at 70F if you remove the atmosphereic pressure. We did that in A/C school with an old coke bottle and a vacuum pump. What alltitude are you running at? Are you running your cooling system sealed or do you have the radiator cap backed off one notch?



When holding a hand over the coolant reservoir and revving the engine, there is no pressure from the coolant so I don't think my head could be cracked again

-Just look for bubbles in the reservoir after it warms up. How much blow-by do you have?

-You could check the temp of the coolant going into vs. coming out of the radiator with a laser temp guage as a process of elmination. Bugs in radiator this time of year will cause problems.

 

[HBarlow]

You have a highly modified engine in a non factory application. You may or may not have adequate air flow or an adquate sized radiator for the heat load.

Running loaded in summer heat at highway speeds and towing heavy at 210* is normal and up to 230* on steep grades is not anything to be overly concerned about.

Removing the thermostat is the worst thing you can do for an overheating issue. In many cases this allows the water pump to flow the coolant so fast it isn't able to transfer heat to the radiator and outside air.

A water pump can fail without catastrophic lock down or seal leaks. The blades of water pumps do wear out and don't pump as well as when new.

 

[S.Morris]

Check your rad cap..... replace with new one.

If cap is sealing you should be able to run 3degF

Over 212 for every 1lb pressure rating of cap.

Also make sure overflow hose to jug is not leaking

... . expansion into jug should return back to rad

When engine cools... . jug level should always return

To same level when engine is cold... .

Go to shop with sniffer that can detect combustion

Gases in cool ant

To rule out leaking head gasket or cracked head.

Steve

 

[JDKammin]

I have seen water pumps that had the impeller come loose on the shaft. If you cannot find a Dodge or Cummins dealership, look for a Case-IH or AGCO dealership. There were several farm tractors that used the 5. 9 engine. As others suggested, get a thermostat back in the truck. Make sure you do not have any air restrictions on the backside of the intercooler. I have seen where the intercooler can get plugged up with dirt, etc and will not allow air to flow thru intercooler and radiator. Worse case scenario, you can remove the thermostat housing and fill the engine up with water to the opening in the block. With the belt removed, start truck up and watch for bubbles. Any bubbles will tell you if you have a compression leaking into the cooling system. I see you are using head studs and firerings, so I cannot think you would have head gasket problems.

 

[fox]

I agree ti is time to look at the water pump. Have you checked for coolant flow? Remove the top hose, since you modded the thermostat, and start it up. If it isn't pushing coolant out, you found the problem.

I see no reason to over heat if it is circulating coolant.

It won't even need a fan at highway speeds if everything is in good order, unless you are running a lot of boost.

 

[fest3er]

Point: I haven't yet had an 'aftermarket' t-stat work in my engine. Only the official Cummins t-stat works right.

Towing a 4000# trailer up the mountains west of Denver, my wimpy engine held at 70-74 MPH in OD all the way up. EGT was about 1100F post turbo, and the coolant temp was up significantly, way up, prolly close to 230; this just showed the engine was working for once in its life.

Grossing 23K#, I would expect the engine to run at 210F or so across the flats with no wind; it's just startin' to work. And hauling that load up mountains? The mighty 5. 9 is workin' its little butt off; it's entitled to run at 230F-240F!

If your unladen coolant temp is significantly higher than 190 when running across the flats at 70-75 and you and your mechanic have eliminated everything else, the water pump would be the next suspect. At 1500-2000 RPM and at temp, you should see rapid coolant flow in the radiator. But first install a genuine Cummins t-stat.

If it still boils out too easily, you might want to consider running the coolant system at higher pressure. But this would entail ensuring that all the parts can run at that higher pressure.

Are you using synthetic lubes in the engine, trans and diff(s)? They can significantly lower operating temps, too.

Last point. Using the trans-to-coolant heat exchanger (as do Dodges with auto trans) is a potential source of excess coolant temp. I don't remember if you're using this feature of the 5. 9.

 

[WDixon27]

i am running the 180* version of this Mr. Gasket 4366 and like it much better then the cummins branded POS i put in there when i discovered the previous owner was running nothing at all, no wigwagging temp gauge and it gets up to temp quickly unlike the cummins unit, i had to run a air blocker infront of the rad to get heat before i made it the 20 miles of interstate to work, i put it in this spring so i won't get to check out the heat for a few months yet but with in a couple miles the gauge is in the middle unlike before

 

[Skydiver]

How many horsepower does the Horton require? This may sound like a conflicting statment, but anything that requires horsepower makes more heat.



Try running disstilled water in the summer months. If that is not enough add some water wetter or engine ice.

 

[CodySanders]

i too had the same problem in salt lake city ut. i replaced everything radiator fan cluch fan thermostate hoses water pump with no luck. i then went back to the thermostate and replaced it with a different cummings one. they make two different temp units and i had the higher temp one 180 i belive on first wich did not work for my heavy towing (18-20k) high hp truck. i switched to there lower one i belive it is 160 or something like that and to my suprise i made it up that dang hill and got the hell out of there. this was a two week ordeal for me and i haven't had a problem since knock on wood.

 

[MMcCallie]

I'm at a shop and just had the water pump pulled. It looks fine but I'm putting the new one I got at NAPA in anyway as a redundancy. I don't expect this will make any improvement. So some of you think I am fine to be pulling mountains at 230 degrees? I just thought that was way too hot. i thought the Cummins liked to run around 160.

I have an Autometer engine temperature gauge that gets its reading from the back of the block underneath the cowl. I assume that the reading there can vary greatly from the temperature of the water through the rest of the system on its way through the radiator, which might be why I've had it boil over when reading around 210 and under.

The Ford PSD cooling system has no overflow jug. The cap is designed to leak at a certain point, has no problem letting coolant out when it gets super hot. I don't expect much blowby, tiny dot of oil after sitting overnight. Last time I had compression checked it was nearly perfect.

There are a couple other issues I'm having that could be related. My AirDog is no longer putting out 50-65 psi. It is now getting as low as the teens, though spends most of its time around 30 psi. I'm also seeing only 37 psi boost with 1,600 EGTs when I was seeing 49 psi boost and 1,300 EGTs leaving MO and into KS. Have pressurized and fixed several small boost leaks, system held 65 psi with no leaks. My elevation has been 7-9,000' since hooking up the trailer and pulling through the mountains of Wyoming and Montana.

I'm going to add some NAPA diesel coolant conditioner and Royal Purple Coolant additive that the diesel guys around Jackson Hole supposedly like. The mechanic who's working on my truck right now thinks the fuel pressure being low is most likely the cause of my low boost and high temps. He just found two fuel leaks, one on the return line from the injectors, and one at the return line on the frame where the factory metal line goes into the AirDog fuel hose. Those two things didn't seem to make a difference. However, when he clamped the return line off back before the tank at an idle I was seeing 35 psi. Without the return line clamped it dropped to 22 psi. The Overflow Valve is new from Dodge, about three weeks old. Guess I'll stop at NAPA again and pickup a brake line hose clamp and zip tie it to the frame. Hoping my new AirDog isn't burned up already, guessing the new overflow valve couldn't handle the pressure.

 

[MMcCallie]

Does anyone know where a 160 degree thermostat can be attained while on the road? Going through Montana, Alberta, British Columbia, Yukon, then Haines, Alaska.

 

[WDixon27]

big block mopar works, that is what my mr gasket unit is sourced from so just look up a old charger or something else with 440 in it

Does anyone know where a 160 degree thermostat can be attained while on the road? Going through Montana, Alberta, British Columbia, Yukon, then Haines, Alaska.

 

[CodySanders]

a cummings big truck dealer would have one if they have them up there or order it from the states. i had the mechanics all baffeled as well. i would hope that is your problem too. the number of the tstat i bought is on this forum some were. that is were i learned of the two different ones. i will tell you my truck takes a long time to warm in the winter with the lower temp one. but worth it to me to be able to tow in winter. now i just plug her in when its cold. to much work to change back and forth. it might even be a 145 but i can't remember the exact temp. they only make two tho a 180 and the lower one. good luck

 

[MMcCallie]

Mechanic ended up thinking it was most likely my fan not pulling strong enough. He thinks I need a shroud that seals tighter around my fan. Putting my hand in front of the condenser I couldn't feel much pull with the fans on at an idle. He said most cars have more pull with the fan locked even at an idle. Anyone know how hard their Dodge pulls through from the front when the fan is on? Might have to have a/c on.

 

[DennyDay]

Does anyone remember the size of the Ford Radiator - - - seems to me that the FROD radiator on our PSD company truck was much smaller than the one on my Cummins, and we had continous over heat problems when pulling a trailer in Texas in the summer. The lack of an expansion tank may be a problem. ALSO - - where is the crankcase vent? Isn't anywhere near the radiator is it?



Just a couple of ideas.



Denny

 

[PBJ2500CTD]

Since you have a newer radiator that is probably clean in and out have you checked the AC condenser for obstructions? Maybe that would account for the low flow detected.
Another often overlooked item is the lower radiator hose. Is it collapsing when it gets hot and under load? Some manufacturers put a spring in the lower hoses to prevent the collapse. I've seen people remove the spring thinking it would somehow wind up in their water pump. Most of them would end up overheating while driving on the freeway in the summer.
And... do you have a transmission temp gauge? What is the temp? A lot of heat can go from the trans to coolant heat exchanger with the loads you state.

 

[Grumpy John 4x4]

Horton fan

Hey MMcCallie where did you find the Horton fan! Thanks

 

[LandShark]

Since you have covered all the bases concerning water flow and air flow, I would lean toward taking a closer look at your fuel system. Injector pressures and spray patterns can make a huge difference in temps.

 

[monkeyman]

I have the flexlite fans and run a 190 degree thermostat. Even with AC on and 90 degrees outside I never run over 194 degrees. I used to have a Horton and I like the electric fans better. Auto zone sells the water pump with a life time guaranty

Rick