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Cooling system issues

7K views 83 replies 14 participants last post by  starkey.rayl 
#1 ·
2001 Ram. Only modifications are S&B intake kit and 4" exhaust system from the turbo back.

Alright, here are the issues. I have searched several times through the forum but have not quite come up with what is going on. First noticed when temperature dropped below 50 degrees F. Coolant temperature would take a long time to warm up to 190. About 20 minutes of highway driving. Once at 190 the thermostat would open and then temperature would drop back to about 160. When into the throttle it would come back up to 190. As soon as I let off the throttle and start to coast to a stop, the temperature quickly drops back to about 160. After about 5 minutes of idling the temperature will come back up to 190. Also with this there is little to no heat in the cab while driving. After it comes back up to temperature while idling there is heat coming out the vents. When at temperature both heater hoses feel hot to the touch. One does feel slightly cooler but not by much at least by feel. Temperature is now down to between 0 deg F and 20 deg F. Same results. I put a piece of card board between the CAC and radiator completely blocking air flow across the radiator. This did not help the heat in the cab but did make a difference on the temperature. Now instead of dropping to 160 it only drops to about 175. Still very slow to heat up. Also this has never overheated, ever. Highest temperature while towing has been 205 and had about 210 once when pulling a very steep hill at highway.

I have done the following. The thermostat has been replaced twice. Heater core has been flushed twice. Coolant is new and system flushed.

Looking to see if anyone else has had this issue and what they have found. Thanks all.
 
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#2 ·
Stat has been replaced twice, when? With what? Still sounds like thermostat Long warmups are normal otherwise. 10-20 min. when driving. Coolant full to top in rad, clean?
 
#3 ·
Thermostat replaced once in April and then twice within the last 2 months with thermostat from Autozone. 190 deg thermostat. Coolant clean and full to top of radiator.
 
#4 ·
I guess it could be something else but that is still thermostat behavior. I am not going to tell you to buy another but if you do get a different brand. Get temp sensor gun and test for consistency. It will not match the gauge but but if it does not match the up and down with the gauge the sending unit is off. Test at the same location near the sensor each time.
In other words it the gauge is 190 and then 160, but the hand sensor shows 180 and 185 at the same time, the truck temp sensor is bad.
 
#5 ·
I will see about doing that over the weekend and see what I can get. I also plan to further check to see what coolant flow I am getting across the heater core from the return hose. I plan to check the water pump and upper/lower radiator hoses for collapse. Thanks for the responses.
 
#6 ·
If it is running at normal or below there is no shortage of flow. Heater core will not have anything to do with your normal and below temps. It can help a tiny bit it it is getting hot and you turn the heater on high, but that is not the case here.
 
#7 ·
Wanting to check the flow across the heater core due to also having very poor heat in the cab in addition to everything else going on.
 
#8 ·
That is fine, Which actuator did you replace? Choices above. Look at the radiator core external in front of the fan on the aback side and look of dirt clogging it. Then the front side.

Here is a little trick for you with the heater core.
Remove both hoses.
Blow out all the water you can through the other open hose end.
Then fill with vinegar or CLR(50/50 maybe) and let sit for a few minutes. Mild acid.
Then rinse out well with a garden hose until clear. That should clean out any corrosion and gunk. Vinegar should have no issues, it is milder. Garden hose pressure should help
As long as you do not leave it too long you should get no leaks unless they are already there if it has copper core.
Gunk of some kid may even gee good.
 
#9 ·
I did try that. I get good flow with the garden hose across the heater core. Flushed heater core the first time with water only. Back flushed it and then flushed it forward. Made very little difference. Tried again using a parts cleaner solution to soak inside. Got a slight bit of dirty fluid out but not much. Flushed good with the garden hose afterward and got good flow again with the garden hose. Wanting to make sure the water pump is pushing coolant through the heater core. Also only thing that has been replaced has been the thermostats. Never did replace any actuator. Did check the blend door actuator at the bottom of the heater housing. It turns both directions freely and can feel a temperature difference between cold and hot (although hot is barely warm).
 
#10 ·
When it does get up to 190, does the heater work then? Does the fan blow good on high.
 
#11 ·
Fan blows good on all speeds. Even at 190 deg while driving heat is poor. After unit idles for 5 to 10 minutes the heat gets better. Does not drive you out of the cab but better. Also when driving with blower motor on a lower speed heat seems a touch better (not much though). As soon as I start driving the heat goes away again. The only time that I had the heat seem better was when I put card board in front of the radiator and pulled a load up the hill. Temperature got to about 215 deg and heat was more noticeable but still not great.
 
#12 ·
Just remembered. I think you have a problem with your blend door. There is a plastic coupler between the actuator and door lever. That coupler often brakes or splits and the shafts rotate inside of it. That is probably broke and the door is not turning all the way with the actuator. Pull off the actuator and you will probably find the coupler broken. A plastic one is available from the dealer or maybe parts stores. A metal one called the "heater treater" is available on line.
Bet you a coke that is it.
 
#13 ·
I will for sure check that. Just found that on another thread. That could take care of part of my issue.
 
#14 ·
So have not had a chance to do much with the holiday yet. Did notice a couple more things while driving unit this weekend so far. Things warmed up a little bit into the high 20s and low 30s. Found that when pulling a hill gauge goes to about 210-215 deg. When it does this, there is GREAT heat in the cab. As soon as getting back onto the flat it cools back to 190 and the vent temp goes back to lukewarm. This is with a piece of cardboard completely blocking off air flow across the radiator. As soon as I can, I am going to check all the temperatures with a temp gun. Just a couple of new observations.
 
#15 ·
These engines do take quite some time to warm up.. but you should have at least tolerable heat... We were at -10F, and I'd be driving for about 10 miles before I got any kind of heat.. After about 20 miles you could be comfortable without a jacket (incidentally, my trip to town is 16 miles..)
 
#16 ·
I have had 3 of these trucks and my current one never had good heat. I recently replaced my dash and when I did it I replaced the heater core and the a/c evaporator. I get noticeable heat as soon as the gauge starts to move.
People aren't very good about changing antifreeze and after a while it builds scale and sludge on everything in the system. The radiator on these trucks is way oversized unless you are doing heavy towing so most people don't have overheating problems but they do have water pump and heat issues. My guess is that the heater core is covered with scale and is not transferring the heat to the cab. You may be able to clean it like you have been trying to do but you may have to replace it.


Sent from my iPhone using Tapatalk
 
#17 ·
Aftermarket thermostats have been problematic for years. IN the past the only reliable stats were out of Mopar, Cummins, or HD at NAPA. Those are pricey but did the job for many of us.
 
#18 ·
Update

So worked on my truck today. Ran a temp gun on things. Found temperature gauge and temp gun within 5 degrees. Hit heater hoses and they were running no difference between hoses and about 20-30 degrees cooler than at thermostat housing where ECT is. This was what I found before doing anything.

So before going over there, I bought a new water pump, lower radiator hose, upper radiator hose, and warrantied out the thermostat again. Also bought new coolant. Drained the coolant. It was good and was not dirty. Replaced both hoses, water pump, and thermostat. Removed the coolant supply line to the heater core and made sure the fitting was not plugged up. It was not. Filled with new coolant. Bleed air out of the system. Ran up to temperature. All seems good. Removed the actuator for the temperature door. Coupler is in good shape and not broken. Actuator is working good and correctly. Door moves freely by hand and with the actuator.

With temp gun reading at lower vent on floor by heater box temperature is at 160. With gauge reading 190 coolant supply hose to heater core reads 195 and return hose reading 170-175. Heat is 10X better in the cab. Still did not feel as hot out the vent as I thought it should be. Drove home and had much better heat. Parked pickup. Started it and moved it several hours later and can hear a gurgling from the heater core. Sounds like I need to bleed it out some more to get all the air out. Will have to recheck once all the air is out of the cooling system. Made some progress at least.
 
#19 ·
Sorry for not seeing this thread earlier, but my opinion is that air has been the problem the whole time. I've had similar things happen with my old Blazer because the heater hoses were routed higher than the top of the radiator. Air bubbles would accumulate at the high spot on the heater hoses and I would get no heat unless I was towing something or unless I drove up a VERY steep slope, like an embankment. Driving up an embankment would move the air bubble into the radiator where the cap would expel it and I'd have good heat for about a month, after which air would get in that high spot again and I'd have to repeat.
 
#20 ·
Hit heater hoses and they were running no difference between hoses
Heater core is plugged up. I get roughly 60-80*F difference between heater hose. Heater hose should NOT be the same temperature. I just got done servicing a Ford F250 (V8 Gasser) for the same problem with both hoses the same temp the heater was weak at 95-105*F at the vent. After blowing out the heater core it was better but not the best. I measured 140-145*F at the vent. The hoses were about 35 to 50*F between hoses. When the heater core is flowing properly you should see roughly 160*F at the vents at minus weather.
 
#21 ·
So after replacing the water pump, coolant, and t-stat had ok heat for a couple days and then back to no heat. So going to replace the heater core as soon as I can get a break from work. So my question is this, after 1 week of temperature running steady at 190 degrees, it started acting up again. After running down the highway, when coming to a stop it drops to 160 degrees. So is there anything else that can cause this issue besides the t-stat? Going to take the t-stat back to autozone and just get the money back instead of warranting it again. I just want to make sure there is nothing else that could be causing this issue besides just the t-stat. Radiator is blocked off completely with cardboard. Thanks.
 
#22 ·
Are you by chance using a "FailSafe" thermostat? Autozone sells those, but you didn't specifically say it was a FailSafe, so I wanted to check. It will say it right on the thermostat box.

A failsafe thermostat has an extra spring that will cause the thermostat to lock completely open if the temperature gets above the spring's setpoint. After it locks completely open, you will experience the symptoms you are describing. The idea behind the failsafe spring is that if the main thermostat spring fails, the failsafe spring kicks in so that the truck will not overheat, although temperatures will fluctuate massively until you replace the thermostat.

A failsafe thermostat with an incorrect setpoint would certainly cause your symptoms.

Also, there is no reason to be blindly returning a thermostat to autozone for replacement. Simply toss it in a pot of water and boil it on the stove (if your wife objects, try to find an old unused pot or get one from goodwill). As it comes up to near boiling you should see the spring actuate and the valve open, and close again after you shut the heat off and let it cool a bit. If you have a cooking thermometer you can measure the precise temp that it opens and closes.
 
#23 ·
It is not listed as a "Failsafe" thermostat. How is testing it in a pot of water going to duplicate the exact issue going on. I can tell that it warms up to the correct temperature and opens. It will then run at that temperature as long as the unit is under load. As soon as the throttle is released and it starts coasting to a stop the temperature drops down to about 160 and will stay there until accelerating. Once accelerating it will come back up to temperature and stay there as long as throttle is being applied.
 
#24 ·
Well it seems like it's opening properly, but when is it closing? Observing it in a pot of water will tell you. There are different ways a thermostat can fail. So for example if it's opening at 190 but not closing until 80, you've found your problem: It opens when the truck first warms up and then doesn't close at all until it cools almost completely. That's not how it's supposed to work, it should cycle open and closed around the 190 degree mark to keep a consistent temp.

If that's the case, I wouldn't trust that brand of thermostat again, whatever it is, since you replaced it so recently and possibly multiple replacements have been doing the same thing.

The other possibility, as I said, is a thermostat that is stuck open, either because it's a failsafe that messed up or otherwise. It can still warm up if it's pulling even if it's stuck open. Taking it out and looking at it would tell you if it's stuck open.

I worked on big rigs at my Dad's shop for years before finishing college and we would have to test thermostats in this way from time to time, sometimes a bad batch of new thermostats would come in and they would all do wierd stuff like this.
 
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#25 ·
Bigfish recommended you check the front of radiator between the intercooler and Rad to see if its clogged with dirt.
I didn't see where you confirmed it wasn't clogged or I missed it but wanted to make sure you checked it.
 
#26 ·
I have it completely blocked off with card board. Between the radiator and CAC is where I put the card board.
 
#28 · (Edited)
Like I tell everyone DO NOT put cardboard between then coolers or in front of the coolers. If the fan locks it can NEVER pull any air through any cooler. So cooling system problems occur. My winter front is on the grill and gives a air space if the fan has to lock then the coolers can do there job correctly.

https://mopar1973man.com/cummins/ar...erior_88/winter-front-for-dodge-cummins-r347/

As seen here kind of...
 
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