Last post on Apr 22, 2012 at 7:27 PM
You are in the Dodge Dakota-2010 and older
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Dodge Dakota, Truck
#224 of 243 Re: OK..Changed the Tstat..and it over heated. [steak2k1]
Jul 30, 2006 (1:23 pm)
did you "burp" the system to eliminate air pockets? There is a procedure for burping the system which includes using the "burping valve" at the high spot of the cooling system.
Also - are you certain that the thermostat you installed is compatable with a "bypass" cooling system? (uses the thermostat to mix the cold [radiator out] and hot [engine out] flows to produce the proper temperature into the engine)
#225 of 243 Re: OK..Changed the Tstat..and it over heated. [steak2k1]
Aug 03, 2006 (5:58 pm)
Are you getting a "Check Gauges" indicator illumination? If not, the PCM believes that the engine is operating at "normal" temperature (between 130 and 264F).
THe Engine Coolant Temperature sensor is located on the front of the engine just below the MAP sensor. It has two wires. I can't tell you what the DC resistance range is, but as the temperature increases the sensor resistance decreases.
#226 of 243 Re: OK..Changed the Tstat..and it over heated. [dustyk]
Aug 08, 2006 (10:39 pm)
Dusty..your comment on the bypass is bang on the dollar. Given that this 4.7 uses said system, I did not use a "bypass" tstat. However I sure would love to get my hands on one if anyone knows where to acquire..??
The 05/06 4.7 Tstat is standard all way round except on one part of the flange, there is samll ~1/8" hole with a brass pin that has flared ends on either side of the Tstat flange.
This apparently opens and closes to allow mixing of the fluids on either side (I am assuming this is how the unit works).
Reason I am after a 180, is simply to keep engine cooler while towing. This came toa head just 2 days ago coming back from a camping trip through Southern BC. Took the Salmo-Kooteny Pass and man oh man that is some grade...up to 8% is parts and minimum 6% overall - 35 Km of it.!!
I was pulling 4360 lbs. (I'd gone over the scales that AM). Temperature was 32C and about 3/4 of the way up I was in 1st gear doing 40 klicks at about 4200 rpm. She heated up good. That was the only time I ever seen the dash sensor light come on. A tad alarming..!
Pulled over, reved it up at 1800 in park and let the motor cool down...did that twice and we finally hit the summit.
After that I had no problems the rest of the 450 km trip home.
So if anyone knows where one can acquire a 54mm OD Tstat that is of the "bypass" type..I would love to hear aout it.
Thanx in advanz,
#227 of 243 95 dodge dakota instrument panel problems
Aug 09, 2006 (1:58 pm)
Driving home from work and the abs and parking light comes on. Then the head lights and instrument panel goes out. Can so one help me on where to start first. Oh by the way the rpm gauge comes on and off and the fuel gauge moves.
#228 of 243 THIS IS HOW THE BYPASS COOLING SYSTEM WORKS
Aug 09, 2006 (5:10 pm)
It is I that have been touting the "bypass" cooling system to you for several weeks. Your description of how a "bypass" thermostat works is incomplete.
A "bypass" thermostat actually "reads" the temperature of the coolant ENTERING the engine. You can think as the "bypass" as the "hot" antifreeze coming out of the engine and the "cold" as being from the radiator. The thermostat then constantly mixes these two flows to maintain the target tempurture.
When engine is 'cold', the thermostat seals off the outlet of the radiator and only allows the coolant to flow thru the bypass circuit effectively recirculating all the antifreeze in the engine around and around. This happens until the "target" temperature is reached. (this allows for faster warmups...thus less emmissions)
At this point, a measured amount of 'cold' antifreeze is allowed out of the radiator to enter the flow. The thermostat constantly "reads" the temperature entering the engine and adjusts the mix of "cold" and "hot" antifreeze to maintain the target tempurature.
Under extreme conditions, the thermostat can actually CLOSE OFF the bypass flow and forces ALL the flow to come from the radiator to enter the engine. (this condition may never actually ever occour.)
The "hole" in the thermostat which you describe allows a very small amount of flow even when the radiator outlet is "sealed off". This small flow allows the antifreeze in the radiator to warm up a bit before it is 'used' in the engine. This is done to keep the engine block from cracking in cold wetaher. Without the hole, it would be possible for -10F antifreeze to flow into a hot engine when the thermostant opens up the radiator outlet. (the engineblock would instantly crack wide open due to this condition!!)
Installing a regular NON-bypass thermostat can effectively scru up the entire cooling system because it does not have the proper components to throttle the "hot" and "cold" flows. Most likely, your cooling system would be incapaable of maintaining a constant tempurture.
A bypass cooling system is so effective, that is why I have recommended to you several times to just leave the original alone. Changing the thermostat to a lower temturture can really mess with the onboard computer because it has several functions that need to key off of the designed target temparture.
If you INSIST on installing a thermostat that deviates from the designed target tempurture, there are some places that offer such a device.... but beware, your onboard computer may never be "satisfied" that the engine has warmed up thus make for poor encoomy and generally unsatisfactory running.
#229 of 243 Dodge Truck Thermostatic Fan Clutch
Aug 12, 2006 (7:00 am)
Noise produced by the fan clutch on a Dodge truck is normal.
The Dodge engines use a viscous clutch fan that permits reduced load and subsequent loss of horsepower at high speeds, yet increased cooling capacity at low speeds. These fans contain a high density silicone filled coupling that connects the fan blades to the water pump shaft. This design utilizes a thermostatic bimetallic coil spring that reacts to the temperature of the radiator discharge air.
As the discharge air temperature through the radiator approaches 165 to 180 degress F, the bimetalic exerts pressure against a slip clutch and allows power of the water pump shaft to be transmitted through hydrostatic coupling to the fan assembly. This raises the speed of the fan blades and increases air flow through the radiator to provide increased cooling.
Sometimes after a vehicle has been driven to operating temperature the bimetalic spring may expand to the maximum coupling position due to localized heat from the engine or radiator after shutdown. After a cooling period the spring may not contract or contract fully. Upon restart the expanded spring causes the fan to spin at engine RPM until enough cool air has been drawn through the radiator, Then the spring contracts. This is what causes that momentary period when the fan is heard after restarts.
Testing the Fan Clutch Assembly
If the fan assembly free-wheels without drag for more than five revolutions when spun by hand, the fan clutch assembly is defective. This test must be conducted when the engine is completely cool.
Fan drive engagement begins when the radiator discharge air flow is between 165 to 180 degrees F. Disengagement begins when the air flow temperature is between 135 to 175 degress F.
There should be no perceptible lateral movement of the fan blades. If so, the fan assembly is defective.
#230 of 243 Re: OK..Changed the Tstat..and it over heated. [steak2k1]
Aug 12, 2006 (7:14 am)
It wasn't me but Bpeebles, who by the way has given some very good advice.
The bypass thermostat is available from any Dodge dealer.
As Bpeebles pointed out, a lower operating temperature will affect emission controls and cause less than optimum engine and vehicle operation. Long engine warm-ups and increase fuel consumption can result. In addition, because of the way the bypass type thermostat operates by providing bypass galleries in the engine block with coolant, you may actually find that a non-bypass thermostat might cause engine block hot spots. What this might cause I do not know.
However, 4.7 equiped Dakotas tow very well in all temperatures from my experience. If you've encountered overheating I would first suspect something else is wrong, either the radiator is partially blocked, the thermostatic fan clutch is defective, or the radiator fan motor is inoperative.
#231 of 243 No more TStat talk ...K.??
Aug 13, 2006 (9:12 pm)
Hey Bpebbles...no nead to lecture..OK??
For one and as I said previously, I re-installed the OEM 195 deg Tstat. After that, I had done, professionally, a complete cooling system change. (non Glycol type). All this was three weeks ago and prior to my vacation trip.
I do appreciate the technical explanation of the "bypass".
..a 180 is not in the picture.
The Hwy I traveled is called Hwy #3 in Southern BC. Check it out. And I can tell you that towing 4300 lbs (checked on the scale), on an 8% grade, at 4-5000' Above sea level and at an outside ambient temperature of around 90+F with a tail wind..It overheated. Ie; the engine temp light came on. The temp gauge was about half way between middle and Overheat.
Now, do I believe there is/was some other thing wrong with my motor..?? No, not at all.
It was damned HOT is all.!
The motor worked damned HARD is all.! 1st gear at 4500 rpm
It was damned STEEP is all.!
I was towing 4300 lbs is all.
Let me tell ya that this climb was an itch with a B.!
This was not the little hills in the Adirondaks of up State NY nor the so called "Rockies" of Idaho cause I've driven those and they are nothing campared to what we have here. Don't believe me..?? Y'all come and see for your self.
No Offense Dusty, but just about anything would have overheated in those conditions..!! As a matter of fact we were not the only ones pulling over in the conveniently placed rest zones (every 300 m) on the shoulder overlooking a 700' drop to the valley below. And ya know, we only had to pull over twice right near the summit. So IMHOP it was not really a huge deal although I was concerned at the time.
Traveling on ~flat type of terrain, these units tows very well indeed. Given I use Premium gas and I use synthetic lubes all round...Bpebbles would be happy to note that I indeed took his advice and used Redline.!
Overall am quite pleased at how the unit performed. But towing in the CDN Rockies is another story. Short of putting a larger engine with way more low end torque and or different gear ratio..not much else to add to this pupply. 'cept the chip.
Not to worry guys, I promise I won't look at another Tstat again.! (-%
#232 of 243 Re: No more TStat talk ...K.?? [steak2k1]
Aug 14, 2006 (5:25 pm)
It was not meant to be a "lecture" -- this is the Dakota FAQ forum and I was submitting a detailed explanation on how the bypass cooling system works. Now folks who need info about their cooling system can get a solid foundation about how it works by looking it up here in the FAQ forum.
If you wish to chat about your dakota or ask questions -- there are several other forums here on edmunds that are better suited than this FAQ forum.
Aug 15, 2006 (6:48 am)
That's fine. I too learned. However it did come across as such. Ergo the comment.