QuestionQUESTION: In July 2011, I replaced my radiator and thermostat car ran fine for about 30 days, then the temp gage started going over half mark when I turned on the heat full it came down. I took it back into the garage and had my reservoir replaced and a new waterpump installed, replaced the rad hose and A/C Hose, installed 6 new spark plugs, it still over heated, but temp gage would come down when I put the heat on full blast. Took the car back to Chrysler and they installed a temp sensor and replaced my upper intake manifold. Just got my car back after a month in the garage and it is still over heating the service manager says the internal temp is normal but the temperature gage still goes high, when I turn on the heat full blast it now runs between half and 3/4. I check under the hood and it is not overheating no bubbling sound or boiling from the reservoir. I am told that everything checks out that the engine is fine. I have spent over 2,000.00 in the past 3 months, please help.
ANSWER: Hi Barbara,
Given all that has been done my thought is that the temperature gauge itself may simply be inaccurate reading false high. It is normal to have the gauge cycle up and down as the thermostat opens and closes, and the normal range of such oscillations is any where between 1/4 and 3/4 if the gauge is accurate. I know it is unnerving to see it reach 3/4 scale but in the absence of any signs of coolant being lost, or steam coming from under the hood, or bubbling sounds early after starting, or excess white smoke out the tailpipe after starting from cold, I would try to drive it for a while and see if you have the needle going often above 3/4 to approach the H or not. If it doesn't actually start releasing steam or coming close to the H then I would readjust my level of concern to take into account the possibility that the gauge is just being pessimistic.
You can pretty much sense a real overheat situation when you have concern by opening the hood as you have done and described what you are looking for.
I have such a gauge in my '89 Chrysler LeBaron so I simply added a 10 ohm resistor into the wire that goes to the gauge which shifted the reading downward so that it subconsciously doesn't keep me on edge when there is no reason to be so.
There is only one 'trick' about the engine that you have which is that whenever the cooling system is drained it has to be refilled in a specific manner so as to remove any air that otherwise might be trapped by means of a bleed valve and collecting hose on the front of the engine and by using a special funnel and associatited hose clamp (Miller tool no. 8195) to refill the reservoir properly. I would assume that the dealer mechanic know about this issue, but you could raise that question with the shop manager just in case it was overlooked.
Clearly if there is evidence of true overheating something has to be repaired. But absent that I would look into more subtle things like I described or try to just accept/live with the gauge as it reads barring any evidence of a true overheat.
Roland
PS Please 'rate' my answer, and where you see the question about a nomination of me to be 'volunteer of the month' consider a 'yes'. Thank you.
---------- FOLLOW-UP ----------
QUESTION: Hi Roland,
I had a chance to drive my car yesterday and noticed that while the temperature gage did go over 1/2 without the heat on full blast, my RPM is also high. When I accelerate it goes to 2000 and then back down to 1500, however when I go 60 mph the RPM stays at 2000 and over, that is when the temperature gage goes to 3/4. When I an idle at a stop light the temp gage goes down right away. Before I had the rad, thermostat, replaced it did the opposite, the temp gage would go up high. I checked under the hood and the fluid is the resorvior is fine. However the right side of rad feels cool while the left side feels hotter.
I am afraid to drive the car without my heater on full blast, also when the temp started to climb to 3/4 the heat coming into the car increased.
My transmission fluid is fine I checked that and so is my oil.
AnswerHere are the details on how to remove air that might be trapped in the upper radiator hose or the thermostat housing. If a mechanic or family member would give this a try it might solve your problem. Thanks for the rating and nomination.
When you refill it you have to do it in such a way as to not trap air in the cooling system. This involves a bleeder valve located on the lower intake manifold, left of center and below the upper intake manifold to which you attach a hose, then open the valve, to route coolant out over the front to collect and re-use to keep filling until full, and also uses a funnel with a septum which allows air to escape as you pour the coolant in, and also you clamp the overflow pipe on the filler bottle. Here is a description of it:
"Close radiator draincock by turning clockwise.
NOTE: IT IS IMPERATIVE THAT THE COOLING SYSTEM AIR BLEED VALVE BE OPENED BEFORE ANY COOLANT IS ADDED TO THE COOLING SYSTEM. FAILURE TO OPEN THE BLEED VALVE FIRST WILL RESULT IN AN INCOMPLETE FILL OF THE SYSTEM.
Open cooling system bleed valve.
Attach a 6.35 mm (0.250 in.) inside diameter clear hose that is 120.0 cm (48 in.) long to the bleed valve. Route the hose away from accessory drive belts and radiator fan. Position the other end of hose into a collecting container. The hose will prevent coolant from contacting accessory drive belts and other components.
Remove cooling system pressure cap. Attach Special Tool 8195, Filling Aid Funnel to coolant pressure container filler neck.
Use the supplied clip to pinch overflow hose that connects between the two chambers of the pressure container
Pour coolant into the larger section of Filling Aid Funnel (the smaller section of funnel is to allow air to escape).
Slowly continue filling until a steady stream of coolant flows from attached hose on bleed valve.
Close bleed valve and continue filling system to top of Filling Aid Funnel. DO NOT overtighten. TIghten to 12.4 N·m (110 lbs. in.).
Remove clip from overflow hose.
Allow coolant in Filling Aid Funnel to drain into overflow chamber of pressure container.
Remove Special Tool 8195, Filling Aid Funnel and install pressure cap on pressure container.
Remove hose from bleed valve.
Start engine and allow to run until thermostat opens and radiator fans cycle.
NOTE:
The engine cooling system will push any remaining air into the pressure container within about one half hour of normal driving. As a result, a drop in coolant level in the pressure container may occur.
If the engine cooling system overheats and pushes coolant into the overflow chamber of the pressure container, this coolant will be sucked back into the cooling system ONLY IF THE PRESSURE CAP IS LEFT ON THE PRESSURE CONTAINER. Removing the pressure cap breaks the vacuum path between the two chambers of the pressure container and the coolant will not return to the cooling system.
Shut off engine and allow it to cool down. This permits coolant to be drawn into the pressure chamber.
With engine COLD, observe coolant level in pressure chamber. Coolant level should be within MIN and MAX marks. Adjust coolant level as necessary.
Once the system is filled properly the funnel is not needed until it has been drained and needs refilling."
Hi Barbara,
The relationship between the rpm and the road speed of course depends upon what gear your transmission has selected. So I can't tell if your rpm was truly higher than it should have been when you noticed the 2000 rpm, which is not really an excessive rpm. At 60 or above I would not be surprised at it being 2,000 rpm. My automatic runs at 2500 rpm at 60 but then it is a 4 cylinder car which needs to do that.
When the temp gauge goes toward the 3/4 line pull over and see whether the radiator fans are running or not would be my first suggestion. That is the main response that is normal at that point on the temp gauge. Let me know if the fans aren't running at 3/4 scale.
One side of the radiator will be cooler than the other but because you had the radiator changed I would believe that is just a normal amount of difference, not something unusual. Only if the cooler side were frankly cold would that be an indication that the coolant is not flowing across the radiator to the other side and back which is what it is supposed to do.
When you say the reservoir 'looks fine' does that mean that there was only coolant in the smaller inboard chamber and the the larger ourboard chamber was virtually empty? That is the way it is supposed to look when the system is cold. If not, then it may not have been filled properly (see note below).
The heat to the cabin will of course be tied to the temp on the gauge because that same coolant flow to the heater core in the cabin. Again, I would not be concerned unless the gauge threatens to go to H mark or you see steam coming from under the hood.
I would drive the car without the heat on and don't be alarmed unless the temp pushes close the H. Then stop and see if the fans are running.
Roland
PS: Keep in mind the possibility that the gauge itself is inaccurate. A shop should have an infra-red thermometer to compare the actual temp at the thermostat housing/radiator with the gauge reading. And at the same time you could go to the last person to work on the system and inquire if they followed the correct procedure to refill the system so as to avoid trapping air within it and did the bleed air out of the bleed valve on the front of the engine as is shown in the manual and use the #8195 funnel. There should not be much if any coolant in the outboard section of the bottle, only the inboard section. The outboard section is expansion space to allow the fully heated coolant to be collected as it expands, only to be sucked back into the radiator as the engine cools to ambient.
