Over COOLING problem
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
This sounds like not enough water flowing past the coolant sensor.
1. Does the low coolant light come on at any time?
2. carry a jug of water and when the temp is low, pull off quickly, open the radiator cap, and refill the water with the idle elevated.
3. Could there have been a heater tube cap that got dislodged into the heater core and with the RPM up the water bypasses the heater core and with slower water flow, then it goes in the heater?
4. Is it possible that the radiator fans are going on when the car is in motion or in gear? roll the window down and listen.
5. THe thermostat could be a problem, but when mine stuck open, I had 150 degrees coasting, going down hill, and 179 degrees every other speed.
1. Does the low coolant light come on at any time?
2. carry a jug of water and when the temp is low, pull off quickly, open the radiator cap, and refill the water with the idle elevated.
3. Could there have been a heater tube cap that got dislodged into the heater core and with the RPM up the water bypasses the heater core and with slower water flow, then it goes in the heater?
4. Is it possible that the radiator fans are going on when the car is in motion or in gear? roll the window down and listen.
5. THe thermostat could be a problem, but when mine stuck open, I had 150 degrees coasting, going down hill, and 179 degrees every other speed.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Have you put the first thermostat and a thermometer in a pan of water on a stove and watched its operation as the water warms up? Does the thermostat close as the water cools off? Since the first thermostat apparently works the same as the second (which is very unlikely that both would be bad) that's at least some confirmation that it's not a thermostat problem.
Thread Starter
Advanced
Joined: Jan 2011
Posts: 55
Likes: 0
From: Hampton VA
The problem remained the same after I changed the thermostat. However, I have noticed that even after driving the vehicle for many miles, When I stop and attempt to check the fluid levels, I can immediately take the radiator cap off without the usual build up of pressure and outpouring of fluid that occurrs when you try to take the cap off of any other vehicle without a cooling off period. It seems that there is no pressure in the system but there is no cooling fluid loss either. And Yes the FSM that I am using is the original that came with the vehicle. My thought on the purge valve that I earlier suggested came from a 1984-1992 Chiltons manual that I also have and it talks about purging air from the system in that manual. I also ensured that the water caps were reved prior to installation.
Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
Disconnect the fan wires. Make sure the heater is in the off position and drive the vehicle and monitor the coolant temperature. This should eliminate the fan and heater core. Let us know result.
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Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
Take some cardboard along , if the fan and heater core doesn't increase your coolant temperature, block off some of the radiator, not totally. This will tell if the new thermostat was defective (wouldn't be the first time a new part was bad). Monitor your oil temperature and check your engine for signs of overheating. Coolant in the radiator is pumped through the engine by the pump and returns to the radiator, flow control is temperature controlled by the thermostat, it's a simple system, we will solve this.
Cruising
Joined: Jan 2011
Posts: 10
Likes: 0
From: Chattanooga TN
Cooling problem
If you are sure that it is over cooling, and not just giving a bad reading at the gauge, you could have a flow problem allowing the coolant to spend too much time in the radiator, just as removing the thermostat will cause a over heating problem due to the coolant flowing too fast through the radiator and not spending enough time in it too cool down, to much time or slow flowing could cause an over cooling problem. also the fans running all the time could cause this problem.
Last edited by pcmusicer; Jan 26, 2011 at 01:50 PM. Reason: another thought
Race Director
Joined: May 2008
Posts: 10,742
Likes: 629
From: Manheim Pennsylvania
Another thing to check; open the radiator cap and check the flow when the thermostat opens, you should notice the flow increase. If the flow is constant, even when the engine is cold, the thermostat is open and doesn't close (the thermostat fails open). These checks should isolate us down to either the fans are coming on when they shouldn't or the thermostat is not working properly. I can't think of anything else in the system that will not allow the engine to come up to normal operating temperature, I can think of lots of things that will make it run hot. You never told us if this car ran cool before the heater core change.
Last edited by Larry/car; Jan 26, 2011 at 02:19 PM.
Racer
Joined: May 2010
Posts: 315
Likes: 0
From: Central New York NY
You really need to get an infrared thermometer from Harbor Freight. If you don't you'll be just guessing at the temps of the hoses, rad, and thermostat housing. They also have alot of other uses, such as, setting the hot water heater, checking for air leaks in winter around doors and windows, etc. They are well worth the $30.
Thread Starter
Advanced
Joined: Jan 2011
Posts: 55
Likes: 0
From: Hampton VA
I have been flying the last 2 days but now I am ready to re attack this problem. I am going to stop at Harbour frieght on the way home and pick up the tool to check the temps. The cooling fans are not running all the time and seem to be cycling on and off as necessary. I am going to change the coolant again this weekend and see what happens. Thanks for all the help with this. I will probably get this figured out right about the time it gets too warm to use the heater again.
Oh and just to confirm, the car has always ran at the correct temperatures until I changed the Heater Core.
Oh and just to confirm, the car has always ran at the correct temperatures until I changed the Heater Core.
Racer
Joined: May 2010
Posts: 315
Likes: 0
From: Central New York NY
Once you can determine the actual temps of things under the hood you'll have a much better handle about what is going on. Those infrared thermometers are really handy. When I tow my camper I check the tires everytime I stop to see if any are building up too much heat.
