pete944

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by ahofam123:
<strong>After I replaced my waterpump, my temp guage was reading in the red. I relaced the thermostat again, the radiator, the sending units and the thermoswitch. After all of this, it was still reading hot. It isn't boiling and the cooling fans come on just before the guage goes into the red so I am just assuming that the guage is miscalibrated or there is a short in the wiring. Before you guys go replacing the entire cooling system, make sure that the guage is reading the correct value.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Is there an easy way to check the calibration of the gauge? Can it be done with a volt/ohm meter?

ahofam123

Here is a way to check the temp sending unit to the guage, I don't know if there is one to test the one to the DME. I got the one to the guage for $15 at Advanced Auto Parts and the one for the DME for $50. <a href="http://frwilk.com/early944/misc/watertemp.htm" target="_blank">http://frwilk.com/early944/misc/watertemp.htm</a>

tazman

One thing I learned while bleeding my system was the upper part of the motor where the temp sensor for the gauge is seems to get hot quicker then the bottom of the motor. I was able to keep my temp down by casually driving the car around and I watched for my oil pressure to start dropping so I knew the motor was warmed up. After the oil pressure showed the engine was warm I was able to bleed the system pretty good then because the thermostat had opened.

Waterguy

For some of the overheaters, temperature gauge calibration may be a problem. For Justin:
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Well, I got the heat to comeback, I had the bleed screw open and then increased the throttle, that caused the needle to drop somewhat, but after I get on it, it goes right back to its current behavior, except now it doesn't want to go down to the top white line, always wants to stay in the red. Coolant was defiately coming out of the bleed screw. Funny thing is, the only hose that is hot is the one that is on top and leads to the bleed screw. All the other one's are cool to the touch.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">this would just be a red herring. If the car is overheating and the coolant is not circulating through the radiator, there is a very short list of possible problems:

1. Blockage in cooling system (thermostat stuck closed.)

2. Lots of air in the cooling system that needs bleeding. Small amounts of air would not cause this. How much coolant have you been able to add to date? When I drained my cooling system, I was able to add 6 liters by raising the front of the car, opening the bleed screw and blowing into the coolant reservoir until coolant came out the bleed screw. Warmed the car up and the coolant circulated but the heater did not work initially. Let it cool down and repeated the process, added about 1.5 liters more coolant, got all the air out and it has worked fine since.

3. Water pump not working. Possibly impeller slipping on shaft.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Well, upon further inspection of the hoses, I found that the coolant expansion tank to radiator hose has a small hole in it from what looks like where the alternator's fins rubbed up against it. That would definately cause a lack of pressure and cause the car to overheat, correct? </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">This would cause you to loose coolant when the system pressurizes, and needs to be fixed. It would not cause the problems you describe. Your coolant is not circulating.

Bri Bro

Well, upon further inspection of the hoses, I found that the coolant expansion tank to radiator hose has a small hole in it from what looks like where the alternator's fins rubbed up against it. That would definitely cause a lack of pressure and cause the car to overheat, correct?

I saw this problem on a 2nd generation RX-7 that also needed to have the air "burped" from the cooling system. We did it three times, and the next day the air was back in the system and the coolant alarm was going off. The problem was a crack in the coolant expansion line, every time the car cooled down, the radiator was pulling in air rather then fluid from the expansion tank.

Is there an easy way to check the calibration of the gauge? Can it be done with a volt/ohm meter?
There are several temp sensors in the 951.

**Temp sensor I - Runs the temperature gauge.
Located in the lower middle part of the head. Can be checked across the sensor after the leads are disconnected. To check the gauge, disconnect the wires to the sensor and put a resistor (from the values below) across the wires. Lower part of first bold mark on gauge is 40C, top bold is 60C. Next mark is 80C, and the next is 100C. Bottom of top mark is 115C.

Model year 82-85
40C = 287 ohms
105C= 33.6 ohms

Model year 85.5 on
40C = 287 ohms
60C = 134 ohms
80C = 69 ohms
100C = 26 ohms

**Temp Sensor II - WILL NOT CAUSE OVERHEATING PROBLEM! Can cause cold start and idle problems. Used for the DME, located on the front, lower part of the head next to the air flow sensor. Can be checked at the sensor with the leads disconnected or with the leads connected, across terminal 13 of the DME and ground.

15-30C = 1.45-3.3 Kohms
40C = 1.0 -1.3 Kohms
80C = 280-360 ohms
100C = 160 - 210 ohms

**The three sensors that go to the "Coolant Fan Relay" to run the fans.
The "Coolant Temp. switch" (what is called fan switch on the Radiator) has two internal temp sensors(three terminals are on the back of the switch). One closes at 92C (terminals 2 to 3) and the other closes at 102C (terminals 1 to 3). The other sensor connecting to the Coolant fan relay is the "Refrigerant Temp. switch" and is set to close at 52C. The refrig temp switch is connected in parallel to the 102C coolant temp switch so if either of these switches exceed their limits the fan motors turn on high. The AC relay is also connected to the Coolant fan relay and turns on the fan when the AC is switched on. If you pull off the Coolant Temp. switch plug and short terminals 2 to 3 the fans should run at low speed. If you short terminal 1 to 3 the fans should run at high speed. If you turn on the AC (AC is charged and in working order) this will also turn on the fan motor.

Putting on the A/C or the heat had no effect on the problem. Then I hooked up both fans directly to the battery and only the drivers side one worked. Does this mean I have a bad motor on the passenger side for sure or is there another explaination for this?

Two things come to mind, check the fuses 10&15 (25A) and the Fan relay ( the really big one). One lead of the fan motor goes to ground so it could be broken, run both power and ground leads to the fan. If the fan will not spin, it is bad.

Justin Browning

Well, I got the new hose in, and the temperature wants to stabalize at the top white line. It still gets to that line rather quickly. How hot should the car get with the stock rated thermostat and all things working appropriately? I don't see any coolant leaking anywhere, but I have other friends telling me they smell coolant. There is also no intermix, the coolant is as clean as can be. If anyone around Grove City would care to come help me out, it would be greatly appreciated.
Thanks guys,
Justin

Justin Browning

Bump..
I really need help to get this fixed, as it is my daily driver.
Thanks in advance,
Justin

Justin Browning

Well, I let the car cool down after class today. It rose to the last white line relatively quickly at idle (about 5 minutes). When it hit the line, the fans did not come on. It went a little over and the fans still did not come on. I pressed the A/C button and the fans came on and stabilized the temp at the last white line. I then turned of the A/C and the fans stayed on until I turned off the car, from which they stayed on for about a minute or so (which I assume is correct). I am getting ready to replace the fan switch, so I will see if that helps.

bf95cab

aside from the thermostat itself, isn't there a valve which can stick and prevent water circulation?
also, could the computer be having a problem analysing the signals it receives, and so not open the valve to circulate the water?
i had a similar problem a couple of years ago. turned out to be the oxygen sensor was bad, so the computer got bad info and the car overheated.

Kevin Baker

Justin, if the fans come on with the A/C and cool the car to the normal temp range, then you can deduce that the water pump is functioning, the T-stat is functioning, and the problem must then be either there is an air pocket right at the thermoswitch for the fans (as the A/C would override the thermoswtich) or the thermo switch is bad as the relay is working via the A/C switch.

jurg

Triple <img border="0" alt="[cherrsagai]" title="" src="graemlins/drink.gif" />

jurg

well i was having the same problem with my car,after changing the T-tat, the thermoswitch, new coolant, burped it, about 5 times and it still was going up to the third mark , the only thing that got the temp down was to bypass the heater valve and heater core, I connected a hose from the water rail in the side of the motor to the back of the head , burped it and
now car worsk fine, so that means that maybe the heater or the heater valve was bad, try it, maybe that helps you like it helped me, I get enough heat here in South Florida,so im going to keep it that way

jurg

Double <img border="0" alt="[cherrsagai]" title="" src="graemlins/drink.gif" /> <img border="0" alt="[cherrsagai]" title="" src="graemlins/drink.gif" />