Overheating

Ethan Keirn · May 31, 2017

wmburns said:
Motor off should be normal battery voltage 12.2 to 12.6. See why the meter needs to be accurate?

Motor running charging voltage should be 13-15 volts depending upon the battery's state of charge.

Turn on every accessory (AC, head lights, brights, brakes) even better. Let the motor reach full operating temperature when the cooling fans turn on. What is the voltage measurement? Is it above 12 volts? If so, the alternator is keeping up with load.

But the other thing that we are trying to confirm is what the voltage is doing when the problem occurs. It's all about change. IE, does the voltage drop or change when the problem happens?

Next put the VOM lead on battery negative and the other lead on the alternator case. This will measure the voltage drop through ground with the motor running. Should be low. Post.

Next put the VOM in the AC scale. Measure the voltage across the battery with the motor running. This will be the amount of AC ripple from the alternator. Should be low. Post.

Sounds like you could use a Ford service manual.

Exactly how have you determined the motor is over heating. Tell us all of the symptoms.

Tell us about the other things done to resolve this problem. Have the cooling fans been tested and confirmed working on BOTH speeds?

What about the pressure cap? Does it hold pressure? When it does over heat does it blow coolant? What is the condition of the coolant?

Under what driving conditions does it over heat? Stop and go city driving or highway cruising?

The details matter here as the information can help to narrow the focus.

As long as tbe vehicle is running it will over heat, the temp gauge goes up almost all the way to the H and it reads about 200-210 with a laser thermometer, once it gets to that temperature it starts to miss and shake when you try to accelerate, we tested the electrical system yesterday all seemed well, but now it looks like it might be the ccrm, so far ive flushed the cooling system and changed the radiator cap, temp sensors, and water pump, and it still seems to be overheating, the highest i saw the temperature go was 220

wmburns · May 31, 2017

So WHY do you think it's the CCRM? Because the fans aren't running? Because IF the fans work on both speeds, then the CCRM is working.

If trying to replace only bad parts, then test the fans by running directly from battery. Test both speeds. There should be an OBVIOUS speed difference between the low speed and high speed. Spin the fans by hand. Do they spin free? If the fan does not run direct from battery then the diagnosis is confirmed. Bad fan.

Note, it's quite common for the fan plug to over heat and melt.

There are detailed tests that can be done with a VOM to positively confirm a bad CCRM. They are a little detailed because the way the fan works the power back feeds through the inactive circuit.

If the fan works on both speeds direct from battery and you are certain that off of the things previously mentioned are OK, then the odds favor a bad CCRM.

OBTW, a reading of 200 at the T-stat housing is not too hot (assuming an accurate reading). The stock T-stat is 192 degrees. At 200 degrees the PCM won't even call for the fan to run. I believe the PCM won't even call for the low speed fan to run until 210 (or so). The high speed fan set point is even higher.

FWIIW. Here is a prime case where an ODB2 scanner could help the trouble shooting. The scanner would tell you what the PCM "thinks" the motor's temperature is. Plus it would tell you what fan speed the PCM is calling for. By comparing the actual fan speed to the commanded fan speed the trouble shooting is focused.

NOTE, IF the problem is related to the fans THEN the motor will not over heat when driven at expressway speeds. Why? Because the fans are not needed above 45 MPH. So if the motor is over heating when driven on the expressway it's over heating for another reason.

NOTE, the SOHC motor will self bleed the cooling system after a couple of heat/cool down cycles. But during the time there is air trapped inside the motor the ECT sensor will read low due to being in contact with air.

It's been my experience that if a motor slowly over heats when driven it's because of a clogged radiator. Of course this assume that everything else has been checked out.

What has been done to rule out a clogged cat? You have an scanning infrared thermometer that can be used to measure how hot the cats are.

What has been done to rule out a base motor problem such as a leaking head gasket? At some point some consideration should be given to running a compression test and/or cylinder leak down test. Or at least testing the coolant for hydro-carbons.

Ethan Keirn · May 31, 2017

wmburns said:
Motor off should be normal battery voltage 12.2 to 12.6. See why the meter needs to be accurate?

Motor running charging voltage should be 13-15 volts depending upon the battery's state of charge.

Turn on every accessory (AC, head lights, brights, brakes) even better. Let the motor reach full operating temperature when the cooling fans turn on. What is the voltage measurement? Is it above 12 volts? If so, the alternator is keeping up with load.

But the other thing that we are trying to confirm is what the voltage is doing when the problem occurs. It's all about change. IE, does the voltage drop or change when the problem happens?

Next put the VOM lead on battery negative and the other lead on the alternator case. This will measure the voltage drop through ground with the motor running. Should be low. Post.

Next put the VOM in the AC scale. Measure the voltage across the battery with the motor running. This will be the amount of AC ripple from the alternator. Should be low. Post.

Sounds like you could use a Ford service manual.

Exactly how have you determined the motor is over heating. Tell us all of the symptoms.

Tell us about the other things done to resolve this problem. Have the cooling fans been tested and confirmed working on BOTH speeds?

What about the pressure cap? Does it hold pressure? When it does over heat does it blow coolant? What is the condition of the coolant?

Under what driving conditions does it over heat? Stop and go city driving or highway cruising?

The details matter here as the information can help to narrow the focus.

As long as tbe vehicle is running it will over heat, the temp gauge goes up almost all the way to the H and it reads about 200-210 with a laser thermometer, once it gets to that temperature it starts to miss and shake when you try to accelerate, we tested the electrical system yesterday all seemed well, but now it looks like it might be the ccrm, so far ive flushed the cooling system and changed the radiator cap, temp sensors, and water pump, and it still seems to be overheating, the highest i saw the temperature go was 220

wmburns said:
So WHY do you think it's the CCRM? Because the fans aren't running? Because IF the fans work on both speeds, then the CCRM is working.

If trying to replace only bad parts, then test the fans by running directly from battery. Test both speeds. There should be an OBVIOUS speed difference between the low speed and high speed. Spin the fans by hand. Do they spin free? If the fan does not run direct from battery then the diagnosis is confirmed. Bad fan.

Note, it's quite common for the fan plug to over heat and melt.

There are detailed tests that can be done with a VOM to positively confirm a bad CCRM. They are a little detailed because the way the fan works the power back feeds through the inactive circuit.

If the fan works on both speeds direct from battery and you are certain that off of the things previously mentioned are OK, then the odds favor a bad CCRM.

OBTW, a reading of 200 at the T-stat housing is not too hot (assuming an accurate reading). The stock T-stat is 192 degrees. At 200 degrees the PCM won't even call for the fan to run. I believe the PCM won't even call for the low speed fan to run until 210 (or so). The high speed fan set point is even higher.

FWIIW. Here is a prime case where an ODB2 scanner could help the trouble shooting. The scanner would tell you what the PCM "thinks" the motor's temperature is. Plus it would tell you what fan speed the PCM is calling for. By comparing the actual fan speed to the commanded fan speed the trouble shooting is focused.

NOTE, IF the problem is related to the fans THEN the motor will not over heat when driven at expressway speeds. Why? Because the fans are not needed above 45 MPH. So if the motor is over heating when driven on the expressway it's over heating for another reason.

NOTE, the SOHC motor will self bleed the cooling system after a couple of heat/cool down cycles. But during the time there is air trapped inside the motor the ECT sensor will read low due to being in contact with air.

It's been my experience that if a motor slowly over heats when driven it's because of a clogged radiator. Of course this assume that everything else has been checked out.

What has been done to rule out a clogged cat? You have an scanning infrared thermometer that can be used to measure how hot the cats are.

What has been done to rule out a base motor problem such as a leaking head gasket? At some point some consideration should be given to running a compression test and/or cylinder leak down test. Or at least testing the coolant for hydro-carbons.

well it doesnt seem that the engine is exceeding operating temperature, the temp gauge must be off or something, but anyway basically what is happening is just that when the engine heats up it begins to miss fire, you can start it up and drive for about 10 minutes and it will run just fine but then it starts to miss and becomes incredibly rough, i dont think there is a head gasket leak because there doesnt appear to be any coolant and oil mixing and i dont think the engine is damaged as i said before it runs just fine before it warms up, im at a loss, the highest i measured the temperature was about 220 degrees is that too hot? What could cause an engine to run perfect when cold and run like crap when it warms up? Maybe its not the cooling system at all, maybe its something electrical, i have no idea

wmburns · May 31, 2017

As for what might cause your symptom, go back and re-read some of my earlier posts. <sound of head banging>

wmburns said:
Turn on every accessory (AC, head lights, brights, brakes) even better. Let the motor reach full operating temperature when the cooling fans turn on. What is the voltage measurement? Is it above 12 volts? If so, the alternator is keeping up with load.

But the other thing that we are trying to confirm is what the voltage is doing when the problem occurs. It's all about change. IE, does the voltage drop or change when the problem happens?

Next put the VOM lead on battery negative and the other lead on the alternator case. This will measure the voltage drop through ground with the motor running. Should be low. Post.

Next put the VOM in the AC scale. Measure the voltage across the battery with the motor running. This will be the amount of AC ripple from the alternator. Should be low. Post.

Did you do the tests where the voltage drop was measured between the alternator case and battery negative comparing load and no load? It might even be necessary to rev the motor to say 2000 RPM's to see if the misfire is motor load related.

Ethan Keirn · May 31, 2017

wmburns said:
As for what might cause your symptom, go back and re-read some of my earlier posts. <sound of head banging>

Did you do the tests where the voltage drop was measured between the alternator case and battery negative comparing load and no load? It might even be necessary to rev the motor to say 2000 RPM's to see if the misfire is motor load related.

Yes we have tested everything like that, coils are good, plug wires are good, plugs were just changed less than 3 months ago so im certain theyre good, the car starts and runs fine cold, its just that once it heats up it starts to miss and wont stop until it cools off

wmburns · May 31, 2017

So what was the actual measured full load voltage between the alternator case and battery negative?

What is the full load voltage measurement at the battery?

If I don't get that actual measurement I'm dropping off of this thread as obviously I'm not getting through.

Ethan Keirn · May 31, 2017

wmburns said:
As for what might cause your symptom, go back and re-read some of my earlier posts. <sound of head banging>

Did you do the tests where the voltage drop was measured between the alternator case and battery negative comparing load and no load? It might even be necessary to rev the motor to say 2000 RPM's to see if the misfire is motor load related.

Yes we have tested everything like that, coils are good, plug wires are good, plugs were just changed less than 3 months ago so im certain theyre good, the car starts and runs fine cold, its just that once it heats up it starts to miss and wont stop until it cools off

wmburns said:
So what was the actual measured full load voltage between the alternator case and battery negative?

What is the full load voltage measurement at the battery?

If I don't get that actual measurement I'm dropping off of this thread as obviously I'm not getting through.

full load for battery was 11.89 volts full load for the alternator is 14.15 volts

wmburns · May 31, 2017

Ethan Keirn said:
full load for battery was 11.89 volts full load for the alternator is 14.15 volts

^^^This PROVES that the alternator is NOT keeping up at full load.

Further there is a 2.26 volt voltage drop between the alternator and the battery which is way to high.

For example on my Mustang the full load voltage at the battery is 13.74 volts. The voltage drop between the alternator case and battery negative is 100mV (that's 0.1 volts). Between the alternator positive and the battery positive it's 99mV (that's 0.099 volts). For a total charging system voltage drop of 199mV

At 2.26 voltage drop your Mustang has a whooping 1,135 percent greater voltage drop in the charging system that my car has.

The generally accepted max voltage drop is 250mV per side. Yours is about 6 times higher than the accepted max.

Your car's charging system is NOT perfect. Likely there's a weak ground somewhere in the system. Also possible there are problems in the Main alternator B+ cable.

If this were my car I would start by removing the grounds around the radiator core support and cleaning them down to shinny metal. Apply a small amount of di-electric grease and re-assemble.

Then I would remove the engine grounding strap from the left hand motor motor mount to the frame rail. Again clean.

Re-test the voltage drop from the alternator case to the battery negative to measure the results of your handiwork. The full load value should be less than 250mV.

If still not below 250mV the next step is to remove the alternator and clean the engine block with a wire wheel brush where the alternator rests. Then clean the mounting tabs of the alternator itself. Apply a small amount of di-electric grease. Repeat the voltage drop measurement.

There are additional checks to make IF the misfire does not go away.

Ethan Keirn · May 31, 2017

wmburns said:
^^^This PROVES that the alternator is NOT keeping up at full load.

Further there is a 2.26 volt voltage drop between the alternator and the battery which is way to high.

For example on my Mustang the full load voltage at the battery is 13.74 volts. The voltage drop between the alternator case and battery negative is 100mV (that's 0.1 volts). Between the alternator positive and the battery positive it's 99mV (that's 0.099 volts). For a total charging system voltage drop of 199mV

At 2.26 voltage drop your Mustang has a whooping 1,135 percent greater voltage drop in the charging system that my car has.

The generally accepted max voltage drop is 250mV per side. Yours is about 6 times higher than the accepted max.

Your car's charging system is NOT perfect. Likely there's a weak ground somewhere in the system. Also possible there are problems in the Main alternator B+ cable.

If this were my car I would start by removing the grounds around the radiator core support and cleaning them down to shinny metal. Apply a small amount of di-electric grease and re-assemble.

Then I would remove the engine grounding strap from the left hand motor motor mount to the frame rail. Again clean.

Re-test the voltage drop from the alternator case to the battery negative to measure the results of your handiwork. The full load value should be less than 250mV.

If still not below 250mV the next step is to remove the alternator and clean the engine block with a wire wheel brush where the alternator rests. Then clean the mounting tabs of the alternator itself. Apply a small amount of di-electric grease. Repeat the voltage measurement.

There are additional checks to make IF the misfire does not go away.

Ok thanks im gonna get on that asap much appreciate the help

wmburns · Jun 4, 2017

To anyone else reading this thread trying to understand HOW to trouble shoot and locate charging system problems especially problems associated with excessive voltage drop. Here's a very good video from the "South Main Auto Repair" channel. Eric O goes through the step by step process a real professional uses to track the problem down. Note how Eric O uses the voltage drop test from the alternator case to the battery negative. Also note the voltage drop test between the alternator B+ and battery positive. Most importantly note the results of the test showing excessive voltage drop (much greater than 250 mV).

Also note how Eric O used the voltage probe to further isolate exactly where the bad connection was. IMO it's important to note that none of these tests required fancy tools. The bulk of the work was done with a simple Volt-Ohm meter (VOM). Later in the video notice how Eric O cleans the electrical terminals before putting it back together. Shinny on both sides.

I'm a fan of the SMA channel and I think that Eric O does a lot to promote sound trouble shooting techniques. However I think that sometimes Eric O over does things for the sake of the video. I personally wouldn't test and re-test the amount that Eric O often does. But on the other hand, Eric O finds negative results (check out the bogus test result from the burnt test clip for example).

I'm a big believer in starting with the basics. I still stand behind the advice given in this thread. While cleaning everything may result in cleaning things that don't need to be cleaned it is a technique that can be explained in a forum post (could you image trying to explained HOW to do all of the tests that Eric O did?).

If this were my car I would start by getting the voltage drop between the alternator case and battery negative with all loads on under the 250mV limit. Then do the same thing to the battery B+. Once the charging system is known to be in tip top shape, continue the more difficult trouble shooting.

Note, IF the dash gauge still reads too high after the charging system is in good repair it may be necessary to perform a voltage drop test from the cluster ground (G203) back to battery negative. The cluster ground is behind the center console and is shared by multiple devices including the radio. This ground is frequently messed up during a radio install.

Ok. Some of you may be asking how this relates to the problem at hand? The reported test (the OP never actually did the tests in the manner requested) shows a possible 2.26 volt drop between the alternator and the battery. That is about a 15 percent voltage drop. Since the dash temperature gauge is driven purely off of a calibrated voltage drop having a system voltage that is 15 percent too low will make the dash gauge read 15 percent too high! This is pure Ohm's law. To put things into perspective let's say the motor's temperature is 220 degrees. This is within normal operating range. Adding 15% to the gauge gives a reading of 253 degrees! Clearly too hot!

IMO the OP benefited from additional cross checking. Otherwise the OP wouldn't have determined the motor wasn't really over heating but the dash temperature gauge was wrong. This clearly shows the benefit of cross checking suspected problems.

Hope this helps someone. Remember. Today's cars simply will not run right without a strong battery and charging system!

View: https://www.youtube.com/watch?v=fYjuP8FBUu8

miss_molly_mustang · Jun 4, 2017

Ethan Keirn said:
Ok i do have a volt meter and ive read a little bit about the forscan, i think i might buy it, so to test the charging system do i just touch the negative tester lead to the negative battery terminal and the positive to the positive battery terminal with the car running? What kind of voltage am I looking for?

I thought my alternator was going out this past Friday. I noticed my headlights were dimmer than usual an so were my interior lights. I stopped on my way home for gas. After I pumped it, I got into my car, cranked it, then sent a text to one of my friends letting them know I was driving so I wouldn't be able to respond. Anyway, after that I start to hear a noise and thought *oh boy, a new noise!* My voltage meter just dropped drastically and then the car cut off. I waited for a second, then tried to crank it again because the meter went up, but no dice. I just had a new battery put in, along with new lines and terminals. Like I said, I thought my alternator was going out, but it was actually my voltage regulator that had a bad connection on the back. Sometimes it can cause the alternator to not pull the juice it needs to.

It was something so basic and I felt like an idiot, but definitely something to consider. Hope this helps!

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