Engine 2004 Mustang GT temp problem

Marashz

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Jul 16, 2018
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I recently purchased a 2004 Mustang GT 40th anniversary from a :poo:ty used car dealership. I have some mechanical background but am looking for advise and wisdom - always!

I noticed after driving the car now for around 200 miles that the temp gauge on fairly hot and humid days would rise up to around 3/4 of the way to H when the car was idling. I noticed that if I quickly get it up to 5th gear @ around 60+ MPH the gauge would lower back down to around normal operating temperature approx. 1/2 of the way to H.

The car recently got an oil change from Ford (I was told by used car dealership)... I checked the oil filter and it is in-fact, brandy new. The oil is still liquid gold as well.

So I checked all fluid levels and realized the coolant was slightly low. So I topped up the fluid. A few days later, same over-heating issue, and the coolant was perfectly full. (Which ended up burning off after heating up so much so I had to top-up again.)

I started to think it was a head gasket leak but...

I purchased a Radiator coolant pressure tester from my local harbor freight and to my surprise I left it for 15 minutes straight and the pressure never dropped. Pressure remained @ 15PSI until I dumped air or unscrewed cap. I retried to test several times for re-assurance.

So it couldn't be a head gasket?
-Oil is not milky
-Not coolant leak/pressure leak

Radiator has bent fins and it appears to have either taken a beating from a small accident or maybe several rocks 130k miles later.

Fan is perfectly functional. Seems to be always running while the A/C is on.

I just replaced Thermostat about 2 hours ago and went for test drive. No problems yet, but it's rather intermitted as is anyways.

Side note:

A/C get's warmer when car starts to heat up.
Could be air pockets in coolant system?
Could be radiator?
Could have been thermostat?
Could be wrong oil? (Definitely feels like 5W-20, although looks over-full on dipstick)
Could be intermittent fan wiring issue?
 
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My vote. CONFIRM that the engine cooling fan works on BOTH speeds.

Note, for the GT model when the AC is on the cooling fan runs on LOW speed (yes that is correct!). So IF the high speed cooling fan was in-op this could explain why the over heat is very intermittent. Further this could explain why it does not not over heat at expressway speed (the cooling fan shuts off when the car's speed is above 45 MPH).

IMO the best way to trouble shoot this is with an ODB2 scanner with bi-directional controls. Simply command the low speed fan to turn on and verify that the fan runs. Next command the High speed fan to come on and verify that it runs.

The next best method is to power the fan directly from a high amp 12 volt source. There should be an obvious speed difference between high and low speed.

Note, on some model years the low speed fan is protected by a CIRCUIT BREAKER. This creates the possibility that the low speed fan operation comes and goes as the CB opens and then resets itself. If this is a case of the fan drawing too much current this means it may have to run for an extended period of time before tripping the circuit breaker.

Usually if a fan draws too much current the problem can be traced to bad bearings. Sometimes it's possible to feel a bad bearing by spinning the fan by hand.

In case you are interested in going the ODB2 route, here's some information on an affordable Windows based ODB2 scanner with bi-direction capability.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

In my experience IF a motor slowly overheats in stop and go driving then one should rule out a clogged radiator. If this were my car that would be the next step to perform after verification of the cooling fans. Of course it would be wise to check to see that the radiator is clean and air flow is not blocked. As well as all air dams, shrouds, and baffles are in place.
 
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Just took the car on a road trip approximately 800 or so miles from New York to New Jersey. Unfortunately the problem wasn't due the the thermostat. Although I do believe it helped... car appears to be a hair cooler.

Now that I have had a chance to drive the car I noticed all the problems:
1) Cruise does not work. (Horn functions perfectly)
2) Temperature climbs @ idle for more than 10 minutes. It appears that the fan functioning but absolutely not turning onto high setting. It always appears to be going the same slow speed.
3) Condensation/slight drip from A/C on passenger side. No it is absolutely not coolant. I wiped it with a white paper towel and it does not have a smell or a color.
4) Evap leak, check engine light - Not worried about this. Going to have it smoke tested tomorrow and fixed ASAP. My smoke tester doesn't have a big enough funnel :(

On the good side; Oil is still gold after 1,000 miles now. Still looks as if changed a day ago.
 
I was considering taking an hour and installing a toggle switch directly from battery to the fan on the trip to stop the annoyance. But I ended up only heating up once and immediately got back to highway speeds within two minutes.

I ordered a new Mishimoto Radiator and Fan from American-Muscle since I do plan on slapping on a S/C and running this car on a track soon. In the meantime, I would like to figure out if this fan thing is a wiring issue or just a fan malfunction.
 
Furthermore after re-reading your post, I have observed exact symptoms of bad bearings as stated in the middle of your post. It appears that the car will absolutely not overheat @ idle until ran for at least 30 minutes. I've started the car and let sit in driveway several times at operating temperature with no increase in temperature. It is only when I drive the car to go get something 20 minutes away, leave the car running, and then walk back out to notice the car temperature rising above 'normal'(1/2<H).

I did spin the fan by hand and I do not know what I should feel. I am uneducated in the aspect of cooling fans and bearings... I have nothing to compare.
 
Before replacing any parts go back and double check the battery and alternator. DOUBLE check and confirm that the voltage at the battery and alternator is above 13 volts at all times.

Why?

Because the engine coolant temperature sensor (ECT) is calibrated from alternator voltage. IF the voltage is low this will make the ECT sensor read high. In addition low alternator voltage will make the fan spin slower. Bottom line. Today's cars simply will not run right without a strong battery and charging system.


Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

Now it's time for some more tests. IF:
  • The fan actually is capable of running on BOTH speeds and
  • The fan shuts off when the PCM calls for high speed fan and
  • The battery and alternator is known to be keeping up with demand
THEN suspect a possible CCRM problem.

Note, I have direct experience helping a coworker with a very similar sounding problem. I told him to check the charging system and to verify that the motor was actually overheating using a scanning infrared thermometer aimed at the T-stat housing. I indicated that his motor was running too good for a motor that was overheating. He ignored me and started replacing parts. Until there were no more parts to replace. Then he started re-wiring the fan with an external fan controller. When that didn't work he wired a direct fan toggle switch to the dash (which didn't solve the problem either).

He finally shows up at my house one day to tell me that he found the problem and fixed it. He also showed me a pile of wiring and other parts removed to restore back to factory. The solution? He found a corroded connection at the motor grounding strap from the left hand motor mount to the car's frame rail. Because he never actually TESTED and confirmed the function of the alternator he didn't know what was happening was:
  • The PCM called for high speed fan.
  • The high speed fan uses much more current than the low speed fan
  • the alternator couldn't keep up with demand (in this case because of a poor ground).
  • the battery voltage dropped
  • The ECT sensor read higher
  • The dash temperature gauge started moving up.
  • BUT the motor never actually over heated. He assumed the motor was hot because the dash gauge said so.
Moral of the story........Don't assume. Test. Start with the basics and work your way up. Don't ignore contradicting symptoms.

In my coworker case think about how much $$ and time was spent replacing parts with no fix. An inexpensive volt-Ohm meter (VOM) and 10 minutes of time would have told him that battery voltage dropped to 12 volts when the high speed fan kicked in.
 
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After I made these replies the other night I realized that I had the problem answer sitting right in front of me. On the trip I left my lights on for around 35 minutes. When I came back my battery was dead as dead. Unfortunately I left my battery pack, voltmeter, and jumper cables at my house so I called tripple A. The gentleman that gave me a jump also did a battery test and told me it was giving bad voltage, amperage and was completely shot. I shrugged it off thinking it was a sale scam and drove home without ever turning the car off. Now that I think of it... that is probably the problem. Going to go check my battery right NOW. Will post back in 5 minutes what kind of readings I get.


P.S: One of the first things I did was purchase an IR thermometer to verify the engine temperature was actually climbing like the temperature gauge was displaying. The car is actually over-heating unfortunately.
 
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I got side tracked.. haven't tested the battery yet. But I was wondering if you could give me information on PATS. I was looking at AutoEnginuity and they have some very nice ready to go tools available for me. But ForScan is super cheap with roughly the same amount of features. I was just curious as to why I need PATS and what it is for? I google'd that it has something to do with the ignition and anti-theft codes. So maybe professional diagnostics are only available if you have these keys otherwise your car will 'lock-out'?

EDIT:
After further research it is just the chip inside your key that is programmed to the vehicle for anti-theft purposes. From what I understand I don't have to worry about PATS as long as I am not trying to reprogram keys or mess with anything in that nature. I will be using this for Diagnostics and Data Logging. I only have one key for the car anyways.
 
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FWIIW, I do have direct experience with the AutoEnginuity product which I chose because I work on more than Ford makes. I personally have used AutoEnginuity to reprogram PATS on:
  • 2005 F150
  • 2009 GM remote FOB
  • The version I was using was not able to program 2012 F150. Later versions are reported to have a "fix" for the later MY's.
I'm a big believer in the game changing nature of regular use of an ODB2 scanner as part of your trouble shooting tool box. I have been able to solve several problems using the product.

But in all honestly I have also been able to solve a ton of problems using an older generic 1 line ODB2 scanner. So the power is in HOW the tool is used.

But you are right with regards to your PATS question. You don't need PATS capability unless you want more keys or replacement keys. The product is soooo much more.

Note, for some model years it's possible to "clone" a working key to make additional working keys

So if you only work on Fords I would say ForScan is right for you. IF you want to work on other makes IMO AutoEnginuity is superior to ForScan.

But having said that I have a love/hate relationship with using a laptop in a car. It's hard to read the screen in direct sunlight. It's hard to drive while using a laptop. It's fragile. Clearly if I had the $$ for a professional dedicated scan tool that's what I would have instead. But I want the power of a professional ODB2 tool without the budget.