JustangGT

Hi all,
I recently took a couple hundred mile road trip. I have an onboard diagnostics unit that outputs data to my phone through bluetooth.

As I was driving home, I noticed that my engine temperature fluctuated excessively.

For what it's worth:
2005 4.6L GT w/ manual transmission
Mostly stock
The outside temperature was about 85°, which is nothing extravagant.
I had the cruise set at about 80mph.
My engine is very healthy and the car is in overall exceptional condition.
Car has 109,000 miles on it

However, climbing any hill would make the engine temperature quickly rise to around 215 - 220°. Steeper hills could easily hit 225 - 230°. Once hill climbing was over, it'd quickly drop back down, but would never get below around 200 - 205°,

Easily and regularly hitting 220 - 230° engine temps during normal cruising in only moderately hot temps just doesn't seem right to me.
Do these cars have known cooling issues?

Are there things I can look into, like a struggling water pump or clogged cooling system?
Are there better radiators available? ( I know upgrading my Bronco from a 2 core to a 4 core made a huge improvement)
Anything else?

Thanks

houtex

Ok, you're spookin' yourself with the reading there. What you describe is quite normal given what you were doing with the car. You use more power, there's gonna be more heat. Just how things are. But the issue is what you're actually seeing from the PID, not what's actually happening to the cooling system.

The engine coolant temperature is not what you're seeing. The 2005-2009 Mustang GT doesn't have a coolant temp sensor. It has a Bank 1 (passenger side) cylinder head temperature sensor, and that's what you're seeing. That will fluctuate quite a bit more than the coolant, and will also read higher than the coolant, and is normal, especially if you're goin' uphill or hittin' the gas for funtimes(tm).

As far as the system itself... The thermostat is a 180 degree thermostat. The stock radiator is quite sufficient for stock use, here in Texas I have frequently sat in a parking lot or been stuck in stop and go traffic on the hottest of days with my A/C on and nary an issue. The entire system for the coolant is aluminum except certain parts of the water pump and the thermostat, but there's no rusting of the core or the block or such, and the aluminum of the block and the heads is quite good at transferring the heat into the coolant, and again, the thermostat is a 180 degree item. The Motorcraft Gold coolant in your car is quite good and works for 10 years, and if it doesn't come out nearly as gold/yellow as new mixed stuff, that'd be more an indicator than anything else somethings amiss. It's really good coolant.

I'd say your car is fine. If it's running like it should and not blowing coolant everywhere, there's nothing to be concerned about. If you're really worried about things, you can modify the thermostat housing or such an add a water temp gauge separate from the car and ensure you're not gonna blow a head gasket.

Overall my thoughts are this: sometimes too much info is not a good thing. Disconnect that monitor and enjoy your car! This ain't no old school Bronco with a 302 or whatever. For that thing, sure, the 4 core might help (although there's an issue with the rear rows not getting enough flow, so it's not near as helpful as you'd think, but capacity is still capacity... I'd probably have done the 3 core myself, as the 4th core is the real issue with the extra cores... it's not really worth it. IMO, after research, you do you and that'll do! )

Hope that helps! And if I'm wrong, then I'm wrong, but that's what I know so far...

Bert

if the coolant hasn't been flushed and changed for a while that MIGHT be worth the time and trouble, just to make you feel better . . . but other than that I wouldn't worry about it either, seems normal like Houtex said

JustangGT

Thanks for the info Houtex. I didn't know about the temp reading being just a PID, and thought it was the actual reading from the temp sensor. FWIW, I have an aftermarket Holley Sniper on the 300 in my Bronco, so the readings I get are direct from the engine and the temp on it is solid as a rock. So, seeing the Mustang's temp climb like that under what seems normal driving didn't sit right with me. But, the insight you gave makes a lot of sense.

As for the 4 core, I might have had my info crossed. I looked up the one I bought and it's a 2 row vs the stock 1 row. Either way though, the one I took out was only about a half inch thick, and the new one is 2 inches thick, so I had "4 times thicker" in my head.

I did note that when the temps would fluctuate on my phone, the needle on the dash didn't. How accurate on the gauges on these?

I'll probably just have it flushed, as I don't believe that's ever been done.

Thanks again.

houtex

If you're gonna flush it, just reverse flush the heater core. Replace the thermostat if that's not been done while the fluid's out. Inspect and/or replace the lower radiator hose at the oil cooler, and possibly replace the oil cooler to block gasket as that's a common thing for both. The lower hose really gets heated up by the block and starts expanding/softening at the block side, and that oil cooler gasket just gets bad too. You've already done the radiator and there's nothing much left in the car to worry about. The small amount of iron in the car won't contribute much rust if the coolant was good, and unless you have rusty fluid coming out, there's no real point to flushing. Myself, I just dumped and filled when I did the timing chains and water pump, all's good. Fluid came out about the same color as the new going in after mixin'. For what my opinion's worth, there ya go.

Only 'real time' gauges on the car are the speedo and the tach. The others (oil, fuel, temp, volts) are driven by a program that samples things and then gives you an indication so you're happy. Temperature will rise from cold to normal and then stick, because people expect that from a temp gauge. It's all trickery though. Oh, it's accurate enough, sure, but it's not direct. It's there to make you feel like you have a temperature gauge when in reality the indicator lamp of 'too dang hot' would do. But gauges, right?

Oil pressure is pretty much a switch indicator for three states: Off/low, normal, high. You'll almost never see 'high' happen.

Fuel is definitely sampled average driven. I don't know the exact timings or number of samples, but I can fool that thing real easy. Half or less of a tank, fling the car into a high speed left turn, and boom, about a minute later I ain't got no fuel! Confused me plenty first time, but what's happening is the fuel's slinging over the saddle into the right half, which doesn't have a gauge, just a pickup for the fuel pump on that side. Fuel sender is sitting in low fuel on the left side, I got 10 miles to go before I'm empty. Flinging the car on a right turn at decent speed will get it reset... and now I got 50 more miles than I should because the left side's filled and the right side is suckin' air. Silly way to do things, but most people don't fling their cars around like I do sometimes. I mean, 90 degree corner at 30 MPH or so is just THAT kind of fun. The fix? Fill the tank up, problem solved.

Also of note for those who might not know but are reading: Ever notice that most fuel needles don't slosh about as the fuel in the tank does? There's two fixes for that symptom that'd normally happen with the float of the sender: A dampener filled with gas that helps, similar to a shock absorber in the suspension, or the gauge is built/programmed to dampen. The built version is a heated element that doesn't move fast as the float bounces, the programmed one is the sampled average thing in these cars.

(Side note: my dad built one for his Falcon using a Ford sender in the tank, an after market made-for-a-Chevy-sender gauge because he liked the look better, and an Arduino setup to drive the gauge based on a table he created in the thing by filling the dry tank one gallon at a time until it read full, and taking readings of the Ford sender as he put a gallon in. Figured some sampling times, making an average, and boom, exactly how they do it in our cars only on a '64 Falcon with a Chevy gauge. He does stuff like that... )

Which brings us to the voltmeter. Poor thing. Totally useless. May as well not be there. But it looks good with the rest, so there it is. 'Tis a silly thing, but again, makes people happy, so there it sits, waiting to not do anything except look pretty for all the good it does. Source: My many batteries/alternators that went out and that thing said NOTHING about it. Nor did the system test. Ammeters, that's where it's at, but thems are dangerous things so they don't.

There ya go. Proceed as you will!

Jaryd21

Yeah what he said