Strange Overheating (new rad/fan)
06-21-2017, 05:39 PM
#1
Thread Starter
Join Date: Feb 2012
Location: PA
Posts: 32
Strange Overheating (new rad/fan)
Hi folks, dealing with something strange here:
My '06 GT temp gauge started to go from the usual "half way" mark and began creeping up 3/4 towards red. Mind you, it's not getting in the red, but these are aluminum heads and I don't want to risk anything.
Plugged in my ScanGauge and got cylinder head temp readings over the course of driving and forcing the temp gauge to rise: Heads are reporting as going up to 240 degrees in frequent stop-and-go with temperatures in the mid 80's to 90's. This shouldn't be happening. Replaced my thermostat with an OEM 195 degree and new coolant. Kept doing it. Made sure all the air was burped out. Kept doing it. Replaced radiator and fan assembly with a Mishimoto and SVT Cobra fan. Keeps doing it.
Car has ~106k on it. Had new lash adjusters and rockers put in, so I don't think it has anything to do with timing, mechanic didn't mention anything that looked out of place with the valve covers and cams out. I do get some feelings of what seems like a misfire or a "pop", or struggle when accelerating at low RPMs -- almost like a cylinder's missing a cycle, or like what a rough idle with a backfire pop feels like.
Two questions:
1. Could it be the CHT sensor? It's not spiking or jumping, it definitely moves up gradually as the heads hit 240 degrees on the dot, and goes back down to normal the second they cool below 240.
2. Could it be a bad coil-on plug, injector, or fuel filter? All are original, to my knowledge (put in new OEM spark plugs). Could it be running lean and causing overheating? It almost seems like the temps rise a bit more when I'm at lower RPMs.
I can pop the radiator cap and even keep my hand on the overflow tank, which leads me to believe the radiator and fan are doing their job keeping the water cool. Water pump doesn't seem to be leaking either.
My '06 GT temp gauge started to go from the usual "half way" mark and began creeping up 3/4 towards red. Mind you, it's not getting in the red, but these are aluminum heads and I don't want to risk anything.
Plugged in my ScanGauge and got cylinder head temp readings over the course of driving and forcing the temp gauge to rise: Heads are reporting as going up to 240 degrees in frequent stop-and-go with temperatures in the mid 80's to 90's. This shouldn't be happening. Replaced my thermostat with an OEM 195 degree and new coolant. Kept doing it. Made sure all the air was burped out. Kept doing it. Replaced radiator and fan assembly with a Mishimoto and SVT Cobra fan. Keeps doing it.
Car has ~106k on it. Had new lash adjusters and rockers put in, so I don't think it has anything to do with timing, mechanic didn't mention anything that looked out of place with the valve covers and cams out. I do get some feelings of what seems like a misfire or a "pop", or struggle when accelerating at low RPMs -- almost like a cylinder's missing a cycle, or like what a rough idle with a backfire pop feels like.
Two questions:
1. Could it be the CHT sensor? It's not spiking or jumping, it definitely moves up gradually as the heads hit 240 degrees on the dot, and goes back down to normal the second they cool below 240.
2. Could it be a bad coil-on plug, injector, or fuel filter? All are original, to my knowledge (put in new OEM spark plugs). Could it be running lean and causing overheating? It almost seems like the temps rise a bit more when I'm at lower RPMs.
I can pop the radiator cap and even keep my hand on the overflow tank, which leads me to believe the radiator and fan are doing their job keeping the water cool. Water pump doesn't seem to be leaking either.
06-22-2017, 03:38 PM
#2
Thread Starter
Join Date: Feb 2012
Location: PA
Posts: 32
73 views and not a single reply? C'mon guys, little help here. I'll keep posting what I find/fix in case anyone else ever deals with this:
Update: I tested out exactly when my GT begins to get a little too hot for comfort: It happens during constant stop-and-go, when I have to feather the gas and clutch to keep crawling. I noticed it also tends to get hotter, quicker, when I notice stutters/misfires/hesitations while accelerating.
Funny part is, with my scanner plugged in and monitoring the fuel system loop status (open/close), I decided to try something completely counter-intuitive, I floored it and did a hard start from 0 to 60. I forced the fuel system into OPEN loop (rich mixture) and lo and behold, after decelerating, temps dropped quickly. Getting home and letting it idle with the A/C on (so electric fan is going on hi constantly), and letting it "chill" at idle, temps subsided to a relative low. Coolant itself is still not hot enough that I don't burn myself touching the reservoir, even (good job Mishimoto/SVT).
This means 1.) my coolant system (radiator, fan, thermostat, pump) is functioning perfectly, because it would overheat at idle otherwise, and 2.) I have to be running lean. With consistent accelerating runs and higher RPMs it seems as though temps are less likely to creep than if I'm slowly accelerating, starting and stopping. A.K.A injectors/fuel pump are pushing less, with too much air.
Side note: My ambient air temps (from the MAF) are displaying crazy hot. Like, 120+ degrees while cruising on the highway when it's 85 degrees outside, and almost 150 at idle. How is that possible? Could a bad MAF be causing problems?
Now if anyone wants to contribute... I'll take suggestions on where I should start looking at faults. Ordered an OEM fuel pump through work (I work at a particular Mustang company). If that doesn't help then my next step will be injectors. After that, maybe a bad coil plug is throwing out some interference with the CHT sensor? Beyond this, I'm out of ideas.
Update: I tested out exactly when my GT begins to get a little too hot for comfort: It happens during constant stop-and-go, when I have to feather the gas and clutch to keep crawling. I noticed it also tends to get hotter, quicker, when I notice stutters/misfires/hesitations while accelerating.
Funny part is, with my scanner plugged in and monitoring the fuel system loop status (open/close), I decided to try something completely counter-intuitive, I floored it and did a hard start from 0 to 60. I forced the fuel system into OPEN loop (rich mixture) and lo and behold, after decelerating, temps dropped quickly. Getting home and letting it idle with the A/C on (so electric fan is going on hi constantly), and letting it "chill" at idle, temps subsided to a relative low. Coolant itself is still not hot enough that I don't burn myself touching the reservoir, even (good job Mishimoto/SVT).
This means 1.) my coolant system (radiator, fan, thermostat, pump) is functioning perfectly, because it would overheat at idle otherwise, and 2.) I have to be running lean. With consistent accelerating runs and higher RPMs it seems as though temps are less likely to creep than if I'm slowly accelerating, starting and stopping. A.K.A injectors/fuel pump are pushing less, with too much air.
Side note: My ambient air temps (from the MAF) are displaying crazy hot. Like, 120+ degrees while cruising on the highway when it's 85 degrees outside, and almost 150 at idle. How is that possible? Could a bad MAF be causing problems?
Now if anyone wants to contribute... I'll take suggestions on where I should start looking at faults. Ordered an OEM fuel pump through work (I work at a particular Mustang company). If that doesn't help then my next step will be injectors. After that, maybe a bad coil plug is throwing out some interference with the CHT sensor? Beyond this, I'm out of ideas.
06-22-2017, 06:07 PM
#3
5th Gear Member
Join Date: Dec 2006
Location: Redding, CA
Posts: 4,552
It sounds to me more like an intermittent fan issue. But I really don't have any idea. Usually things like water pumps, fans and other support pieces either work 100% or not at all. Its a weird issue...
06-23-2017, 01:11 AM
#4
It does seem that the engine's running lean in closed loop. Have you changed the fuel filter recently? Did you pull any fault codes? Perhaps O2 sensor wiring shorting out somewhere?
Your ambient temperature readings seem typical of a "cold air intake" that's without a heat shield.
Your ambient temperature readings seem typical of a "cold air intake" that's without a heat shield.
06-23-2017, 06:17 AM
#5
Thread Starter
Join Date: Feb 2012
Location: PA
Posts: 32
It does seem that the engine's running lean in closed loop. Have you changed the fuel filter recently? Did you pull any fault codes? Perhaps O2 sensor wiring shorting out somewhere?
Your ambient temperature readings seem typical of a "cold air intake" that's without a heat shield.
Your ambient temperature readings seem typical of a "cold air intake" that's without a heat shield.
06-26-2017, 08:41 AM
#8
Thread Starter
Join Date: Feb 2012
Location: PA
Posts: 32
THanks, algregory.
Derf00, I replaced my radiator and coolant just a few days ago. I've been messing around with the fuel system loop status while monitoring temps and I've verified it runs lean in closed loop (immediately begins cooling down in open loop on decel/after hard accel). I'll be replacing the fuel filter today and if that fails, I'll try to clean up or replace my injectors.
V/r
Travis
Derf00, I replaced my radiator and coolant just a few days ago. I've been messing around with the fuel system loop status while monitoring temps and I've verified it runs lean in closed loop (immediately begins cooling down in open loop on decel/after hard accel). I'll be replacing the fuel filter today and if that fails, I'll try to clean up or replace my injectors.
V/r
Travis
06-26-2017, 01:24 PM
#9
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
THanks, algregory.
Derf00, I replaced my radiator and coolant just a few days ago. I've been messing around with the fuel system loop status while monitoring temps and I've verified it runs lean in closed loop (immediately begins cooling down in open loop on decel/after hard accel). I'll be replacing the fuel filter today and if that fails, I'll try to clean up or replace my injectors.
V/r
Travis
Derf00, I replaced my radiator and coolant just a few days ago. I've been messing around with the fuel system loop status while monitoring temps and I've verified it runs lean in closed loop (immediately begins cooling down in open loop on decel/after hard accel). I'll be replacing the fuel filter today and if that fails, I'll try to clean up or replace my injectors.
V/r
Travis
Unless you're running a lean A/F mixture, I wouldn't see a need to mess with your fuel system.
06-28-2017, 09:18 AM
#10
Thread Starter
Join Date: Feb 2012
Location: PA
Posts: 32
Hmm, I'm still looking at the cooling system. What about the reservoir cap? Have you pressure tested it and/or your cooling system. The reservoir cap has a designated pressure it's supposed to hold just like the old school caps on the radiators. If that fails or isn't holding the right pressure (too low) the system could overheat.
Unless you're running a lean A/F mixture, I wouldn't see a need to mess with your fuel system.
Unless you're running a lean A/F mixture, I wouldn't see a need to mess with your fuel system.
I changed the air filter and fuel filter (original filter looked like it was storing years-old coca cola and was totally clogged) and it helped to a degree (pun intended). This only further tells me that it's air-fuel related. I ordered a new MAF sensor and I'm going to do the O2 sensors as well. Since there are 4 sensors in total, and given the lack of apparent maintenance the previous owner did, I'm assuming these are probably wonky and need replacement.