427 overheating issue
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Instructor
Joined: Jun 2007
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From: Tallahassee FL
427 overheating issue
Forged 427 with stock cooling system except for 160 degree t-stat instead of stocker. A6 car. It always got hotter than I wanted (220 ish in summer with AC while in traffic) but a few days ago it overheated and puked some coolant, gave me the change oil message. I re-fill the system and change the oil, all seems ok.
Today, everything starts out ok, but then it starts to overheat again. I turn the AC off and roll the windows down. The fans aren't running. I turn the AC on again, they start right up, fully blast.
I'm thinking a bad t-stat because I can keep it cool enough to run (213 or so) with the heat full blast AC off so it appears water is circulating in the block, but never hits the radiator. This week is cooler than it has been in the past, so this issue isn't environment related. The fans always worked, AC on or not, in the past so that's new.
Ideas?
Today, everything starts out ok, but then it starts to overheat again. I turn the AC off and roll the windows down. The fans aren't running. I turn the AC on again, they start right up, fully blast.
I'm thinking a bad t-stat because I can keep it cool enough to run (213 or so) with the heat full blast AC off so it appears water is circulating in the block, but never hits the radiator. This week is cooler than it has been in the past, so this issue isn't environment related. The fans always worked, AC on or not, in the past so that's new.
Ideas?
Melting Slicks
Joined: Sep 2005
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From: merritt island fl
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You answered your own question- fan operating differently. If the thermostat was stuck closed you would never be able to keep it cool enough, no matter what else you did.
Thread Starter
Instructor
Joined: Jun 2007
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From: Tallahassee FL
Even when driving down the road with AC on and fans running it was overheating. When the AC is on, the fans work. I checked all the fuses and relays, I can't find an issue. With the newer fan-controls, there aren't any relays, just a single 60A J-fuse.
What all sensors are involved in commanding the fans to come on? The fans are programmed to come on earlier due to the 160 t-stat and that's worked up until a few days ago. The digital reading of the coolant temp as well as the analog readings appear to be correct, what's left? Cyl head temp? I thought it was commanded off of coolant temp alone.
What all sensors are involved in commanding the fans to come on? The fans are programmed to come on earlier due to the 160 t-stat and that's worked up until a few days ago. The digital reading of the coolant temp as well as the analog readings appear to be correct, what's left? Cyl head temp? I thought it was commanded off of coolant temp alone.
Burning Brakes
Joined: May 2002
Posts: 970
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From: brooklyn ny
Sounds like a tuning issue. The fans should be on with the AC on. They should come on when temps hit 200 no matter what. If your car was tuned maybe the fans are comming on at less then 100%. ( The fan speed is variable)See your tuner.
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Instructor
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From: Tallahassee FL
Its been running on the same tune (which I assisted with) since around Jan of this year. The fans do come on with AC and did come on during run with no AC, so this is new. No tuning changes have been made since Jan of this year. They also used to come on after shut-down on hot days, but not yesterday.
New symptom: squeaky water pump. Loud enough to be a concern. I'm thinking that the pump is failing, possibly causing water to not his the sensors that control fan conditions?
New symptom: squeaky water pump. Loud enough to be a concern. I'm thinking that the pump is failing, possibly causing water to not his the sensors that control fan conditions?
Burning Brakes
Joined: May 2002
Posts: 970
Likes: 3
From: brooklyn ny
You might want to run a compression test. I once had a car that ran really hot, it was a symptom of impending failure. Bad bearing and rings generated too much heat and the car only ran cool at 70mph. Maybe the bottom is was poorly done.
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Thread Starter
Instructor
Joined: Jun 2007
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From: Tallahassee FL
Hmmm... could be. Plugs looked ok for heat and combustion when I checked a few days ago though.
I put the stock t-stat in and the fans started working normally, I couldn't get the temp over 203 with AC cranked either. Im gonna watch over it and see what it does. I'm still wondering why the fans didn't activate before. Possibly a sensor that wasn't getting circulation due to t-stat? Strange...
I put the stock t-stat in and the fans started working normally, I couldn't get the temp over 203 with AC cranked either. Im gonna watch over it and see what it does. I'm still wondering why the fans didn't activate before. Possibly a sensor that wasn't getting circulation due to t-stat? Strange...
Team Owner
Joined: Jun 2005
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From: Northern, VA
St. Jude Donor '15
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One thing I read several months ago, fellow went through 3 stats before he found a fourth that worked. All were brand new. Yours was working for awhile and then may not have been working correctly by your example of putting back in the original. I suggest whatever stat you buy in the future, test it in/on the stove first. And since that first squeak from the water pump, I don't think you want to find out later that it's bad; replace it now. If a compression chk is easy to do, it can't hurt to have some peace of mind either, per ken's suggestion. It could still be the tune regardless of how it's worked up until now. Any codes?
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From: Tallahassee FL
No codes, and I don't think there are any air pockets.
A new symptom cropped up, or I first noticed it yesterday. It was fine with the old t-stat, but now it appears to be acting up again. Coolant temps were at 205, AC on full blast. AC turned off (air was coming out, but the compressor was off) and the fans stopped. It was parked in the driveway just idling, I was getting ready to drive off and then that. I turned off the air, the fans still didn't come on. No codes, no indication as to why the fans went off and the AC turned off.
I'm kinda lost. I'm going to do some logging with HPT to try and see what the PCM is seeing and commanding.
Stupid cars.
A new symptom cropped up, or I first noticed it yesterday. It was fine with the old t-stat, but now it appears to be acting up again. Coolant temps were at 205, AC on full blast. AC turned off (air was coming out, but the compressor was off) and the fans stopped. It was parked in the driveway just idling, I was getting ready to drive off and then that. I turned off the air, the fans still didn't come on. No codes, no indication as to why the fans went off and the AC turned off.
I'm kinda lost. I'm going to do some logging with HPT to try and see what the PCM is seeing and commanding.
Stupid cars.
Thread Starter
Instructor
Joined: Jun 2007
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From: Tallahassee FL
Update:
well, not really, but I started the car a few minutes ago, hadn't been run since yesterday at last update. The AC won't work anymore and the fans don't bother to come on. No codes, no nothing. Feels like an electrical gremlin at this point, but what? It's intermittent so it doesn't feel like a fuse. I guess it could be a relay, but we're talking about two different systems: AC and fans.
well, not really, but I started the car a few minutes ago, hadn't been run since yesterday at last update. The AC won't work anymore and the fans don't bother to come on. No codes, no nothing. Feels like an electrical gremlin at this point, but what? It's intermittent so it doesn't feel like a fuse. I guess it could be a relay, but we're talking about two different systems: AC and fans.
Thread Starter
Instructor
Joined: Jun 2007
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From: Tallahassee FL
Hooked up HP Tuners and did some logging. Fans are commanded on when expected, but don't work. Then, out of nowhere (around 228 degrees coolant temp) they started working. Coolant gets to 199 in a hurry.
No pending or stored DTC's, no explanation.
I'm lost. Can't be the fuse or a short, they work... then they don't. All this from cold start idling in my driveway.
No pending or stored DTC's, no explanation.
I'm lost. Can't be the fuse or a short, they work... then they don't. All this from cold start idling in my driveway.
Thread Starter
Instructor
Joined: Jun 2007
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From: Tallahassee FL
I would think a fan controller error would set a DTC, but I could be wrong. Beyond that, would it cause the A/C compressor not to come on?
Another anomoly: the internal blower motor (for climate control) changes speed when manually set. So, when not in auto mode, there is an audible change in speed and air intensity. All while the AC really isn't working anyway. Never had that problem before either, though it could be related to the A/C not working.
Another anomoly: the internal blower motor (for climate control) changes speed when manually set. So, when not in auto mode, there is an audible change in speed and air intensity. All while the AC really isn't working anyway. Never had that problem before either, though it could be related to the A/C not working.
Melting Slicks
Joined: Sep 2005
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From: merritt island fl
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I would think a fan controller error would set a DTC, but I could be wrong. Beyond that, would it cause the A/C compressor not to come on?
Another anomoly: the internal blower motor (for climate control) changes speed when manually set. So, when not in auto mode, there is an audible change in speed and air intensity. All while the AC really isn't working anyway. Never had that problem before either, though it could be related to the A/C not working.
Another anomoly: the internal blower motor (for climate control) changes speed when manually set. So, when not in auto mode, there is an audible change in speed and air intensity. All while the AC really isn't working anyway. Never had that problem before either, though it could be related to the A/C not working.
Thread Starter
Instructor
Joined: Jun 2007
Posts: 130
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From: Tallahassee FL
I'm trying to track the issue from the fans back for the time being... Anybody have a pin-out schematic for the PCM? I need to track fan operation to and from the controller I guess.
