[NamelessTech]

Hey all,
My bull is acting really oddly. Had the thermostat and coolant temp sensor replaced around 2-weeks ago, for a little extra info.

I've had this happen a few times now, even after getting both of those replaced, where highway driving won't really be an issue, but as soon as I'm doing any city driving, my temp gauge will start to climb. It hasn't overheated, thankfully, but it does get a bit warmer than I'd like. The odd thing about this? When I pull into a parking spot, and put it in park (with the engine ) the temp gauge drops back down to a little left of dead center, where it usually sits.

I'm a bit stumped as to what this could be, as are the fine folks at the Firestone I took it to this afternoon. They told me to bring it to a dealer, as it has "major electrical issues" that they couldn't bring up wiring diagrams for. They also mentioned that it would be a huge safety risk to continue to drive it, for fear of an electrical fire. Another interesting tidbit: I drove it back to where I'm staying, without the air on, and I didn't have a single issue. No spike in coolant temp, or anything of the like, even while city driving.

Now, it's an '06 SEL with a Vulcan, and 206k miles. Water pump doesn't have a leak, and cooling system seems to be working properly.

Any insight would be appreciated, and thanks for reading!

-NT

 

[chartmaker]

Hey all,
My bull is acting really oddly. Had the thermostat and coolant temp sensor replaced around 2-weeks ago, for a little extra info.

I've had this happen a few times now, even after getting both of those replaced, where highway driving won't really be an issue, but as soon as I'm doing any city driving, my temp gauge will start to climb. It hasn't overheated, thankfully, but it does get a bit warmer than I'd like. The odd thing about this? When I pull into a parking spot, and put it in park (with the engine ) the temp gauge drops back down to a little left of dead center, where it usually sits.

I'm a bit stumped as to what this could be, as are the fine folks at the Firestone I took it to this afternoon. They told me to bring it to a dealer, as it has "major electrical issues" that they couldn't bring up wiring diagrams for. They also mentioned that it would be a huge safety risk to continue to drive it, for fear of an electrical fire. Another interesting tidbit: I drove it back to where I'm staying, without the air on, and I didn't have a single issue. No spike in coolant temp, or anything of the like, even while city driving.

Now, it's an '06 SEL with a Vulcan, and 206k miles. Water pump doesn't have a leak, and cooling system seems to be working properly.

Any insight would be appreciated, and thanks for reading!

-NT

The car's temp gage has no numbers on it. For a reason. It is about half as accurate as the gas gage. So you do not know that you have a cooling system issue. First easy check, with the engine on, A/C on, raise the hood and see if both fans are running. It is a visual, keep your hands well outside the area. Anytime the A/C is on, the fans should both be running on low speed. Good idea to use a garden hose and flush the condneser and engine rad out to get rid of bugs and dirt. I do this with the engine off but on warm day so it dries out.
-chart-

 

[DoctorHugocat]

I have one question immediately; when you had the thermostat replaced, do you know if you had a Motorcraft thermostat fitted? I had a lot of odd fluctuations in my cooling temp similar to those you describe when I fitted aftermarket thermostats. Disappeared when I replaced with Motorcraft.

Secondly, out of interest, what made Firestone think you have electrical issues from the symptoms you describe? Cooling sure, but electrical? Are there other symptoms?

I agree 100% with Chartmaker's suggestions; check the cooling fans and make sure your condenser/radiator are clear.....

 

[Architect]

And then you have the possibility the thermostat is incorrectly installed. Once incorrectly installed, replacing it with a new one wont help, because you of course put the new one in exactly the way the old one came out.

The spring of the thermostat should be towards the engine. You do not need to open the thermostat housing to check this. You can take off the coolant hose to the radiator and feel inside. You should feel the smooth bridge and not the spring.

 

[NamelessTech]

I have one question immediately; when you had the thermostat replaced, do you know if you had a Motorcraft thermostat fitted? I had a lot of odd fluctuations in my cooling temp similar to those you describe when I fitted aftermarket thermostats. Disappeared when I replaced with Motorcraft.

Secondly, out of interest, what made Firestone think you have electrical issues from the symptoms you describe? Cooling sure, but electrical? Are there other symptoms?

I agree 100% with Chartmaker's suggestions; check the cooling fans and make sure your condenser/radiator are clear.....

I'm not sure, but I very much doubt they put a Motorcraft in. I'll have to check my invoice, and if they didn't.. well, I guess I'll be ordering a new one.

As for the electrical issues, I wasn't really told much beyond that and it being unsafe to drive and a "electrical fire risk." I've not really had much issue with the power in it. Could get the alternator checked out, start with something I can absolutely service myself. The tech said he had one of the techs that's savvy with electric systems check it out, and he couldn't figure it out without looking at a wiring diagram that they couldn't pull up. Not a very helpful statement, and worrying at that.

 

[NamelessTech]

And then you have the possibility the thermostat is incorrectly installed. Once incorrectly installed, replacing it with a new one wont help, because you of course put the new one in exactly the way the old one came out.

The spring of the thermostat should be towards the engine. You do not need to open the thermostat housing to check this. You can take off the coolant hose to the radiator and feel inside. You should feel the smooth bridge and not the spring.

I'll have time this weekend to take a gander, see if this isn't the issue. For now, I have it parked and am bumming rides off of friends to/from work.

 

[NamelessTech]

The car's temp gage has no numbers on it. For a reason. It is about half as accurate as the gas gage. So you do not know that you have a cooling system issue. First easy check, with the engine on, A/C on, raise the hood and see if both fans are running. It is a visual, keep your hands well outside the area. Anytime the A/C is on, the fans should both be running on low speed. Good idea to use a garden hose and flush the condneser and engine rad out to get rid of bugs and dirt. I do this with the engine off but on warm day so it dries out.
-chart-

I'll have to find a place with a hose, but I should give them a good wash. Finding a warm day shouldn't be too challenging, as I recently moved to the North Dallas area in Texas 😂 I'll also check the fans, though I do remember hearing them run previously.

 

[Architect]

and he couldn't figure it out without looking at a wiring diagram that they couldn't pull up.

Here is the

2006 PCM pinout

The sensor is a 2-pin sensor between pin 38 and a common pin 91 of the PCM. Don't think a short here is going to cause a fire.

 

[NamelessTech]

Here is the

2006 PCM pinout

The sensor is a 2-pin sensor between pin 38 and a common pin 91 of the PCM. Don't think a short here is going to cause a fire.

I don't know if it's a PCM Short they were talking about, but... I will absolutely keep this in mind.

 

[MERCrunner]

I'll just throw this out there...the Temp gauge on my '04 Sable DOHC (279K miles) started going whack last summer. Some days it would act normal...but, most days it would start out randomly reading any place it wanted on the gauge when cold and move clockwise from there. Very disconcerting at first until I remembered I could access actual engine temp via the electronic info center on my car and temp was always within range. If I reset the electronics or disconnected the battery, it would act normal for a few driving cycles before going wonky again. Never was afraid of driving it due to "major electrical problems". Oh...and for years now, when it's very cold outside, half the dash warning lights stay on once the car is started and odometer blanks out until car's interior warms up and car is shut off and restarted. Then, all is well. Learned to live with that, also.

 

[Automender12345]

Why did you replace the thermostat in the first place, same issues?

 

[DoctorHugocat]

Why did you replace the thermostat in the first place, same issues?

Good question! If I were you I'd investigate the thermostat first and also that the cooling fans are kicking in properly. Lots of good ideas here, including the PCM. That Firestone couldn't have been less useful, but I'm sure we can all figure it out.....let us know what you find.

 

[helifino]

And then you have the possibility the thermostat is incorrectly installed. Once incorrectly installed, replacing it with a new one wont help, because you of course put the new one in exactly the way the old one came out.

The spring of the thermostat should be towards the engine. You do not need to open the thermostat housing to check this. You can take off the coolant hose to the radiator and feel inside. You should feel the smooth bridge and not the spring.

Also there's a small brass pin on the Motorcraft units which is supposed to be at the top. This allows the burping of any air trapped in the system.

 

[aleo101]

I'm having simular problems--- I believe I have air in the system and need to drain out the fluid, and use a vacuum refill system. Whenever you open your system (themostat, etc) when you refill air can get in and find a pocket and circulates and when the bubble hits the water pump, it cavitates. when the temp goes up "gun' the engine to about 2500-3000 and see if the temps drops fast. If so, most likely air stuck in system. I did some work and let some air back in by mistake, and can't purdge so I'm gonna drain and vacuum refill this week, in fact. Got a kit on Ebay for 40 bucks. Find out if your service guys did a vacuum refill or not. I bet not.