Temperature Gauge Fluctuates. Yours?

Audiophile · May 15, 2014

I've noticed over the last several weeks my temperature gauge will fluctuate somewhat. I'm very particular and certainly don't want to run my car hot so I don't like it, at all.

According to the gauge, I'm used to seeing it around 190 degrees, or somewhere close to that. On occasion, it will fluctuate up to 220-240. That seems excessive, but I'm no expert in this area, so I wanted to check in with you guys. What do your's normally run? Does it fluctuate at all?

Some further info, its been pretty hot here in So. CA. Today, high is supposed to be around 102 I think. If I run my A/C, that seems to make it go up some. I had a new radiator installed back in October.

As soon as I began to see this happening, I ordered a new thermostat and a temp. sending unit. I have not installed it yet.

Opinions and/or thoughts?

As always, thanks in advance!!

dnbonds · May 15, 2014

Is it the stock gauge on the instrument cluster or an aftermarket gauge?

Edit: Didn't see you got a new sending unit. That might fix it. I'm unsure if the gauge uses vacuum lines so that could be another cause.

My oil pressure gauge was flopping around a lot and I replaced the sending unit. The flopping lessened but it's still there. I'm pretty sure I have a vacuum leak somewhere.

Audiophile · May 15, 2014

Dang it, my bad. Yes, its the stock gauge. Should have included that info.

dnbonds · May 15, 2014

I tried to get that edit in before you posted but I wasn't fast enough lol.

jAEded · May 15, 2014

Mine is kind of steady. If I have the headlights on than it jumps up almost a half bar. I'm not actually sure if the car is running hotter or if there is interference in the dash wiring that causes it to go up when the lights are on. Jrichkter might know.

If I drive with no accessories on, than the gauge is steady at about the half way mark. Light on its up about half a bar from mid way.

jAEded · May 15, 2014

PS - its been f*ckn hot here in so cal. My car has been running like a dog with the AC on.

Audiophile · May 15, 2014

jAEded said:
PS - its been f*ckn hot here in so cal. My car has been running like a dog with the AC on.

You in So. CA? Where if you don't mind me asking? I'm in what they call the Inland Empire. Been here for about 8 months or so and am trying to find some fellow Mustang enthusiasts.

jAEded · May 15, 2014

Ventura area. You aren't too far away.. I work close to the beach, but I think its still going to be 90+ today.

Mustang5L5 · May 15, 2014

My stock guage never moves. My autometer mechanical gauge however does.

I trust my stock guage as far as I can throw my car

jAEded · May 15, 2014

Might be worth looking at the thermostat. I just had to do mine. I was running a full bar below halfway, all the time. If I accelerated it would drop lower as the water pump spun up.

Usually when the stock sender fails the needle stay in one spot. Could be the gauge itself? I would default to you might have a cooling system issue. The stock gauges aren't accurate but they do work.

tamadrummer88 · May 15, 2014

Mine would stay at the middle or slightly below. In the summer, even on the freeway, the temp gauge would go up. Sometimes it would get hot to the point where id have to pull over and let it cool a bit. The stock fan has some cracks in it so that could be the culprit. When i put back the top end ill change the fan.

dnbonds · May 15, 2014

tamadrummer88 said:
Mine would stay at the middle or slightly below. In the summer, even on the freeway, the temp gauge would go up. Sometimes it would get hot to the point where id have to pull over and let it cool a bit. The stock fan has some cracks in it so that could be the culprit. When i put back the top end ill change the fan.

That's a good idea. I need a new fan because mine has cracks as well. That'll be something to do when I have my engine out.

End of hijack, continue. lol

tamadrummer88 · May 15, 2014

dnbonds said:
That's a good idea. I need a new fan because mine has cracks as well. That'll be something to do when I have my engine out.

End of hijack, continue. lol

Or could be that the clutch is worn and the fan is just freewheeling.

dnbonds · May 15, 2014

tamadrummer88 said:
Or could be that the clutch is worn and the fan is just freewheeling.

I don't want the blades shooting off either. I'm going to look into an electric cooling fan.

2000xp8 · May 16, 2014

This topic is covered pretty often.
#1 is to get a mechanical autometer mounted within visibility while driving.
#2 would be to run a mr gaskets 180 thermostat. 180 is NOT too cold, 160 however is.

Then see where you are at. The stock guage is useless, regardless of whether or not the sending unit is new.
I prefer to know where i am temp wise within a couple degrees, not give or take 20.

If i thought my car was at 240 degrees, i'd be freaking out.

Noobz347 · May 16, 2014

My gauge fluctuates...

It's the stock gauge and has proven so far, to be reliable and consistent (that doesn't mean that it is, it just means that I believe to be).

I think that the problem I have is the same as the one already talked about in this thread. The clutch fan. I've been threatening to replace with an electric unit but haven't gotten on it yet.

89oem · May 16, 2014

my stock sits underscoring the M. a month ago it wasnt that high, replaced sending unit and its back at same.

102 and heavy traffic could move it i guess...

stock gauge is fine if you use it to observe a change in behaviour as you have....imo

when was the last time you changed and flushed coolant?

Audiophile · May 16, 2014

Coolant was changed and flushed last Oct. when I had the radiator replaced.

I ordered and have received a 180 degree thermostat as well as the new sending unit. I just need to put them in. (Although I hear its a pain in the ....)

Since I have those parts already, I'll see if they make a difference. If not, I'll get another gauge. Either way, I always keep a close eye on it.

jAEded · May 16, 2014

Radiator cap too. If your cap is dumping pressure before 16 psi it would cause the car to run hotter.

Sending unit isn't too bad. I think you can get to it without removing anything. IACT sucks to get to. Thermostat is probably the most work.

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