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Eleventeenth Gear Poster
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Discussion Starter #1
I've had my car for over 2 years and have never had a problem with the cooling system. Now all of a sudden the temp needle is all over the place. I don’t really trust any of the stock gauges in my car, but it still worries me, ya know? The needle normally sits a little less than a quarter of the way up no matter what kind of driving I’m doing, and the last two days it has gone a little past the half way mark a few times. The way this happens is very strange to me though.

Monday and today I had to do a couple of things before I went to work. I drove the car about 20 minutes and everything was fine, nothing out of the normal. I’d get to where I was going, park, shut the car off, and go do what I had to do. I had the car off for maybe 5-7 minutes on Monday, and probably 2 minutes today before I got back in and started it to go on to the next place. Both times within probably a minute or so, the needle went from its normal zone, to a little over the half way mark!!! I’m wondering WTF?

Both times, as soon as I saw it was that high I stopped to check the coolant level and make sure nothing was leaking or smelled like coolant or anything. Everything looked fine both times.

I can drive with the AC on high with no problems until I shut the car off for a few minutes, then restart it. After that, having the AC on will raise the temp (according to the gauge :rolleyes: ), so I have to drive around in the South Florida HEAT with the AC off when the needle gets up and starts to worry me.

I already have a 180* T-stat and a CustomChip along with 2 degree cooler plugs. Thursday I will have time to work on the car. I have already bought some more coolant, some radiator flush, and some Water Wetter. I plan to flush it out real well, hose out the fins, check the hoses, check the water pump, check the elec. Fan, and put new 50/50 water/coolant mixture in as well as the water wetter at the end. Is there anything else I should check or do? I want to flush the radiator out with the flush fluid I bought and force flush it with the garden hose. To do that should I just remove the lower hose and rad. cap and spray the hose in there or what? How do I check to see if the fan works properly, or at all? Also, how much fluid does the cooling system of a 94 3.8 LX hold? Thanks for any help or suggestions.
 

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I could bet money

that the temp sending unit has gone haywire, but just to be safe, do a full system flush with new fluid, and make sure to flush the radiator really well.
 

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Overheating

The prior posting about flushing is a good idea to prevent future problems since the cooling system additives are only good for 3 years, and yours is used.

What you are seeing is normal. When an engine is running, everything in it except the oil and water, are between 250-1500 degrees. When the engine is running, the oil and water keep extracting the heat, and every thing is fine. When you turn off the engine, the heat is still being transfered into the water, but the water is no longer being cooled. It is normal for the water to get to 240-250 just after being turned off. When you restarted it just a few mins later, the hotter water in the block was circulated through the radiator, and dropped quickly. One way to reduce this some, is to drive easier prior to shutting it off, or idle it for 1-2 mins prior to turning off. Turning the A/C off 2-3 mins prior to parking will help lower the over all temp also.
 

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Eleventeenth Gear Poster
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3,067 Posts
Discussion Starter #4
Thanks guys.

Can anyone give me any details on the temp sending unit? Like where its located on a 94 3.8 LX, how to tell if it needs to be replaced, or anything else I should know about it?

Also, any advice on the best way to flush out the radiator, and how to check the electric fan?

Thanks again.
 

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hey Aaron

dude, make sure that your rad is not clogged up, but in a 3.8 that seems like a normal driving temp, my cars temp, rides from the middle to the M in NORM and right back down when the fan kicks in, as long as it dosent go to the H and it stays in the normal range, then its safe, what i was telling ya about your rad, my car was overheating all the time, and i didnt know what it was, i took the car to the dealer, where they changed my headgaskets, i took it to different mechanics, and no one new why it was overheating, so i decided on changing my rad, i got me a new one, and my car hasnt overheated since, so make sure its not clogged up.

also, go to the 3.8 section in the forums, theirs a post their about overheating, i posted their and acouple of other guys, maybe that can help.

p.s. i do know what it is to ride down here in Miami with no A/C.

Marvin M.
 

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Similar problems in a '95 4.6..

A while back when I first got my '95 4.6 Cougar, I wasn't accustomed to the temp gauges fluctuating as much as they do...My previous Cougars (an '89 and a '90 3.8) never seemed to do that much, but they had the digital dashes in them, so when I set foot in the '95, and took it for a few test drives, I wasn't surprised by the temp gauge sitting down by the 'N' (about 1/4 way up).

Driving in rush hour, however, where I sit for extended periods of time travelling at velocities around 2mph, the temp gauge seemed to be out of control...bouncing back and forth across the entire spectrum as denoted by the word "NORM" on my gauge.

Didn't seem right to me, so I checked a bunch of stuff, and finally got the multimeter out and checked the output values from the engine coolant temperature sensors against the table in my Chiltons, and against the lo- and hi-speed fan temps (as provided by some wonderful folks here, back in the old forum -- 216 deg. low speed, 228 deg. high speed), and everything checked out...so, I haven't worried about it since. :) Just so long as it doesn't pass beyond the safe "NORM" range and into the red...
 

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Eleventeenth Gear Poster
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Discussion Starter #7
I think I have whatever problem there was, fixed. I did everything I said above and now the temp gauge stays in its normal area. I drove it around a lot yesterday and today, and made a few quick stops, and the gauge never jumped up. So all is good...and hopefully it will stay that way. Thanks for ther help guys.
 

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VERY Important....

You do NOT HAVE to or even NEED to run 50/50 antifreeze to water. It's a waste and not as efficient. You can get by just as well if not better with a 25/75 mix. And ONLY use distilled water. Water is a much better conductor of heat than the "coolant" ever will be. And with the water wetter, it's even better.

The 3:1 water/AF is great for just about anybody south of Wisconsin. There they'll need to run 2:1 (33% AF/67% water) which will still protect down to 20 below or better. If you live up north of Edmonton or in Alaska, then 50/50 probably isn't a bad idea. But they need to run water wetter too. Not to keep the engine cool, but to transfer the heat into the water faster (and hence to your cold tootsies).

Just some helpful info from your favorite Grand Poobah.
 
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Temp sender

I agree with the post earlier... your temp sending unit could have a bad wire... only like $8 for the part, I'd replace it just because its a nice thing to know its been replaced :)
 
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