I think my water temp guage is off...going to 270*!

TheUser · Jul 5, 2004

I think my water temp guage is off. It's stock, and i've read stock guages are not the best, so I suppose I shouldn't be surprised. I replaced the coolant temperature switch, water pump, thermostat (160*), new radiator cap, and i've done a coolant flush and refilled w/ anti-freeze/distilled water; I left the cap off to let the air get out. I still have this problem:

The car will idle at 180ish*(at the "A" in NORMAL) on the guage (with rad. cap off, I put a turkey thermo. in there and it read 145-150 - kinda weird considering the 160* thermo, but regardless). I take off and the car stays fine for about 1/3 mile or so, then it jumps up to about 210(between "R" and "M", then about another 1/3 mile and it starts rising again and before long, it's all the way to 270 on the guage. I get home, shut it off, pull the rad cap (let pressure off first) and stick the thermo in there...190-195. I'm not sure what's going on here. I'm not sure if i'm really overheating or if my guage is off. I was thinking about driving it, pulling the temp switch from the lower intake and checking the temp right in there right after driving it and see what it is - that would tell me if my guages are off or if i'm really overheating. When I get home, the coolant is bubbling in the overflow and the rad. and the rad. has overflowed into the overflow...like it should do, right?

I've read that, in town, a lot of times overheating is caused by a bad fan. I could swap the fan from my LX 5.0 on there and see if that helps. I've thought about upgrading to a Mark 8 fan w/ DCC control unit. I've also thought about new autometer guages. The radiator is old i'm sure. I really don't want to go blowing all this money if I can have a normal-temp car w/o doing so. Does anyone see a problem with pulling the coolant switch and testing temp in the lower intake?

timewarped1972 · Jul 5, 2004

all i can say is if you were at 270 you'd know it in a hurry........you'd be boiling big time ..........if the radiators the stock 2 core get atleast a replacement 3 core thats what im doing it isnt worth the worry..........next for me as well will be an after market temp guage........

90mustangGT · Jul 5, 2004

Factory gauges. You have to remember it's kind of old, with the wiring technology and quality of the 1980's. I had this problem, it would shoot way up but the engine was cool. Put a autometer gauge in and solved the problem.

stangbear427 · Jul 5, 2004

Agreed. Get an Autometer. If it was getting that hot you wouldn't be scratching your head about it. Mine did the same thing, every once in a while, and since I got my mechanical Autometers it's been interesting to see how the car really runs. I used to worry about all kinds of things for nothing every day. As for your other issue of confusion, let me try to explain:

TheUser said:
The car will idle at 180ish*(at the "A" in NORMAL) on the guage (with rad. cap off, I put a turkey thermo. in there and it read 145-150 - kinda weird considering the 160* thermo, but regardless)... I get home, shut it off, pull the rad cap (let pressure off first) and stick the thermo in there...190-195. I'm not sure what's going on here.

This is thinking logically, but isn't actually how it works. Putting in a 160* t-stat doesn't mean the car will run at 160*, it means that it won't start letting coolant go into the engine full force until it is 160*. So, 160* is the temp at which the t-stat "opens". At that time the coolant system will attempt to keep it from getting any hotter than that, but depending upon the weather and how good of a cooling system you have, it may not be able to. Considering your car was designed to run at 192*, it isn't surprising that it's in the 190-195* range after you've taken a blast in it. All that 160* t-stat does for you is make your car warm up slower, as it lets coolant start flowing sooner than the stock spec one does. How hot it gets after the t-stat opens is up to your fan, rad, h2o pump, etc... which, IMO, can never be good enough and should all be modified to be more efficient than stock unless you live somewhere like Alaska.

I think though, that your car is fine, the stock gauge is crying wolf, and it should be punished accordingly with replacement. Excuses to upgrade are good
Good luck

2000xp8 · Jul 5, 2004

I'm not reading any of this, put an autometer gauge in and get back to us with the results.

green · Jul 5, 2004

ya its probally not reading right, cause if the temp reached 270 you wouldent have an engine right now.

RacEoHolic330 · Jul 5, 2004

dude, you gotta get rid of that 160* thermostat. It's just too cold for the car to run right. Put a 180* in.

Killer50stang · Jul 5, 2004

You can go to Autozone and pick up a temp gauge for nothing around $14 or so. If you're under 200, you're fine. I would pickup a 3 core radiator. They go for around $120 brand new on EBAY. Check this one out. http://cgi.ebay.com/ebaymotors/ws/e...tem=7909305287&category=33602&sspagename=WDVW

Good Luck!

TheUser · Jul 5, 2004

Thanks for all of the responses! I figured if it were getting 270* the motor might not be in the best of shape. My head gaskets are copper, so i doubt they'd blow, but i'm sure other things might not be up for the abuse. Regardless, I put the car up and refuse to drive it until I have accurate-reading guages. I'm planning on buy auto meter guages now.

"I'm not reading any of this, put an autometer gauge in and get back to us with the results."

I understand what you're saying - it's a lot to read - but sort of a rude way of putting it. Nonetheless, thanks for your contribution

Is the 160* really that bad? I don't think it will make a differnce except the heater won't be of much use. I know the O2's are in closed loop until around 160*, but as stated, the car will not remain 160*, that's simply when the thermostat opens.

Killer50Stang: I'm not sure about the quality of a radiator on ebay. I bought one from ebay for my Grand Cherokee, but I don't think i'm willing to do that for the GT. I think I'll see how the stock one does w/ the new guages and go from there.

dude5l · Jul 5, 2004

TheUser said:
"I'm not reading any of this, put an autometer gauge in and get back to us with the results."

I understand what you're saying - it's a lot to read - but sort of a rude way of putting it. Nonetheless, thanks for your contribution

.

I don't think he was trying to be rude, since it wasn't that long of a post, I think he was just saying to get an accurate reading before trying to diagnose the problem.

stangbear427 · Jul 5, 2004

I don't think he was trying to be rude either, he just has a tendancy to be incredibly blunt sometimes; a character issue I can relate to far more than I'd like to admit...
Regardless, his advice was sound. Get some gauges in there worth looking at, and take it from there one step at a time.

Killer50stang · Jul 5, 2004

TheUser said:
Thanks for all of the responses! I figured if it were getting 270* the motor might not be in the best of shape. My head gaskets are copper, so i doubt they'd blow, but i'm sure other things might not be up for the abuse. Regardless, I put the car up and refuse to drive it until I have accurate-reading guages. I'm planning on buy auto meter guages now.

"I'm not reading any of this, put an autometer gauge in and get back to us with the results."

I understand what you're saying - it's a lot to read - but sort of a rude way of putting it. Nonetheless, thanks for your contribution

Is the 160* really that bad? I don't think it will make a differnce except the heater won't be of much use. I know the O2's are in closed loop until around 160*, but as stated, the car will not remain 160*, that's simply when the thermostat opens.

Killer50Stang: I'm not sure about the quality of a radiator on ebay. I bought one from ebay for my Grand Cherokee, but I don't think i'm willing to do that for the GT. I think I'll see how the stock one does w/ the new guages and go from there.

Just letting you know. The 3-core I bought works great! It'll save you about $150 from one from Summit or Jegs. Good Luck!

TheUser · Jul 5, 2004

Realizing there was a good probability that the stock guage was inaccurate, I replaced it with a "sunpro" water temp guage from Autozone. I know it's not autometer, but I get to work on my car on the weekends only and I wanted to try to get it fixed so I can drive the car this week. Installed the guage and temp at idle was about 180-195..cool. Took it for a drive and it slowly rose to 210 and then all the way up to 270 shortly thereafter.

stangbear427 · Jul 5, 2004

Was it elctric or mechanical- if electric does it reuse the stock wiring and sender or come with new stuff? Don't know much about Sunpro, except that it's against my religious principles to shop at the parts store that sells them...

TheUser · Jul 5, 2004

It's an electric guage and says run 18 guage wire. I ran 14 guage wire. I tapped into the blower motor fuse (#9). The guage seems to work fine. I guess now it's up to my radiator and/or fan. It overflows into the overflow take (which, I assume, it is supposed to do), so when I pop my rad. cap off, it's down like 10-12 inches. I make sure it's topped off before I take off, however.

HISSIN50 · Jul 5, 2004

i did not read the whole novel, but if you want: on a cold motor, pop the rad cap off and start it up. get a turkey thermometer and stick it in the rad cap hole. let it warm up and compare temps from the aftermarket gauge and the turkey thermometer. go from there. that way you can see what each is saying (i know the dynamics of stuff is different w/o the pressure in the system, but it can help with troubleshooting).

and dont ever use the turkey thermometer again for living-creature consumption.
can someone actually run at 270*, for real. i didnt think so.
just what i might try. good luck.

2000xp8 · Jul 5, 2004

Sorry, i really didn't mean to be rude, i probably should of added a smiley or something, there was just alot to read, and technically speaking none of it means anything if you are judging by a stock gauge.
it's just that the factory gauge is plain old useless, mine used to rise when i turned the parking lights on.

The money i spent on my autometer gauges (oil and water temp) was some of the best money i ever spent.

Also thanks guys for explaing that i didn't mean to be rude, now if you were planning on a turbo wing or altezzas you can assume that if i'm rude i mean it. lol

90MustangHatch · Jul 5, 2004

TheUser said:
It's an electric guage and says run 18 guage wire. I ran 14 guage wire. I tapped into the blower motor fuse (#9). The guage seems to work fine. I guess now it's up to my radiator and/or fan. It overflows into the overflow take (which, I assume, it is supposed to do), so when I pop my rad. cap off, it's down like 10-12 inches. I make sure it's topped off before I take off, however.

my car used to do this same thing. it would run for a bit and all of a sudden the gauge would shoot to 260-270. it seemed odd cause i didnt think it had time to even get that hot. let it cool and popped of rad. cap. coolant was low. so i filled it up and repeated this once or twice more and it stopped doing it. hope that helps some.

TheUser · Jul 5, 2004

90MustangHatch said:
my car used to do this same thing. it would run for a bit and all of a sudden the gauge would shoot to 260-270. it seemed odd cause i didnt think it had time to even get that hot. let it cool and popped of rad. cap. coolant was low. so i filled it up and repeated this once or twice more and it stopped doing it. hope that helps some.

I suppose that's worth a shot. I have done this and it's low when I pop the cap, but since the overlow was up to the "full when hot" mark, I figured it was in there and there was no problem. Isn't it normal to run a car and pop the cap to find the rad. isn't all the way full, but down like 10 inches or so?

As far as someone being able to run at 270 for real...I don't know. I wouldn't believe it either, but I've seen two guages that read the same (stock and sunpro), so :shrug. I'm still thinking about running it and pulling the freaking coolant switch out and testing right at the intake...that should give me a good indication of whether or not I should believe either of those guages...

Oh and it says "coolant low" most of the time...isn't that switch for it in the overflow tank? I've cleaned those tips and fill the coolant in the overflow past the end of the thing, but it still says "low coolant" a lot of the time. Is there another "low coolant" switch that I may not be aware of?

2000xp8 · Jul 5, 2004

Doesn't the car shut itself down at 270 to protect itself from destruction?

I think my water temp guage is off...going to 270*!

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