Coolant Temp gauge/sender problem

[ydphtwl]

I have a 96 LT4. My temp gauge is normal most of the time. I have had a couple of occasions lately where, in traffic, the gauge will read very high, so high that you would think you would be loosing coolant. I have checked the coolant level after it cools down and it is full. During the time when it is reading hot, the oil temp runs around 220 deg. Could this be a fan issue. I seldom run my AC. When it is hot and I get back on a highway at cruising speed for a while, it will very gradually cool down a bit.
Any ideas?
Ken

 

[all4c4lt4]

The LT4 runs "hot" due to GMs need to meet emissions requirements. While the temps you are seeing are in the normal operating range, most people (including me) do not want to run that hot. Install a 180 or 160 degree thermostat and have the computer reprogrammed to turn the fans on earlier (factory 220). A local tuner could do that or it is one of the few useful operations of a Hypertech programmer (only by these used imo, not worth the money). With doing only these things I never run hotter than 194.

Also its a good idea to pull your rad and clean it as junk builds up from these "street sweepers".

 

[ydphtwl]

Thanks for the tips. I may have some issue. Today when I got off the freeway on a surface road it got hot, so I stopped and opened the hood and the fans were not running. I turned on the AC and the fans came on and the temps went back to normal very fast. Could I have a bad fan temp sender and the AC forces it on?
Ken

 

[tlong]

Runnin' hot

Greetings from Alpharetta.

Let's see here. If the fans come on when AC engaged the sensor is good on the pressure line. The cooling fans should engage at 235 F. on their own. You probably never got there.

Cooling off the engine has been beat to death here. Check the radiator and condensor for trash. Consider pulling the radiator and straightening fins and really cleaning it. Add water wetter. Get a new cap-that is cheap maintenance and might be all you need.

Get a new thermostat. I have a HyperTech 180 and it works better than the stock 180. A 160 won't help the high end, only cruise temp. Your current thermostat may be lazy.

When did you change coolant? Is the system burped? Air pockets can raise the temp too.

The final and best thing is to reprogram the fans to lower start temp. That's assuming the fan temp switch is good. The test is the 235 F.

I did this drill and have one less thing to worry about. Hope it helps you.

 

[ydphtwl]

TLong,
Thanks for your advice. I have owned the 96 for a couple of months, long time 87 owner. The previous owner had just replaced the radiator, hoses, etc., a month or so before I purchased the car. I do not know about the thermostat. I have already made plans to replace it. I just want to make sure I don't have a defective temp sensor, relay, etc. What is the procedure to make sure there are no air pockets? When I let it cool down and check the coolant, it is alway full. However, when I bypassed the throttle body, very little fluid came out. I was worried about getting it on my Optispark and had rags stuffed in all the holes but very little came out. I felt like I had a problem when I turned on the AC and the water temp and the oil temp dropped to where I would consider normal. If my 87 was running a little hot in the summer time and I turned on the AC, it would heat up even more. Still in the learning curve on the 96 but so far I love it!!
Ken

 

[vettered91]

Re: Runnin' hot

The final and best thing is to reprogram the fans to lower start temp. That's assuming the fan temp switch is good. The test is the 235 F.
[/B]

Do what tlong says;
but first of all and for your own peace of mind do the 235* test, let the engine idle till it reachs the 235*. At this temp the first fan should be on (not too sure but the second will be on at something like 248*)
This way you can be sure there's no problem with the coolant temp sensor. (I bet it's OK)

Down here it's warm 95% of the year so I have the 160* Hyper stat and my first fan turns on at 187*(+-). Most of the time I'm in stop lights (every day vette) and I'd never been hapier with my temps!

Good luck

 

[tlong]

New '96

First let me drive your LT-4 for a few weeks to make sure it's OK. Yeah sure. I love my'96 too. The granny that had it never used much up on it. I am a lowly, pitifully slow LT-1.

When you change the thermostat drain about a half gallon from the bottom of the radiator. Make sure the proper type; use NAPA Stant or Hypertech LT-4. Most use 180*. Aluminum components were designed to operate at these temps. Too cool is uncool.

After you put the housing on refill. There is a little brass bolt on the housing for air bleeding. Use utmost caution over the Opti- you know that already.

The conditions you describe are alarming for most new owners, but that's considered normal. Most prefer cooler. It is absolutely bizarre to watch the temp drop drastically with AC on. Just the opposite of logic. But it brings those big ol' fans with it. These radiators are race inspired , and race cars move 99% of the time.

Hypertech is the best way to control fan start-up. Research that a bit more and decide if necessary. You'll wear out the fans much faster set too low. They turn off at 50 mph. What a smart car!

In the mean time don't embarass too many people off the line with that sleeper Vette. Exercise extreme caution if you see ZR-1 or ZO6 anywhere on them.

Tim

 

[ydphtwl]

Thanks Tim,
Hope to meet you at a local thing or something. Might let you drive it with me in the navigator chair!! Other than my 87 Vette, most of my experience is with streetrods which also have cooling problems. They are usually fixed by overkill on the components. I am building a 53 Studebaker with a 489 BBC/Richmond R.O.D. and Frankland Quickie. I have a Griffin Winston Cup radiator in it and it is about 4" thick with electric fans, high volume pump, etc. I might jump on a ZR1 or a Z06 with it (straight line/top end) but not with the LT4. My Vette is a 100K car but feels and smell like new. I love this car and just want to make sure I don't "cook" the engine.
Ken

 

[tlong]

Frankland

A Quickie is better than nothing.

You probably don't have a cooling problem. Do the thermo change and enjoy your hot mama.

I really want to start participating in Vette stuff around here but have to get over the Bowling Green 50th. We went on the big deal caravan from Kennesaw and showed at 8:15 A.M. For weeks it was touted as hundreds of cars from Ga/Fl. There were 7 there. They had left at 6:30! Whassup with that? A million rules and they left 2 hours early? I have gone anarchist since.

The vast majority were C-5s. Sorry but new ones don't rate the attitude I got from many owners. I had a '63 for years and didn't think I was way too cool for everybody. Rant rant....

Hope to meet you also along with the fine 84-96 best vette people.

Tim

 

[Greg@NASA]

Whew, that's a relief!!

Wish I'd read this thread last week.....waiting in line in a drive-thru and the analog temp gauge starts climbing real fast....the digital temp looked more like believable temps, but it scared me pretty bad. Little did I know that it wasn't hot enuff for the fans to come on..

Still trying to get some pictures of my new toy, got a new digital camera, but how do I post pics??? Any help would be appreciated..

Will be in Acworth the week of Christmas, but alas....not with the 'Vette..

Seasons Greetings to all


Greg