Ok to make a long story short, about a year ago I installed a ram air intake system from my fog lights to the intake hose. In order to do so I removed a panel that was between the radiator and foglights of the car. The air dam is still on the car might I add. Shortlty after this my car ran a little hot, around 220-230. Thinking this was normal I disregarded it. Here I am now the following summer and my car Is hitting 260 after about 20-30min.
At first it takes a while to heat up, so I thing the T stat is still good. I have not done any other mods to the car since the intake. A few days ago I removed the ram air system allowing air to go to the radiator directly from my foglights. I had no change in temp. I dont' think the panel I removed which I like to call the air guide would cause this. Many people have z28's with the same intake system and have no cooloing issues.

Also on a related issue if I drive around for while allowing to hit the 260 area the car doesn't start after letting it cool for about a half an hour or so. This has happened twice, but after a few tries the car starts. Is this cooling related too?

 

Another thing I realized is that I Had a problem with my cats clanking. The brick inside broke up and I was losing power. The guy at the muffler shop bang it through or something and the clanking stopped and power is normal. Could there still be peice in there causeing the exhaust fumes to build up thus causing the high temps?

 

If the cats are damaged, banging on them won't fix the problem. If the pieces are floating around or obstructing the flow, you'll have heat and after a while, burnt valves.
Is your cooling fan operating?
What are you running for coolant and what mix (%)

 

A commonly overlooked issue (It's happened to me), are you low on coolant at all? Perhaps an air bubble has developed? No abnormally large amount of bent fins?

And yes, if there is a loose piece on the cat, causing it to be clogged, it will create more heat.

Do you have a factory starter? If so, the second issue, regarding hot starts, Isn't cooling related, it's the factory starter being too weak. Replace with an aftermarket mini-starter or an LT-1 starter.

 

Not to disregard anyone else's advice, but my car was doing the same thing. Was the thermostat. The water pressure will blow the stat open, before blowing the radiator cap, I was told. So a bad thermostat will allow your car to heat to 260 before pressure forces it open. Now I've got a 160 stat and the car is much happier. (I live in So Cal though, so if you have winters you might want to run 170 or 180 degree thermostat.)

Also, quite often, cars won't start right away if the motor is very hot--something called "heat soak" occurs, when a hot motor is turned off right away--coolant hasn't carried away the excess temp, and the pistons will actually swell a bit, effectively seizing the motor until it cools off a bit.

Also, is your fan coming on? It won't until 235 degrees or so anyway, but it keeps it below 260. Manual fanswitch is the answer of course.

Thermostat takes 10 mins to change.

 

Ok to follow up with your guys advice, there is plenty of coolant in the system. When the car hits 260 the excess is at full hot. As far as the fans the primary does come on as for the second I am not sure. I here it come on when I put the heater on, but when I park the car and open the hood Its not on even when the gauge is at 260. I do have access to a multimeter, I am mobile installer for Best Buy. Should I check the relays? Does it make a difference if the the car is gear, if so i'll have my friend help with that.

I appreciate the help so far guys, I gotta get this fixed otherwise I am selling the car. There should be no reason for this to happen the car has 76000 miles on it.

 

I'm sure you will figure it out--also, check all the other threads on cooling. A common problem on these cars. GM made them to run hot to begin with, for emissions purposes. Lots can be done to make them run colder, the thermostat being the first thing, next is a manual fanswitch.

One way to tell if the thermostat is working--the car should warm up to a certain point, say 195 degrees which is the stock thermostat setting, then drop back a bit. If it just keeps going up, it's likely the thermostat. They cost 6 bucks at autozone (make sure they give you the right one), and it's located just under the waterneck on your intake if you don't already know this.

Try not to drive much until you get it fixed. I'm guessing thermostat, and in my humble opinion you should change it out to a 160 degree and see what happens. Also, check all the other cooling threads too. You'll be running cold in no time.

 

Thanks man, I hope its the stat. If thats what it is then Ill have a new found love in my car again. Appreciate the help.

 

Know what you mean, always such a bummer when something goes wrong. I was crushed the other day when I noticed a new dashboard crack (a new dash skin is available from F-body Motorsports, add to the list). Oh well, that's what maintaining a car is all about. And these are special cars. I'd rather be fixing my F-body than driving a brand new Maytag.

Since you are in NJ, you may want the 170 degree stat (it's a GM part, think you have to get it from a dealer), or 180, so your heater will work in the winter. The 160 is best for performance, I think, but you'd have to change it for winter. All the info you need is on these threads. I'm sure you already thought of this, but check your oil as well--not enough or too dirty makes it run hot too. In fact, I would change it once you get your temp back down--heat kills the oil. Also, make sure your oil looks normal. I'm sure it does. My car survived a couple of weeks of a bad thermostat--I thought it was just because it was summertime and now the car is fine. Good luck.

 

my car has the same problem, i took the thermostat out all together and it still gets all the way up on the temp gauge, my coolant and oil is fine along with my radiator. for now im stuck, i was thinking possibly a temp sensor issue?

 

If it were the sender of the wiring, then the temp would jump straight up when you turn the key.
You say the radiator is good.
Is this the 13 year original or a new replacement.
Pulling thermostats isn't fixing the problem, it's trying to cover up the symptoms.

 

Some more questions that answers would help in diagnosing your problems... Does it overheat more at slower speeds or hiway speeds? When was the system last flushed? Have you checked the mixture with a hydrometer (I think that is what it is called anyway... the doodad you check antifreeze with anyway)? Do you know if your temp guage is working correctly? What kind of condition is your rad cap in? and hoses? and t-stat? and waterpump? and radiator in general? Is your air deflector in place? Are your fans working as supposed to?
Yes, any and all of these questions can affect the temp, and the answers can help point you in the right direction for what to check/fix.

 

I know we should let this subject die, it seems like the original poster has quit responding.

I wanted to make one comment. Over the past month I had the same problem with the gauge hitting 260 in my 88 IROC.

I did a lot of things, replaced thermostat, replaced radiator (old one was 1/3 clogged) cleaned a lot of leaves out from between radiator and A/C condensor, and flushed system. It still would read 260.

When cold the gauge read at the bottom of the scale, like it should, but it would rapidly rise and keep rising to 260*. I found a chart on the TGO boards showing the ohm value for the GM temp senders and used it to test my wiring and sending unit. Everything was correct, except for the gauge. The gauge was reading much higher than it was supposed to acording to that chart.

I dissassembled the cluster and replaced the gauge with another one from a salvage yard. Same problem.

I studied the back of the gauge and realized there is a resistor (ceramic block w/metal contacts) between two posts. One of those posts is the negative or ground for the gauge. I found that both gauges had resistors that were either 84 or 86 ohms resistance across the back of the gauge.

Knowing the sender was working right, I removed the resistor/block and just for a test I wired a variable potentionmeter (radio shack) to the two posts, and plugged the gauge back in. This permitted me to adjust resistance across the two posts with the gauge in the cluster. Make sure the test leads don't touch the case of the guage, just the two posts, or your reading's will be off.

I fired up the car and let it idle until the cooling fan came on (stock = 227*) and adjusted the potentiometer until the gauge read just about right just above 220*. This was tough because the potentiometer I got (0 - 10k ohm) was very sensitive to just the mildest touch. I would recommend a very low resistance one.

Making sure I didn't adjust the potentiometer as I disconnected it from the test wires, I measured resistance across the two leads and found 37 ohms.

So I found a 22 and 15 ohm resistor, and soldered them in series. I covered this assembly with heat-shrink for insulation, and put eyelets on each end.

To keep them isolated from the gauge case, I turned the original ceramic block/resistor over and put it back on the gauge. To make sure the original resistor didn't make any contact I used very small heat shrink and made some insulators for the bottom of the two posts. I then put the resistors I had soldered together on the gauge between the two posts.

Since then, I've checked it over and over, comparing the gauge to the cooling fan operation cycle and I even went to a local shop and had them check the readout with a scan tool. It seems to be accurate.

If you go this route, don't trust my 37ohm findings test it yourself with a multimeter. You may find a totally different value.

Also, realize this should only be done after checking the rest of the cooling system and senders, but don't forget that the gauge may be off and the rest of the system could be working just fine!

 

Okay.

First off make sure you don't have bubbles and hoses aren't collapsing under throttle.

Then if you want to change your stat, do NOT get ANYTHING below 180. It's a waste and could cause your car to run too cool. I run a stock 195* stat, and never goes above 195.

Is your radiator extremely rusty and thus making flow hard?

Is your fluid contaminated and sludgey?

When was the last time your cooling system was worked on?

Are you sure your gauge is accurate?

 

Have to disagree with the last post. I am using a 160 degree thermostat, and my car runs way better now, idles smoother, may even be making more power. Many people on these threads who have modded/hotrodded their third gens use the 160*, in fact that's the temp set by Hypertech, the co. that makes aftermarket stats and chips for our cars.

Some people use the 170 degree stat, available from GM. The stock 195 degree stat was used for emissions purposes, to cook every last atom of gas in the cylinder. It also cooks your engine over time. Now, if you live in a very cold region, a 160 degree is not for you, maybe go 180 so your heater works properly, and your motor warms up. No engine needs to run at 200 degrees.

Yes, 160 degrees is too cold for winter, I've heard. I live in So Cal though, so thls is not an issue for me. Some people swap in the colder stat for summer, put the stock back in in winter. At any rate, the 160 degree unit works great for me. My .02, and based on reading about other people's cars on this site.

Third Gens Rule