Hello all, I am new to the forum here and looking for some help diagnosing an overtemp. I've tries reviewing other issues and I am thinking I am on the right track, but any advise would be appreciated.

I just purchased an 85 Camaro, V8 305 ci. And am having issues with it overheating.

What I am thinking is happening is that it is overheating before the thermostat gets a chance to open, or is only partially opening. Below is a brief synopsis:

I only have an idiot light, no analog temp needle.

Basically, when I first start it up, the temp light comes on for a second and shuts off after ignition like it should. When I first start driving for a few minutes, it is off, but as I drive longer it will go from dim red to a bright red. Seems to be brighter when accelerating and dim or go out when coasting or idling.

Also, if I turn it on and let it idle at park, after 5-10 minutes the light will come on as well.

The upper radiator hose stays cold until right about the time the light comes on, then becomes luke warm at best. The lower radiator hose and cap are ice cold. Anti-freeze levels are good, no boiling when it over heats.

I purchased a new radiator cap because the old one was probably shot regardless. I've tried burping the system but the rad tank is full and no airbubbles after 5-10 minutes (by time the temp light comes on) and the resevoir no bubbles as well.

One thing I did notice is that their is no drop in the radiator level when the thermostat does (or should be opening, once again temp light comes on first).

I think regardless is does need a new radiator because the one on there looks junk, and I've gone ahead and purchased a new one and a thermostat and hoses to replace. Supposedly the water pump is new.

I haven't noticed any leaks; reservoir level seems pretty constant and I checked the oil to see if the head gasket is leaking and no indications of it, nor white smoke out the exhaust etc.


I think that's about the size of it; just wondering if anyone had any ideas as to what I might be missing or if I'm on the right track.

 

its could just be the light coming on through back feeding or something. the car isnt overheating unless water starts boiling into the overflow tank. get a laser thermometer and check the actual temps on various parts of the cooling system and see how hot the engine is really getting. or invest in a water temp gauge.

if you want to verify the thermostat is working, take it out and heat a pot of water to its rated opening temp them drop the tstat in it. if it opens then all is well.

 

Im learning a lot on the fly, so im enjoying owning this car already (part of the project was to learn about vehicles....im strange I know).

Anyway, if the thermostat is stuck closed, and the antifreeze is only cycling in the engine, how would the reservoir ever boil?

Also, what causes the idiot light to come on? A wire from the sending unit? Basic stuff I know but haven't totally figured it out between the Haynes manual and the shop book oil picked up.

Thanks.

 

There is a sender in the drivers side head, between 1 & 3 spark plugs. You might have a lose/shorted wire.

 

the coolant can still flow through the heater core and into the rad. the water flow is never completely cut off even if the tstat is closed.

 

AFAIK,IROCs and z28s always came with"gauge"
instrument panels-someone must have swapped the
clusters for some reason or you may have a sport coupe
dressed as an iroc.Idiot light senders are just a
thermostatic on/off switch-if there is a"gauge " sender
hooked to an idiot light it might cause the connected
bulb to glow brighter as the sender heats up.
The changes in brightness with changing engine speed
is an electrical fault-probably a bad engine to body
ground connection.

 

Great info. Ill be honest. Im brand newnew to allcome of this. When I type the vin in it comes up with base irocz. Anyway, I plan on swapping radiators and putting a new thermostat in this weekend. Ill let ya know and ill check the wiring too.

 

vin cant tell if its an iroc or not. only the spid sheet can.

 

[QUOTE=travis401;5093947]vin cant tell if its an iroc or not. only the spid sheet can.[/QUOTE

Where can I find that?

 

usually found stuck to the back of the center console storage compartment, sometimes it might be located elsewhere

 

I kept having the same problem. I'd go ahead and change the thermostat and see what happens. I just changed mine for $37.50 all told: thermostat, gasket, gasket sealant, and 2 gal of premixed coolant. Turned out I was low on coolant by almost half a gallon. Filled it up and changed the stat and temps stayed very consistent, but now I have a small leak in either the water pump or lower radiator hose. It might also be a problem with the cap since I have seen a bit of steam coming from it since I changed the stat. The leak is so small its a couple drops an hour at best which would leave a small almost unnoticeable spot on the pavement until you start having temp issues. I know its not the heater core because I don't have a standing puddle of coolant in the passenger side floor.

My leak had to have happened in the last few days. I didn't have any issues with it until Friday and that's when I found out whats going on.

 

I had the same issue with my 91, I tried different thermostats and checked the water pump but the car would still over heat. It ended up being a partially clogged radiator. I could see water flowing in the radiator but it was not getting hot because not much was going through the motor.

 

Thank you all for your help. Definitely some great ideas.

 

Ok all... here is the follow up:

Swapped radiator, hoses, t-stat, seals etc. Can tell a big difference in flow with radiator and the upper hose is getting nice and warn and lowered is cooler.

Still getting the base gage cluster idiot light coming on at different intensities as the car warms up. I found the green wire hooked to it. On lowered right side of engine. Is it possible that there is a bad unit? Or that it is the wrong init? Or shouldn't it just be a switch and not a sending unit because I have no gauge? Car really doesn't seem like its overheating. Arghhhhh Damn light lol.

 

Still confused on why you have a light instead of a gauge....

Got a pic of the dash?

Idiot light should just be On or Off.. Not vary in intensity...

I wonder what would happen if you used an idiot light with a Gauge sender? I suspect thats might be whats going on here.. Previous owner had a problem with stock cluster.. Swapped in a V6 Cluster... Didnt change senders.....

 

highly probable. see if you can get just the idiot light switch and replace whatever that green wire is hooked to and see what it does.

 

At some point in this car's life, a base model gage cluster was installed. The sped goes to 85mph, there are three idiot lights for oil, water temp and battle and a fuel gauge so at this point im definitely inclined to believe that as the water temp increases, the sending unit that is installed is probable for a gauge and not a switch for an idiot light. Thus the varying intensities of the light. Id like to get a real gauge cluster and install th.

 

Just so you know I figured out that its a v6 cluster installed on a v8 vehicle and engine...im assuming at this point a cluster swap is in order.

 

im sure you can pick one up from the classifieds for cheap.