Allright, here's the summary on my car. I've never, ever had an overheating problem with the car, it CONSTANTLY runs at about 175-180 during normal driving around town and on the highway, and if i'm in traffic or really driving the car hard, then it still never gets above about 210*. The car has a 180* stat in it and the fan turns on at 180* and off at 165* (I think).

Anyways, my registration expired last month, and when I went to renew it I was told I had to go through emissions. I didn't think much of it, so I just looked over the car, backed off the timing a tad, leaned out the idle mixture screws (didn't touch the jetting or metering rods/springs) and turned the idle up a little. I added a bottle of drygas to the tank and went off to the emissions test.

After about 2 minutes on the dyno the guy calls me over and goes, "it's getting a little hot, should I shut it down?" I glanced at the gauge and noticed it was just above the 250* mark. He shut it down, and after helping them with speedy dry on the shop floor, I went home and changed things. I turned the idle back down, and richened up the mixture screws. I re-topped off the coolant and went back to the test.

Once again after about 2 minutes the same thing happened. He called me over, this time again and it was at 250* again. I told him to shut it down and apologized for the problems i've been causing them and making a mess all over their shop floor (again).

At this point I noticed the electric fan wasn't kicking on. I've never had a problem with the fan until now. I replaced the relay, checked all the grounds and checked the fuse and everything checks out. There's one wire going into the radiator to measure coolant temp. It's for the fan, and not the one that goes into the cylinder head to actually send coolant temp to the gauge. Is it possible that sensor got ruined when it got too hot?

Also, i'm planning on flushing out the whole cooling system tomorrow, as well as replacing the thermostat housing (I checked and the thermostat is still good) since it leaks a little bit, and although the air leak might not do much, i'd just like to eliminate any possibiliities.

Obviously other then the fan, does anyone know why it would over heat like this? The first time the fan worked just fine and it still overheated, plus the coolant is only a year old.

-Thanks for your help, Brandon

 

Was a fan placed in front of the car? if not, that could cause some problems. In NJ, if it's above a certain temperature outside/in th shop, it's a law that a fan must be put in front of the car. The radiator may just have needed more air than the fans put trough it, since the engine had the extra load, without outside air coming in.

 

No, there wasn't a fan used in front of the car. It was about 90-95 degrees the day we went with a fair amount of humidity also.

 

I think you hit the nail there when you said "Under Normal Driving Conditions". Not sure if the factory designed the car for an extented stay on the dynamometer. I know the 85 and up cars are great at cooling

How long does the car have to stay on the dyno in CT?

Can you convert over to a pulley driven fan for the test?

I would "think" that the electric fan would kick in so it is good you are checking into that. For the dyno test this is really your only cooling flow (unless you convert to pulley driver fan).

The factory designed the electric fan "to assist" cooling the car in special situations (idling in traffic), not while the wheels are in motion because the air dam is directing the air into the radiator. In the case of the illustrious state inspection center, your vehicle is not actually in motion therefore not pulling in the outside air to cool the radiator.

You also want to make sure everything is working properly and you have enough coolant, etc.

 

and how many of you guys have had the car idling warm when not under load much less putting a load on the engine without the extra air getting through the radiator?

 

The car isn't stock, the engine is an iron headed 355 SBC, i'm running an aluminum radiator right now, I checked the coolant level and that was fine, plus I tested in with a hydrometer and it passed too. I still think i'll flush it anyways though, just too elminate any variables.

I believe at the longest the test takes 3 minutes, but usually a car passes by the 2 minute or so mark.


What? I'm not sure what your saying here.

 

They are ment to put a fan infront of it, over here they have a big box like thing it is like a high flow aircon system. It keeps the car ICE cold when on the DYNO.

 

Well, the first time when the car overheated I think I musta done something to the fan somehow. It won't turn on at all now no matter how hot the car gets.

I pulled the radiator today and flushed it, everything seemed fine, pulled off the water pump and everything was good there too.

When I went to take off the electric fan I accidentally pull out the wire going to what i'm assuming is the coolant temp sensor for the fan. It goes into the radiator and through the other side, and the wire went to the fan motor.

Does anyone know where I could get one of these sensors or how to replace it?

 

???

 

Real easy fix, just ground that wire that went to the probe then the fan/fans will come on with ignition.

 

Yeah, that whole fan in front of the car while on the dyno is of key importance too. I bought my car to get tested last year to some bullshit garage, and not only did they not put a fan in front of my car on an 80 degree day but they almost let it over heat and didnt say a damn thing to me, and this was right after i rebuilt the motor, it was right at the red mark on the temp gauge, little to say i was pissed and i had to sit in the parking lot and let it cool down before i could leave.

 

Okay, but say I don't want the fans to come on all the time, in the summer it'll be fine, but what about winter or something?


I hear ya dude, that's EXACTLY what happened to me, I was in the parking lot for 15 minutes before I could start it up and leave again. Oh well, at least they didn't charge me and didn't really mind that my car pissed a few quearts of coolant all over their garage.

 

Allright, well I think the motor is gone in the electric fan, does that happen often? There's 2 wires coming out of the motor, one that went to a relay, and one that went to a ground. When I ground out the one wire and put the other to the battery, nothing happens, the motor doesn't engage or anything.

Is the motor gone or what?

 

yep, your fan motor died, its not unusual.

after you know your fan is working right, when you go back, ask them to put their fan in front of the car too.
i don't know what the law is up there, but here its required.

 

I just ran into the same problem. I have an 88. I went in this morning to get it emission tested, and after running it for a few minutes I was informed that it was overheating. After I got home, I opened the hood and the fan wasn't running. Glad to know I am not the only one with this problem!