I have been working on a 96 LT1 A4 for a guy and after recently replacing the WP, Opti, Plugs, Wires, and T-stat he wanted us to do some light tuning on the car including turning the fans on sooner to keep the car cooler in stop and go traffic. I installed a GM 170 stat, throughly flushed the cooling system and refilled it with GO5, Distilled Water, and one bottle of Water Wetter and in 100 degree weather with the A/C on the car runs 220 to 230 in traffic an 210-215 on the freeway. When I filled the system I used my Snap-On vacuum bleeder which should eliminate any air pockets in the system and I also cracked the bleeder screw open after the car reached operating temp just to be sure there wasn't any air trapped and all I got was a steady stream of water. I have had him keep an eye on the coolant level since I gave him the car back and it has only taken maybe 8-10 oz more which isn't much at all. If I turn the A/C off it only drops about 5-10 degrees. I have the fans coming on at 170 on the primary fan and 175 on the secondary fan. The engine is stock except for a cat back system, and unfortunately the owner can't remember exactly how hot the car ran before we worked on it but he thinks it is about the same. I'm thinking it might be an airflow problem through the radiator at this point and I am familiar with the 84-89 style radiators and how they can collect lots of leaves and debris off the road and plug up really bad but I'm not sure if the 90-96's with the radiator layed back are prone to the same thing? This car has 79k on it and looks to be pretty original, also, the front spoiler is in place too.

 

The latter C-4s are just as prone to collecting debris between the radiator an ac condensor as the early ones are.

 

My 95 LT1 W/128000 miles, radiator was badly obstructed with leaves, grass, ect. The A/C Condensor to my surprise was as equally obstructed, but not with leaves ect, but with small asphalt, and sand granules.

My overheating problem was reaching 160 deg idling, no A/C.
After my "clean-up" Highway temps run at 194-205 deg W/WO A/C, and out-side temperature's exceeding 100 deg.

Bottom line is these cooling systems need to be clean.

 

My opinion is that you have the fans coming on way to early. At those turn-on temps the fans are going to be on all the time and the car will not reach its operating temp therefore always running a bit rich, higher emissions and so on.

I would suggest turn-on for the fans to be 210 primary, 220 secondary. That way they will only come on in traffic.

Just my opinion though....

 

My 92 was running hot - 240 ish in traffic
When I replaced my radiator with a dewitts I found debris in the old fins and a bad fan.
With the dewitts and fixed fan I run 190 (thermostat temp) Even after 30 min on road courses with 95+ ambient air temp. Traffic it can get to just over 200.

 

How about installing two radiators! That's what a double row core will do

 

Your car will never pass smog check in CA at that temp. I had the same issue with my 96, but I replaced the radiator with a new one, had it flushed, replaced hoses, and installed a new 190°F stat. With a temp outside of 100°F+, my car in traffic never goes over 210°F with the AC running. Turning off the AC will make the temp go higher. While moving over 50, the car stays between 195-200°F.
Most of my problem was with the old radiator which was the original. When it was pulled, the mechanic called me over to inspect it. It looked like it had mud at the bottom, and the outside was full of debris.

 

I believe that the reason this is so ... is because turning on the AC will by default turn both fans on to their high speed setting regardless of the water temp with the AC off the factory setting for the fans are in the 220 - 230 area. Check out the FSM and I believe you will find this to be the case.

The best thing that you can do for your customer is to convince him to let you install a new GM radiator. With 80K on his car you simply wouldn't believe the amount of dirt & grit between the fins (that you cannot see) hurting the radiators ability to do it's job.

 

If your customer wants to keep the Vette and forget the overheating problems tell them to invest in a Dewitts radiator.
I had higher temps than that and now I have temps in the 170's to 180's on the highway and I haven't went above 210 in traffic.
Herb

 

and

 

I have to take exception to this. My 1992 A/4 runs 173 degrees, fans come on at 193 and off at 183. In traffic for 45 minutes stop and go temp reaches 200. I have a 160 thermo, Griffen 3 core rad. All new hoses, w/p and opti. I just had it smogged a week ago and it passed with flying colors.

 

Sounds like the first thing I need to do is take a close look at the radiator. If it is plugged I will either get it cleaned out or just replace it. The Dewitt's radiators are nice and I will be doing that to my 85 very soon but for this car I think a stock one will be fine. After I'm done I might bump the fan operating temps up a bit however I don't think smog will be a problem because I have done this same combination on two LT1 F-Bodies and both smogged without issue first time. If I could keep the car at or below 200 with the A/C on in traffic I would be satisfied.

 

In traffic, 90*F ambient temp, A/C and both fans on, stock otherwise you should expect to see about 205*F temp. That would be very normal and nothing to worry about. If you want to go lower put in the DeWitts radiator or one similiar.

 

Great, that's what I'm looking for then, thanks!

 

To the OP: How do you have one fan running before the other? From the factory, the 96 fans run in tandem. Lo and Hi speed. Thats why there are three relays. I agree with the restricted airflow theory. The fins can get clogged with small junk.

My 96 runs at about 205 all the time. a perfect temp.

 

We have one fan running before the other as commanded by the ECU, the tuner has access to start either fan at the temp he commands in the tune.

 

AC head press > 189 Fans Lo
AC head press > 225 Fans Hi

Temp 219 Fans Lo
Temp 228 Fans Hi

Eng Oil Temp >270 Fans Lo
Eng Oil Temp >277 Fans Hi

 

That would require rewiring as well as a reprogram.

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Are you sure you used the correct t-stat (LT1 style)? I have never seen a 170 for a LT1. The factory t-stat is a 180 and some companys make a 160.
BTW due to reverse flow, the factory 180 will run a engine tempature of 195 or so. The water goes from the radiator, through the t-stat and then through the engine.

 

Yes it is an LT-1, it's from GM the part number is 10220957