Dsiclaimer: Don't want to initiatte another thermostat war. I'm here in South Texas and run with the A/C almost year round. Whats a normal expectation for engine cooling performance while parked with A/C on? My car is a 86 with a DeWitts radiator, single fan, Edel high flow water pump. Engine mods include headers, heads, camshaft, and larger TPI. Have set the ECM constants fan on at at 195 and fan off at 185.

My car runs plenty cool easily on the highway - 180F (or whatever thermostat temp is installed) even in middle of summer with A/C on. But, once stopped it begins a slow increase and doens't appear to stop. I tested it last week - in idle, parked with A/C on full and it got to 236F after about 20 minutes. Fan was running with fan duty cycle data logged at 100%. The wide range in cooling between parked and moving, 55F, seems large.

Saw on some other posts where some guys (running mostly stock it appeared) would reach a steady state temp while parked - some reported they could even see the fan run a complete a cyle - kick on and then bring temps down to the fan turn off at 211F. Also, saw various opinions about what a normal upper limit could or should be.

Would like to be able to leave it parked with the AC on without a worry that it would get excessively hot. Request answers to these questions:
1. What is normal cooling expectation for idle/parked/AC/hot day? and how did my engine changes affect this?
2. What mods (that I haven't done) can improve cooling in this situation?
3. The optional L98 second fan - was that fan located in front of the radiator? Anyone do a retrofit?
4. Whats the specific definition of the fan duty cycle in the $6E data log - it appears to have only two values - either 0% or 100%
Thanks!

 

Well, I may not be much help, but in Norhtern Kentucky when it gets to nearly 100 degrees at 90 percent humidity my 94 will get to 230 in a few minutes in traffic and over 240 if I let it sit there a little longer. One time I saw 244 flash for a second while I waited for my wife at the mall. I ran a switch off the relays so I can turn the fans on anytime I want.

First thing I would try is something like Purple Ice then move on to additional or aftermarket cooling fans. I see fans on Ebay all the time. You could add your own fan with its own switch.

 

Thanks for the reply - when you manually turn the fans on with your switch in days like that about how much cooler does it run. Maybe I have something wrong with my fan.

 

Since you have no airflow when parked. Your only real source of cooling is the fan operation. The coolant temp should depend 100% on the fan operation. If the fan is unable to draw the coolant temp down until the fan shut off point, then you have a problem.

If the fan works, the usual culprit is inaccurate ECM (or dash) sending units or debris in the radiator. You might see 236 on the dash, but the ECM is reading off a different sensor.

When the fan is forced on manually, it will pull the coolant temp down until the thermostat starts pinching off coolant flow at whatever temp its rated at. It'll do this in hot weather too (within reason), just takes longer.

 

It would be hard to turn this into a thermostat war, because all your concerns are at temps above the stat temp, where the stat has no effect any more. Once the stat is open it can do mo more. It is out of the picture. Since it cools well on the road, It just about has to be an air flow problem. It could be aggravated by a coolant flow restriction, too. With that radiator it ought to run just about any temp you want. Has the cooling system been flushed, really well, lately? Has the radiator been out recently to clean between the rad and the condenser? In your climate, a reduced concentration of antifreeze could help. Water is a better thermal conductor than antifreeze or a mixture, but you need a certain amount for water pump lubricants and corrosion inhibitors. Personally, I have seen some dramatic temp reductions using Water Wetter, but I didn't pay close attention to what it did at idle.

RACE ON!!!

 

You could try 75% distilled water and 25% coolant. Add a can of water wetter. I think you have the right radiator and your fans are set OK. I don't think that dual fans will help. Check for debri in front of the radiator. Best advice is don't let it idle for 20 min. with the AC on in hot weather.

 

With everything working it can idle all day with the a/c on with the stock radiator. I hate suggesting masking the problem. He already bought an expensive radiator he maybe didn't need.

 

I don't understand why people want to re-engineer things without first making sure everything is working as it's supposed to. My car is completely stock, and it can sit and idle as long as I need it too.
NOTE: It will idle cooler with the A/C on than with it off, since this causes the electric fans to run.

If your car is overheating at idle, then it's because something is not working as it was designed. Service the equipment before trying to be re-invent the wheel.

 

Tried to synthesize all the ideas and recommendations into the following approach.
- Have a data point that a serviced stock system can maintain coolant temp in upper range (say 220F) all day long with fan on.
- Didn't get any specific feedback on parked steady state temps for built up motors. Will assume they can have similar cooling performance (Let me know if that is inaccurate please).
- Will review data logs real time to compare ECM coolant temp and the cockpit gauge for accuracy.
- Will eliminate as a problem the radiator (new), thermostat (working), water pump (new), and clogging debris (clean).
- Will re burp the air out of the cooling system.
- Will focus on the fan/airflow since it cools so well while driving. I see the fan running, starting at the desired set temp. However can't determine if it is making its rated speed and airflow. It is the stock fan that came with the car (I'm the original owner). Doesn't sound particularly loud or fast - will try to compare to someone else's C4. Didn't get any replies on the fan duty cycle question so guess it is not useful in measuring cooling performance.
- Will further investigate the background around the aux fan that came with some of these L98s. Assume the factory added these because there were some cases where they had cooling problems too. Maybe I am in that situation now with the built up motor - perhaps extra heat produced by the engine mods - 10.5 compression with the new aluminum heads and higher idle in particular.
Let me know what else you may recommend please.

 

me to I have to investigate in the duty cycle of the fan(S).
I have a 90 with stock dual fan .
I have also a fan manual switch (a friend wired some wire to a switch). I really understand about electric stuffs...
Even now that I have a Dewitts rad (it made a tremendous difference...) the fans are not able to reach the lower temp to stop the fans. (I used a 160 stat for this summer...I'll switch back to 180 in the winter-).
What I noticed is:
option 1)Car not started but with the key ON.
I turn the manual switch to ON and I can hear the fans starting.
Yes they turns ...but not so fast especially if compared to the option 2.
option 2)Car not started but with the key ON, I gruond A and B terminal on the ALDL. It force the diagnostic.... and the fans starts. The fans in this option 2 are turning at least 2 times faster than option 1
BTW, I can't compare the 2 situation or the situation with the fans started by the reached temp in the chip, because the engine is idleing.
In addition I never tryed to start the car with the ALDL grounded.
-Beppe-

 

Maybe your friend wired the switch to run direct power to fans using small gauge wire.
Best option to control fans, is to wire the switch so it sends ground to cooling fan relays, just like the ECM and pressure/temp switches do.

 

parameters in fan settings include:
fan one duty cycle is if mph is<min. and ac press. (set at 99.6%)
minimum mph for using fan one duty cycle, (set at 35 mph)
minimum mph for fan one if ac on, (set at 11mph)
fan one turn on (ac on) 209f., fan one turn off (ac on) 200f.
fan one turn on (ac off)200f. fan one turn off (ac off) 189f.
*numbers above reflect a stock ARAP bin file I have here but is not a 32, regardless, any or all can be changed in the programming.

 

Yes, it can idle all day and hit 240F.

http://gmtips.com/3rd-degree/dox/tips/cool/cool.htm

 

The early models of dual fan equipped C4's are equipped with more than just 2 fans. My 85 has the factory option and has the fan in front of the radiator, has another cooling addition at the oil filter location, just a mini cooling tank that mounts above the oil filter and can be added to your car. And the radiator is referred to as heavy duty. Going down the highway the electric fans are not used if temp is low enough, just not needed to pull/push air through the radiator. The 85 option V08 was not offered as such in 86, but you could get KC4 Engine Oil Cooler, V01 Heavy Duty Radiator, and B4P Radiator Boost Fan as options which was what was included in the 85's V08 Heavy Duty Cooling option.

 

I wired my fans to switch in the cabin by ground both relays.

How big of a drop in temp do I get? Could not really tell you. If I am in traffic and I see the digital gauge go over 210, I flip them on. This weekend the fans brought temps down under 200 and held them while we were in stop and go traffic for 30 mins. Once under 195 I turned them off or if we were moving over 40mph. I run a 180deg thermostat. I recently replaced my front spoiler & mounting rod and cleaned out leaves from the radiator. My 94 is lowered and the front spoilers need to be replaced annually. When they are bent out of shape or broken I see my temps rise on the highway.

 

My car is stock. WHen my car is idling the fan comes on at 227F and goes off at 217F. It will do that as long as the engine is running no matter how hot it is. This is probably not much help to your problem. I know guys who have used that wetter stuff and it seems to have cooled the engine down a little more.

 

I added an aftermarket fan in front of the radiator on my 87. It will still get hot but it takes longer to get there. THe best part is, my AC blows colder than a welldiggers *** no matter how hot the weather.

 

I really hope your not trusting the accuracy of the factory temp gauge...

 

Maybe your fan isn't running long enough. Try leaving it on while you are in bed at night. I heard. somewhere, that fan motors are cheap.

RACE ON!!!

 

The single fan works fine for this Year.

A/C operation should be cooler as the fan comes on sooner and stays on longer. It has to to reach/maintain the target system pressure of 200 psi which is going to squeeze gas into the Evaporator at 25 to 30 psi. These numbers translate into a condensor temp of about 100 to 120 degrees which a functioning system will reach in about 60 seconds -regardless of coolant temp - if the system is right. Don't keep it there and it can get dangerous. That temp of course is far less than the engine was designed to run at - that's one of the reasons it has a thermostat (and it's one of the reasons a/c operation is emissions exempt).

If it's overheating with the a/c on and the radiator is new, air flow is unrestricted, and the shroud is in good shape, then the a/c system is plugged up or overcharged (real easy with an R134 conversion). You check it out by hooking up a manifold gage set so that you can verify a high side average of 200 psi - and better yet that the fan is coming on within it's parameters for a/c operation (and it may not be if you've installed a manual fan switch - that's one parameter the ECM can actually do quite well - the pressure/temp signal is from the condensor -not the radiator or coolant and so it has nothing to do with what's on your display). The other possibility is that you've overtaxed the electrical system by running both fans and when the alternator can't keep up, the fans slowdown and it overheats. Check voltage.