Temp Increase with AC on
 

I replaced my 305 motor with a 330 HP crate 350. I didn't change the radiator as they are the same stock parts.
When I turn on the AC the temperture creaps up generally gets to about 240 degrees before I decide thats high enough and turn the air off. Once the air is turned off the temperture returns to the Normal Modified 180 degrees. The temperture being this high is OK as it is something that doesn't hurt the motor, but the big problem is the higher the operation temperture the worse my AC works, and therefore the more the compressor is on, and the higher the temperture gets.

I added a 3000 CFM second pusher fan to the front of the radiator that only comes on with the AC, but that didn't solve the problem. The timing is correct, and the coolant is new and full. The radiator is fully functional, and the pump is new.

I'm considering buying a $500 radiator so I can run my AC all the time in the summer heat, but something tells me even that will cause another problem... if you have ever heard of this before or have some suggestions to help remove the excess heat, let me know.

I have preformed a Heat Transfer Analysis on my Radiator and it is running fine for the operation of the engine, but I'm not really sure how much heat the AC is adding as it is obvious that the AC is taking the Radiator beyond its threshold point.

PLEASE HELP

Re: Temp Increase with AC on
 

Doesn't seem like you have any other choice but to buy a new radiator, the 3000 cfm fan was a good idea, but i suppose it's still not enough.

You need a quality 3-core radiator, like griffin or be cool.

Re: Temp Increase with AC on
 

Make sure you get the right size radiator (height-wise especially). I'd recommend becool also. The Summit brand "direct fit" I purchased a few years ago is slightly taller than stock and has a larger outlet, making it interfere with the TPI airlid and it was a PITA to find the right hose.

Re: Temp Increase with AC on
 

Your stock radiator should be fine. I'm running near the same motor for three years and no problems cooling with AC even using the stock single fan. Assuming everything cools properly with A/C off I'd look at airflow. Verify that you've got proper air flow THROUGH the condenser and radiator coils. With your auxilary AC fan on can you feel the air pushing through from the opposite side? Are you running both fans with A/C on?

Re: Temp Increase with AC on
 

the pusher fan that is in front of the radiatior is pushing the heat from the condensor in to the radiator and adding extra heat to the cooling system. placement is key to fans. duel fan set up like most irocs had. both on the same side. that should fix the problem.

Re: Temp Increase with AC on
 

I tried to put both on the same side but it wouldn't fit. Both fans are too large, this is why i put one as a pusher and the other a puller. The regular fan is on all the time as my fan switch has malfunctioned on. Since it is stuck on and I live in Orlando Florida I can't see a reason to have it actually turn off, its almost always hot outside.

As for the Radiator, What should I buy that isn't $500 or more.
Thanks,

Re: Temp Increase with AC on
 

Just for fun, how are the temps with the auxiliary fan not running?

Pusher or puller it doesn't matter whether you are pulling or pushing the air through the coils. Heat exchange is going to be unaffected. The air is still passing through both sets of coils.

Re: Temp Increase with AC on
 

Actually the tempertures run the same, they just get there faster. An example is traffic driving, gets to 240 degrees in about 20 minutes with AC and Fan one, without fan gets to 240 with AC on in about 13 minutes.

It helped, just not enough... its just too hot in the summer time.

Re: Temp Increase with AC on
 

BeCool sells a direct fit radiator for 82-92 TransAm and Firebirds. It does cost right around 450-500 though however...it's very nearly a direct fit. The mods needed are detailed in the instructions and if you have a dremmel and a ratchet you've got all the tools you need. With my stock single electric fan It dropped the operating temp of my car which has a new 350 in it down to the 160 of the thermo stat but it will still creep up with the AC on to around 180-195. ON the highway it sticks right at about 180 with the AC on. I'm thinking of getting one of those radiator cap thermostats to see if my stock thermostat is at all accurate. As I did the engine swap in the winter, I haven't seen how the system will react to 90+ degree days yet but I'm hoping that it'll be enough.

Re: Temp Increase with AC on
 

You didn't mention if you have a Firebird of Camaro. If it's a firebird, make sure your air damn is in good shape. That actually helps alot.

Re: Temp Increase with AC on
 

The air dam is there, its just half the size. I don't have cooling problems when i'm on the Highway, only when at idle or stuck in traffic and the air dam doesn't do anything at these speeds.

Re: Temp Increase with AC on
 

That's when mine starts to heat up as well though it is yet to be hot enough outside to be a problem. I'll have to see how I answer this issue in July and August.

Re: Temp Increase with AC on
 

I started another thread about replacing the stock radiator, as i'm not sure which one to get or if there is a difference / Fit / etc.
https://www.thirdgen.org/forums/cool...-both-fit.html

Re: Temp Increase with AC on
 

i am having the same problem with the karr overheating with the a/c on and running fine with a/c off. the karr does not overheat with the a/c on at 50 mph or higher. but while drving in the city, when idling at a light and at low speeds around 30mph it does. this happeds when 85 + degrees outside


new acdelco water pump replaced feb 2010 due to leaking and original
i have a stock replacement radiator from spectra CU750 ( replaced since june 2010)

i have a 180 thermostat from napa and its working.

i have a direct drive mechanical fan installed by the previuos owner.


my air dam is in great shape

Re: Temp Increase with AC on
 

What kind of shape is your A/C condenser in? Lots of bent/broken fins? Dirty? Is there anything (plastic bag) stuck between the condenser and the radiator? Even 1 single plastic bag stuck in there will make a big difference.

I run a Champion 3 core in Houston and it never gets even close to 240° and that's with the stock dual fan setup (with 200° fan switch)

Re: Temp Increase with AC on
 

You did not mention the age (how old) is the current radiator you chose not to replace.

Anytime I have ever replaced an engine I always have replaced the radiator along with other components as typically I did not know their age and therefore possible condition. New engine New radiator or a radiator that has been to the radiator shop and cleaned/repaired at a minimium A good clean radiator is definitly something to consider.

New technology replacement radiators have become very cheap. I certainly replace the radiator if you have not done so.

Re: Temp Increase with AC on
 

Your car is carb or tpi? what kind of fan controller are you using? Does it have a low speed and a high speed?

Re: Temp Increase with AC on
 

the a/c condenser is original to the car and it is clean and clear of all debris. that was the first thing i checked

do you run with a/c ?




it is crossfire injection 305 and the fan runs all the time

Re: Temp Increase with AC on
 

If the car overheats less than 50 mph, its probably the air dam. In my case only a new radiator fixed the problem. As for bent fins on the radiator that was a great thing to look for.. make the condenser more efficient should make the air flow better. Before changing things though, remember 240 degrees really isn't that hot for a cast iron motor, but if you start putting on aluminum heads and all that jazz, please upgrade the radiator. Changing the engine to 5.7L instead of 5.0 and increasing the compression by planning the heads to 60's increased the compression which made the radiator run to close to maximum power.

Thanks everyone for the help on this!;)

Re: Temp Increase with AC on
 

it looks like i need a 3 core radiator

Re: Temp Increase with AC on
 

I wouldn't think you would need that on a stock engine. Are you running one of those flex fans? If so, I would remove it and replace with an original clutch/fan set up or a good electric fan. Those flex fans don't work that well.

Re: Temp Increase with AC on
 

there is no clutch with my fan. it is a direct drive fan (replaced by previous owner). the fan runs all the time.

and the aftermarket spectra stock replacement radiator, is not as good as the original gm radiator was. its time to upgrade

Re: Temp Increase with AC on
 

I reread your post - and changed mine. Is it a flex fan?

Re: Temp Increase with AC on
 

One of these things?
http://www.jegs.com/images/photos/4001017.jpg

They don't work as well as a good OEM fan and heavy duty clutch.

Re: Temp Increase with AC on
 

that does not look like mine at all. my unit does have 6 blades though


similar to this http://www.jegs.com/i/Flex-a-lite/400/5717/10002/-1


http://www.jegs.com/images/photos/400/400/400-5717.jpg


with no a/c on the radiator cools fine in all temperatures and speeds

Re: Temp Increase with AC on
 

Is it designed to flatten at high rpms?

Re: Temp Increase with AC on
 

Yes it is a flex fan my parts guy confirmed it he thinks it may be a old flex ilite fan

Re: Temp Increase with AC on
 

Just saw the pic you added. It looks heavy duty. Definitely not the problem.

Re: Temp Increase with AC on
 

Yeah it is

Re: Temp Increase with AC on
 

Ive got a stock replacement (But 3-row) Modine unit in my car with the factory single fan, it runs 160 all day with a 300hp vortec-heads 350 in it and a 195 thermostat. I imagine the sensor in the cylinder head doesnt get as hot as the coolant at the t-stat, but I do see it rise to 190 when it's cold before it drops to 160, on cooler days it will even get the t-stat to close for a minute and I watch the temps rise...

Anyway, point is the stock setups on these cars is pretty good. Stock single electric fan is plenty. The only real upgrade I have is the radiator, but it's still just a parts store 3-row model.

It's a Modine 438918 if anyone is curious. Modine doesnt make them anymore but I remember that part number cross referencing with a few other manufacturers, likely hte exact same part since I dont think Modine is around anymore.

http://www.discountautoparts.com/ite...-RAD&weight=30

http://www.amazon.com/Proliance-0433.../dp/B000C8ES80

Like I said, I've got a nearly 10:1 compression, relatively small cammed Vortec 355 that makes around 300-330hp depending on which calculator you go by.... and it runs at 160 all day long.

Re: Temp Increase with AC on
 

Today was a good test of my setup. I got off work a bit earlier than usual. This put me right in rush hour traffic instead of after rush hour. To complicate things, there was a semi truck carrying fuel that overturned and completely shut down the highway I normally take home. The alternate highway (which is usually slower on a good day) was a parking lot......I chose to go through residential areas with 8,000 stop lights as well as increased traffic, due to the city trying to avoid the highways.

So my hour long drive home consisted of 25 mph or slower the entire way home. Air conditioning was on the whole way.

I have a 180° thermostat, stock dual fans. The fans were both on the whole way home (since the A/C was on, never mind the coolant temps)

My temp gauges settled on 190-195° for 3/4th of the way home. Hovered on 200° for the last 1/4 of the way. Weather in case you were wondering was 90°/55% humidity (about normal for Houston at this time of year)

I equate the good performance of this from having the 3 core Champion radiator (all aluminum). You can't put a bigger radiator in there without some serious cutting going on. There just isn't room from both a depth perspective (A/C compressor just "barely" touches the air intake hose on the Firebirds). The radiator is taller than stock, but will clear the stock upper radiator support after trimming the rubber tabs.

Now if you're wondering about air conditioning and how much it increases the temperatures. An R-134a setup under the above conditions would run about 300-320 psi. The temp/pressure of this would be 160-165°F......This is a lot of heat for a radiator to have to deal with. The stock radiator in my car with the same weather and grueling traffic conditions used to run about 225-235°.

Re: Temp Increase with AC on
 

Do you have a link to this radiator? What car did you use and what motor does it have?

Re: Temp Increase with AC on
 

It's the one in the sticky thread at the top of the Cooling section.

https://www.thirdgen.org/forums/cool...guys-want.html

My comments and pictures for it are on page 8 of the thread. I'm running it on my 89 GTA. L98 with mild mods.