[Vroom_vroom]

need some help problem solving my new found over heating issue.

so i finally got around to putting my vintage air in my firebird (77) its a non ac car that now has ice cold ac but overheats and by a lot.

i am running a cold case radiator with fans from a 2001 camaro, and a 180 super stant.

even with the ac off its will creep up to 200 and with it on it will keep going as high as you will let it. 235 and i pulled the plug. car has always ran dead on 180 before the ac install. the car overheats at idle and going 55 down the road you can still see the temps keep climbing.

where do i start from here? ordered a cast iron flow kooler as its the only thing i can think of at this point.

[Redpiston]

I would replace the thermostat first. Maybe you got a faulty one. Also confirm you actually have flow through the system

[Vroom_vroom]

Thermostat has been verified, water pump is my last suspect. It’s a cheap o gmb so summit will have a flowkooler here tomorrow. It has flow but I’m wondering if it’s not enough and the bigger radiator has been covering for it?

[bhill86]

I would wonder, if you always ran at 180° with the same setup minus having AC physically installed, is the addition of the condenser creating enough of an airflow restriction to cause this? Possible that combined with those particular fans isn’t allowing enough airflow at speed nor at idle with the fan(s) pulling.

Other considerations include the proper pully combination since your car was a non-AC car. I’m sure someone can chime in with the specs but AC cars had different pullys that would overdrive the water pump.

[HWYSTR455]

Well, those fans only have like 2500cfm, so suspect they were borderline to begin with.

That said, you still have to look at all the common causes, idle speed, idle timing, pump, stat, air flow and blockage, etc etc.

Once you put a condenser in front of a rad, it is going to block some air flow. So your stuff needs to be in order before you start an AC install.

Do you have a PWM fan controller? If so, setup the AC-on feature and have the fans run at any temp at 35-40%, and ramp on temp above that. I don't think it's going to help, because pretty sure the fans don't flow enough, but it's worth a try.



.

[Vroom_vroom]

The fans don’t do anything going down the highway is my thing.

Even with the ac off it still happens but on a much slower pace. In that situation the only things that have changed is the condenser is now blocking some air flow and the heater core now has a shut off valve.

[HWYSTR455]

Originally Posted by Vroom_vroom

The fans don’t do anything going down the highway is my thing.

Even with the ac off it still happens but on a much slower pace. In that situation the only things that have changed is the condenser is now blocking some air flow and the heater core now has a shut off valve.

Fans can block flow going down the road, especially if the fans are spinning slower than the air flowing in from the grill. Many aftermarket fan have relief ports with some type of flap that is held closed when the fans are creating a 'vacuum' when running.

In some cases, the fans/shroud are not enough of a restriction to cause lack of cooling when the fans are not running. But in those cases the shroud/fans were designed larger or with a known amount of restriction in mind.

A 455ci engine produces more heat than a 350ci, so thinking a fan that cools a 350 will cool a 455 is flawed. That's why I was saying that it was probably borderline to begin with. You add a 'load' like AC and cooling demand goes up.

Not sure of your setup, but just to say, when going to a different fan setup, many times some of the original baffles are omitted (or overlooked), and less air is forced thru the core. This can also cause hot air to be drawn from the engine compartment around to the core. Or forced air from the grill to go around the core.

Maybe post pics so all have a better idea of the whole situation. That way less 'generic' responses will be posted.


.

[rohrt]

Are you overheating while at idle or driving or both?

[Vroom_vroom]

Originally Posted by rohrt

Are you overheating while at idle or driving or both?

Both.

Will have to get some better pictures of my shroud and fan set up but this is what I have at the moment. Fans a centered so it has the same spacing on the bottom and the shroud is sealed to the radiator. They pull a massive amount of air fwiw, they are lt1 fans not ls.

[HWYSTR455]

I see one issue in the pic. The shroud is too close to the core. Might just be the pic tho.

Those fans don't cover much of the core.

Is the radiator sealed to the core well or is there a gap? How about along the top of rad to top plate, is there a gap there?


.

[Vroom_vroom]

Fans sit 3/4 of an inch above the core of I remember right. I’ll have so stick a tape on it, there is some air gap on the sides of the radiator to the core support but nothing on the top or bottom.

[HWYSTR455]

Yeah that's too close. And those are 12" fans? If so, you're only getting 'pull' thru the core the circumference of the fans. The rest of the core isn't being used.



.

[HWYSTR455]

You need at minimum 2-3" away from the core, the shroud isn't doing anything when they are too close.

.

[b-man]

Might be worth considering running an air conditioning water pump pulley if you aren’t already and switching out those electric fans for a factory 19-1/2” clutch fan and shroud using a severe duty clutch.

Those 2001 F-body fans and shroud are likely better suited for keeping up with the cooling needs of the all aluminum 346 cubic inch V8 they were originally designed for.

[dataway]

The factories made the shrouds a large "funnel" shape for a reason, and they kept the fan a considerable distance from the radiator for a reason. Air does not like to turn sharp corners.
And at highway speeds the incoming air basically only has two 12" circles to go through.
Two 12" circles offer a total of 226 square inches of air flow space. A single 19.5" opening provides 298 square inches.
That shallow, flat shroud is killing you, tons of dead air all around those fans.

[b-man]

Definitely that shroud is blocking half the airflow, a factory setup would allow plenty of flow at highway speeds.

The 19-1/2”’ clutch fans move a lot of air, especially with the severe duty clutch which made a big difference on my Le Mans.

[lust4speed]

I'll disagree with fans not being needed at highway speed. On my '67 GTO and many other cars there is a high pressure area that forms under the car that basically kills much of the airflow through the radiator. If it were not for the fan there wouldn't be much more flow than when sitting still. Now a good air dam can work wonders and actually create a low pressure area under the car and then the statement that fan(s) were not needed would be true. Did your car come with an air dam and is there one in place now?

Then we get to the two problems discussed above. Those fans are too wimpy to pull enough air and the shroud blocks what little air can get through the radiator - and I would bet that a temp gun might show that there are two cooler circular areas in the radiator in front of the fans with the remaining core area showing much higher temps.

[Vroom_vroom]

Car has the air dam In place, we tested the cfm on the fans and it was just over 3200 cfm so not sure where everyone is getting there numbers from. The shroud being too close sounds like the most probable answer. Gotta get back on it but can’t till Monday.

[JLMounce]

Did the 2nd gen birds with AC come with an upper close-out like the first gen cars? I notice that from the bumper to the core, there is no upper closeouts. Now that you have two radiators to flow air through, you may be pushing cool outside air above the core instead of through the radiator.

On the first gen cars, if it was AC equipped from the factory, the car would have the upper and lower closeouts with the lower having an air damn. There would also be a rubber seal across the top of the core support to seal it to the hood.

It would additionally have the 6" water pump pulley and there would also be an AC fast idle solenoid. Your vintage air already blocks off the heater core, a the factory would have also done.

I also agree that your shroud is problematic. It's too close to the radiator, is flat, 90* to the airflow path and doesn't have any reliefs for airflow at highway speeds. I would want to see the shroud set further back with a cone shape towards the fans.

[Vroom_vroom]

Reworked my fan shroud, could only get it 2 inches from the core before I ran into interference from the steering box. Also got some air slots cut into it with flaps . Hopefully that will at least solve the overheating at speed. Got my area for flow up to 313. If this turns into a bust I suppose it’s time for a new fan/shroud combo.

Ordered the wrong water pump so I’m on pause until Tuesday. The pump I pulled out had a cast impeller and decent clearance.