Cooling question

[LunaEros]

I know these Jag v8s in our cars run on the hot side (which I'm not a fan of) but does anyone elses car run cooler in hot weather when the AC is on as opposed to when it's off?

Today it was 85° here and I usually have a somewhat heavy foot. With the AC off it wanted to go north of 212° but with the AC on I could keep it from 200°-210°. And went I went easier on her it dropped into the 190°s.
I know the fan is supposed to switch to high speed when the AC is on but is there another switch or something else that's supposed to also switch it to high speed with the AC off if it starts getting to hot? I'm wondering if that's the case and some switch or something on mine isn't working.

 

[joegr]

Yes, it will overcool with the AC on at low speeds and at idle. It's not that the fan doesn't run fast enough with the AC off, it does. It's that in order to cool the AC evaporator, it ends up over cooling the radiator.
Also, it's not that the AJ8s particularly run hotter. All of the more modern engine designs do. The hotter they run, the less energy they waste as heat and the better mileage they get. There are GM engines the run a good bit hotter at times.
Also, note that the fan does not really have a high or low speed. It is a continuously variable design. (In practice, the way it is controlled, there are really 16 or so speeds.) It is not triggered to a higher speed just by the AC being on. It looks at the high side AC system pressure. Fan speed is increased as needed to keep that pressure down where it works best. The fan doesn't get really serious about cooling the engine till it is around 230 degrees.
Sounds like yours "works as designed."

 

[LunaEros]

Yeah, mine's got up to 228° before. I've heard on here that that's basically boiling over. I hate it getting that hot.

 

[AmsterDutch]

Yeah, mine's got up to 228° before. I've heard on here that that's basically boiling over. I hate it getting that hot.

228 is awful hot ...If I was running that hot I would flush the coolant system a couple times and have it bled with a pressurized bleeder

 

[LunaEros]

It only got that hot one day when I was running errands for 3-4 hours and was very irritated at the traffic so my foot was quite heavy.

 

[LunaEros]

The fan doesn't get really serious about cooling the engine till it is around 230 degrees.
Sounds like yours "works as designed."

So 230° when it's hot outside and the car's being run somewhat hard is normal or is that right about where it's considered to be overheated and "boiling over"?

On average on warmer days it runs anywhere from 200-220

 

[joegr]

Yeah, 230 is where you start to get a little concerned.

 

[LunaEros]

Yeah, 230 is where you start to get a little concerned.

Wow. Ok. That makes me feel a little easier. Because I had read on here some others that said when you start getting to 219 or so it's overheating.
But I think I'll trust your word more since I've seen you have so much knowledge about these cars you're pretty much an LS Guru.

 

[milehighmikey]

That's where having a healthy radiator cap comes into play. If the pressure holds to spec, you have to hit 250 or so to boil, as long as you are well pressurized.

 

[LunaEros]

That's where having a healthy radiator cap comes into play. If the pressure holds to spec, you have to hit 250 or so to boil, as long as you are well pressurized.

Cool. That puts my concern even more at ease since my system holds pressure very well.

 

[smegun]

Yes, it will overcool with the AC on at low speeds and at idle. It's not that the fan doesn't run fast enough with the AC off, it does. It's that in order to cool the AC evaporator, it ends up over cooling the radiator.
Also, it's not that the AJ8s particularly run hotter. All of the more modern engine designs do. The hotter they run, the less energy they waste as heat and the better mileage they get. There are GM engines the run a good bit hotter at times.
Also, note that the fan does not really have a high or low speed. It is a continuously variable design. (In practice, the way it is controlled, there are really 16 or so speeds.) It is not triggered to a higher speed just by the AC being on. It looks at the high side AC system pressure. Fan speed is increased as needed to keep that pressure down where it works best. The fan doesn't get really serious about cooling the engine till it is around 230 degrees.
Sounds like yours "works as designed."

ive been bleeding the coolant system and i dont have a charge on the a/c at all i can get around the block but then my fan starts to rev up and my temps climb i get in the driveway and idle eventually the fan slows down and im back at square 1 should i put some 134 in to equalize to try and get to a point i can drive it ? could that i dont have any charge on ac be reason that im overheating and fan is climbing ?

 

[joegr]

No, no charge in the AC system is not the cause of your problem(s).