LS-coupe cooling saga continues :(

[dville_gt]

Is the heater hooked up in this car? If so when she starts running warm, turn the heater on full blast, if the temperature goes down the slightest, than you don't have enough radiator or the radiator effiency is poor. If it a new radiator, I have had poor effiency radiators new out of the box only to replace them with another. I use this test alot to solve some heating problems with customers cars.

DON

a/c seems to run pretty good, car has no tint and it's hot outside so it's not frosty cold, but does pretty good. car has a heater core but i am not running any lines to it right now, i could go get the hose and run it, but i didn't want to introduce another possible place for air bubbles until i figured this issue out (and obviously my need for a heater right now is null)

Is the AC system overcharged? Too much head pressure? Hard on the engine and will make it run hotter. Was it weighed in, or just added can by can?

we charged it can by can with a manifold gauge setup, if anything i think it is a little undercharged, in 100* temp the low side read 40psi earlier today (don't have a highside gauge here to check it)

Since the problem seems to center around the use of the AC system, could there be a problem with the charge(over or undercharged) that would be causing the excessive heat? Could there be a problem with the sizing of the AC condenser or some blockage in that system?

Dville, Does the A/C system seem to be working correctly?


I'm far from an expert regarding A/C systems, so I'm just looking for some type of cause/effect.

could be, i can pretty easily turn the compressor by hand, feels normal, no unusual drag or anything can be felt when manually twisting the clutched side of the compressor. the sizing of the condenser could be a problem since it is an f-body condenser and an escalade compressor, but i dont know for sure.

the escalde condenser is 34"x18"x.6" =367 square inches, the f-body is 27"x16"x.7" = 302 square inches, so it is a smaller condenser then what the factory used with that compressor. not sure how much effect this would have on temperature though.

[71chevellejohn]

Did you pull a vacuum on the A/C system before adding the cans?

[greenbullitt]

Well shit. Last time I had an issue like this that I couldnt trace down, it ended up being a blown head gasket. water out the exhaust. Im interested to see what it ends up being.

Hell it passed a block test before we started trying any of this

[DC COBRA]

I would not be worried about adding any air bubbles to the system by hooking up a heater core, once the thermostat opens air bubbles will be gone. Although if you do this and the temp does happen to come down the slightest you just found your problem, radiator not big enough or it is just not efficient.

DON

[71chevellejohn]

I would not be worried about adding any air bubbles to the system by hooking up a heater core, once the thermostat opens air bubbles will be gone. Although if you do this and the temp does happen to come down the slightest you just found your problem, radiator not big enough or it is just not efficient.

DON

He already went up to a larger radiator - the same one that "2165 turbo rail" is using on his Turbo LS Engine. I don't think he had any significant drop in temp installing this upgraded radiator.

[dville_gt]

just took it out for a cruise, 41 minutes long, ac blasting nice and cold the whole way, highest temp i saw was 219, mostly it ran 212-214 on the highway, 208-210 in the city. not bad temps. ambient was about 95 degrees, maybe slightly warmer at the beginning of the cruise and slightly lower at the end. was reading 208 when i pulled into the garage.

so the car can do okay in 95* weather, over 100 seems to present the problem.

part of me wants to just deal with it, keeping an eye on it during these last few "real hot" weeks of summer then come back next summer with a plan. the other part of me wants to figure this out, i didn't dump all this money into this car just to not be able to drive it w/ac during the hottest part of the year!

how much is 100% water (plus an additive like water wetter) worth in terms of degrees? how bad is that on the rest of the system?

anything else anyone can think of to buy me say 10* degrees of cooling capacity?

on a side note, has anyone else ever had a fairly large discrepancy between the factory ect gauge read through the pcm and an electric autometer gauge? per the autometer my temps never got over 210, per the ect they got to 219. not sure which to trust, they are mounted in the same location (just in opposite cylinder heads, same spot on each head). the factory ect sensor has about 70k miles on it, the autometer has about 800. the advantage to the factory is that it reads on the laptop in 1* increments versus just looking at an autometer gauge and guesstimating what it is reading.

[Txstang1]

Hell it passed a block test before we started trying any of this

Right on, I thought I had read that.

[slownbmta]

just took it out for a cruise, 41 minutes long, ac blasting nice and cold the whole way, highest temp i saw was 219, mostly it ran 212-214 on the highway, 208-210 in the city. not bad temps. ambient was about 95 degrees, maybe slightly warmer at the beginning of the cruise and slightly lower at the end. was reading 208 when i pulled into the garage.

so the car can do okay in 95* weather, over 100 seems to present the problem.

part of me wants to just deal with it, keeping an eye on it during these last few "real hot" weeks of summer then come back next summer with a plan. the other part of me wants to figure this out, i didn't dump all this money into this car just to not be able to drive it w/ac during the hottest part of the year!

how much is 100% water (plus an additive like water wetter) worth in terms of degrees? how bad is that on the rest of the system?

anything else anyone can think of to buy me say 10* degrees of cooling capacity?

on a side note, has anyone else ever had a fairly large discrepancy between the factory ect gauge read through the pcm and an electric autometer gauge? per the autometer my temps never got over 210, per the ect they got to 219. not sure which to trust, they are mounted in the same location (just in opposite cylinder heads, same spot on each head). the factory ect sensor has about 70k miles on it, the autometer has about 800. the advantage to the factory is that it reads on the laptop in 1* increments versus just looking at an autometer gauge and guesstimating what it is reading.

Out there i'm sure but I wonder if they are both right, and one side of the motor is stopped up or not flowing as good (water).

[Magnimike1]

Out there i'm sure but I wonder if they are both right, and one side of the motor is stopped up or not flowing as good.

You don't think the headers are affecting the temp sensors in the heads? False readings? It did it on my truck until I moved the sensor to the intake.

[bonnie&clyde]

it may have already been covered but why dont u go dual fan? on my 93 i never see it go above 200 and thats on the hottest days

[dville_gt]

Out there i'm sure but I wonder if they are both right, and one side of the motor is stopped up or not flowing as good (water).

Could be, I am going to pick up a new ECT sensor ($10) just to eliminate that possibility. I know the autometer sender uses an ohm rating like this
1123 ohms = 100 degrees F
65 ohms = 250 degrees F

aka -7ohms per additional degree above 100

From what I can find the factory ECT sensor should read as follows:
0v = -38*
5v = 284*

64.4* per volt starting at -38*

So the only way I can think to test them is let the car completely cool, then check the resistance on the autometer compared to the voltage seen on the ect wire. Then calculate (assuming these both follow a straight line curve) and see how close they are to each other. At 100* the autometer should have 1123ohms of resistance and the ect should have 2.15v on the sensor wire.

Any input on my testing logic would be great.

You don't think the headers are affecting the temp sensors in the heads? False readings? It did it on my truck until I moved the sensor to the intake.

Seemed likely to me (there is a picture a page or two back) since both sensors are literally a few mm away from the header flange (that is over 500*), but this idea was axed since the sensors should only be reading the coolant and should be unaffected by the massive heat monster that is so close to them.

it may have already been covered but why dont u go dual fan? on my 93 i never see it go above 200 and thats on the hottest days

I was running dual fans off of a LT1 but they were not as powerful even both running full tilt as this Tarus fans is on highspeed.

[Strychnine]

how much is 100% water (plus an additive like water wetter) worth in terms of degrees? how bad is that on the rest of the system?

When it comes to plain ol' heat rejection (excluding any sort of 'water wetter') 100% H20 is ideal for heat transfer. Heat rejection from engine components to coolant increases ~5% when going from 50/50 to straight water.


"top tank temp" = engine out temp / radiator inlet temp

test data and radiator supplier “Rules of Thumb” indicate that the differential in Top Tank Temperature between 100% Water Vs 50/50 Ethylene Glycol/Water will increase the by 5 deg F when 50/50 E.G./Water is utilized.
This 5 deg. is an “average” for systems that are either coolant or airside limited. The primary reason for a higher Top Tank Temperature with 50/50 coolant is due to a lower effectiveness in rejecting heat vs 100% water.

But if you're actually 'boiling over' then the glycol will increase the boiling temp of the mix.

[dville_gt]

When it comes to plain ol' heat rejection (excluding any sort of 'water wetter') 100% H20 is ideal for heat transfer. Heat rejection from engine components to coolant increases ~5% when going from 50/50 to straight water.


"top tank temp" = engine out temp / radiator inlet temp




But if you're actually 'boiling over' then the glycol will increase the boiling temp of the mix.

I've never boiled over, the highest temp I've shown via my ECT sensor is just north of 230*. Obviously the straight distilled water (plus additive) would need to be drained before the first freeze, but if it'd buy me 5% @ 230* that'd be 12* which would put me sub 220 which is acceptable. Might be the only option sans a high output water pump (which cost north of $400) and even that might not work.

I am running a 17psi cap right now so it seems like straight water might not have a good chance of never boiling over since it'd have to get over 250*

[forbes]

i don't know your whole setup, but just throwing this out. i know your an automatic with a pretty high stall. are you running a trans cooler or only into the tank on the radiator? maybe your trans fluid is contributing to the heat build up?

[Strychnine]

Seemed likely to me (there is a picture a page or two back) since both sensors are literally a few mm away from the header flange (that is over 500*), but this idea was axed since the sensors should only be reading the coolant and should be unaffected by the massive heat monster that is so close to them.

My opinion...
I would run the sensor in the manifold near the t-stat housing where the coolant from all passages is mixing again.

The engine is always going to have localized hot spots. What you're looking for is the average temp, or what the radiator is going to be seeing. That's what the complete system is designed for.

Your overall cooling system health is gauged by heat rejeciton capability of your radiator... or the differential between radiator inlet and outlet (or radiator inlet to ambient), not the differential between one single point and ambient.


I know some guys will say this is "cheating the system" because you're just changing your measurement, but you have to think about what the system was designed for. Overall (average) engine heat rejection.




FWIW, our coolant temp sensors (that feed the ECM) are very close to the thermostat housing and when I do full load cooling tests my jacket water thermocouples are always in the radiator inlet tube.