Running a little hot, but only when a/c is on

[mike100]

Facts:
-------------------------
-Ambient temp 90-100F
-Gets hot when stuck in traffic- (0-20 mph).
-Coolant runs at 232 deg F with a/c on which is a couple of needle widths from the red zone on analog gauge.
-cools down when going 50 mph with a/c on
-cools down even faster at any speed when a/c off
-Will heat up parked in the shade with a/c on (car already hot from driving in traffic).
-chip programmed to run both fans over 205 degrees.
-orig water pump
-coolant full

It reached 232F (peak of 234) with the a/c on and would not get hotter. The car will also cool itself down to 205 degrees (a/c off) parked with the fans running until they turn off. Both fans spin, but I have not checked the bearing on the r/h one yet, but the left fan spins full speed.

theories-
Needs a new radiator? it was out 18 months ago and was totally cleaned at that time.

Garbage blocking a portion of the rad air flow? the condenser is totally clear though.

Even though it does not overheat per se, 230 is a touch warm and it pings a lot running like that. I did not notice any thing like this last summer.

[VetteMed]

I'd definitely check to be sure the fans are running at full speed, I'd also suggest seeing how much current the motors are drawing.

If it's been a few years since you've disassembled and cleaned the cooling stack, you're probably due for it.

[mike100]

You want to have some fun (I think this is what you were doing since you apparently have digital feed back on coolant temperatures).....Use the HVAC system to see a digital readout of coolant temperature. Press and hold both [fan up] and [fan down] buttons simultaneously for 5 seconds. Then press [fan up] untill you get to 16. Then press center fan auto button.

...

Now having said that...I am running around 200 deg F but does get up to 220 deg F once in a while if I sit idling with AC on a hot day (100 deg F). I have a Ron Davis Radiator and I have eliminated TB coolant.

I shall wait to see what others have to say on this subject especially here in CA where we have 106 deg F tomorrow and above 100 deg F all next week. It will be interesting to hear some real life HOT WEATHER ZR1 Coolant test results here in CA this next week.

...

Maybe keep AC off when stuck in traffic :D

Yeah, I was actually looking for the hvac readout trick, but then I remembered the tech-1 rides in the storage bin, so I plugged it in and purposely drove out again into rush hour traffic to see if the temps stabilized.

[mike100]

I'd definitely check to be sure the fans are running at full speed, I'd also suggest seeing how much current the motors are drawing.

If it's been a few years since you've disassembled and cleaned the cooling stack, you're probably due for it.

I had the radiator and oil cooler out in Feb 2011. The radiator was power flushed, but I suspect that the total capacity has diminished. I think it is still on the original unit. I will probably look at the fans when the car cools off.

Last year I drove the Phoenix to get Bill B to rebuild my ZF and it was maybe about 90 degrees or so in April and I had no issues then. Maybe there is a layer of dirt I can't see behind the condenser, but if I take the radiator out, maybe I'll just get a new one this time.

[VetteMed]

Stock replacement radiators are cheap enough -- probably makes sense to just replace if there's any doubts.

[scottfab]

You haven't said what other mods you have besides the chip (running both fans full on after 205deg).
And when you run at 10-20mph and it heats up what gear are you're in?
It maybe time to upgrade to a Ron Davis unit.

From what I've read it seems about normal for a stock system running in hot ambient temps.
These cooling systems were not the best. Known issue for quite a while.
I run stock and religiously clean the front of the stack (I use a screen in front) and I see high temps like yours in the same situations. However because I have an almost stock chip I keep the AC on to keep the fans on. When I see 230deg I back way off normal diving and pamper it.

[sammy]

mike really take a look at the condenser. its very easy for these thing to get a film of dirt in them and it really plays havoc with the air flow as i found out . also if you have a radiator comb run it though the condenser. mine was really beat up on the bottom .

[lakemeadzmonster]

I drove thru areas that hit 116 degree's this week. Living in Las Vegas it happens. With A/C on and going at least 45mph needle stays close to middle with a 180 degree thermostat. But no problems driving for hours on end if ( continually staying moving through that temperature ).

If you slow way down or get into stop and go it heats up pretty fast. The asphalt temperature is we'll over 140 degrees, look the car is inches from it, the air is super heated as it is drawn in as we'll.

I try to turn the A/C off in stop and go and at stops and it helps keep it reasonable. I will check it using the radio for a gauge for tempature accuracy and see what it is in the upper range.

[mike100]

You haven't said what other mods you have besides the chip (running both fans full on after 205deg).
....

stock manifolds and oem thermostat (1 year old). a couple of extra degrees of ign timing in the chip, but it is actually close to stock in the mid range load cells to run 91 octane. A little manifold porting, but BLM's are pretty close to 128 at cruise rpms so I would say the car is effectively stock.

I drove it (hard) down to the cars and coffee meet up spot this morning and the gauge would not exceed 50% so obviously the water flow is functional. I think either I found the limit of the cooling system and all the cars may run hot in this condition, or my system is partially compromised. I will probably pull the rad when I get a chance in the coming weeks. bottom line- it is 22 years old.

[GOLDCYLON]

stock manifolds and oem thermostat (1 year old). a couple of extra degrees of ign timing in the chip, but it is actually close to stock in the mid range load cells to run 91 octane. A little manifold porting, but BLM's are pretty close to 128 at cruise rpms so I would say the car is effectively stock.

I drove it (hard) down to the cars and coffee meet up spot this morning and the gauge would not exceed 50% so obviously the water flow is functional. I think either I found the limit of the cooling system and all the cars may run hot in this condition, or my system is partially compromised. I will probably pull the rad when I get a chance in the coming weeks. bottom line- it is 22 years old.


I suggest just a stock replacement. Like you said its 22 years old I did this a few years ago for gp. The fins has so much sand and silt in it not to mention the leafs, debris and other crap all affecting cooling. The plastic ends were swelled a little bit as well. Make a project out of it as its a great time to replace you belt and hoses while your there if needed. GC

[Paul in VA]

All excellent points. I have found that, at coolant change I add a bottle of Water Wetter (A Red Line Oil product; similar products available from others) and it also helps to lower temperatures a little more than just the coolant change alone. My understanding is that these type of products help to break the water's surface tension so that the water is better able to get closer to the heated metal and thus absorb and transfer heat better (at least that is what I think). I would be interested in hearing from anyone using a product like this, in these more extreme climates. Dois it help you?

[GOLDCYLON]

All excellent points. I have found that, at coolant change I add a bottle of Water Wetter (A Red Line Oil product; similar products available from others) and it also helps to lower temperatures a little more than just the coolant change alone. My understanding is that these type of products help to break the water's surface tension so that the water is better able to get closer to the heated metal and thus absorb and transfer heat better (at least that is what I think). I would be interested in hearing from anyone using a product like this, in these more extreme climates. Dois it help you?


Paul Ive never used it before IMHO its a snake oil product. I used to work in autoparts when I was in college. Its in the same line as the Desert Protection Package the dealership used to sell as a sealant for the paint out here in AZ so many years ago. Basically Mop n Glo

[scottfab]

All excellent points. I have found that, at coolant change I add a bottle of Water Wetter (A Red Line Oil product; similar products available from others) and it also helps to lower temperatures a little more than just the coolant change alone. My understanding is that these type of products help to break the water's surface tension so that the water is better able to get closer to the heated metal and thus absorb and transfer heat better (at least that is what I think). I would be interested in hearing from anyone using a product like this, in these more extreme climates. Dois it help you?

This has been heavily debated on the old list server many times. I can tell you this, it's a much more complex subject than you'd think.
Terms like "nucleate boiling" and "non-aqueous" coolants that keep pressures down up to 350deg but which are designed for the short use life span of race engines.

Here is a review of "water wetter":
http://www.thetruthaboutcars.com/2008/01/redline-waterwetter%C2%AE-review/
Keep in mind it's just one view.


In my experience of reading and looking at the various results folks get from different solutions the improved Ron Davis (and similar) radiators are the way to go. I still have the stock one but when the time comes..... no question but that I'll swap for the bigger unit.

[mike100]

UPDATED:

pulled the shroud off and had a look before ordering a new radiator. There was a fair amount of dirt and grit stuck to some left over oily sheen probably from the oil cooler repair 18 months ago. looks to cover 25-30% of the entire radiator, and, naturally, over the useful part that flows through the passenger side fan duct area.

http://i29.photobucket.com/albums/c265/mschrameck/Cars/radiatoroil_grit_sm.jpg

http://i29.photobucket.com/albums/c265/mschrameck/Cars/rad_dirt2.jpg

I tried to clean as much of the oil up last time when the whole oil cooler and radiator where removed, but it had been leaking with the previous owner for so long, that oil was coming out of all kinds of nooks for weeks after. Anyhow, gonna try to go with the cleaning rather than drain the water and take everything apart. the oil cooler and condensor looked ok, except they are going to get a once over on fin combing due to minor pebble and bug damage.

[mike100]

Are you saying the two fans spin at different speeds?

...

I know the newer vettes control speed, but I was inferring that there is a possibility that one of the fans was going out with bearing friction and was not spinning- I don't think that is the case with my car since they spin easy on the bearings still.

also the condensor was 99% clear of debris from a casual inspection through the inlet. It was pretty dirt after all.

[scottfab]

Here is a fairly easy way to keep from having to clean the radiator stack:
http://www.zr1netregistry.com/ZR1_radiatorscreen.htm

I clean this screen out 3 - 4 times a year.
It fills quickly with junk that would otherwise go up into the stack.

[mike100]

There was minimal debris, although a little bit none-the-less- mostly appeared to be dirt build up with an oily base to stick to. Nevertheless, I somewhat feel like a noob for posting before looking- everybody nose that C4's suck up more stuff up the schnoze than a coke addict.

[scottfab]

There was minimal debris, although a little bit none-the-less- mostly appeared to be dirt build up with an oily base to stick to. Nevertheless, I somewhat feel like a noob for posting before looking- everybody nose that C4's suck up more stuff up the schnoze than a coke addict.


If you do install a screen you want one that stops the small debis too.
I used a two layer approach. The 1/2in mesh give structural support and the smaller mesh screen stops even those very small pebbles that get lodged in the radiator fins. (or worse pop a hole in the radiator)
Also you'll note it is mounted behind the wing (see link) and support bars so to be less noticeable. There are no alterations to the car when mounting. No holes to drill and is not visible when looking at the car from the front.

I did this mesh back in 98 after cleaning the radiator stack. It's been very low maintenance. It takes just a few swipes of a stiff bristle brush and you have a hand full of crap to throw away.
http://www.zr1netregistry.com/ZR1_radiatorscreen.htm

[tf95ZR1]

If you do install a screen you want one that stops the small debis too.
I used a two layer approach. The 1/2in mesh give structural support and the smaller mesh screen stops even those very small pebbles that get lodged in the radiator fins. (or worse pop a hole in the radiator)

Do you think this (significantly) reduces air flow through the stack? Probably still better than collecting crap.