OCS1667

I think I have the over heating problem understood, but not solved. I have discovered the following facts.
1. I live in an area that the temps get above 100 for 3mo or more and the avg. temp. can be 90 degrees for 2-3 mos. Living on the coast or in a climate that does not reach these temps, you would probably not have this problem

2. The temperature drop between the upper hose and the lower hose is only 9 degrees. In talking to those who are in the know that drop should be at least 20 degrees and can be even more.
3. I found that I’m not getting the air flow through the radiator.
4. I have a new Dewitt radiator with the supplied fan, not sure of the cfm is powerful enough to do the job, I will contact them about this.
5. I have a Classic Air conditioner installed and working fine, and that on a hot day puts an extra strain on the system.
6. The air escaping between the air conditioner coil and the radiator is probably 20% or more. If you place you hand on the top of the core support you can feel a large amount of air escaping. On the passenger side of the radiator there is hardly any air flow at all.
7. The fan for the radiator sits very close to it. The factory fan is located 10” away from the radiator.
8. The distance between the air conditioner coil and the radiator is about 3” with air escaping on the sides and not passing through the radiator.

I will try putting some type of foam or rubber between the top of the core support and the radiator and see if that helps. I already wired the fans for the air conditioner coil and the radiator fans to work together even if the air is not on. I’m also considering having some shrouding made for air escaping between the air conditioner coil and the radiator to get the maximum amount of air through the radiator.
Any thoughts or suggestions on what I have laid out.

Dennis

stingrayl76

Dennis,

Your #6 point struck a chord with me in that I don't think you should have a positive air pressure between the condenser and the radiator.
Make sure your electric fan is pulling air and not pushing it. If it is pushing, it is wired backwards. Also check the factory fan. If it is installed backwards, it will push instead of pull the air.
Just a thought,
Dave

buns

(1)...I recall, years ago, reading an article on radiators, that basically said that once the ambient air temperature reaches 100 degrees farenheight, no radiator could be expected to keep the engine running at it's proper temperature.

(2)...Here is a Frequently Asked Question from the Permacool website.

Q..."How much airflow (cfm) do I need to cool my engine?"

A...A four cylinder engine requires 1600 cfm; a six cylinder engine requires 2,000 cfm, a small V-8 engine requires 3,000 cfm and large V-8 engines require 4500+ cfm.


(3) From what I gather from DeWitts website, they use Spal fans, the largest being the 16", which is 2350 CFM.

(4) Permacool says you need a 3000 CFM fan for a small V-8, yet they do not offer one for sale.

(5) The only fan I could find that has more than 3000 CFM that will fit a Corvette rad is made by Flexalite. It is 3300 CFM, has a shroud built around it and draws 18 amps.


This is all I know about this subject.


Flexalite 180 fan pic:

67pete

The distance the fan is to the radiator is not critical as long as you have a shroud. If you have the shroud in place, the fan should be roughly 1/2 in and 1/2 out for proper draw. There can be some (albeit not much) positive pressure between the 2 cores, also do you have the foam around the radiator core and a flap on top?

I believe the air flow #'s are for when the engine is at max load, which is when you are usually at speed, this is when the natural airflow takes over to get the right cooling effect.

ctjackster

yeah, ok, but know this - when brand new a C2 Corvette SB, sold in AZ, did not simply become unusable for the entire summer (I would suggest that many were sold with AC as well). Not many C2 Corvettes would have been sold in southern CA, or NM, or AZ, or Texas if the entire fleet simply became unusable for the summer.

I would suggest getting the thing into a stock oem configuration and working (cooling sufficiently) there, and then add back in the aftermarket AC evaporator, and determine at that point how much aux fan you need to correct for it. (Let's face it, if you cannot drive the car on a hot day with your aftermarket AC installed and running, and you live in a climate where it is often 100 degrees or more, well you have yourself a nice car to gaze at and polish in your garage. I'd temprorarily remove the evaporator and the aux fan(s) and get it in operational shape there, then move forward.)

stingrayl76

Good plan Jack. Back to basics.

JohnZ

You didn't mention a shroud - do you have the factory shroud?

Kent in KC

No experience with Classic, but I've installed Vintage Air units in two streetrods and a '63 SWC (which now resides in SoCal). The condenser is always installed as close as possible to the radiator core to prevent air escape between the two. Also sounds like you have two electric fans(?) - the mass of two motors/blades etc. may be reducing the cooling area of both cores causing a problem. By the way, both street rods ('32 and '34 Fords) used the Cooling Components electric fan/shroud (2700 CFM) and the SWC used stock mechanical fan only. No overheating problems.

OCS1667

To your question, John yes, I have the factory shroud with deflector on the bottom.

Kent, you mention the two fans supplied by Classic. I will disconnect one and see if that improves the air flow. I will have to be careful of the head pressure and check it when I shut 1 fan down.

Any thoughts on Purple Ice, I understand that it should drop the temp. by 10-15%.
Dennis
I do appricate all the advice,from all, by the way got the avatar car photo posted, all done after 2.5 years +.

0Tom@Dewitt

You started this thread with "I think I have a problem...But you never posted any specific temperatures or if these numbers were confirmed with an IR gun.

No additive is going to help solve an overheating problem, if you have one. Oh, you are going to get one or two guys here raving about wetter water or some other magic fluid but believe me when I say, that for every guy that said it worked I get 100 that said it did nothing. The factory aluminum radiator is the highest rated unit you can get and then you purchased the SP020 which boosts that rating even higher.

The differential temperature (delta T) means nothing but many of the "experts" will tell you a specific number to expect. Just because you see 9 degrees delta T doesn't mean the radiator isn't working. It means the media you are using to cool the fluid isn't doing a real good job and that media is 100 degree air. If that air was 50 degrees you might see a delta T of 30 degrees. The post on minimum air flow is just wrong. We have rad/kit combinations that use 1700 cfm fans without any cooling issue whatsoever. Spal says the target is 2000 cfm with 70% coverage of the core. Yours has 2360 cfm with 90% coverage. It sounds like you still have the stock engine fan on there and that isn't necessary and it might even be a bad idea. I read somewhere a guy did that and the mechanical fan sucked the electric fan blades back into the guarding and blew it up.

Here is a standard check list I made up that solves 90% of the question we get :

Standard Check List



1. Distilled water is very important because it is the only fluid that contains no minerals. Do not use tap water, well water, or softened water as all of these will contain elements that will void our warranty. Several companies sell coolant premixed (50/50) with 50% distilled water and 50% coolant. Follow the manufactures instructions for fluid life and changing intervals.

2. What mix (ratio) are you running? Cooling systems are designed to have a 50/50 mix of anti-freeze and distilled water only. The higher the water content, the more cooling you will see. The problem with high or straight water systems is that the inhibitor package is not enough to prevent the cooling components from rotting out. If you have too much anti-freeze or “waterless” coolant, you will run hotter for the same basic reason, water cools better. You best bet is to run 50/50 and no others additives are required.

3. Have you confirmed your gauge readings with an (IR) Infrared Gun? These cost about $60 and they are a great tool for checking the gauge/sending unit. Some sending units will read accurately up to a certain point and then read 20-30 degrees off. Don’t be mislead by a wrong gauge. Get a second opinion with an IR gun.

4. Cars with mechanical clutch fans should be checked for function. Fan clutches operate from both centrifical force and temperature. With the engine off, and the engine cold, the fan should be free to turn. Once the engine is warmed up, the fan should be much more difficult to turn. It also should not free turn after the engine is shut off.

5. High speed overheating can be a result of a collapsed spring in the outlet (lower) hose. Most lower hoses have a metal coil spring inside to prevent the hose from sucking closed when the water is flowing at maximum. If you can squeeze this hose closed with your hand, then spring is probably missing or rotted out.

6. Low speed or idle overheating can be related to timing issues. Many older cars used a vacuum advance on the distributor but most people assume this works and do not check for actual function. This vacuum should be routed to a “non-ported” vacuum and should add 12-15 degrees additional advance when connected. Similar problems can occur with special (trick) distributors, HEI conversions, and/or cams that do not match.

7. Engine too tight? Believe it or not, this happens all the time. Many people do not follow the clearance specifications in the manuals and try to “out do” General Motors. Clearances are necessary to hold oil, oil reduces friction, and friction creates heat. Some engines will simply run hot because it is too tight and nothing you can do will change it. You might be able to knock off a few degrees with a synthetic oil, and run a 60/40 (more water) mix to get through the summer months. You could go straight water for a parade day, and change it back later.


8. Additives will only remove a few dollars from your pocket! The “magic” additives sold today will not lower the temperature. Everyone of these products work only if you dilute the system to high water content and it is the water that does it, not the additive.
9. Electric fans move a lot more air than the older engine driven units. In most cases, they are not required however adding an electric fan to any radiator will boost the radiator cooling capacity. Puller fans work better than pusher type fans.

10. C4 & C5 models are designed to run hotter (220 F) than previous years. There is nothing wrong with your car if you see temperatures in this range.

That should give you a few things to think about. When someone is chasing a cooling problem almost 100% of the time people will only look at the radiator. After all, this is responsible for cooling, right? True but your final temperature is a result of two important components.
Heat generated - Heat Removed = final temperature.
Why is it that the heat generated is NEVER considered?

OCS1667

Tom, thank you for the call last night.
I will make sure my heat numbers are accurate and not just what the gauge in the instrument cluster says. I had corrected the sending unit before we spoke and found it not to be 25ohms but 45 which gave me a false reading. That was replaced before we spoke. Reading the Corvette Cooling System you refered me to on page "5" it refers to the factory sealing the area between the core support and the radiator in addition the condensor unit to the core support with foam and or rubber, if you have air and the reasons for it. As I told you on the phone before reading the article I felt a large amount of air escaping from this area betwen the core support and the radiator and not much comming through the radiator. I filled the area between the core support and the radiator with some foam and felt a big increase in the air flow coming from the radiator. Driving awhile in 95 deg. heat. I stopped of at a shop and had them check it with the IR gun and it was reading 200 deg. and my gauge was at the hash mark between 180 & 240 which on my gauge is max.
At this time I feel I'm on the right track, I'm hoping if any one out there can confirm that the factory supplied sealing material in these areas it could help us all.
Dennis

Road machine

It sounds to me that you have not installed the fans properly. Any fan either electric or engine driven needs a shroud around it to work properly. It sounds to me as though you have the original shroud for the engine driven fan still on and you have fans pushing the air into the engine compartment from the outside of the radiator. If that is the case the shroud in the engine compartment will do nothing but possibly make air flow worse, and if there are no shrouds around the pusher fans you are also limiting air flow. The first test that I would conduct is the highway drive test. If at highway speed the car runs cool but at slow speed it runs hot it is air flow related. If it is not airflow related then start looking at the water pump, thermostat, cloged radiator, or as mentioned above overly tight motor. If it is air flow related, you must be sure there are no air leaks in the air stream (air comming out from between the condenser and radiator is a definite no no) and the fans should if at all possible be pulling and and be shrouded.

magicv8

IMO if you can run down the road on a 100F day at 60-70mph with the A-C running, you have enough cooling capacity. If you bring the speed up to 85-90mph with A-C on a 100F day you may run out of capacity and need a larger rad (as a generality - a new Dewitt SB rad should do it), better pump, lower the front license plate, etcetra.

If the car overheats idling on a hot day, raise the hood. If it gets cooler, you need more air through the rad. Solutions include: rad seals, A-C hood seals, shroud seals, larger fan, remove engine splash shields, plug stinger hood depresion to seal to A-C rad seal, high flow water pump (with balanced flow tstat).

All the above assumes manifold vacuum controling the vacuum advance (not carb ported vacuum) and correct (lots of) advance.

Been there, done all that.

PS: My roadster has a 16inch 2200cfm Derale fan pulling air through the factory BB shroud. It does the job with factory A-C running.

OCS1667

Jose, I have said that I have a serpentine belt system with a Dewitt radiator elect fan combo mfg. along with the shroud. The condenser has two pusher fans. I believe you are right as I have also discovered I have air escaping between the core support and the radiator in additon to around the condenser. I have taken action to correct this by sealing the opening between the radiator and the core support, and it appears to be working. I read the article on Corvette Cooling System page "5" in a thread and it confirms that this will cause a problem. I believe everything else is right, then the air flow has to be the culpert.
One thing else that tom brought up, use a IR gun to be sure of temps, and don't rely on the gauge.
I'm waiting to hear from someone who has factory air, and the use of seals by the factory.
Thanks for you help.
Dennis

Rons65

My last C2 and my present C2 both were/are factory air convertibles. My 65 300 hp had numerous cooling issues and with a new DeWitt radiator, spal fan, factory shroud, seals all in place, timing set up correctly, etc, etc still had an issue in traffic - but, it never puked....just ran hot - verified with IR gun. Current owner has gone through the motor and from what I hear everything is ok.

My current 66 is a L79 350 hp with factory a/c. Motor is rebuilt, timing correct, DeWitt radiator (no extra fan), etc. Runs cool at all times and even when it heats up in traffic here in Scottsdale, still does not exceed 220! Runs normal at 180-190. These temps are been verified with my IR gun numerous times.

So, every car is different and its my opinion (had numerous Corvettes and other air cars, BUT I am not an expert in anything ....well, blondes maybe.... ) a correctly set up cooling system, timing correct and motor in good shape and correct, your car should not overheat even if pushed! Something is wrong somewhere and the other posts have some great information....Tom DeWitt has been super with my needs over the years and he is an expert in this area! Good luck and keep us posted on your progress! Ron

OCS1667

magicv8, I was not aware that their are seals to correct this problem, but stumbled on this fact when I felt a large amount of air I thought was escaping between the core support and the radiator, not to mention condensor. I had some foam, and I packed the above area. I could not believe the air increase flowing from the fan-radiator combo, guessing a 30% increase. As they say I got immediate relief, dropping 20 degrees using a IR gun to 200. I will have to remove the hood to see what I can do with the condenser.
By the way I tried to address you by your real name, and could not find it, are you a CIA type. Thanks for you help.
Dennis

OCS1667

BINGO
The one thing I failed to do was look at my corvette catalogs after finding out that seals are used to beat this problem.
Guess what, in the ZIP catalog bottom of page "102" they offer seals to eliminate this problem.
They offer nothing for the 65 except the 396. I know the 66-67 will work. I did install a seal mounted on the bottom of the shroud.
1. Support lower seal w/ air [? is this the seal on the shroud].
2. Support upper seal w/clips,327 w/air
Anyone know of anything else I might require.
Dennis

firstgear

good discussion

ctjackster

We all hope for the best for you, and the "seal it up" effort surely might help, but I kinda doubt it will, on its own, "eliminate the problem". I am guessing you will need to revisit your aux fan - stock fan - shroud issues, assuming everything else has been ruled out.

magicv8

Dennis, I even have a website on the Corvette Forum showing the seals I used on the shroud on this page: http://www.corvetteforum.net/classic...e/index7.shtml

The Details page link will show some older info.

I have a BB shroud, but the same seals will work on an SB shroud too. - Dave

PS: The real reason I switched to weatherstrip for rad seals is that the catalog seals and the auto/marine weatherstrip you can get at local stores shrink a little as years go by. The seals are engine heat "cured", and when they shrink, they leak air or fall out.