OCS1667

I just wanted to update you all where I'm at.

I ordered a clutch fan from a supplier, but as usual, they flaked on me, may be a good thing. After two weeks no product, after I was told it would ship next day. They charged my credit card so I thought it had shipped. Owner apologized, and after a discussion of way I wanted his product he believed it would not help. His theory is that if your going down the highway and it's getting hotter with all the air coming through the engine compartment, the problem is elsewhere.

One more thing, Purple Ice does not work, period. Had to try it, and those who questioned it's use, are right.

I removed the thermostat, as recommended by many of you. Started to heat up as before, and it was about 220 degrees on the gauge when I arrived at the shop I use for help. Left the car idling to retrieve the IR gun. The outlet coming from the radiator to the engine was 20+ cooler then the bottom hose from the engine. This is a good thing knowing the radiator is doing what it was designed to do. The IR gun was 202 degrees, I then poked my head into the cockpit, and noted the temp. gauge was coming down, and was now at a 190 degrees, and continuing downward. The IR gun agreed too, I got a big smile, here's is a positive happening.

They recommended I take it on the freeway and drive at a constant speed and see what happens. It was hanging around 190 until I hit the highway, and bang up she goes again, right to the 240 mark. I drove it home and noticed the temp was slowly coming down after I slowed way down.
I called the shop and explained what had occurred. They told me that without the thermostat acting as a restricted to slow the water down, it was moving so fast that the radiator did not have a chance to cool the water. At this point, I want to state, that with the the thermostat the temp. never came down at idle, the temp continued to rise.

They are recommending a restrictor that opens all the way at idle or at slower speeds but at highway speeds it restricts the water flow giving the radiator a chance to reduce the temp of the water. Isn't that what a thermostat is designed to do.

To check, I boiled water keeping the temp gauge in the water along with the thermostat, as the temp. reached 180 the thermostat was bairley open, maybe an 1/8" and it did not open much more, and never fully, possibly 3/8". The spring had about a 1/4" of travel to go to be fully open.

I know if it works it works, [the restrictor] but has anyone else experienced this type of cure, or due I try another thermostat, remember it's + 100 here every day so it will run hotter.

Keep your fingers crossed this works.
Dennis

macdarren

I haven't been following your problem, though I think I posted about my weird fix on a previous post....(springs)....anyway my 2 cents are that the restrictor/thermostat is not the answer and I totally do not buy that old you need a restriction to allow the water to sit in the radiator to cool...I can see no logic to that at all....the water is pushed across the radiator it will cool (is cooling according to your IR gun.) Pushing it faster may in fact mean the water cools less but the amount of heat taken out of the system should be the same as that is a function of the air flow, it is just that more water will be cooled in the same time but it will be cooled less. In fact I could make a case that this is better while the water will not have as big a temp differential in the in vs out temps the fact that the difference between the air and the water will be greater means more total heat flow out of the water and thus out of the motor. Yes it might be at first the gauge would read higher as the water is starting out hotter into the motor but then all the water should be cooling more and temp would drop. I have heard that restriction 'theory' many times but never have I seen it demonstrated to be true. My own experiences sure have never born it out.

I hate to say this but I think your radiator is not operating as efficiently as it should. Is it new? I ask because even here in CA on a warm day I usually see about 40 degrees F between inlet temp and outlet temp.....yours seems low. If this were the case then it would explain what I gather your problem is...over heating on the freeway. When you are pushing out more power to maintain speed your car is making more heat, your rad is not dumping it fast enough (restrictions or not) and the car starts to warm...take it off the freeway and generally make less power and less heat and the radiator slowly catches back up (at least with no restriction according to your post).

If your rad is new check it for hot and cool spots with the IR gun maybe it has some defect and is not passing water in places. If the rad is not new and this is a developing problem I would say it is shot, time for a new one. Even a non-stock motor should not make alot more heat to produce the same power at cruise as a stock engine (HP=Heat) I would say if the rad is new and not obstructed and the pump is working (which it seems to be) that your solution is going to be air flow....you need more air through the rad....sealing things up front to force more air through, opening things in the back (gills and splash guards maybe) to let the heat out, and electrics to help would all be way to improve air flow.....and again I will mention my experience was keeping the nose of the car from lifting with new springs helped me.

Lastly I don't know if you mentioned or not but if this is an A/C car be sure the evaporator is in good shape...those thin AL fins get smashed easily and really can restrict air flow.....

Darren

wmf62

sounds like you need a new thermostat, maybe a 180.
Bill

stn6ray

I have played around for years (at great expense) to try to keep my big block 66' cool with no success. I tried top of the line electric fans, stock fans, every kind of trick from drilling holes in the thermostat, water wetter, high pressure radiator caps and of course high flow aluminum water pumps. Even though I have a Griffin aluminum radiator, nothing worked, until I came across a trick part that the pro-touring set have been using for years on Chevelles and first gen Camaros. You basically install an electric fan from a 98' Lincoln Mark VIII which pulls around 4900 CFM and ever since I did, the damn thing cannot overheat. As crazy as it sounds, I almost look forward to traffic so I can laugh at how my baby doesnt break 200 degrees on a hot day. Anyways, do a google search on this upgrade and you will find a wealth of information on it. Best part is that not only does it work like you wouldnt believe, it looks trick too. It is a really nice looking part. Just thought I would pass this on. Good luck.

Matt Gruber

OCS
at 7:00 AM does it stay under 200?

Donald #31176

How old is the radiator? Hi speed overheating is usually inefficient heat transfer of the radiator. Also is the spring in the lower radiator hose intact?

Coves4me

OCS1667, Assuming your radiator is OK and your timing and fan clutch are spot on, I would look at your carb jetting. You my be running too lean. I don't know if you have to use "oxygenated" fuel in Palm Springs, but if you do your car is running lean with the normal jetting in the carb. Oxygenated fuel was the EPA's answer to reducing emissions in larger metro areas by combining an additive (MTBE or ethanol) with gasoline to bond additional oxygen atoms at the molecular level, thus burning more air than fuel in the combustion chamber. As such, you may want to try richening up the carb by increasing the main jet sizes in 2-jet size increments to see if that doesn't help. Here in Dallas, it made a BIG difference in both of our car's driveability and cooling.

GaryS

As I understand it, the temperature rating of a thermostat is the OPENING temp not the fully opened temperature. I would say that your thermostat is acting perfectly normal.

The indications you are getting, a rise in temperature when at highway speed, is indicative of a radiator not up to the task of cooling your engines heat output. Higher speed means more BTUs for your rad to handle. More BTUs with an inadequate radiator cooling capacity or partially clogged radiator means increased temps. The rest of your cooling system sure sounds like it is acting as designed.

I have read the theory of water moving to fast through the rad too fast to cool but I am not sure that I have a lot of faith in that theory. What would a restrictor do that your thermostat isn't already doing? If the thermostat is partially opened at 180, then it is acting as a restrictor, isn't it?

I had similar issues with a 66 327/350hp that I owned for a long time. I could not drive on the highway for more than 10 minutes without overheating but it would drive all day long in town. A new repro Harrison rad from DeWitts solved my problems.

Just my opinion.

Gary

mdz06vetter

replace the radiator

66L72

i used to have all sorts of overheating problems; typical BB midyear;

during my restoration i decided the whole project wouldnt be worthwhile if the car still had those issues. it is totally stock except for a dewitt aluminum rad.
now it drives all day long at 180 and peaks at 200 if i let it idle in the driveway or get stuck in traffic.
call Tom Dewitt. one of the best vendors on our forum. he will talk you through the problem and if you need a rad he has the best as far as i am concerned

OCS1667

Guys I have been through it all, except for removal of the thermostat which I just did. I have talked to Tom Dewitt re. a newer design rad. with a higher capacity. If you check my zip code 92211 You'll note temps. in the 100's + in the desert. I thought I was on to something when the temps. were coming down at idle or slower speed because of the removal of the thermostat. By the way, air was off during the test.

I spoke earlier of air flow in a earlier post. I have a condenser mounted in front of core support with 2-12'' fans wired in sink with elect. rad. fan. All blowing in the right direction, all the time. Do you think that I have to much blockage, and the fans are not able to move enough air through rad. to cool. Would you agree if this is true that I should pursue the original clutch fan set up, or try stn6ray 4900cfm fan idea.

1. No air in lines.
2. checked water flow, good and the right direction.
3. Hi flow Stewart reverse water w/correct pulley. Vintage Air serpentine belt system.
5. Heads were removed for visual check along with high pressure air to check water passages.
6. Everything is new, no swap meet or used parts in cooling system.
7. No leaks anywhere.
8. IR gun is right on with temp. gauge in car.
9. Drilled 3-3/16" in thermostat[180] per Vintage Air instructions.
10. Distributor complete rebuild to include elect ignition by T.I. Specialties.
11. New Air condition system included new heater core.
12. Thermostat is new and IR gun supports it 's functioning correctly.
13. New Holly 650 runs very smooth.
14. New Dewitt rad. w/elect fan.
15. Correct head gaskets.
16. Noted air loss between core support and rad.. Filled opening and noted greater volume of air flow through shroud, no change noted.

I can't think of anything else other than it's very frustrating.

Dennis

richbopp

Dennis,

AC on..... AC off.... any difference in the temp?

JohnZ

If it heats up at highway speed, normally it's one or more of the following:

Not enough radiator (not an issue if you have a DeWitts aluminum)

Not enough airflow - electric fans block airflow - are yours "pushers" or "pullers", and how many of them are mounted?

Restricted coolant flow (get a good thermostat - Robertshaw #330-180 or Mr. Gasket #4364); yours isn't opening far enough. DO NOT run without a thermostat - it's a calibrated opening.

Blown head gasket, adding combustion heat to the coolant.

stn6ray

Trust me on this one. I was in your shoes and I could not find any answers on the Vette forums, due to the originality factor. But I can guarantee you that it will work and it fits perfectly. The only thing you modify is the radiator itself to mount it to. It is a perfect fit and since the fan comes with its own black built-in shroud, you can hardly notice it from a stock fan shroud.

The bottom line is this, it is all about surface area to the radiator and airflow, none of the other stop gap tricks work. People will suggest a lower temp thermostat, this only opens at a lower temp, it does not cool the engine better. People will suggest a high pressure radiator cap, this only allows the system to generate a higher level of pressure before the coolant escapes, this helps a little but will not cure the problem. The exotic chemicals are all a waste of money, bottom line water works great and is the best coolant of all. Look, the whole point is if you have a quality aluminum radiator (people seem to prefer DeWitts and Griffins) and if the rest of the system is functioning properly, namely the water pump, hoses, etc. Than the only remaining issue is airflow, and the only way to get it is a fan, a powerful fan. The Motocraft part I told you about is the best there is hands down. I bought the top of the line Flex-a-Lite from Summit, total junk. Ceased working and almost cost me my L89 aluminum head motor. My suggestion again is do the Google search and see what other Chevy forums (that are less woried about all stock NCRS and are focused on which parts solve the problem) are doing. I too was skeptical, that I would never really be able to enjoy my big block beast, but afterwards, I would smile like a kid when I would glance at the temp gauge. Again it worked so well that I put one on my 1968 SS camaro and my 69' Bronco off-roader which sees ridiculous desert heat and still cannot overheat.

To get you started, here is a good link to a site showing the install. It has part numbers and some pics.

http://members.tccoa.com/392bird/markviii.htm


Do what works and what works is this setup. Good luck.

Matt Gruber

i'd bet the lower hose is sucking itself shut.

Tyler Townsley

Had simular problem many years ago on my 66. Could not get it to cool right at speeds above 55 or so. MY cure was a 3in spoiler. It cured the temp and the light at speed feeling of the car. With the stock front the air pressure in the engine bay traps the air in the engine compartment which leads to the overheating as there is no flow through the radiator. The lip shifts this pressure such that it is pulled out and you get flow and as a side benefit better at speed handeling. Ecklers used to sell them and they can be notched to allow the bumpers to be installed. Most people never even notice there is a spoile on the car. I would post a picture but car is being fixed after t-boneing another car. Repair included a new spoiler.

The painter removes all the glass before spraing the car and he found the rear glass had come unglued all along the bottom and most of the top. He was pretty sure it was on the way to being blow out. There was no visual indication of a problem. When he ran his cutter wire it encountered very little resistance. This was a 66 original no hit cat i bought in 74.

Tyler

OCS1667

John thanks for the assistance. The points you bring up re. air flow is what I am looking at now. I have a new Dewitts replacement w/2400cfm fan. There is a condenser in front with 2 fans wired in sink. The factory shroud is there, and as I said earlier maybe their is to much of an obstruction to let enough air through. But the following does not add up.

1. Why is the temp gauge coming down when I'm at idle or at a slower speed since the removal of the thermostat, and then climb at higher speed, or is that as some inform me that the coolant does not have time to get rid of the heat since it is traveling to fast through the rad. and that's what the thermostat does, it retricts the flow enough by design to slow the flow of water when fully open.

I plan to go as soon as I finish this note to you and check on those two thermostats and take the one back with me to see if there is a problem with it, not opening enough, and or design.

The other point is the air flow, but it did cool down at idle as indicated by the IR gun and a visual of the temp gauge verifying the drop in temp..[ 20+points from the top to the bottom]. Would you not conclude there is enough air, and at highway there should be gobs of air.

I believe what you are saying everything being equal, and with the right thermostat this could be the cause and cure. I hope so.

I'll let you know what happens. Thanks again for your help.
Dennis

Matt Gruber

Tyler makes a good point.
i've added an airflow test to my site.

Hitch

The reason that you are seeing your temps come down at idle and low speed with out the thermostat is that it seems yours is not opening enough. You stated that it barely opened when you put it into 180 degree water. Get you the Robert Shaw that John recommended.
Also why don't you post some pics of the front of the car the front of the radiator and the engine bay where the front of the motor is. I think that this may be helpful. Dave

vetsvette2002

It really is as simple as John says.

Don