If radiator is original it probably need a recore job or replacement. It might not leak or have any other issues but if the cores are seperated from the fins in several places that would cause overheating. What about thermostat? Had it checked lately? you could go from a 180 degree to a 170 or 160 unit.

 

If your car is overheating while driving it down the highway, a pusher fan is not going to resolve your issue. You need to find out what's causing your issue.
Have you checked the thermostat to make sure it's opening and at what temp?
What's the timing set to (initial vs full) ?
What water pump are you running and what's the condition of it?
How far are the fan blades inside the shroud?
When it does get hot, how hot?
Where is the temp sending unit mounted?

 

Radiator is actually fairly new and in pretty good shape. I am seeing some corrosion in it so there might be a blockage. I'm going to try and flush the system. Not sure about the thermostat but i think it is okay. I was told that the RS's were notorious for overheating because of the hideaway headlights causing a lack of airflow. I wanted to see if there was a way to increase airflow for cheap. Was also considering removing the mechanical fan and installing an electrical one w a shroud. (Black Majic or something similar)

 

I was told that the RS's were notorious for overheating because of the hideaway headlights causing a lack of airflow.

Complete and total BS, just so you know. If the same person told you the radiator was "pretty new", I would consider that potentially BS as well.

Also, FWIW, do you know that your car has an "open" cooling system (unless it has been modified)?? Unlike a newer car, with an overflow bottle which can catch fluid as the system heats up and return it to the radiator when things cool off, your new toy has a fluid level which should be several inches below the top of the cap neck when cold. Some radiators have a "full cold" type of marking on them, but sometimes you just have trial and error until it quits puking fluid out at operating temp. So if someone fills it full to the neck when cold, it will certainly puke fluid until it drops the level enough.

Also, would need to know more about temps under iddferent conditions/loads. I really don't think the temp spiking to 215 stopped after running on the freeway in So Cal in July is bad at all.

 

All good questions but I'm not sure I can answer them all. I guess it's a little more complicated that I had hoped.

The fan blades, on top, are about 1/2 in the shroud and 1/2 out. At the bottom, the fan blades are completely inside the shroud but just barely. Where should they be?

I think the water pump is new, but I'm not sure which one it is. I was on the freeway coming home and when I stopped for gas I was spewing fluid everywhere. Guess it hit 215 degrees. After the air temp cooled down I stayed below 190.

I just got the car a week ago. I can call the previous owner and prob find a few of those things out.

 

It is not an air flow issue if its over heating on the road
A lower temp thermostat will not change anything except how fast the engine warms up...unless it is the wrong spec for the engine (flow spec.)
The cooling systems are far to over built on these cars for timing way off to have any significant effect....modern cars yes it has a huge effect because the cooling system is designed to be only just large enough when the engine is in tune

There are many older threads coving what to do and how
1/ Back flush the radiator and pull the stop **** and see if any crap inside
2/Check or replace the cap
3/Check..well its out, they are cheap..replace the thermostat...with a 180 and make sure it meets 67 to 73 sb specs.....also check before putting in
4/Check radiator for blocked cores...1st start of the day feel for cold spots as it warms up...If blocked cores, get it manually cleaned
5/Check bottom hose still has the renforcing spring in it.
6/Get a HC check on the radiator...(Very cheap, generally free)...checking for a very clean spark plug indicates blown head gasket also.

 

Adding to Steps list..
7 Check if Thermostat is in upside down
8 Look for water in the oil

 

Also...check the hoses...they can cause ya grief.

capt

 

To add to what Eric and Bill have said, my 68 RS runs at a nice cool 175-180 all the time so the hideaway headlights have nothing to do with your issue. You have a 350 motor, any clue what's been done to it ? High compression motors build more heat. Headers help to shed some along with adding HP. High volume water pumps are a must on really pumped small blocks.

I'd flush the radiator, replace the t-stat with a 160F, and new coolant and see what happens.

 

Interesting! That very well may be the case. I was looking for an overflow only to find out that they dont make them for the 68 so that makes sense.

The engine #'s dont match so this engine is newer than the original. Will that make a difference with the open cooling system? If I add an overflow & essentially close the system can that cause any damage?

I'm noticing what appears to be rust in the fluid because he was running only water and it is exposed to the air due to the open system so I plan to flush everything anyway.

Thanks for all of your help everyone. This is my first classic car and I've only driven it home so far. I guess it is all a learning process!

 

Interesting! If I add an overflow & essentially close the system can that cause any damage?
I'm noticing what appears to be rust in the fluid because he was running only water and it is exposed to the air due to the open system so I plan to flush everything anyway.

An open system will have an air pocket at the top of the radiator.
Adding an overflow bottle gives the fluid a place to expand to when it heats up. When it cools, it draws the fluid back into the radiator and eliminates the air pocket that would be there otherwise. It's just a better way to do things and won't hurt your system in any way; it will help with cooling and slow down corrosion.

 

If it is over heating on the highway the lower radiator hose is collapsing at speed.

 

I wouldn't say that timing specifically has anything to do with it, but I would check out the full manifold vacuum setup JohnZ describes on CRG. Made all my distributor cars run great and cool.

 

Easy test for the bottom hose is to try to squeeze it in the center with the cap off. If it collapses replace it and go from there. Be sure to use a hose with the spring inside of it

 

If it is the lower hose, take the old one with you when you get a replacement. I have an 89 block with a long water pump and a 4 core radiator so the hose listed in the parts books doesn't work. I use a NAPA #7400 and have to trim ~1.5" off it.

Aren't these contraptions fun

 

replace the t-stat with a 160F, and new coolant and see what happens.

Didnt you read the post ablove...the thermostat all it does is warm the engine up quick to the operating temp fast.
This is to bring the engine oil temp, toleraces etc up to the correct operating temp..less engine wear on starts and warm up and running
The spec for chev sb is 180 deg...If you are running specialist fuels like LPG 140 or 160

The thermostat, unless it is is faulty, has nothing to do with over heating.

Next thing you know some bright spark will come up and suggest colder spark plugs make it run colder.

 

A thermostat can absolutley cause overheating. If the thermostat is too cool it will not close. Therefore it will keep circulating the fluid constantly getting it hotter and hotter. It will never allow it to be trapped in the radiator to cool it down. Sounds strange but sometimes you have to run hotter termostat to keep it cool. Particularly on modified engines. Seen it time and time again with the local kids who haven't built up the experience yet for the ins and outs. But that's OK because that's what this website is for.

Unless your motor is wildly built. I would:
Check radiator and flush. Depending on what comes out, this might be your only step.
Check radiator hoses. Replace as needed.
Replace the thermostat. For the cost of thermostat and gasket, just replace it.
Make sure antifeeze is good.
Check and adjust timing if needed.

Start there and see what happens.

 

A thermostat can absolutley cause overheating. If the thermostat is too cool it will not close. Therefore it will keep circulating the fluid constantly getting it hotter and hotter. It will never allow it to be trapped in the radiator to cool it down. Sounds strange but sometimes you have to run hotter termostat to keep it cool. Particularly on modified engines. Seen it time and time again with the local kids who haven't built up the experience yet for the ins and outs. But that's OK because that's what this website is for.

And all too often websites like this give incorrect information and continue to spread old wives tales.

Whenever the engine reaches the operating temperature of the thermostat, the fluid circulates continuously. Back in the 'old days' people would run a 160* thermostat, or none at all, in the summer.

Mark

 

Perfect! Thats sort of what I though. I found a pretty cool stainless overflow so I'll probably just do that. Thanks for your help

 

If the thermostat is too cool it will not close. Therefore it will keep circulating the fluid constantly getting it hotter and hotter.

Sry wrong..been there done that...no thermostat can cause the engine to run hot becuse of your logic....with a thermosts in and the center ripped off it will not get hot...assuming that you are using a SBC correct thermostat...the thermostat housing creats a restriction in the flow enough to let the coolant to cool in the radiator
My engine would not go over about 110 deg
Also check out Smokey Yunkics experimants on this subject which he delves into in quite some detail.

 

There is probably a lot of info here on the forums about setting up a closed system with a coolant recovery tank on a 1st gen. Here's a thread I just found while answerng another question, but I am sure there are many more to find with search:

http://www.camaros.net/forums/showthread.php?t=176027

 

Do you know what mixture of antifreeze you have? If you go from 50/50 to a mix of 25% antifreeze and 75% water you will lower your temp by almost 10 F. In your area that 25% antifreeze should be enough. Don't go 100% water or you will have internal corrosion issues.

 

And all too often websites like this give incorrect information and continue to spread old wives tales.

Yep and the marketting proganda BS of many products feed of the old wives tales, promotting even further.

Do you know what mixture of antifreeze you have? If you go from 50/50 to a mix of 25% antifreeze and 75% water you will lower your temp by almost 10 F.

The anti freeze decreases the BOILING TEMP and increases the FREEZING TEMP
It also has anti corrostion chemicals in it to prevent electrolytic corrossion between the mixing of metals and alloys.
Any possible reduction in running temp is rubbish, simply because a system and engine in good condition the thermostat determines the running temp.
If there are issues of going significantly going over the thermostat temp indicates something is wrong with the engine or cooling system.

 

The anti freeze decreases the BOILING TEMP and increases the FREEZING TEMP
It also has anti corrostion chemicals in it to prevent electrolytic corrossion between the mixing of metals and alloys.
Any possible reduction in running temp is rubbish, simply because a system and engine in good condition the thermostat determines the running temp.
If there are issues of going significantly going over the thermostat temp indicates something is wrong with the engine or cooling system.

I disagree. Many of our old muscle cars often exceed the thermostat temperature because the original cooling systems have degraded and were marginal to begin with. The original question is how to help this car with "minimal investment". Reducing the antifreeze/water ratio is well documented and an established solution to lowering the coolant temperature.

Let me quote this excellent article regarding the best coolant selection for old muscle cars written by automotive engineer Patrick Bedard with help from Zerex chemist Dr. Turcotte:

http://www.caranddriver.com/features/02q2/dr._turcotte_writes_a_few_coolant_prescriptions.-column

“All the antifreezes I know have one side effect that's troubling for a few of our special cars. Ethylene glycol, which makes up 96 percent of what's in the bottle, has about half the heat-transfer capability of plain water. So when you mix antifreeze and water in the recommended 50-50 proportions, you give up a quarter of your system's cooling capacity. No problem for new cars; they're engineered with capacity to spare. But I remember British roadsters of the '50s and '60s that would boil on the streets of New York in the summer, and street rods are notorious for overheating. You could cure the cooling problems of those cars by circulating plain water through the system.
Most NASCAR racers do that. But corrosion sets in amazingly fast. Turcotte showed me a sample of coolant that had run 35 laps. It had flakes of red snow swirling through it-rust. I've seen similar rapid rusting when I've used plain water to leak-check a rebuilt engine.
Another approach: Increase the proportion of water in your mix, thereby trimming back both freeze and corrosion protection to gain heat transfer. Turcotte agrees that's a possibility, and he says he tests with dilutions down to 25 and 16 percent. "They survive," he says. Still, his do-no-harm approach shies from any antifreeze proportion below 40 percent.”

 

lower radiator hose colapsing like others said maybe, also thermostat maybe (check in boiling water and see if it opens. Also make sure there's a decent antifreeze mix - should be freeze protected down to below zero if it has enough. The ball testers are cheap, maybe a couple bucks and accurate enough for your check on anti freeze mix ratio. If you put new stuff in go 50:50 mix. If you aren't keeping it cool when there's an air gap at the top after that, I would be looking at for a new radiator. It will cost a couple hundred dollars but will most likely solve all your problems. Get an aluminum one off Ebay from someone with good feed back is what I would do, 3 or 4 core that has stock mounting points and clips for your fan shroud. You can spend a lot of time and money on everything else when a radiator would have fixed it fast.

 

Like everyone else said, the cheapest approaches include radiator flush & fill with 75% water 25% coolant, new thermostat, new radiator cap.

 

original cooling systems have degraded and were marginal to begin with.

And there is another old wives tail
The old cars be it american Aussie, English way over built their coooling systems..And the old wives tails start cause ppl think a simple flush, even on a regular basis means the radiator is fine...
I really dont think anyone here, in the states has actually pulled off the headers and re cored or ever manually cleaned out a radiator...and until you guys stop just R$R and start getting into real re building and reconstruction rather than just head up the road and buy a new replacement...its all just assumption....

How many of you when rebuilding an engine treat the cooling system in the exactly the same way as one replaces a oil pump or a bearing....and that means pulling the radiator headers even if the radiator has only seen 1000 miles..manually clean out, re solder up and pressure and warp test the radiator...do you even know what a warp test is?

 

I don't have a clue what a radiator WARP test is. My point is simply that ethylene glycol has about half the heat-transfer capability of water. If you use a 25% antifreeze you gain better efficiency and lower coolant temperature.

 

The OEM cooling system was developed to operate properly with a 50-50 anti-freeze/water mix, which also provides boilover protection to 265*F with a 15 psi radiator cap. If the cooling system is in good condition and hasn't been "catalog re-engineered", it'll work fine.

90% of all cooling problems are related to the radiator and/or airflow through it; in this instance, if the car heats up going down the highway (where airflow isn't an issue), odds are that the radiator is the problem. No cooling system designer ever expected the radiator to maintain its heat transfer efficiency for more than ten years.

The link below will take you to a technical article I wrote, published in "Corvette Enthusiast" magazine, that explains in detail how the cooling system works and how each of its components contribute to proper operation; it also debunks some of the "internet misinformation" you find every day about cooling problems. The article is focused on Corvettes, but the principles are the same for Camaros.

http://www.camaros.org/pdf/corv_cooling2.pdf

:beers: