Hello all,

I purchased my 1968 Firebird 350 a bit North of Chicago last weekend. I drove it back on an 80 degree Labor Day Friday in heavy stop and go traffic (5 hours to travel 195 miles). The water temp gauge reached 220 degrees when I was sitting still (idling) at one point. The oil light started flashing, the engine starting knocking hard an I thought it was going to stall. At that point, I exited the highway, drove around a local neighborhood and it cooled back down to 195. I was able to get back on the highway and learned that if I maintained at least 5 MPH (keeping a distance between me and the car in front of me), the car never reached 220 again.

Now that I'm back in Michigan, I've had the chance to drive the car around our local highways. Yesterday I was on a 15 mile trip, it was 85 degrees out, I was traveling at 70 MPH constantly and the temp was at about 200 degrees.

I guess I have a few questions:

1. Is 200 degrees normal on a short drive, doing 70 MPH with the outside temp at 85?
2. I don't know what thermostat I have in the car. I assume a 190. Should I look at a 160, especially if I'm going to be in start and stop traffic on a hot day?
3. What do the rest of you do when you end up in start and stop traffic in hot weather?

There are a few things you can do but cooling systems, especially since you don't know the car are challenging. In my experience 90% of overheating problems are NOT related to the thermostat. You should be running at 190-205 not more. Get yourself an infrared thermometer and verify the temp, hit the gage in a couple of different spots, lower radiator hose, upper, water pump etc. and note the readings. If lower and upper radiator hose temp fluctuates, it is your radiator. Check the water pump for flow, check to make sure you have enough coolant, if you have A/C make sure your fan clutch/fan works. Get yourself a manual to read up on how to check all these things if you don't know.

I should have specified. I have a new 3 core aluminum radiator with dual electric fans and a shroud. The Bird also has AC, but I've never turned it on while driving. The top has been down instead

What do the rest of you do when you end up in start and stop traffic in hot weather? Does this type of driving cause you an issue?

Factory clutch fan and factory fan shroud will fix it.

X2

Yep, x3. Dump the electric fans and go back to the factory HD cooling package with the 19 inch 7 blade clutch fan.

Those of us who have been around here a while have noticed that practically every time somebody with a new to them FGF comes here with a cooling problem, it's because some previous owner thought they knew better than the factory engineers and installed electric fans.

Welcome..!

I run a 185F thermo and rarely get up to 200 in traffic if I'm just cruising. Although, I do have the factory HD cooling.

Assuming the water pump has been replaced:
- Impeller to intermediate plate clearance may be too large
- WP Plate is corroded and not sealing
- WP internal seals not sealing

As on most cars, a high water to coolant ratio may cause an issue too.

I run stock thermostat and stock everything else. No problem with heating up. We have a big cruise once a year and you are stop and go for hours in 80-90 degree heat. I have seat in traffic for three hours moving inch by inch. No heat issues.

Get you a thermal heat gun and check temperatures. A lot of time gauges are wrong. Hitting 220 at times should not be an issue on the cast heads and engines. The hot warning light does not turn on till 245.

Timing has a lot to do heat. I run stock timing on ported vacuum.

You lower and upper radiator hose should be different in temps. Lower should be about 165-170 and the upper will be your running temps as it comes out of the engine.

Your oil light coming on could be oil pump related, pre assure dropped and knocking started. Might want to really check it or keep an eye on it.

A 2-row alum rad, with 1.25" wide tubes will help cool most engines.


http://www.firebirdcentral.com/1967_1969_Firebird_Aluminum_Radiator_Automatic_p/rad-403.htm


https://www.summitracing.com/parts/gri-8...CANoaAsd98P8HAQ

I had that duel electric set up... I dumped it after 2 rides and went back to stock fan..... no more cooling issues...

I have have seen in the past was engines that did not have proper combination of coolent and additives for the cooling system that the water pumps that had the stamped steel impellers were rusted away pretty bad to the point that they really didn't function.
Just another thing to add to the check list.

Thanks all. I just replaced the thermostat that was in the car when I purchased it. I didn't know what temp version was installed and wanted to make sure it was working properly. The old one was stamped a 180 and I installed a new 180 and gasket. The new thermostat change didn't seem to make any difference. I also made sure the electric fans were wired correctly and pulling in the correct direction. I'll try replacing the electric fans probably over the winter. It's not a big issue with the cooler temps as summer winds down in Michigan. Thanks again for all the suggestions!!!

Another experience with electric fans... Bigchief, Harold and woven said the same thing to me as well.. Dump the electric, let the stock setup do the job. I had some bigger problems as well. In my case. the car would run at 220, hot days it would overheat in the 240-260 range (I'd shut it off to cool) when idle.
I picked these guys brains and they really helped out, so I followed their advice. I can probably pull all the threads on the forum I read, but the to sum it up:
1. Dump the electrics and take them out (blocks air flow).
2. Time vehicle properly.
3. Impellar spacing (this is big...)
The thing that surprised me the most, I had some crud building on the intake manifold, so cleaned it out.

Lots of things to try and look for on our cars. See my list below. Some easy and some not so easy. For our birds I would start with HD clutch fan since you have the issue at idle. Make sure you have the shroud in place too. At the some time I would also clearance the WP divider plate. Lots of post on this one over at the PY site.

The 350 cars didn't have the bat wing baffles on top, (not sure the correct name) but it doesn't mean you can't add them. That and the rubber diverts that force the air flow threw the radiator instead of around the radiator.

One thing that I will say about the HD clutch fans. They will move some air. Growing up on the farm and pulling into a gravel driveway you will get a nice plume of dust under the car on a dry day just from the air flow. You don't get this from an electric fan.



*Clogged/Dirty Radiator not flowing properly - radiator flush
*Collapsed hoses (needs a spring).
* Blow-by finding it way into coolant->Causes foaming->drastically reduces heat transfer (Do a Pressure Test) Blown head gasket for example.
*Divider plate clearance appropriately
*Test thermostat in boiling water
*Air pockets? Drill 1/4 hole in thermostat to pass air pockets.
*Type of impeller - Cast is always better and not all cast impellers are the same some are deeper then others.
*Fan shroud in place? air dams in place? baffles in place? Fan clearance around fan shroud
*Temp infrared gun can be a great troubleshooting tool- compare input temp to output temps of the radiator and look for cool spots or hot spots. Can be used to compare accuracy of gauge/Sender.
*faulty gauge - A second gauge check is always a good idea
*clutch Flex or Electric - Its tough to beat a good factory 7 blade with HD clutch.
*If electric - is your fan a puller or pusher? pusher fans are not good ,they also block radiator
*rich or lean carb setting.
*Vacuum leaks cause lean conditions Carb bolted down? Orange intake alignment pieces?
*timing issue - Try simply backoff on the timing and see what happens
*Over heating at idle or driving - Generally If at idle or very low speed, then it is likely an airflow problem. If at speed, then it is likely a coolant flow issue
*Retarded cam - Cam not degreed in correctly on ILC. Read about this more then once.
*WP pulley diameter for trouble shooting
*deck height - Piston down in the hole makes for bad quench.
*8 relief pistons notorious for ping and heat related issues.
*Clutch fan test. Cold should spin 3 times or more when you shut off the motor. Hot should spin less then 3.
*Adjust Clutch fan for max friction.

http://forums.maxperformanceinc.com/forums/showthread.php?t=395910
21 Reasons why your engine may run Hot. More Racing Tips

A lean air/Fuel Ratio (Also check fuel pump and Filter)
Too much timing/retarded timin/advanced curve malfunction
Clogged Radiator/Collapsed Hose (restricted water flow)
Clogged Engine (restricted water flow)
Stuck Thermostat / Incorect Thermostat
Bad Water Pump
Incorrect Water Pump Speed (too slow/too fast)

Radiator Too Thick
Wrong Pressure Cap
No Shroud Around Fan. Improper Fan Position Within Shroud.
Bad Fan Design - Stock Factory Type Usually Works Best.
High Volume or High Pressure Oil Pump
Electric Fan (Pullers/Pushers) Blocking Air Flow
Too Much Antifreeze
Wrong Type Antifreeze
Flow Test: Begin with cool engine. Remove radiator cap. Start engine. Bring engine up to operating temperature so that the thermostat opens. Increase engine speed to 2000 rpm. If water gushes out of radiator there is a flow restrictionin the system. This must be corrected for proper cooling.
Wrong Spark Plugs (ie. Heat Range)
Wrong Gasoline Type (Try 89 or 92 Octane)
Clogged Catalytic Converter.
Clogged Injector System.
Exhaust getting into the water due to a cracked head or blown head gasket. Have your local radiator shop test your system for carbon dioxide.

I have electric fans on mine, I wouldn't take a stock fan off and put on electric but they were there when I bought the car. I've sat at traffic lights idling in 105-110 degree temps with no overheating issues. I have 10.5:1 static compression ratio and idle at 550-600rpm. If they work on mine they should work on yours.

That's a pretty good list Rohrt posted of things to check. If the cooling system is not plugged or obstructed in any way I would look for other reasons of overheating, vacuum leaks and improper timing being on top of the list. An engine with retarded timing may transfer a lot of heat to the cooling system by burning the charge as it goes out the exhaust. I've cooled idles just by switching the vacuum advance hose from stepped source to manifold source.

X2 On what Bluebird said!

I just thought of another item you could try if you went through rohrt's list and still running hot. Try an over flow tank if you don't have one. I don't know when they were first installed in Pontiacs, must be some time around 68?
The radiator is a heat exchanger, transferring some heat from the coolant to the air passing through the core fins, and works best when completely full of coolant fluid. Any air in the radiator will reduce the efficiency of the rad. The cap on a non overflow system holds coolant in the radiator up to the pressure rating of the cap, about 15-16 psi, then releases some fluid to drop the pressure below that which will damage the cooling system. Because the pressure inside the radiator is higher than atmospheric the boiling temperature of the fluid increases to about 245 degrees from the 212 degrees of water at atmospheric pressure. With an overflow recovery system the cap lets the released fluid back into the radiator after it cools thus always having the radiator completely full of coolant and void of air.
Make sure you get a new return style cap with the overflow tank, I run one with a 7 psi rating.

I think the bat wings he's referring to are the X panels.

Well, I believe my issue has been found with the heat up at idle. There was no diverter plate installed on the water pump. I'm also installing an insulator between the intake and the carb to prevent gas boiling in case it does ever get hot again. Thanks for all the helpful suggestions!!!