Hot 79

[Bill Jones]

I recently bought a 79 vette with 48,000 miles on it. This is number 6 for me. This is a nice clean car. I took it to the Palm Beach auto show last weekend and came in first place in my class. I just got back from a 20 mile trip and for the most part as long as I kept the car under 40 mph the temp stay about 180. From 50 to 80 mph the temp went up to 225 with no A/C. When I got back down to 45 mph it started cooling down. I have replace the waterpump, raditor, fanclutch, hoses, seals, 160, 180, and no thermostat and nothing has changed. I'm afraid if I keep running at 225 something will happen to the motor. I also put two quarts of 40 below. Please help. Thank you advance.

 

[JohnZ]

First, put the 180* thermostat back in - thermostats have nothing to do with maximum operating temperature - they only control MINIMUM operating temperature, and modulate coolant flow through a calibrated restriction to maintain the coolant at their rated temperature IF the cooling system is capable of cooling to that level.

Is the plastic lower air deflector panel in place under your front fascia? They're easily damaged or broken off, and they are the KEY element in highway cooling for C3's; if it's missing, nothing else you do will make it cool at highway speed. The car was designed as a "bottom-breather", and the deflector is what makes the system work at speed.

If the deflector is in place (and all the seals are in place) and you've got a correct new radiator for the application (4-row core, 26.2"x 17" core dimensions), and the coil spring is still in place in the lower radiator hose (to keep highway speed engine rpm/water pump suction from collapsing the hose), it should cool with no problem, just like it did when it was new. If the foregoing is true and it still heats up on the highway, you MAY have a head gasket problem; most good shops can test your coolant for combustion gases to confirm this or rule it out.

 

[78SilvAnniv]

Welcome to CACC Bill!

Run hot temps.

We had nothing but problems with our 78 in the summer. Winter driving was just fine, but when summer temps soared, so did my water temp! (50-60mph approx 210, >60mph approx 220+ depending on speed and duration) If I tried to use the AC it climbed to 245 in just a few minutes!

Check your fan shroud in addition to the lower air deflector.

I think we tried everything to get this vette to run lower temps.
New engine. (orig. engine also ran hot)
New radiator.
New hoses.
New water pump.
New clutch fan yearly. (9 years)
New fan shroud. (ours had a notch cut out on top from a broken motor mount)
Thermostats.
Coolant, water wetter...et cetera...

No improvement UNTIL...
...we removed the clutch fan and installed a quality flex fan. Now I have yet to reach 195 at any speed, any time of the year EVEN with AC!

I have read many posts of pros and cons regarding the flex fan, but this was the only thing that worked for my engine after trying everything else.
Heidi

 

[Bill Jones]

I've tried everything else so I will try the flex fan. My spoiler on the front is like new. I was told the flex fan made a lot of noise. Is this true and where cloud I get a good flex fan at?

 

[77-4speed]

Yup,

The flex fan is quite a bit more noisy, but it works. I bought a flex-lite fan from Oreilly's. You'll also need the adapter kit to keep the correct spacing. The folks at Oreilly's should know exactly what you need. Expect somewhere around $40 I think.

Russ

 

[DDLS3]

flex fans are available in these two places as well. You will find knowledgeable folks at either place Summitt Racing 1-800-230-3030 www.summitracing.com or Jegs 1-800-345-4545 www.jegs.com I have purchased from both and they are great folks to deal with on performance or custom parts.

 

[desertsled]

My 79 ran very hot also .(250 degrees) but only during highway speeds. our 79"s also have secondary electric fans. Make sure it works. The switch is on the pass. side of the engine just above the plugs. Pull the plug and jump the terminals. It should come on. (the fan is between the rad and the condenser.) The stock switch should come on at 225. Mine didnt work so I tried to find one but could"nt. I did find one that comes on at 170. I like that one anyway.

 

[Mako]

I'm afraid if I keep running at 225 something will happen to the motor. I also put two quarts of 40 below. Please help. Thank you advance.

Excessively retarded timing will cause this as well. If the outer ring of the dampener has slipped, which is common on original parts, you will set the timing too retarded without knowing it.

Put #1 at TDC firing and check the timing mark on the dampener, it should read 0*. You can sanity check it against the distributor rotor as well to ensure the timing chain hasn't slipped a tooth.

Good luck!
Mako

 

[vigman]

I agree with John on the stat

And the air dam....

A flex fan will pull more air at lower speeds.. but when your MOVING FAST either fan can get in the way ( as far as air flow goes ).

Make sure the electric fan is working ( if you have it) and clean the front of the A/C evaporator with soap & water ( or degreaser )

Something is blocking/ diverting the air flow.




Vig!

 

[resto75]

I have a black plastic flex fan on mine and it's quiet and always runs cool. It was on the car when I bought it so i can't take any credit for it. I was wondering why it was on there as everything else is upgraded from original such as Griffen radiator, chrome water pump, all alum custom built fan shroud, all chrome pulleys,,etc,,,so I am wondering about this cheap looking $14.95 plastic fan,, maybe the last owner knew something we don't.

 

[JHL]

If you have checked everything else out go with Mako`s tip and get the timing checked out it is usually the culprit if all else is ok. I run mine with no mechanical fan at all relying only on the original electric fan and have no problems. If you can borrow a Mityvac from some one that has the right attachments you can quickly check for head gasket problems alternatively any garage should be able to do a quick check for a few bucks and point you in the right direction.

J.