Hello Everyone,
Hope to find some help. Got a 79 Vette with a 350 c.i. and it only overheats on the highway if going faster than 55 m.p.h. In town no problem. Owner before me took off the snorkel from the radiator to the air cleaner and this being my first Vette I am not sure if I am missing and scoops. Should there be one under the front end? Any help would be great!!! :confused:

 

Could be a few things. Yes, there should be a lower front valence (rubber) that directs air into the radiator. Also, the fan shroud should be in place and not cut. By not having the snorkel, air can now pass over the top of the radiator, instead of going through it. Another possibility is that the radiator could be clogged, or the carb could be jetted too lean.

I don't have the snorkels or foam on top of the radiator and I don't have a problem. However, I used to have a problem above 65. I found out that the radiator had not been flushed in who-knows-how-many years and the bottom half was filled with crud. There is no way to really tell without opening it up.

By the way, welcome to the forum. How long have you had the 79?

 

Thanks for the post!!! I was leaning towards the radiator as it looks somewhat crusty but had many people saying it should'nt be overheating on the highway but I don't think they realize the rake on the radiator. I suppose it would not have to be very dirty to cause overheating if very little air is actually going thru it.
I have had the car 6 years. A birthday present for my wife. Hope to give it some TLC this year. Is still in storage as we still have over a foot of snow.

 

How long has it been since you've changed the coolant? Yes, the vettes have a big problem with overheating because there is such a small amount of space for the air to even get to the front of the radiator. That's why all of the rubber and foam pieces really need to be in place. I'm sure my temps would drop if I put the foam on top to replace the snorkel intake that I removed. But mine's really not bad anymore.

 

start with the basics :yesnod: do a coolant flush first , bet there is a ton of brown water in there:smash:

 

I had the same problem with my '79 L48 as well...especially in summer with A/C on. Replaced the clogged radiator and put in a new water pump and went to a flex fan. Ended up putting a 195 thermostat back in because it ran too cold in the spring and fall. I've had this combination for several years and it works great. Good luck.

 

I went through hell chasing the same overheating problem in my BB, Follow these steps and you will solve the sucker.
1) Check your timing, if it is off it will cause overheating at HWY speeds
2) Make sure all the seals are installed around the Rad, the 1/2 inch water pipe insulating tubes sold at all harware stores work great for this
3) Flush your rad and fill with 50/50 anti-freez and use distilled water only
4) Make sure the small chin spoiler is installed just under the front nose
I will bet your life this will solve your overheating.

 

I had the same problem on my '79. It was the fan-clutch.

 

Look for belt slippage, a dying water pump, bad hood seals, air in the system, bad fan clutch, etc. I'd start by:

1. Flushing the system and then burping it of any air. To do this, jack up the front end, open the radiator cap, and let the car run for fifteen minutes. Also, squeeze the top hose a few times to purge the air.

2. Test your thermostat also. To do this, get a thermometer, I like yeast thermometers the best, and then heat some water. Watch for at what temperature the thermostat opens.

3. Double check the quality of the fan clutch. It should freewheel when cool.

4. Test the quality of your water pump by pinching the upper radiator hose with your hand, while the engine is running. You should feel pressure build.

5. Make sure all your hood seals are present. And yes, the rubber air scoop at the bottom of the nose is very important.

6. Make sure your radiator is clean and free of leaves, etc.

Good Luck! :yesnod:

 

This may not be your problem, but I encountered a problem with overheating in my 75...turns out that the rear wheel bearings didn't have enough grease, and I broke a spindle soon after I bought it...there was too much friction and drag from the wheel bearings...which actually caused the wheels to lock up at about 5mph after driving on the freeway for only about 10 min. When the bearings cooled down there was no indication of a problem, suspected brakes and overhauled them.

Just a reminder that overheating may not be due to cooling system if the engine is working way too hard.

 

Mighty Mouse,

The #4 above is very likely the cause of overheating on the highway. Do that first and try it again, bet it works.

Chris

:flag

 

I thought I needed a new water pump, but here's what I did:

1) Flushed the radiator (mine was still in good shape)
2) Replaced radiator seals (I have a Bubba tip for this one)
3) Checked fan clutch (when warm, turn off the car and watch the fan, it should only spin 4-5 times before stopping)
4) Replaced Tstat with 160* Tstat
5) Filled radiator with 85% Distilled water and 15% anti-freeze
6) Added one bottle of Water Wetter

After this, my car wouldn't run OVER 160* unless I was sitting in traffic here in Florida in the dead of summer for an hour, and then it got up to 200. I switched to a 180* stat because the car ran TOO cool.

Here's the Bubba tip for the rad seals. If you have removed your snorkel for your air cleaner (which I have), I got a piece of 3" foam rubber pipe insulation from Home Depot, cut it the width of the radiator, and squeezed it down between the radiator and the radiator support, running the complete length of the top of the radiator. This seals it up well, and does not let the air go up and over the radiator. Because the pipe insulation is foam rubber and the width is greater than the width of the gap, the radiator support is able to hold it in without the use of any adhesive. If I ever want to remove it, I can just pull it out. Just a Bubba tip that actually works pretty well. :D


[Modified by 79MakoL82, 8:04 AM 4/4/2002]

 

Want to thank everyone for posting. I've learned allot and feel better about getting the info from Corvette owners as these babies are like no other. Just found this forum last night and I am very excited to be able to tap into your knowledge to acquire some of my own. This is an AWESOME forum. Thanks again everyone!!! :reddevil

 

Can anyone post a picture of this chin spoiler? I dont think i have one and I'm encountering the same problem.!!!

Thanks!!!!

 

I had the same exact problem with the 350 in my '73. The temperature would slowly creep up to about 210 degrees while driving on the freeway, then would cool down to about 175 while idling or driving in slower traffic. I had heard from a friend that the problem was most likely the OEM fan clutch which is designed to turn the fan at only about 60 percent of engine RPM when fully engaged. The result is that the fan ends up actually blocking air thru the radiator at highway speeds instead of pulling it thru. I installed a Flex-a-lite thermal fan clutch which is designed to turn at about 90 percent of engine RPM when fully engaged, and I also dumped a bottle of Red Line Water Wetter into the radiator. This seemed to solve the problem. Hope this helps.

Bill

 

Funny, I don't have one, but no overheating problems either.. then again I have the clutch fan adapter so no clutch, so at highway speeds (damn 4.11) the fan is spinning over 3200 rpm rock solid...
I'd like to see a good pic of one installed too tho!

 

Why do you think it is overheating? On a hot day with a 192 thermostat, and the system pressurized at 14-15 pounds, a 210 reading on the gauge at highway speed is not unusual.