well as some of you know I did a head, cam, intake & carb change I thought everything was good until today. I went for a ride and it started to over heat after I got up to 50 mph. slowed down to 35 mph and temp came back down to 190. I can let it sit and run for an hour and never goes over 190. No problems while I was doing the cam break in with temp. I did not have this problem until today I drove it for a short distance after I did the work and this did not happen. I checked the coolant and there was foamy stuff in the radiator. I checked the oil it looks fine no water and it is not low. Someone told me I might have a leak in the trans cooling part of the radiator letting trans fluid into the radiator and this will cause this, The engine is running fine no miss or smoke.

 

The biggest culprit for overheating while driving in a C3 is the lower air dam missing, seals around the radiator missing or damaged, and the fan clutch and shroud missing or damaged.

Make sure you have all of the above in place and operational, and you should have no issues.


-Shawn

 

I have an opening at the top where the stock air breather went and about a 4" opening at the top on both sides between the AC cond and radiator. I let it cool off and I do not see and type oil floating on the coolant. The return line inside the overflow tank had came off so when it started heating the coolant that went into the overflow tank could not get back in to the radiator. So the radiator was low by about 2-3 in. I got fed up after all I've done in the last week and just parked it in the shop.

 

I would think the foaming in the radiator would have red/pink tint to it if was getting trans fluid in it. Any chance of a head or intake gasket being placed wrong and blocking off a coolant passage?

 

No I did make sue all the gaskets were installed correct I have been doing some searching but found nothing that will help me yet. One thing I did think about was I have not put the heater on heat since I did the work and I'm not sure if the bottom radiator hose spring fell out but I should be able to tell be squeezing it I would think. Maybe I don't have the radiator sealed good enough. After all I did take the stock plastic air intake that goes over the radiator off and there is a opening there. I'm concerned about the foaming in the radiator but the coolant was low. After it was cooled off the coolant looks fine nothing floating on it.

 

No overheating problems before the swap ? Might be a timing issue, it will run hot if it's retarded too much.

 

Yep, timing will do it. Go to the link I gave you at the top of the tech and performance page. Follow it closely and it should solve your problem. Might have an air bubble trapped too.

 

You need to seal off the top and both sides of the radiator or the air just goes around the easiest path. The air needs to be forced through the radiator. The other would be the lower radiator hose. If you didn't put the spring inside to keep it from collapsing this will also cause you a problem.
Good Luck

 

I will check the timing I was going to hook up the vac advance today and set the timing but my timing light would not work. I'm still wondering about the foam. Maybe it was because the water went into the over flow tank and the radiator was low. But I had the cap off and it is good flow in the radiator I could see that. What could cause the foam if I have now water in the oil. Oil is not low, trans fluid is not low, and not smoking or no smell of coolant from exhaust.

 

Well let me fill you in today I set the timing I had to go to between 12 & 14 to reach the 36 degrees total then hook up the vac advance. Took her out and it still wanted to heat up to around 205 degrees while going 60mph drop back to below 45 mph and temp came back down to around 185 degrees. I drained the coolant and took the thermostat out and flushed everything with plain water until it ran clear. I left the thermostat out and went for a ride about 25 miles at 60 mph and it barley reached 150 degrees. Stopped and let ideal for about 10 min never went over 150 degrees. I checked the water and it was still clear and clean. I ran it hard and never went over 150 degrees. 1st gear until 6000 rpm shifted to 2nd gear laid rubber took 2nd gear to 6000 rpm shifted to 3rd gear squawked the tires. Still never over 150 degrees. I think I'm going to get a 160 thermostat and fill it back with 50/50 coolant. It does run so much better with the vac advance hooked up and the timing set. Never heard any signs of pinging or spark knock. Man I was relieved to say the least!!!!
Oh I also put the stock cold air vent that went to the air breather back over the radiator and filled the gaps around the radiator with foam pipe insulation until I can get some new foam for it.

 

Sound like your good to go. Enjoy the ride, sounds like it runs like a vette should now.

 

Your on the right track. Get a Robertshaw or Mr gasket brand thermostat. 160 degrees will work just fine. Dr rebuild has the correct seals for the radiator. They are quality seals not the cheap stuff. Eckler's has the Robertshaw part number 41794 160degrees for 17.99
Good Luck

 

Yea I'm happy now I'm going to check the water today after work and if it shows any signs of not being clear I'll drain and fill one more time. Drive it for a while and then drain and fill with coolant. I feel much better about it now though.

 

Well now what??? I took my 77 back out again and temp went to 185-195 degrees while running 60 mph. Yesterday it would not go over 150 degrees. I can let off the gas and the temp starts to fall right a way. Let it ideal and it will run at around 150 degrees. I was wondering if the radiator cap could have anything to do with it mine is 7lbs. I think I might pull it out and have the radiator rodded out. Anyone have a idea of the cost to do this I was told a local shop would charge around $75.00.

 

Get some prestone radiator flush and follow directions, Reverse flush the cooling system, Robert Shaw 160 degree thermostat, 50/50 antifreeze. Antifreeze helps cool as well as keeping your coolant from freezing. 195 is not a problem. A higher HP engine creates more heat. Welcome to the club. Think your cap is supposed to be a 16#.

 

Should I block off the heater core so as not to create any leaks when I do the flush?

 

Sounds like an air lock. Turn heater to max heat when doing your next coolant top-up and make sure you eliminate air lock.

 

No, a flush should not cause any leaks.

 

I always thought a flush was some type acid cleaner that might eat through the heater core or radiator.

 

Well today I bought some Prestone Super radiator Flush I will flush my cooling system check for leaks and see if it works. I looked in the radiator while I was running it today and could see where some of the tube were not flow water as good as others. I did not fill the system up all the way with water and the top 2 tubes were flowing water better that the ones below them. If the flush does not work I'm pulling the radiator out and having it rodded out and redone. One of the 2 will bring my cooling system back to where it needs to be to keep my 77 running like it should NOT OVER HEATING!!!! I'm also installing a new 16lb cap to replace the 7 lb one on it now.