Just replaced the radiator on my 71 with a Heavy Duty 3 row model. Ran it today for the first time and it still seems to run hot. Temp gauge says around 210 degrees. Water is actually boiling in the radiator after I turn off engine. I replaced thermostat before radiator because I thought it may be that. The radiator I replaced was a Heavy Duty 2 row type. Engine is a 1969 350 4bbl. Could it be that I put a thermostat that has the wrong temp setting. Not sure which one I put in at this point. Any help is apreciated.

Your thermostat isn't in upside down is it? Get all the air out? 220 is hot 210 isn't as bad but still not were I like it

Your thermostat isn't in upside down is it? Get all the air out? 220 is hot 210 isn't as bad but still not were I like it

Not in upside down. What do you mean by get all the air out? I ran the car with the defroster on high heat until it was blowing very hot air then made sure the radiator was full. It's a good 50 50 mix of antifreeze and water. I am confused. I am not losing any fluid and there are no leaks anywhere. New upper and lower hoses.

did you change the cap when you changed the rad? it could be that the cap is not allowing pressure to build up and letting the water/coolant boil. and you could also take the thermostat out and check to make sure it is opening all the way just out it in a pot of water on the stove, it would also be handy to have a thermometer to see exactly at what temp it is opening.

If the water is really boiling like you said, then you have a pressure prob in the cooling system. (not holding pressure, rad. cap seal leaking air, hoses leaking air, etc)

water boils at 212* at sea level

Water under pressure boils at a higher rate. The cooling system should be between 14-18 psi

that's 254* to 266* before water will boil at sea level with 14-18 psi system.

Then anti frezze added to that will increase the boiling point more.

Now to answer your question....
What's too hot? Ask 50 people and you'll get 50 answers.

I would say 240-250* is too hot.. It's not the temp you want it too run, but a temp that is too hot.

some say as cool as it will run is good, I like 185-195*. This temp has been proven to make the best power, and longest engine life.

Some stock from factory cars will run hotter than that though, in the 200-215* range. So I say 180-215* is the lowest and highest ends of the scale you really want to be on

what type of fan are you using (that might be your prob)

OK, Thanks so far for the advice. Here is what I have found and done to try to correct the problem. I found that my radiator cap rubber was split so I replaced it and also noticed that my fan clutch was not pushing the fan fast enough. I replaced it and between the two the car run a little cooler. The radiator does not boil over now but it is still running about 210 on the highway but cooler in town. Town hangs around 200. The fan is the factory fan setup. Using a factory fan shroud. May tear the thermostat out and make sure it is a 180 temp stat. It may be a 190 but not sure.

what temp gauge are you running? It might be as simple as a mis-calibrated gauge.
Even if you have a 190* 'stat in there, you should be running 190* down the highway as long as you are at a reasonable speed http://www.nastyz28.com/ubb/wink.gif.

<font face="Arial,Verdana" size="2">Originally posted by BluEyes:

Even if you have a 190* 'stat in there, you should be running 190* down the highway as long as you are at a reasonable speed http://www.nastyz28.com/ubb/wink.gif. </font>

Not true. My car runs about 200 all the time and a little higher on the high way, but I also have 4.10 gears.

I've got a stock gauge with a new sensor.

Have you checked your waterpump and belt?....it could be slipping.

I have two temperature gauges on mine. One sender is in the driver's side head and that goes to an aftermarket gauge which reads about 185 - 190 after warmup. The other gauge is a factory gauge in the cluster and the sender is in the intake near the 185* thermostat. The factory gauge runs around 210 when warmed up.

<font face="Arial,Verdana" size="2">Originally posted by 71cmro:
I've got a stock gauge with a new sensor.</font>

What did it run at BEFORE you replaced the sensor? What I am getting at here is that your resistance sweep could be the wrong range for your gauge. I've got one like that in my big block because I couldn't get the one out of my small original block's head without destroying it. I would run a mechanical gauge and see what it is REALLY doing. You could be at or below your target temp and never know it with the wrong sensor. My factory gauge reads about 15º higher than the mechanical gauge does.

Hard to tell what it was before I replaced the sensor. It began occasionally boiling out of the overflow on highway trips when I kept it at 75-80mph. I then installed the factory gauge cluster as part of my restoration and then got a picture of the temperature. Right away it was reading 210 on the highway with a new thermostat. This was my starting point before replacing the 2 row radiator with the 3 row. Hopeful that this would help and it did a little but not as much as I thought. Still boiled in the radiator until I replaced the radiator cap and the fan clutch. Now it is running a little cooler and I noticed that the temperature in town rises and drops and I atribute this to the fan clutch doing it's job. But on the highway it is still reading 205-210. If these traditionally read a bit on the hot side then I think I am ok but the engine just seems so hot as compared to my other cars after I drive them.

Have you checked your ignition timing? Make sure it's not too advanced. Make sure that you have no vaccum leaks. This could lean you out to the point where it would make the engine run hotter. If there are no leaks, check the carburetor calibration.

If you have detonation, then this is mostlikely the reason why you're running a bit on the hot side.

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Gordon

1979 Camaro Berlinetta

Is the waterpump airbound? Sometimes it takes awhile to purge the air. I drill a single 1/8 inch hole in the stat (outer fixed edge of stat) this helps to purge air from the system when the stat is closed, it also reduces the over - under shoot when the stat is opening.

I checked the waterpump and the air holes are clear. I am not comfortable adjusting a carburator. If anyone has any advice on adjusting a 1969 4bbl rochester quadrajet then I am all ears. I looked for vacuum leaks but could not find any. My car does seem to run a bit lean. Strong smelling engine.

Qjets are fairly simple to adjust. If you have a Haynes manual then you can look it up in there. Basically there are two needles at the front of the throttle body that adjust your rich/lean mixture. You can't really see the needles as they are sorta deep in the holes but they are easy to locate. You will need to pick up a carb adjustment tool to fit the heads on the needle screws. I got mine at Pep Boys with 4 different style sockets for under ten bucks. Turn clocwise to richen the mixture, and counter clockwise to lean it. Only turn them about 1/8th-1/4th a turn at a time.

What about running a even cooler stat? say a 165?

Do you have any antifreeze mixed in with the water?

You do have a fan shroud on right?

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71 RS/SS 350
Yes I drive it and I don't treat if very well when I do!

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First off, I would not be too concerned about running at 210deg. A stock 85-96 Vette will run about 220. Technically speaking (from a thermodynamic standpoint) you want the engine to run as hot as possiable to improve combustion efficiency.
As long as the coolant temp stays below 250 deg and you are not pinging than nothing is being hurt.

That said, I find that 90% of the time a car is running too hot on the freeway that there is a vaccum leak somewhere that is making the engine run lean.
Your engine fan has zero effect on the tempature of your engine over about 20MPH.

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1971 Camaro
383 stroker ~500HP
M21 4spd
12" brakes
16x10" Wheels
Autocross competitive
Engine Designer - The Speed Merchant, San Jose, CA
http://www.speedmerchant.com/

To answer a few questions, I do have the fan shroud on correctly and I have a 50/50 mix of water and antifreeze. I took the car on a 200 mile round trip this weekend and while the needle kept hovering at 210 on the highway it did not want to spit out anything out of the overflow bottle as it did before I changed the radiator, fan clutch and radiator cap. I am beginning to think that I must have a vacuum leak somewhere and I know my carb needs adjusted. I just need to find out how to adjust it without throwing it out of wack. I have always noticed that it is very strong smelling of gas but more like burnt gas. Not straight gas lying there. I also notice that it tends to want to bog down a bit when I take off. Not too bad but enough to notice. I may need to go ahead and replace the vacuum hoses just to be safe and if anyone can provide any more advice on adjusting the carb then that would be great. Thanks to everyone so far who has put in their 2 cents. All worthwile advice.

I dunno, but i was always told and brought up with the notion that running cooler makes more power, if i was running 210 i would be seriously worried about it, i think thats just too hot.
In my 78 Z which has a 355, i run a 165 t-stat. granted in the fall its pretty cold blooded.
but on a hot humid summer day she never even gets close to 200, more like 185.
If you get the chance run your car on a cool foggy night, it will run smoother cause of the the moisture in the air, after a rain.
This ain't B.S., you try it for yourself.
Just my .02!

Here is where I am at this point. I replace the vacuum lines on my Carb. I took the thermostat out to be sure of what it was and it was installed right but it was a 195 degree thermostat. I tossed it and put in a 160 degree stat last night. I won't be driving the car in the winter time so the extra heat is not necessary. Tonight I will take it out and see where it is temperature wise. I will also attempt to adjust the carb when I get back from vacation since I feel that it is running too rich.

I'm having the same problems except I'm using an Edelbrock carb, 3 core stock radiator and electric fan on a 355 c.i.. Mine runs about 205 but when I shut it off, go into the house and drive it again it gets up to 220, then when I shut it off an let it sit it'll drain the battery cause the fan kicks off at 200. lol

I'm going to try some of the things people here suggested tonight.

I'm running about 13 degrees BTDC so I'm going to change it to 10 and richen up the mixture, burp the radiator and see what happens.

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Tommy

Cats...the reason God created water.

75 Camaro
78 Camaro
80 Camaro
81 Trans-Am
87 Iroc-Z28