67 DeVille Running HOT

[fabbrofour]

My 429 is running real hot. I installed a new water pump, fan clutch, lower radiator hose, belts and 180 degree thermostat a couple of months ago because the car was starting to run warm. I hadn't driven it until this past week. The temp gauge is going to the 3/4 mark when I'm on the highway. In town the gauge stays just below the center mark. All the hoses, radiator and the engine get extremely hot.

I'm having problems with the heater/AC controls and I'm not getting any heat out of the heater, but I'm thinking that wouldn't cause the engine to run hot. Since both heater hoses are hot I'm assuming I've got circulation through the heater core.

I've thought of taking the thermostat out to see what that will do.  I've visually checked to make sure the lower radiator hose isn't collapsing when it gets warm and it appears fine.

I tried removing the radiator cap to see if there is movement in the radiator, but coolant just bubbles out.

Any thoughts or suggestions are appreciated.

[austingta]

Overheating on the highway is usually a water flow problem. The radiator is the first line of defense there... is it clean and free-flowing? After the thermostat warms up and opens, you should see good circulation when you look into the radiator with the cap off.

Be careful...begin with a cold engine, and take the cap off before you start it up.

[Coupe Deville]

Hello. First off I would use a thermoter like a cheap inferred thermometer, to messure the actual temp of the engine, hoses, ect. The gauge could be reading wrong but not likley. Could you have installed the therostat upside down?

[Glen]

The proper check for the lower radiator hose is to squeeze it by hand to see if it collapses.  You want to do that when the engine is cold of course.   Even though you bought a new lower radiator hose it does not hurt to check it. 

[Julien Abrahams]

I had the very similar symptoms. My first tip is: check the settings of your regulator. You can check this easily with a multimeter at the battery. Run the engine, and measure battery voltage. This should be around 14 Volts. Slowly bring up the revs of the engine, and watch the voltmeter. If the settings of the regulator are correct, it will stay around 14 volts. In my case, it would rise to almost 18 volts, indicating a wrongly adjusted regulator (took the regulator and generator off, got it checked and readjusted at a local shop for free.).
I think this because you say that the gauge reads 3/4 on the highway, and around 1/2 in town (which was exactly what my gauge was saying as well). If it would be a radiator or water pump/hoses problem, I believe it would be running hot in town and especially during idle. At idle, the only air passing through the radiator is drawn in through the fan. And although it never hurts to check, I think it is unlikely that the problem lies in the: thermostat, hose, pump radiator or fan clutch.
You can check if your water pump turns by removing the radiator cap when the engine is cold, then start the engine. As it warms up, the thermostat will open, and you will see the coolant start to move when you look down the opening. Doing this will also help remove any air bubbles that might be present.

[Jeff Rosansky CLC #28373]

Hate to say it, but make sure the fan isn't on backwards.
Jeff

[Scot Minesinger]

No warm air from the heater could be a clue.  If air is blowing across heater core for sure and valve is open, then you have a water flow problem.  Sounds like bad thermostat.  Those infrared temp indicators are handy for helping diagnose this problem.  Measure temp of water going in radiator and going out - there should be like a 30'F difference.  If real high then low flow, if not at all then no flow.

["Cadillac Kid" Greg Surfas 15364]

Richard,
The above include some good suggestions, but I would suggest before you start chasing a problem, make sure it actually exists.  Even if temporarily, install a mechanical gage where your temperature sensor is and see exactly what the operating temperatures are.  The engine itself is hot to the touch, being something over 300 degrees, and normal operating temperature of the cooling system ,190 degrees is extremely hot to the touch.
Verify the problem and quantify it.
Greg Surfas

[txturbo]

I've had this same problem on several cars in the past. If your radiator is still the original my guess would be it's partially clogged. Easy way to test it is to feel the center with your hand. Radiators tend to start clogging in the center and the clogging continues out to the edges from there. If the edges are hot and the center is cool or cold you found the problem. Second most likely cause is timing. Make sure your mechanical advance inside the distributor isn't seized up.

[Jeff Rosansky CLC #28373]

Yes, make sure the sensor is good. Make sure it is grounded properly as crap may be corrupting the ground.  If you can get the sensor out, stick it in a coffee cup/pirex measuring cup on a hotplate with a candy thermometer in there.  Compare the temps to see if it is close. 
Jeff

[fabbrofour]

Thanks for the recommendations. I think I have a plugged radiator. I started the car with the thremostat in and there was water flow, but not that much. I removed the thermostst and the water flow increased, but it still wasn't what I would have expected, however the engine did run cooler. I took it out for a drive and the temp gauge came up to center after about 15 miles on the highway. I put the thermostat in a pan of water and it opened fully as the water got close to boiling, so it appears to be working correctly.

Since I don't know what work has been done on the car in the past, I'm thinking I'll just pull the radiator and have it gone through. I't not that big of a job and at least I'll know what I have for a healthy radiator. I'm confident that the temp gauge and sending unit are working correctly, but Im going to purchase an infrared heat gun and confirm that - good recommendation. I did double check to make sure I had reinstalled the fan correctly and it is.

I don't have any heat coming out of the heater, which is another issue. I have issues with the heater/AC system, i.e. the fan will come on for a few seconds in the heat position and then cut out. The fan stays on in the defrost position but I don't get any warm air even thorugh both heater hoses are warm. I'm thinking my heater control valve isn't opening. I hope I don't have a plugged heater core as I really don't feel like pulling that if I don't have to. I'll chase that issue after I get the radiator flushed and put back in.