I have an '89 Cadillac Brougham (RWD with the 307), and a few years ago I installed a digital coolant temperature gauge. Over the last few months I've noticed the engine temperature has been higher than normal.

The temperature usually sits between 200º and 215º, but when I get into traffic or drive below 35mph, it starts spiking to around 250º. Sometimes, the temperature will also start climbing when I'm driving with the throttle part way open, at highway speed; if I get out of the throttle or accelerate, the temp goes back down.

So far I've replaced the thermostat, radiator, pressure cap, heater core, and fan clutch. I checked the lower heater hose, and it felt firm at both ends, but I couldn't really get a good grip on it. I also checked the water pump, and it is not leaking.

I'm planning on flushing the cooling system and replacing the thermostat (just in case). Is there anything else I should check?

 

Start the car cold and remove the radiator cap. Look down into the radiator and see if the water is actually circulating. Also look for bubbles. Does the car run right? Has it lost power?

 

Just a thought, but the 307 had a lot of EGR and that is factored into the timing curve. The EGR tubes frequently clog up. It might explain the running hot at part throttle.

 

When it gets hot at idle, see if a rag will get sucked up on the front of the radiator. If not, the the fan isn't pulling enough air through it or the fins are plugged. Is there a fan schroud on it?

 

Any way to confirm that the gauge is accurate and that it is really overheating?
Do both heater hoses get hot with the heater on? Use an infra red heat gauge to check these not your hands.

If the car sits for long periods also check for cold spots in the radiator with an infra red temp gauge indicating blocked tubes. The radiator has been replaced but increasing temp going on a highway is often a radiator problem.

What anti-freeze/water ratio are you running? Too much anti-freeze reduces heat transfer. Don't exceed 50/50 unless you must.

Does it have a heat riser valve on the exhaust manifold and if yes, does it open?

 

Thank you for the replies...

oldcutlass:

The engine has never run perfect in the five years since I got the car. Almost every time I drive it, the check engine light comes on (the only trouble code I get is 45- rich fuel mixture). I've replaced the plugs, wires, O2 sensor, fuel filter, and vacuum lines, so the carburettor probably needs to be adjusted.

I have not noticed any change in the the engine's power or idle quality, since the cooling issue started.


captjim:

How would I go about checking or cleaning the passages for the EGR?


M-14:

Yes there is a fan shroud. There is also an air-dam under the car, but it has a few cracks in it; the car is so long, I have to curb the tires to fit into parking spots, and the air-dam usually hits the curb.


Sugar Bear:

I use Prestone 50/50 mix.

The gauge seems to be accurate at 150º, which is the temperature the Electronic Climate Control allows heated air into the cabin. The gauge usually reads around 210º, and I've been told that 210 is normal operating temperature for the 307.

However, on the few occasions that I allowed the temperature to rise to 260º, where the gauge maxed out (and the factory warning light was set to come on), the engine never boiled over. The coolant in the expansion tank was only to the "Check Hot Line," and there was nothing steaming or sizzling. So I don't know if the gauge loses accuracy at higher temperatures.

The sender for the gauge is where the factory temperature sensor was, so the warning light is disconnected.

Also, there is a heat riser on the exhaust. It's been a while since I checked the THERMAC, so I will look into that.

 

When its hot does the fan clutch feel loose or tight? When you rev it up, does it move alot of air?
Egr shouldn't be causing an over heatng, esp at idle b/c it should be open.
Get it hot at idle, then take a water hose & rinse down the raidator, does it cool down? To me it sounds like your ok when your moving w/ plenty of air flow.

 

I just put in a new thermal clutch the other day. I replaced the original clutch in November (because of the temperature spiking at idle), and temperatures were running normal until mid January, when I started having the same problem. After replacing the new clutch, I'm still having the same issues.

I checked the one I just put in. With the engine idling, I could not stop the fan blades with a piece of cardboard. When I stopped the engine, the temperature was reading 230º, and when I spun the fan blades by hand, they only freewheeled a quarter of a turn.

I've heard mixed opinions about how much the clutch is supposed to freewheel when hot. Some say it should not move at all, and others say no more than one full revolution. With the engine and clutch cold, the fan only freewheels about a half of a turn.


I live in Ohio, and it only in the 20's outside (it was 61 on Tuesday). If I rinse off the radiator, do I need to worry about it icing over? Or would the heat of the engine dry it before that happened?

 

No, it'll dry quickly. What you want to see is the temp drop when you do this.
Anotherthing you can check is a build up of debris between the radiator & the condensor.
Sounds like the clutch is ok. Does it really blow air when you rev it?

 

Do you have anyway of checking the temperature with another gauge or infrared thermometer to confirm that it is overheating?

 

Unfortunately, I only have the one gauge. I don't have an infrared thermometer either, but I can get one.

 

I took the car out today (its only driven once or twice a week), and took the radiator cap off while the engine was idling; I couldn't tell if anything was circulating, because the engine was vibrating the fluid too much.

I took it to a dealership to have the coolant flushed, and had their tech pressure test the cap and inspect the belts and hoses. The cap and belts needed replaced, but the hoses were fine.

On the drive home, the temperature mostly stayed between 180º and 205º. Once or twice, it spiked to around 250º, but immediately dropped (before, it would spike to a high temperature, and stay there). When driving in traffic, or below 35mph, the temperature did not rise above 210º.

I don't know if these temperatures are normal for the 307, but this is the pattern of readings I've been getting since I installed the gauge about 3 years ago.

 

Normal temperature is that it should hit the thermostat temperature (spec is probably 195°) and stay there like it's glued.

With the oscillations you describe, I would question how well the thermostat is working, and whether there is any air trapped anywhere.

I have no specific experience with the 307, so I'm afraid I can't comment more specifically.

- Eric

 

The thermostat for the 307 is a 195°, and the operating temperature isn't supposed to match the spec on the thermostat. It's supposed to sit about 10 to 15 degrees above the thermostat spec.

I replaced the thermostat a little over a year ago (when the radiator went), and I noticed no difference in temperature readings; the engine still ran in the same range.

That being said, I agree that the wide range of temperatures, indicates that the thermostat could be getting a little sticky (or was defective from day one). It'll be the next the thing I put in.

 

Who told you that? It's not what I've ever experienced.

- Eric

 

The 195 degree spec is a minimum operating temperature of the engine. Some engines will maintain that temp and some won't. If it's rising and falling really fast then you have an air pocket in the system. If the engine runs like crap, and you have a check engine light, then there are other issues causing your hi temps.

 

Temps of over 230 are not normal for the 307. Mine stays right at 180 and has never gone above 200 that I remember.
Do get an infrared thermometer and verify your gauge.
When the car is idling and running hot, pop the hood and make sure there is a roaring sound from the fan and enough airflow to muss your hair up when you poke your head under the hood.

 

Hair?