5 dec (F) outside and rad fan keeps blowing

[Ian Stock]

It's bitterly cold here in Toronto - below zero (F) some days. The engine temp gauge is at about the half way point. I'm not getting really warm air out of the heater. To make matters more interesting, the rad fan seems to be on regardless of engine temp or outside temp.

(The "Check Engine" light is on too!)

Any suggestions? I just want a warm car.

Ian

 

[Rusty]

If it's what I think it is, don't drive the car.

If there's no heat, and the blower is working, you've got no coolant going into the heater box. And if there's no coolant in the heater box, which is the highest point of the cooling system (on 7's and 9's anyway) it means you are losing coolant somewhere. IF this is the scenario, that annoying cold weather we are experiencing is the only thing between you and a new engine.

I had a similar situation happen on the first cold night of the fall 03. Turned on the heat, the fan worked but no heat coming out. Later that night on the drive home, my engine blew. I mean it was done. Melted a piston, warped the head...the works. Incredible heat builds up when you have no coolant...my electric fan stayed on trying to cool things off until the battery died. I had to install another engine. Turns out there was a hairline crack in the hot-side water jacket of the TD05 turbo. Couldn't see it when it was on the engine because it was on the bottom of the casing, and because the coolant was only escaping during driving (and instantly vaporising from the heat ), there were no drips or leaks showing. And no smell. I suppose it took a few days for the coolant to get to the point where there was no more cooling of the block, but I didn't notice anything wrong. never went under the hood the two days before this happened. No indication from the temp gauge either, which is odd.

Anyway, the Volvo system is designed with this feature; No heat when the fan is blowing means no coolant. I wish they'd put a light on the dash that goes on when the coolant gets low, but for some reason, they felt that it was better to go the way they did...

Don't drive the car until you (or someone) check out where that coolant is going. The alternative can be quite...spendy.

good luck

RS

 

[Mike F]

It's bitterly cold here in Toronto - below zero (F) some days. The engine temp gauge is at about the half way point. I'm not getting really warm air out of the heater. To make matters more interesting, the rad fan seems to be on regardless of engine temp or outside temp.

(The "Check Engine" light is on too!)

Any suggestions? I just want a warm car.

Ian

My guess it the thermostat is not closing properly. The ECU is "smart" enough to look at the coolant temperature when the car starts. It then "knows" that it should warm up after a given amount of time. If the engine doesn't warm up, the ECU doesn't assume the thermostat is bad, it assumes the temperature sensor is bad. So the ECU "thinks" it has no idea what the engine temperature is, so it turns the fan on (and the check engine light), just in case the engine is hot. The gauge you see is not really a gauge, it reads exactly in the middle for a wide range of normal operating temperatures, reading high or low only when the coolant temperature is extreme.

To change the thermostat, release pressure in the cooling system, lift up the coolant overflow bottle, disconnect the wire for the sensor and clamp the hose on the bottom of it with a pair of needle nose vice grips. This way you will spill almost no coolant. You need a long T40 torx bit to loosen the thermostat housing bolts.

 

[Ian Stock]

The car is a 1998 S70. Per comment below, there is a light that indicates low coolant. My experience is that it is quite sensitive. As soon as it's down a pint, the light goes on. (It's only happened to me once.)

Ian

 

[Fred Flintstone]

If the defroster is on, the AC is on, the radiator fan will run and the air in the car will be cooler.

John

 

[Guest]

It's bitterly cold here in Toronto - below zero (F) some days. The engine temp gauge is at about the half way point. I'm not getting really warm air out of the heater. To make matters more interesting, the rad fan seems to be on regardless of engine temp or outside temp.

(The "Check Engine" light is on too!)

Thermostat is probably ok if the temp gauge is in the middle, but the coolant temp sensor that feeds the ECU information is open or short circuit, so the ecu is unaware of the actual engine temperature- as a safety precaution its running the fan all the time.

However the ecu is smart enough to know that from air temp signals and so many minutes from cold start the engine should be at a certain temperature so is able to fuel it reasonably correctly- with help from the o2 sensor etc.

The CTS on these engines is a dual element unit, so make sure you fit the correct one.

Tim..

 

[Jim Carriere]

If the defroster is on, the AC is on, the radiator fan will run and the air in the car will be cooler.

This is generally but not completely true.

The short answer, like you say, is to try turning off the defroster.

The AC turns the radiator fan on via a pressure (or maybe temperature, I can't remember which) sensor on the high pressure side of the freon circuit. Normally, the radiator fan won't necessarily be on 100% of the time, especially in colder weather and when the car is moving, but also even if it is still.

For example, while waiting in a drive-through line on a cool day, I've heard my radiator fan cycle off for a few seconds, then back on again for several seconds.

The windshield defroster, using AC, will put more demand on the condensor since the heater fan is on high. This will probably result in the radiator fan being on full time until the car is moving with some speed.