5 dec (F) outside and rad fan keeps blowing

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

 

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

 

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.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

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

 

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

John

 

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..

 

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.