This morning it was teeth chattering cccccold, about -5F.

My 92 745 started right up, and came up to normal temp on the gauge, as usual but when I turned the heater fan on, only cold air blew out. I drove several miles (freezing) then SUDDENLY, the heat starts to flow. Normally, the heater blasts the heat right out, after about 5 minutes it is fully warmed up. Not today, it was about 20 minutes, and the whole time time the temp gauge right where it is supposed to be. I am puzzled.

Normal coolant level in the overfill tank (about 1/2 full), no coolant loss, hoses good, coolant flushed and replaced Nov 2003. What gives???

I would appreciate any thoughts as I am not looking forward to another morning drive like today, it will be even colder this weekend. BRRRRRRRRR.

Thanks for the help

Steve Martinsen in CT

Check the vacuum hose going to the heater control valve. Old cold hose, split end, and not pushed on all the way, could cause the problem.
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Tom F. Couple of Volvos Mods, RainX & cup holders.

While you're checking the valve, feel the heater core hoses at the firewall. If one hose is significantly cooler, your heater core is partially blocked. This can often be cleared by disconnecting the hoses and reverse flushing the core with a garden hose.
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Paul NW Indiana '89 740 Turbo 110,000

I used to think CT was cold until I moved to MN.

Have your antifreeze checked, it may not be as good as you think it is. It should test at -32. If a hose froze up, that would explain it all. You should get a flush every 2-3 years.

Klaus
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98 V70Rawd(101Kmi), 95 854T(85K mi), 75 164E(173K mi)

Yea you are getting the leftovers we had from last weekend! You think its cold now how about trying out some MAN SIZE COLD! So far we have endured -37F where I live (by Mora MN) and its enough to make the biggest guy run for the house and thaw out those..... .. you know the ones that shrivled up into almost nothing! I now own many acres of mixed land and had a tree split from the cold on saturday morning when it was -32F. Sunday brought -37F and no pressure from my propane tank. The good thing was my diesel 760 started after being outside all night however coolant in the radiator froze leaving me with a blowtorch defroster and over 100 miles of driving on a 3/4 hot temp gauge.

Now my question for you is do you have the automatic climate control or the standard system? Mine has the auto climate and a theromstat that keeps the blower from running when the interior is below +50F, turning on the defrost solves this problem but its an annoyance. Another remote idea would be an air pocket in the heater core that is locking the coolant away and the third idea barring the simple things like split hoses or other vacuum losses would be a frozen core. When water/antifreeze gets to the critical temp of actually freezing the glycol compounds seperate out and away from the forming ice crystals and settles to the bottom. Once the ice crystals melt the water will remix with the glycols with no problems in itself, not sure about the device that it froze in however. An idea would be to use a hair dryer or other heater rated at 1250 watts or better and place it at the air intake for the interior and set the blower to the low position if you have the manual climate control. If its automatic use the defrost setting to start the blower motor. It might take a while to melt any ice thats present in the heater core but it sure beats freeze driving. This is how I thawed out my radiator however I used a 15,000 watt generator load bank on my second go-around and simulated a 110 degree day of hot air blasts. Sure took care of those snow boogers in a hurry. Only cost me 3 gallons of diesel for the generator and a half hour of cursing because my fingers refused to move while making electrical connections... I'm really nuts now!

988