97 4Runner with no heat? (1 Viewer)

[Enginerd]

I'm hoping someone here can help me diagnose a problem with my my brother-in-laws truck.

I got a call from him this morning from Lake Placid, NY. It was about -10 and he was preparing to load up the family and drive back home (about 4 hours south). He fired up the truck and let it warm up, but no heat came out of the vents. Checked the temp gauge and it was reading where it normally does. He left the truck running while he set up the DVD player, still no heat (from either front or rear heater). Snow was melting off the hood, radiator cap was warm to the touch, and the truck was running fine. So they bundled up the kids like they were hiking up Everest and headed home, expecting to be freezing for the entire ride. A few miles into the trip, heat started pouring out of the vents.

Any idea what this could be? I would think an open thermostat would have left the temp gauge reading low, which is wasn't. Frozen coolant in the heater core surely would have cracked something. I'm stumped.

As a side note, in the summer the truck started to overheat while sitting in traffic on a 100 degree day in NYC. Once he got it moving, it cooled right down. Took it to the shop and they couldn't find any issues. Flushed the cooling system for good measure and never had another problem.

It seems to be working now, but I'm curious what could cause these symptoms, and what we can do to prevent it from happening in the future.

 

[brian2sun]

I'm wondering if maybe the valve to let the coolant flow throught the heater core was frozen shut (on the firewall side).

 

[raydouble]

How old is the coolant?

Was the coolant filled with the heater valve open?

Can you verify the heater valve works?

 

[Enginerd]

I'm wondering if maybe the valve to let the coolant flow throught the heater core was frozen shut (on the firewall side).

I'm not sure how the valve is actuated on this truck (it's not mine). If it is a direct cable from the slider in the passnger compartment to the valve in the engine bay, then I doubt it was stuck. The heat would have been on pretty high when he shut off the truck, so he should have had at least some heat, but he maintains it was ice cold.
If that value is remotely actuated using vacuum, then that could be the cause of it I suppose.

How old is the coolant?

Was the coolant filled with the heater valve open?

Can you verify the heater valve works?

Coolant is less than 6 months old. Not sure how it was filled (it was done by a local mechanic that the family has used for decades without issue). Checking the heater valve seems like the only option.

He also informed me today that is was not -10, but -27. That's cold. I'm not sure what the coolant is rated to, but maybe it froze in one of the rubber lines in the engine bay, and then thawed after 20 minutes. Seems unlikely though.

I'll have him check that valve, but the truck is not likely to see temps like that for another year, so it will be a hard situation to recreate for testing.

 

[raydouble]

That is cold.....
depending on the concentration, it could have froze.

 

[Bogo]

You can also end up with slushed coolant at those temps. That can plug up a hose.

 

[Duane]

well I would confirm the coolant level is correct and get the coolant checked to see how cold it is good for. A hydrometer was usually used and perhaps they use a refractometer now or whatever if the coolant is some other chemical makeup now.

Living in a southern part of Canada a normal mixture good for -36 to -42 or so seems to be accepted. Degrees celsius and fahrenheit are equal at -40 so shoot for that in New York state as well I would think.

I am also thinking that too much antifreeze or glycol reduces the ability to disipate heat which is a bad thing for cooling in the summer. If I lived in southern arizona perhaps the mixture is better 70%water where as up here we would use only 50% water.
Maybe double check it doesn't have too much glycol as this might account for both scenarios!
just my 2 cents