Freightliner classic no heat

Discussion in 'Freightliner Forum' started by Zeeny, Oct 24, 2014.

  1. snowwy

    snowwy Road Train Member

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    your going to have a hard time with heat at 150 degrees. you have heat while driving down the road cuz the truck is running hotter. probably around 180.

    the hotter your water gets, the better your heater. also, what's your idle. should be at least 800 rpm.
    is the radiator fan running? that'll keep it cold. shouldn't be on at all. and probably won't come on period, in the cold temps. the heater alone does a good job at cooling the cooling system.

    you need to get the water up to 180 to see how the heater works, before diagnosing anything else. unless you also have other issues that are evident along with your water temp.
     
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  3. GrapeApe

    GrapeApe Road Train Member

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    150 is a bit cool, but should give you warm air. Make sure the coolant is full, our 2000 Classics with C15's lose heat at idle just before the low coolant light comes on. The way they're plumbed, they get air bound easy. The hot/cold valve under the heater core may also be plugging up restricting flow. At higher RPM, you get more flow.

    Try this: With the truck warmed up to 150, turn on the heat then rev it up. If you start to get heat before the engine temp rises much, then you have a coolant flow issue. If the coolant is full, check for restrictions.
     
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  4. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    if I read post correctly.engine temp.is not going above 150?If so,thermostats are issue.Have also found that Classics have a tendency to clog heater cores more than other trucks.good luck.
     
  5. Zeeny

    Zeeny Light Load Member

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    Nov 16, 2013
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    No it gets hotter than 150,when your going down the road it will operate normal 180 or so
     
  6. Freightlinerbob

    Freightlinerbob Road Train Member

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    With the truck aired up and everything quiet, run the vent knob or lever through its various positions and listen.

    Can you hear the various flaps opening and closing?

    Sometimes when the control and various cylinders start to wear out, it will close all flaps but driving down the road things shake up and magically open up.

    Having a similar issue right now on my Columbia.
     
  7. xsetra

    xsetra Road Train Member

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    The only way I know of to check your thermostats is to remove them and put in and out of boiling water and watch them open and close.
    I was under bunk working on heater. I had one of my fan housings off. You could check and make sure all your venting is hooked up also.
     
  8. snowwy

    snowwy Road Train Member

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    given that my espar has decide to not function anymore. i'm left with the idle for heat now. the fan comes on with idle, cools engine to 160.

    this truck is 2 years old. have to crank up the fan to a higher number when sitting and idle. it don't push the same air flow as it does when it's going down the highway. for instance, #1 fan speed down the highway puts out more air then #4 fan speed at idle. kind of sucks when you want a/c while your waiting to load/unload.
     
  9. Crabman

    Crabman Bobtail Member

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    Nov 27, 2019
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    I have replaced thermostats heater cores and hoses and at idle the heater core goes clod
     
  10. Crabman

    Crabman Bobtail Member

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    Nov 27, 2019
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    I have replaced thermostats and both heater cores and all the hoses and at idle the heater core pipes go cold on both sides and blows cold air.
     
  11. Rideandrepair

    Rideandrepair Road Train Member

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    I noticed the same thing yesterday, however my waterpump is leaking, gone bad. Also running with cap loose. It may be because my caps loose, but I really think it’s because the impeller on the waterpump is slipping, as it’s getting worse. You might have a bad radiator cap, it takes a 10 lb. cap. But I’d suspect a slipping waterpump impeller, I’ve had them go bad in the past, without any leaking at the weephole, at least not enough to notice. After ruling out thermostats, heater cores and valves, I’d check waterpump. Take the hose off the top of it, using a big screwdriver, try to turn the impeller, it shouldn’t turn. If it turns, it’s slipping.
     
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