Car guys, help needed; heater issue

Discussion in 'The Pub' started by dewey decibel, Jan 21, 2015.

  1. dewey decibel

    dewey decibel Member

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    It’s a 2001 Honda Civic EX with about 130,00 miles. Currently the heater is blowing cold at idle and under about 40mph. It blows strong, just cold air. Once I get on the freeway it blows pretty hot. The main thing is it starts to overheat (while blowing cold air), then the temp gauge will drop and it will blow hot air again. First time it did I put about 1/4 bottle of antifreeze in the radiator, hard to see the overflow tank but it was probably low if anything. Now there is definitely enough in the overflow (too much if anything) and the radiator seems good.


    What am I looking at here, thermostat? Water pump? I think I can do the thermostat easy, the water pump was recommended at 100,000 miles (along with the main belt) and I didn’t do it. I plan to try and "burp" the system tomorrow, but I really don't think air in the system is the problem. I just relocated to a different city and am jobless so I’m trying to avoid taking it in, any help is appreciated!











    unless you tell me it’s a head gasket, I don’t wanna hear that… :bkw
     
  2. Tone Meister

    Tone Meister Member

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    It'll blow cold air if the coolant is too low, so check that first because that is what it sounds like.
     
  3. SteveO

    SteveO Member

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    If the system is full of water & purged of air and the symptoms continue, the next thing to check is the thermostat. Whatever the cause, the problem is that hot water isn't flowing through the heater core (when it's blowing cold).
     
  4. figgy

    figgy Member

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    you need to change that belt. do it now.
     
  5. Woodenfish

    Woodenfish Member

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    I would be careful and have a very experienced tech take a look at it asap. I think you have a blown head gasket. :hide2
     
  6. krusty1053

    krusty1053 Member

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    The thing that concerns me is that you haven't mentioned any cooling system maintenance. Coupled with your low coolant, you could have a leak. Any signs under the car after parking?

    Check that the system is actually pressurized when hot. Squeeze a hose. If it seems soft, you still haven't gotten the air out, or your rad cap is bad and not allowing the system to build pressure. If it appears pressurized, shut the engine off and see if it remains pressurized. If it doesn't for long, you might have head gasket issues, or another external leak. First things first, though. The symptoms you describe from your temperature gauge definitely indicate air in the system. The question is - how did it get there, and where is the coolant going? You need to do a thorough leak search to rule out a leak vs. a simple bad rad cap, and hope it is not an internal engine leak. Pull your dipstick and check your oil too for signs of coolant.
     
  7. SteveO

    SteveO Member

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    A blown head gasket that causes enough coolant loss to affect the heater operation is pretty easy to spot-there will either be so much steam pouring out of the exhaust pipe that you would notice it immediately, or checking the dipstick the oil will look like chocolate milk (from the water). If there's no steam coming from the exhaust and the oil looks good on the dipstick, chances are very slim that the head gasket is an issue.

    However, if the car overheats enough the head gasket will eventually blow out.
     
  8. ScioBro

    ScioBro Supporting Member

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  9. krusty1053

    krusty1053 Member

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    Depending on the stage or degree of gasket failure, the most serious symptoms may not be as obvious as that.

    I had a BMW many years ago that blew a head gasket. There was no steam in the exhaust, and the symptoms were much as the OP described on his Honda. I topped the coolant up many times, couldn't get it to retain pressure or blow hot air, couldn't seem to get all the air out, etc, etc. Eventually I found traces of oil in the coolant and changed the head gasket. That solved it. As an aside, changing a head gasket on a 7-series outdoors at -20deg is no fun. I could turn one bolt at a time, and run into the house to warm my hands in between.

    Note to the OP - Next time you change your timing belt, change the water pump too. It's right there, driven by the belt, and is trivial to change at that time. Ignore it at your peril (ask me how I know). Their water pumps typically have bushings rather than bearings, made of oil impregnated bronze that gains good lubrication from the coolant itself. This design is simple, generally very reliable, and cheap.
     
  10. krusty1053

    krusty1053 Member

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    The big question is the apparent loss of coolant. Perhaps this is a red herring, and the OP simply topped it up (too much, perhaps) and it wasn't really low. In that case, the thermostat is a definite suspect.
     
  11. cram

    cram Member

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    I'd check the thermostat first .
    it's the most common problem for a car of that age in this area of concern.
    I've replaced them on a gti and a prelude back when I drove those cars.
    It's likely corroded so it cannot expand to let flow through to the heater coil.

    If you find that to be the case it's not that expensive for a fix.

    Run through the lines in your coolant system. You could have old hoses or something bigger that's a problem.

    All of these things are the result of long miles and built up corrosion.

    Those are my first thoughts when reading the op.

    (if you change your oil and you see normal conditions there in the fluid, none of the headgasket issues are likely present - you can bridge between the coolant/oil and that's where problems occur...)
     
  12. radicool

    radicool Member

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    Even unemployed, you can probably afford a new thermostat, so try that first. Every time one of my cars has had your car's symptoms, it was the thermostat.
     
  13. GasMask

    GasMask Member

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    A bad thermostat will cause the exact symptoms you describe. It's an easy cheap fix. You can also try (as a diagnostic measure) simply removing the thermostat, and see if that fixes the problem.
     
  14. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    Don't overheat that puppy, you'll warp the head :mad: Then you'll be in for a lot of expensive repair.

    1. Check coolant level.

    2. If that is ok, change thermostat.

    3. If level is low, find out where the cooant went and fix that.

    A. leaky radiator
    B. leaky hose.
    C. leaky waterpump.
    D. Leaky heater core or hoses.
    E. Head gasket.

    E1. If head gasket is sucking water, you'll probably have steam coming out of your exhaust and water in your oil (oil will look like runny brown poo).

    I think that about covers it.
     
  15. dewey decibel

    dewey decibel Member

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    Thanks for the responses. I haven't seen any sign of drips under the car (should be easy to spot with the snow). The overflow tank was really full a couple days ago, now it's down to normal levels. The radiator (when cold) was low so I put another 1/4 bottle or so in and drove it for 20 minutes- once it got up to temp it put out heat fine and the temp gauge held steady. So I guess I got a leak somewhere...

    I need to find a hill so I can try and get the air out of the system, but since it put heat out pretty steady after I topped the radiator off I don't think that's it. Checked the oil after and it looked normal, no water coming off the exhaust.


    I told you not to tell me that! :bitch:D
     
  16. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    That's good. It sounds like your thermostat is sticking and overheating the engine causing it to overflow. I'd replace that and then top it off .... see how that works.
     
  17. dewey decibel

    dewey decibel Member

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    OK, since I topped off the radiator (that last post) the car has been running fine- steady heat and steady temp. I was going to go pick up a thermostat today but figured I'd check the radiator first, and it's low again. The overflow is about where it was last week (a bit over maximum). I haven't seen any sign of a leak under the car, the area around the hose with the thermostat housing is messy, but not any worse than the rest of the block. If the thermostat is stuck closed would the radiator purge it's self when it's too hot, which would account for the loss of coolant? Or does it get sent to the overflow? I guess I'm confused as to how the system works. There's pressure in the system as when I opened the cap I could hear the air release.
     
  18. dewey decibel

    dewey decibel Member

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    Also when I last topped the radiator off I did it while the engine was cold, so maybe it just didn't fill the entire system.
     
  19. DYNA BILL

    DYNA BILL Member

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    Just for the heck of it, feel the passenger side carpet. If it's wet, could be a leaky heater core.
    I'm not really familiar with the location of the heater core on that car though, to be honest.
    Most likely suspect would be a stuck thermostat.
    If you decide to get into it, you can test to see if it's the thermostat by putting it in a pan of water heating on the stove, and when the water temp reaches the temp printed on the end of the 'stat (usually 180 or 190) it should open up.
    If it does, that's not your problem. But since you've got it out anyway, I'd just go ahead and put in a new one. They're only a few bucks.
     
  20. DYNA BILL

    DYNA BILL Member

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    If the thermostat is not opening, there is no passage for the coolant to properly circulate between the radiator and the engine. All it's doing is circulating through the engine and heater core and back into the radiator. And since the coolant can't get from the radiator to the engine (or visa versa), it's gotta go somewhere, most likely the overflow tank when the pressure builds up enough PSI to open up the radiator cap (look at it, it should have a spring and a pressure rating on it).
    Also, it could be that the thermostat is opening, but not all the way. That would allow some cooling, but not nearly enough. You said the engine temp was holding steady. A stuck thermostat almost always makes the engine overheat.

    Edited to echo what OlAndrew said: Change the radiator cap first.
     
    Last edited: Jan 24, 2015

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