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Pontiac Montana Heating / Cooling Problems



  • armesarmes Posts: 32
    Overheating, bad emmission readings, rough running and loss of power can be caused by several things. Having too rich of fuel mixture and liaking head gaskets can cause all of these symptoms, Are you loosing coolant from the system with or without visible leakage from the cooling system?
  • sar781sar781 Posts: 3
    No I am not loosing coolant of any kind, it just has a loss of power, and a metalic vibrating kind of racket coming from underneath the vehicle when i gas it going down the road. Engine light is on, oil is good, so is the coolant. Fuel filter has been replaced its good. Might make a note here we did move from Oregon to Oklahoma, major climate change, is there a way to reset the computer without going to find someone with a code reader????
  • ecoffinecoffin Posts: 1
    Had the same problem with my 2002 Montana. Motor was over-heating but only cold air was being blown.

    On my first visit to the garage, the mecanic said it was my thermostat and changed it. The problem went away for two weeks and came back.

    Went back to the garage and this time he flushed by cooling system. This worked for about two weeks and the problem came back.

    I decided to change garages. This time the mecanic identified the problem! There was a tiny hole at the bottom of the radiator where air was entering and thus creating a blockage in the cooling system.

    Apparently, the reason why the problem was going away for two weeks previously was that air in the system was removed when the mecanic would change the thermostat or flush the line and it would take about 14 days to accumulate sufficient air to cause the problem to return.

    I am happy to report that the problem has not returned yet. Mecanic appears to have identified the smoking gun.

    You may want to check this out (very difficult to detect these holes because they do not necessarily cause a visual leak of Prestone on your driveway).

    Best regards,

  • armesarmes Posts: 32
    You used to be able to take the fuse for the ECM ( computer ) and wait 30 seconds or so, put it back in and start/drive the vehicle for a few miles while it relearned everything. Now you have to go to the dealer and have them check/reprogram through there computer systems. Need to have engine codes read to find out what makes the check engine light come on. Most local auto parts stores will read the diagnostic codes for free. Garages charge $ 40 to $ 60 to check diagnostic codes. ;)
  • armesarmes Posts: 32
    I have a 02 that started overheating the same way. They told me I had leaking head gaskets. Spent $1300 for that and still had the problem with overheating and floaters in the radiator. Floaters turned out to be engine oil. I was coming from a small crack in the oil cooler. It was bleeding oil into the cooling system because the oil pressure was higher than the water pressure in the cooling system. They took the cooling lines off the cooler and bypassed them together. This isolated the oil cooler to oil only. After the engine warmed up, the crack opened up and oil started coming out the water ports on the cooler. Replaced the cooler, cleaned all the oil out of the cooling system ( hard to do ) and the problem went away. Cost $245 fo a new cooler. They installed it for free ( they got 1300 the first time for unneeded work )!!! The oil had coated the inside of the cooling system and reduced the ability to transfer heat. :mad:
  • julieinidjulieinid Posts: 1
    All I did was flush the radiator on my 2001 Pontiac Montana now it over heats like crazy! can't even make it out of driveway, what's goin on?
  • Hi,

    Did you bleed the system? If not, some air is in the system and it overheats easily. So, have a look at two places which are identical. The first one is on left side and the other one on the right side. Try to see on top of the return heater hose along the valve cover on the top left side and near the thermostat on the right side. You will see a small screw on top of each place. These screws are the bleeders. Do you get them? Because these bleeders are at a higher level than the radiator, then some air is emprisoned in the system when the radiator is emptied. What you need to do is this:

    1) Feel the system with antifreeze through the plastic bowl on the right side (driver's side);
    2) Open both bleeders. If antifreeze does not appear, start the motor;
    3) Always watch two things: a) the temperature light or gage; and b) the airflow from the heater - put it on warm at maximum. A trick: when the air is warm, the motor is cool - if the air is cold, then the motor overheats...
    4) Let the motor running. You will see some antifreeze going out of both bleeder (you can go one bleeder at the time after a while, in quick alternance);
    5) When antifreeze will go out on a current basis (you will see some splashes coming from a mix of air and liquid), then no more air is in the system. So, make sure to do this thing for both bleeders.
    6) Be careful: if the temp gage is going up, just stop the motor a few minutes with the bleeders open. It could be useful too, in the process of evacuating the air, to press the gas pedal and have the motor running between 1500 and 2000 RPM. This accelerates the process.

    If you doing this for the very first time, you will have to coordinate several things at once. So don't panic. Follow the temp gage and never let it going up to the maximum. Stop the engine if it goes up 3/4 of the maximum (so a line or two above the midpoint on the temp gage). In some cases, you might need to repeat all the operation, as some air could take a couple of minutes to be totally evacuated.


  • jennpagejennpage Posts: 1
    I have a 2006 Pontiac Montana....I live in Georgia so it is almost always humid down here. Recently my van started acting weird... Sometimes when I have the air conditioner on and I stop at red light or stop sign then press the gas pedal to acts like it does want to go until I turn off the air conditioner. Then it acts fine. This does not happen all the time usually when it is very hot out. I don't think it is the transmission because it is not jerking or giving me any other signs to indicate it. Does anyone have any suggestions or may know what is causing this? Thanks :0)
  • gmcustsvcgmcustsvc Posts: 4,251
    Hello Jennpage,
    Have you had anyone diagnose your concern? Can you please email me your VIN and current mileage? You can get my email by clicking on gmcustsvc. Thank you,
    Mariah GM Customer Service
  • This just happened on my daughter's 2000 Montana. The solution is to replace the alternator. It has 3 sets of diodes ; 1 for keeping the battery charged and the others for running your electrical systems.When the temp outside goes up, there is a problem with them sticking. replaced hers and everything's fine now.
  • pashukopashuko Posts: 3
    yes my 2003 pontiac montana on a long run wit the a/c on it throws the water to the inside and the carpet gets all wet wat can i do
  • ray80ray80 Posts: 1,652
    First and easiest thing to check if so equipped is the cabin air filters.
  • Ok I have a 2000 Pontiac Montana with 152K and while sitting in the van today with the car off keys in pocket the air conditioner came on and ran for aprox 5-10 seconds. I was puzzled and over the span of two hours it did this 4 times and each time it came on for about 5-10 seconds. Any ideas??? Again the car is off keys are not in the ignition and the air conditioner is on off. I'm wondering how long this has been going on and how often is it doing it harmful to the van?
  • Just happening looking into this forum for my overheating problem, I thought this might help someone else later as a pay back for others' useful inputs.
    I had this problem before and was thinking of changing the blower, but my friend at a GM dealer just changed the air filter at the heater core, I do not know exactly the location of it, it could be under the glove compartment where you can find the heater core, I believe. After that I had very strong hot air after that clogged air filter replaced.
  • jflettjflett Posts: 1
    ok was it the pump or the rad itself as i own a 2000 and it is doing the same thing just paid had thermostat changed heat for 24 hours and cold again thinking of a flush but afraid to do so if this is not the problem so just to double check if it was the rad or pump as your headline says pump but details lead to rad????
  • Your original post said:

    Last week, the heater stopped blowing in my 1998 Pontiac Transport van when I start it using the (ProStart) remote control starter. The van starts fine with the remote, but the headlights and heater don't work until I actually go in the van and turn the key to on. The heater is left turned on the mddle blower setting all the time, so it isn't a problem that it got turned off previously. Any ideas what would cause this? Thanks for any help!

    The PROSTART REMOTE CONTROL STARTER is a system that duplicates starting the vehicle with the key using a remote hence the name "remote control starter". At the ignition switch there are 2 accessory wires that need to be energized for the heater to work properly during remote start. When you are entering the van and turning on the key you are now energizing the second accessory wire that the PROSTART system is not connected to. This is a common installation error we see on a regular basis. There is a separate heater circuit that will not function unless it is properly connected. If the heat works fine when you start the vehicle with the key and not with the remote starter the problem is with the remote starter installation. If you have no heat with the key or the PROSTART system, that is a separate issue completely.
  • GMCUSTSVC! Maybe you can tell me why my van doesnt put out hot air when climate control is on hot and also why when you go to HOT the air flow goes to about 20% . The GM tech up here said there was a damper he wired in a way to make more air flow but you could fool me with what he did. WE dont see any true improvement and it gets cold up here in MICH.

    Thank you :mad:
  • Your post to jjallen07 is confussing me .. I am jjallen07 and own a 2004 Montana and DO NOT HAVE A REMOTE Start.....Have a large air flow problem when i go to heat. HAve good air flow in COLD Mode but only maybe 20% airflow in HOT. A GM TECH wired a damper in a position that was suppose to give us beter air flow but it didnt...takes for ever to get the car heated up (25 to 30 mins) and then it is only warm enough to keep from freezeing. If we didnt have rear heat/air i think it would be undriveable in the winter...... :mad:
  • newt25newt25 Posts: 1
    I have a 2000 Ponitac Montana. The A/C works on the back vents and on the right side dash vents, but NOT the left side dash vents. I only get luke warm air from the left vents. Any help would be appreciated.
  • reikureiku Posts: 2
    Ok I am sorry up front if there is am answer to my issue. I really did read a lot of threads. That being said. I have a 2002 Montana. The ac blows warm. The temp knob works to turn on heat just fine. I pulled out the unit with fan sped temp and placement of air flow. It's electronic. I checked board and saw no burn spots. The wire hat ears that attach seem fine as well. The compressor does not come on as far as I cam tell seeing as I never feel or hear drag. I had a friend that tried to charge it with freon. Assuming it was low side port that between engine and radiator by the heat shield to exhaust? I was told it would not take any. I checked the condenser for leakage and see none. I read compressor will not run low on freon. Is that right? Is there anything that would cause the compressor not to run. The ac worked I turned it off the shortly later tried to turn it back on and nothing Texas heat is unbearable this time of year. Any help would be amazing.
  • laboymclaboymc Posts: 1

    I have a 2000 Pontiac Montana and the A/C when I turn it on won't turn until I reach speed 4 or 5 and when it does it goes on and off. The air is cold and I don't have problems when the air comes out, which comes out cold. The problem I am having is that it doesn't stay on. What is the problem when something like this occurs?
  • I have the same problem with a 2002 Montana. In the cooling mode, the cold air on the right side is excellent, but the two left vents for the driver are "half-cool". I suspect that a damper or flap is not opening or closing all the way, and thus allowing outside warm air to be mixed with cold air, but only for the left side. Anyone have suggestions on where to start under the dash?
  • As you may have noticed that the first post in this topic the owner complained of water coming out of the vents. The 2003 model of the Montana had serious condensation issues with the airconditioning. GMs solution was to install an aftermarket kit that activates the blower when humidity levels get too high in the condensor box. The reason they came up with this solution was to PREVENT Legionellosis (Legionnaires' disease, an advanced form of pneumonia) from forming in the condensor box. SO THE ANSWER TO YOU QUESTION IS THAT IT IS NORMAL FOR YOUR AIRCONDITIONER BLOWER TO KICK IN FOR 5 TO 10 SECONDS EVEN WHEN THE KEYS ARE NOT IN THE IGNITION. HOWEVER, this can lead to a dead battery it you live in a high humidity area! The only way to prevent this is to install a deep cycle marine battery. ALSO BE WARNED: IF YOUR FAN EVER QUITS AND THE FUSES IN THE FUSE BOX ARE OK, YOU HAVE TO CHECK THE FUSE FOR THE AFTERMARKET KIT, FOUND BEHIND THE KICKPANEL OF THE PASSAENGER SIDE DASHBOARD.
  • I just bought a 2001 montana nd it makes a whining noise when turnin kinda idols high nd today it over heated on me the heater works selectively and to fix the problem as soon as possible any ideas??
  • jpfjpf Posts: 496
    Check for low engine coolant. Most likely it's the intake manifold gasket. Good luck.
  • Review the message board back to message 60 and come forward. Some good insights here relative to overheating and to heater and cooling problems. My left right A/C vent temperature problem (see # 79) was partially cured by removing all the plastic under the sterring column. Then lubricating all levers. I also repositioned a ground strap that was interfeering with one of the moving levers. Back to your over heating issue: If you are in a warm climate, remove radiator cap, add water hose, run heater, idle engine, open drain on radiator. Check cabin air filter for cleanliness, vacuum as required(2 of them), remove thermostat or replace. Keep us informed on your progress. Howard741
  • zuccyzuccy Posts: 1
    I have a 2007 Montana with just over 100k and I started having the exact same problem. I checked the rad fluid level and it all seems ok. Did anyone ever find out what the exact problem is ?
  • nygentnygent Posts: 1
    edited November 2011
    Anyone know if the 2003 Montana has Bleeder Valves for the Cooling System? If yes, locations of these?

    Possibly have air in system likely due to intake gasket leak although not sure yet. Also have P303 misfire but unknown if related to gaskets. For now I need to be able to get air out of cooling system due to temp guage spikes and warning light of Hot Coolant.

    Any other methods for bleeding air appreciated. Heard one person suggest parkin vehicle on hill with front end higher than rear then using funnel in radiator filled with coolant to then bleed valves, keep funnel filled...repeat. then run engine bleed valves while funnel still filled. Do until no more air escapes valves.

    Finally if air bubbles come from radiator cap opening it indicates likely intake gasket leak. Is this a good idicator of intake gasket leak?

  • jjallen07jjallen07 Posts: 7
    edited November 2011
    I had taken out my filters along time ago thinking it was that. I have also had it to the dealership twice. They diabled the air restrictor flow damper but that did not help. Still have VERY LOW AIR FLOW in HEAT ONLY. Heater Core replaced, Thermostat replaced, GM even checked the fluid flow. I can tell you that the CORE gets hot, as I have experienced the heat when touching it while trying to trouble shoot the air flow. A/C is ok. Think there is a flow ristriction that GM doesnt even know how to fix. IF I could i would remove some of the "flow doors". I believe that this is a design flaw that after several years of heat and cold, the plastic DAMPERS warp and do not function correctly. ....... :Just a note, that "fix" cost about 600.00 to do nothing....Thank God we have a REAR AIR/HEAT on the van or it would never get warm.... :sick:
  • I have a 2000 Montana with 280,000 km ( 175,000 mi ).
    2years ago I changed the rad. (It was heavy with sludge ).
    I flushed the heater core.
    I changed the thermostat.
    All new hoses and new antifreeze.
    Works good now.
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