Overheating jeep & intermitant hot & cold air when heaters on ful
Hi, could be a blocked heater coil. Though I doubt it.
Some more info would be helpfull, but i'll try to give some help.
firstly, is the fan clutch working? it;ll look as though it is, and still spin the fan, but if you stand near the engine with the engine running and hood open and don't feel a force of air blowing out of the engine bay then the fan clutch could be weak. A way to test this is to very carefully and slowly try to stop the fan turning using a broom handle. if the fan clutch is working, then it;ll just kick the broom handle out of the way. you won't be able to stop it. If it isn't working, you'll be able to continue to place the broom handle and the fan will stop turning. as simple as that. If the fan clutch is faulty, you're engine will overheat. Especially at stop lights, parked with the engine running, and it'll kick out your coolant when you turn the engine off after it's hot.
secondly, if fan clutch ok, turn air con off and run engine. then turn air con on and see if the electric fan comes on immediately. With air con on, the electric fan should come on straight away. If not, the electric fan is faulty, and this could be a fuse, relay, or switch, or even the fan itself.
thirdly, if this is only occuring when you run at constant speed, and not at idle after a while, then there's a blockage in the coolant circulation. The radiator may need flushing, or the hose is getting kinked. Under vacuum, the hose can collapse and stop the circulation making the engine overheat as it gets hotter at high rev. sometimes, there are coils in the hoses to prevent this, and you may be missing one or two. These are usually at elbows where the hose connects to the engine, radiator.
Lastly, head gasket or crack in the head. check the spark plugs. If they look too clean, like they've been steamed clean, then you may have coolant leaking into the combustion chamber. At higher revs, this will cause heat and pressure buidup in the coolant system, eventually leading to overheating at speed. The crack/leak may only become more prevalent at higher revs, thus higher pressure. Even the slightest/smallest leak can cause this problem at speed but not at idle.
Good luck. Check the components first. Make sure the fans are working, then check the hoses for coils, and then the spark plugs. spark plugs should have a little carbon buildup. If it's the crack or gasket, then the plugs will look too clean. It may only be one plug/cylinder, so check them all.
Jan 24, 2009 |
1997 Dodge Intrepid