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Car Forum / Driving, Maintenance, Tuning / 4x4 Cars / November 2003Continued: REPAIR QUESTION: Radiator chronically overheats!!
Greetings all: I previously posted to these newsgroups concerning a vexing problem I was having with an engine that crhonically overheats. A brief recap: I have a '96 jeep cherokee. Whenever I drive it more than a few miles, the radiator overheats and boils over. I was told at one garage that the radiator was bad. Replaced it. Same problem. Another place said the thermosat was bad. Replaced it, no change. I know the water pump is good. Since that time, I've found out a few more wrinkles to the fold....... To make a long story short, I disovered two things: 1)So long as the heater is on, the engine will NOT boil over....no matter how far I drive. 2)When I stop at red lights, the heater starts to blow COLD air. It heats up again as soon as I start driving again. Ever since I discovered point (1), I have been driving with the heater on full blast and have not had a problem.....except that it gets AWFULLY hot inside the car! I'm curious to know if this additional information will clue anyone in as to what's going on wrong with this vehicle. Any and all suggestions appreciatd!! > Greetings all: > [quoted text clipped - 26 lines] > > Any and all suggestions appreciatd!! You are sure the water pump is good? Sounds like at idle no hot water is getting to your heater core.  Signature____________________ Remove "X" from email address to reply. >Greetings all: > [quoted text clipped - 26 lines] > >Any and all suggestions appreciatd!! Are you sure all the air is burped out of that thing? And what makes you sure the water pump is good? The impeller could be eaten away. > >Greetings all: > > [quoted text clipped - 29 lines] > Are you sure all the air is burped out of that thing? And what makes > you sure the water pump is good? The impeller could be eaten away. If your heater starts blowing cold, you DO have air in the system I think. The theory of the bad water pump impeller has merit as well. Hi, Thanks for the response.... > Are you sure all the air is burped out of that thing? And what makes > you sure the water pump is good? The impeller could be eaten away. No, I'm not sure about the air. Others have mentiont that. I would have assumed that they would have done that when they replaced the radiator...but I can't say for sure. Is that something I can do myself? As for the water pump, I had it replaced very recently. Plus, if it weren't working, wouldn't it mean that I'd *never* get hot air out of the heater (because no water would circulate)? Thnx! > Hi, > [quoted text clipped - 11 lines] > weren't working, wouldn't it mean that I'd *never* get hot air out of > the heater (because no water would circulate)? You minght consider having the cooling system pressure tested and/or haved the coolant tested for the presence of exhaust gas to see if you are getting an exhaust gas leak into the cooling system. When I've had head gasket leaks in my engine, one of the first signs I've had was lack of heater output, due to the exhaust gas filling the top of the cooling system. Would also hear a gurgling sound out of the heater core when the engine was reved. It also may be trapped air as mentioned above, try running the engine with the radiator cap off until the t-stat opens and see if the air will be released. SignatureRoger Approximately 11/3/03 06:44, Quiet Voice uttered for posterity: > Hi, > [quoted text clipped - 11 lines] > weren't working, wouldn't it mean that I'd *never* get hot air out of > the heater (because no water would circulate)? Neither presumption is warranted. When the radiator is replaced, air bubbles in the engine can happen and are a pig to get rid of. As for the water pump, if it can only pump enough water at high rpm, you'd get cold air at low speed. Actually, I wonder if they installed the wrong water pump, and the impeller is being spun backwards. Since it is just centrifugal, I could be convinced that it might actually push a *little* water at high rpm when run backwards... Nothing other than a water pump flow test is good enough to prove or disprove that it is the cause. SignatureMy governor can kick your governor's a.s > Hi, > [quoted text clipped - 13 lines] > > Thnx! If the impeller is corroded it would move water at higher rpms but maybe not at idle. A new pump should have a good impeller on it though. Signature____________________ Remove "X" from email address to reply. Even with a new waterpump, you can have low flow at idle or low speed due to a poorly designed or made impeller. There are many substandard aftermarket pump out there, so if it was a cheapie, look at buying a better pump. HTH Paul E. Signature"I'd rather have a bottle in front of me than a frontal lobotomy." > Hi, > [quoted text clipped - 13 lines] > > Thnx! Blowing cold when idling means you either have an air lock in the cooling system or the wrong waterpump in it. They make 2 waterpumps for that engine. I have seen them mixed up in the box. One is a normal rotation pump for the V-belt version and the other is a reverse rotation pump for the serpentine belt. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > Greetings all: > [quoted text clipped - 26 lines] > > Any and all suggestions appreciatd!! your heater core is a lot like a little radiator, whenever your heat is on the motor usually runs cooler. and a lot of cars have vacume operated heaters, when your siting a stop lights the motor is ideling and not producing enough vacume to turn it on, so the blower fan is just pumping air from outside air. make shure you have the right water pump and make shure its turning the right direction. and if you havent flushed your coolant, that couldent hurt. Strange engine you have there. The only time I get a vacuum higher than at idle is when I'm using engine braking with the throttle closed or for the short period after I close the throttle during a shift. Sounds like a developing consensis that it's a pump issue. > your heater core is a lot like a little radiator, whenever your heat > is on the motor usually runs cooler. and a lot of cars have vacume [quoted text clipped - 3 lines] > pump and make shure its turning the right direction. and if you havent > flushed your coolant, that couldent hurt. SignatureWill Honea <whonea@codenet.net> > Blowing cold when idling means you either have an air lock in the > cooling system or the wrong waterpump in it. [quoted text clipped - 39 lines] > > > > Any and all suggestions appreciatd!! He didn't say that the problem happened right after installing the new water pump. If so, Mike, your answer is beautiful. But if he had the pump changed because of the problem, maybe he's been chronically low on water for some time, suggesting he's losing coolant. The pressure test is a good idea right off. And is he checking the coolant? Adding? This can't be diagnosed from the driver's seat. And lastly, circulate that air bubble long enough and you will blow a head gasket if not done already. > Greetings all: > [quoted text clipped - 26 lines] > > Any and all suggestions appreciatd!! Did you replace the hoses as well? Could be a collapsed lower radiator hose. SignatureWill Honea <whonea@codenet.net> |
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