Argh! What can cause overheating *other* than thermostat? Is it possible waterpump not circulating?
08-03-2003, 06:25 PM
#1
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Argh! What can cause overheating *other* than thermostat? Is it possible waterpump not circulating?
It was a tough couple days. Almost wrecked due to an OVERHEAT! Wtf? I swapped in a new thermostat...and now, completely removed the thermostat altogether- same result. The digital temp sensor bounces up from neutral to hot and eventually the car overheats. It holds pressure and coolant, is it possible that the water is not circulating even though there are no leaks? What would be a way to determine if it was circulating? Thanks.
08-03-2003, 06:29 PM
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You either have a clog or the fan isn't coming on
Just sit with it idling and watch the temp and listen for the fan to engage.
If the fan engages, then its probably a clog.
If the fan doesn't engage, I would start with the temperature switch at the bottom of the radiator.
If the fan engages, then its probably a clog.
If the fan doesn't engage, I would start with the temperature switch at the bottom of the radiator.
08-03-2003, 06:43 PM
#3
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Fan occasionally comes on. It'll heat up at speed. Rad not clogged, if I hose into the top, it comes
out of the expansion tank. I am wondering if the pump is pumping. Can it stop internally w/o leaking? Can the *block* have a clog? Damn it!
08-03-2003, 07:13 PM
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Air bubble
The cooling system on my '85 CGT became very erratic, with the temp guage and idiot light not agreeing with eachother.
It turned out that there was a rather large air pocket in the system; the fan wouln't turn on predictably and I would get no heat ("cabin heater") unless the engine was revved. If memory serves me, this is because the fan temp sensor and guage temp sensors are at different points/heights in the cooling system.
Filling the resevior only will not properly fill the cooling system. You must disconnect the hose that runs between the thermostat housing and the upper radiator inlet. With the heater on/hot, hold the hose above the level of the engine/radiator and pour coolant in(this will be slow if the car is cold and the thermostat is closed) until it comes out of the radiator.
Replace the hose, start the car allowing it to heat up and crack open the bleeder bolt on the upper left hand of the radiator. Do this until liquid coolant escapes, then close it. You may have to repeat these steps several times to get a stubborn bubble out.
After I performed the above steps, my heat worked properly, the fan came on at sane intervals and the car wouldn't overheat in traffic jams. That is until I discovered my coolant was slowly leaking out of a spent coolant pump (DOH!) The joys of timing belt driven water pumps...
Doug
It turned out that there was a rather large air pocket in the system; the fan wouln't turn on predictably and I would get no heat ("cabin heater") unless the engine was revved. If memory serves me, this is because the fan temp sensor and guage temp sensors are at different points/heights in the cooling system.
Filling the resevior only will not properly fill the cooling system. You must disconnect the hose that runs between the thermostat housing and the upper radiator inlet. With the heater on/hot, hold the hose above the level of the engine/radiator and pour coolant in(this will be slow if the car is cold and the thermostat is closed) until it comes out of the radiator.
Replace the hose, start the car allowing it to heat up and crack open the bleeder bolt on the upper left hand of the radiator. Do this until liquid coolant escapes, then close it. You may have to repeat these steps several times to get a stubborn bubble out.
After I performed the above steps, my heat worked properly, the fan came on at sane intervals and the car wouldn't overheat in traffic jams. That is until I discovered my coolant was slowly leaking out of a spent coolant pump (DOH!) The joys of timing belt driven water pumps...
Doug
08-03-2003, 09:58 PM
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Re: Kind of a long post, sorry about this but it might be worth reading
If it wasn't circulating I would guess that your heater core wouldn't put out a constant hot air. So does it put out real hot air and is it constantly hot. It would grow cooler if it wasn't circualting properly I haphazard to guess. I read that the fan is comming on, does it come on regulary at the same reading on the temp gauge? You may try replaing the sending unit. Also look for poor connection with the radiator fan. How is the temp when your driving at higher speed? does it drop? Is this a idle heating problem or? When I replaced my radiator last week I got a new temp switch for the fan. Also, I hope you have the shrouding still in there around the radiator and have those flaps on the bottom of the fan shroud or the fan won't work to it's best, they are very needed flaps. Also make sure they move freely so when you start to move they open up by air force and let air though... I really like this part and am impressed with how audi thought of this shrouding. There are other things to watch as well, if your fuel is running lean that will heat up the engine, if you have the timing advanced it could make it run a little hotter. Taking the thermostat out really doesn't help and should be left in but take it out and put it in a test water condition with a thermostat to make sure it's working and opening when it's rated to open.
Also, drain and fill the car with around 70% water and 30% antifreeze. You def. don't want to use too much antifreeze, it doesn't disapait heat nearly as good as water and try distilled water instead of tap water. How old is the car and radiator? Has it been flushed recently? You may have buildups in it... It can be tricky getting the air out. I din't have that much truble but play with it.. I was heating up till I removed that bolt on the top of the radiator and then the water in the coolent tank can flooding into the engine. RUN THE HEATER while adding water, it's critical if you have A/C to have the temp slide all the way to hot and then water will flow into the heater core. It may not if you don't have it set in this setting and should be important. I alway's run it with the fan at full bore as it will only help cool the engine down more and help keep it from getting out of control so to speak, it helps cool the engine down as it's just another radiator and helps remove heat. But CHECK to make sure the thermostat is working right. Do your best to remove air and go slow as you need to so you won't overheat and damage the head or warp valves and the cyl. head.
The manual said to run it this way, filling it as needed with the coolant tank till the fan comes on and then it pretty much assumes it's done and just needs to be topped off.
Wish I could be more help but all I can say is I wish you luck and hope you get it going dude....
Also, did you use pipe thread tape or compound on the temp sensor? I do not recomend doing this at all if it has to be grounded by contact with the radiator's threads. If so and you insulate it that can throw it off. A lot of people do this with their temp gauges and then they don't know why the readings are so far off as they require a good ground and don't get it when this is used. If you used it, take it off and use the gasket/washer that fits the thermal switch. That is all it needs if you torque it right of tighten it as close to 18ft.lb's as possible. I've never used any sealing or thread tape and do not have any leaking. It leaks when people over tighten it or leave it too loose. Also, make sure your not putting the cap on the overflow res. bottle too tight, it's important that this be tightened properly or it will screw up the requireed pressure for your cooling system as this cap acts like any radiator cap and holds and releases pressure when it exceeds it's limits.. Very very important..
Sorry this is so long but I do not want to forget something that may be the key but I'm no real expert and just throwing common sence items for yo uto consider... I wish you good luck..
Brandon..
Also, drain and fill the car with around 70% water and 30% antifreeze. You def. don't want to use too much antifreeze, it doesn't disapait heat nearly as good as water and try distilled water instead of tap water. How old is the car and radiator? Has it been flushed recently? You may have buildups in it... It can be tricky getting the air out. I din't have that much truble but play with it.. I was heating up till I removed that bolt on the top of the radiator and then the water in the coolent tank can flooding into the engine. RUN THE HEATER while adding water, it's critical if you have A/C to have the temp slide all the way to hot and then water will flow into the heater core. It may not if you don't have it set in this setting and should be important. I alway's run it with the fan at full bore as it will only help cool the engine down more and help keep it from getting out of control so to speak, it helps cool the engine down as it's just another radiator and helps remove heat. But CHECK to make sure the thermostat is working right. Do your best to remove air and go slow as you need to so you won't overheat and damage the head or warp valves and the cyl. head.
The manual said to run it this way, filling it as needed with the coolant tank till the fan comes on and then it pretty much assumes it's done and just needs to be topped off.
Wish I could be more help but all I can say is I wish you luck and hope you get it going dude....
Also, did you use pipe thread tape or compound on the temp sensor? I do not recomend doing this at all if it has to be grounded by contact with the radiator's threads. If so and you insulate it that can throw it off. A lot of people do this with their temp gauges and then they don't know why the readings are so far off as they require a good ground and don't get it when this is used. If you used it, take it off and use the gasket/washer that fits the thermal switch. That is all it needs if you torque it right of tighten it as close to 18ft.lb's as possible. I've never used any sealing or thread tape and do not have any leaking. It leaks when people over tighten it or leave it too loose. Also, make sure your not putting the cap on the overflow res. bottle too tight, it's important that this be tightened properly or it will screw up the requireed pressure for your cooling system as this cap acts like any radiator cap and holds and releases pressure when it exceeds it's limits.. Very very important..
Sorry this is so long but I do not want to forget something that may be the key but I'm no real expert and just throwing common sence items for yo uto consider... I wish you good luck..
Brandon..
08-04-2003, 03:49 AM
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impeller separation...
Recently played the exact same game on my inlaws ford while they were visiting. changed the thermostat, cleared bubbles, etc. 7 hours later, i discovered the impeller on the water pump inside the water jacket was not turning with the outside belt. no leaks, no noises, just not moving water and overheating. check that water pump.
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08-04-2003, 04:46 AM
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Lots of good points in the above posts.
1. Water pump itself could be bad. This is not as common, but possible. Run heat on the AC and see if water is circulating through the heater core. Thats a good check.
2. The system may have trapped air. If you have a bleeder bolt on the top of your radiator make sure you're venting the system as you fill and the system is allowed to heat up. The thermostat has to open for the system to flow so it has to heat up that much(87C) and might seem to boil at first as that fluid rushes into the radiator. But as soon as it does, the block should refill with cold water from the radiator and the fan should kick in.
Also check the temp on the radiator itself. If there is no flow, the radiator shouldn't get that hot. So if the pump is working, the radiator will get hot. Check at the top and the bottom. If the temp is above 87C then the thermostat is wide open and the fan should be going like crazy. I still think fan is not going as often and strong as it should.
2. The system may have trapped air. If you have a bleeder bolt on the top of your radiator make sure you're venting the system as you fill and the system is allowed to heat up. The thermostat has to open for the system to flow so it has to heat up that much(87C) and might seem to boil at first as that fluid rushes into the radiator. But as soon as it does, the block should refill with cold water from the radiator and the fan should kick in.
Also check the temp on the radiator itself. If there is no flow, the radiator shouldn't get that hot. So if the pump is working, the radiator will get hot. Check at the top and the bottom. If the temp is above 87C then the thermostat is wide open and the fan should be going like crazy. I still think fan is not going as often and strong as it should.
08-04-2003, 07:03 AM
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I, too, was experiencing cooling troubles...
I began by filling the system with Prestone radiator flush. Then, I drove three hours to Aspen, Colorado and back to Breckenfridge before draining and refilling with orange Prestone and distilled water. Combined with changing the 'stat (87c); changing the fan switch, but the biggest drop in temp came when I used my power washer, minus the gun, to flush out the fins from the fan side.
I took off both shrouds (top and side, bottom is long gone) and could see the crap coming out. I also bought a rattle can of bed liner at WalMart and used that to coat the cardboard side shroud - looks great!
Initially, my temp gauge needle would approach the second line from the top. Now, it hovers between the lines on the thermometer graphic and the top of thermometer.
Good luck.
I took off both shrouds (top and side, bottom is long gone) and could see the crap coming out. I also bought a rattle can of bed liner at WalMart and used that to coat the cardboard side shroud - looks great!
Initially, my temp gauge needle would approach the second line from the top. Now, it hovers between the lines on the thermometer graphic and the top of thermometer.
Good luck.
