Engine runs hot in idle

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What could cause the engine to keep increasing past the temp setpoint while idling? Already swapped out the fan clutch and not change. Radiator flushed and tested OK.
Guv Bob
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Impeller blades on water pump wore out or gone maybe. A long shot but when all else is ok then worth a look see. Jim
What could cause the engine to keep increasing past the temp setpoint while idling? Already swapped out the fan clutch and not change. Radiator flushed and tested OK.
Guv Bob
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Did you "burp" the system after the radiator flush? Is this on your Eclipse still? My 2000 GS had to be burped when it was flushed (2.4L 4-cyl.)
--
SC Tom



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royal pain. Some others too - but I remember on the old R12 I rallyed for 3 seasons it could take half an hour to bleed it untill I made up a "header tank" that we connected to the bleeder on the defroster (yup, it had one) and hung about 2 feet higher than the roof, pouring the coolant in from the top 'till no more bubbles came out the catch tank (kept recycling it 'till the bubbles were gone and kept the remaining gallon for future top-up, or the street car.)
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This is a 97 Aerostar. Don't know - flushed and checked by reputable radiator shop used for many years though.
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have you verified that the fan is actually working??? KB
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On Wed, 15 Aug 2012 17:19:13 +0000 (UTC), Kevin Bottorff

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3L
Last weekend I was going to replace the thermostat and did some more checks first. I turned on the engine and just let it come up to temp. Watching the fluid with the rad cap off, I could see that the coolant start to churn pretty strong at exactly mid-scale. The temp kept creeping up. When it got to nearly full scale I increased the idle speed and within a minute it started dropping and ended up at midscale again. So I didn't replace it then.
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Fan is solid - blades are fine. It's attached to the clutch and turns with shaft from water pump. Is that what you mean?
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yea I thought it might be a elect. one. I would go ahead and replace the tstat anyway. buddy just put on on his chev pkup for a heat at idle issue and now that is fixed. KB
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Sounds like a plan. Will try to get to in the morning.
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On Wed, 22 Aug 2012 18:55:09 -0700, "Guv Bob"

thermostat. Does this thing have a fan shroud installed? How close is the fan to the rad? Does the fan "tighten up" when the engine heats up? If it was designed with a fan shroud, it needs it. If there was a fan spacer, ditto. Thermostatic fans have a thermostatic spring that coontrols the valving in the" torque converter" in the fan hub - and that "converter" runs in (usually) a silicone oil that thickens with heat. If that sucker isn't tightening up with higher temperatures, it WILL overheat at idle (and run just fine at speed when ram air cooling causes the temperature at the fan to drop, allowing it to "uncouple", thereby reducing drag and letting more horsepower get to the wheels)
A missing fan shroud or too much space between the fan and rad also causes poor cooling while sitting at idle, and sometimes still cools fine at speed.
Think about it. All a thermostat, on MOST engines, does, is cause (or allow) the engine to warm up quickly to a minimum operating temperature, after which it stays wide open unless too much air flows through the rad and the MINIMUM temperature is not maintained - where it closes off to allow the engine to warm up again. If the engine runs hot at basically closed throttle - with very little gasoline being burned, and virtually no power being produced - but runs fine at higher power settings, where more fuel is being burned, and more heat produced, it is NOT a bad thermostat. You can take that to the bank.
And it is almost certain it is not a bad rad. Bad rads cannot shed the heat under load at highway speeds - again where more heat is being produced. It almost HAS to be an air-flow problem if it overheats at idle and not on the road.
The only other possibility is a water pump problem - but MOST water pump problems also show up under higher speed and higher power conditions. The ONLY water pump problem I have ever run across that caused overheating at idle and not at speed was terribly intermittent - and SOMETIMES also overheated at speed - and that was a loose impeller in a 1963 170 inch slant six in a Valiant. When it got warmed up the impeller came loose on the shaft and spun. Then it would sometimes tighten up again. Intermittent and unpredictable and TERRIBLY irritating. Does not sound like this is the problem on this vehicle, but IF the fan spacing is right, and the fan clutch IS working, and the shroud is properly installed, I would not rule it out.
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snipped-for-privacy@snyder.on.ca wrote in

I realize it does not make sence but I have seen more than once a slow heat up at idle fixed by replacing the tsat. The stats are not a quality that they used to be. If it is overheated even once, put a new stat in it. They fail very easy now days. And it sounds like its been overheated more than once. Stat is cheep and easy, good place to start. KB
Does this thing have a fan shroud installed? How close is

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On Thu, 23 Aug 2012 14:36:30 +0000 (UTC), Kevin Bottorff

If it heats up on the road too, or heats up at idle then all of a sudden drops down to normal again it could be a 'stat. If it heats up at idle, is fine at speed, and heats up again as soon as you come back down to idle it is NOT a 'stat problem. And if the 'stat that is there is not a problem, installing some unknown peice of chinese kaka is more likely to CAUSE a problem down the road than to fix it.

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Thanks, Clare. I replaced the fan clutch thinking air flow was the likely problem too. Shroud, distance to radiator, blockage all are fine.
I still have the old fan clutch and when the new one (on the car) is cold, they both have the same resistance to turning. When the engine is hot, I turn it off and turn the fan blade and it doesn't feel any different.
I'll horse around with it a little more, maybe change the thermostat since it's easy. Them I'm thinking about bolting down the fan so that it turns the same hot or cold. Always though these fan clutches were a dumb idea.
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Thanks, Clare. I replaced the fan clutch thinking air flow was the likely problem too. Shroud, distance to radiator, blockage all are fine.
I still have the old fan clutch and when the new one (on the car) is cold, they both have the same resistance to turning. When the engine is hot, I turn it off and turn the fan blade and it doesn't feel any different.
I'll horse around with it a little more, maybe change the thermostat since it's easy. Them I'm thinking about bolting down the fan so that it turns the same hot or cold. Always though these fan clutches were a dumb idea.
The other thing that is happening is that it takes 10-15 minutes at road speed to come up to temperature, but only about 5 minutes if start and sit in the driveway.
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On Sun, 26 Aug 2012 22:28:59 -0700, "Guv Bob"

both have the same resistance to turning. When the engine is hot, I turn it off and turn the fan blade and it doesn't feel any different.

easy. Them I'm thinking about bolting down the fan so that it turns the same hot or cold. Always though these fan clutches were a dumb idea.

to come up to temperature, but only about 5 minutes if start and sit in the driveway.

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I'm hardly driving it these days and have been putting off changed the thermostat or investigated any further. Any idea what kind of damage (if any) it would do to run at 90% of full scale for an extended length of time? It never has reached full scale. Already checked out the sensor and gauge and they seem to be reading properly.
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On Sun, 23 Sep 2012 16:35:08 -0700, "Guv Bob"

they both have the same resistance to turning. When the engine is hot, I turn it off and turn the fan blade and it doesn't feel any different.

it's easy. Them I'm thinking about bolting down the fan so that it turns the same hot or cold. Always though these fan clutches were a dumb idea.

speed to come up to temperature, but only about 5 minutes if start and sit in the driveway.

thermostat or investigated any further. Any idea what kind of damage (if any) it would do to run at 90% of full scale for an extended length of time? It never has reached full scale. Already checked out the sensor and gauge and they seem to be reading properly.

failure, and warp heads etc. Not a good idea to ignore. You might want to check to be sure the temp guage is reading close to accurate too.
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Welp! Last weekend it started to get hot, so I let it cool down and checked the coolant. Added about a quart of coolant. I squeezed the hose at the thermostat a few times to get out as much air as I could, but that's all. Since then no troubles.
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