Stupid mistake, overheated truck

[womcat]

Like the title says, I overheated my truck. I have a '98 Chevy with a 4.3 and 165,000 miles. At the beginning of winter, I put on a new water pump, and decided to leave the fan off since I normally end up cardboarding the front anyway. It still stays nice and cool, as long as you don't sit idling for too long. Well I sat in my girlfriends driveway the other night with it running and the lights off, totally forgetting about the fan. Not sure how long we were there, but I started to hear the coolant bubble into the reservoir and remembered. I turned on the lights and the temp gauge was close to 250 deg., not good. I took off immediately to get some air moving, and it cooled right off and seemed to run ok. Do you think I did any damage? I am currently running PP and it does have the oil cooler lines to the radiator. Not sure how hot vortec heads can get before doing damage? Dumb move not having the fan on there

 

[eljefino]

I think you could have done a lot worse overheating due to losing coolant. You had it full, just a little cavitation from the boiling.

If you didn't quite peg the stock gauge you should be fine. Those gauges aren't the best and should (*should*) be calibrated to freak the driver out before permanent damage occurs.

 

[Topo]

I only had that happen on my KTM 525 Enduro. It not only boiled the radiator, the gas starting boiling to..LOL!

 

[Bill in Utah]

That is why they put a clutch on the fan...

I doubt you did any damage. Did you get a check engine light? I don't remember if the 98 had aluminum heads (I know its still has the iron block) but again I doubt you have any long lasting problems.

The big question is when today did you get the fan back on?

Bill

 

[Tegger]

Originally Posted By: womcat
decided to leave the fan off

I'm very, very puzzled why you'd do that on a '98. The fan is not what controls the engine's temperature; that's the thermostat's job.

But once the thermostat is open, the thermostat needs to be able to count on the return-fluid having been cooled as it traveled though the rad. If you're parked and you've fixed it so air isn't forced through the rad as needed by the fan, then you've defeated your cooling system's design.

 

[hemitom]

I would say you caught it in time. no real coolant lose

 

[pair of Blazers]

Originally Posted By: Bill in Utah
That is why they put a clutch on the fan...

I doubt you did any damage. Did you get a check engine light? I don't remember if the 98 had aluminum heads (I know its still has the iron block) but again I doubt you have any long lasting problems.

The big question is when today did you get the fan back on?

Bill

they have iron heads. hope you changed the oil at least.

 

[Bluestream]

Originally Posted By: pair of Blazers
Originally Posted By: Bill in Utah
That is why they put a clutch on the fan...

I doubt you did any damage. Did you get a check engine light? I don't remember if the 98 had aluminum heads (I know its still has the iron block) but again I doubt you have any long lasting problems.

The big question is when today did you get the fan back on?

Bill

they have iron heads. hope you changed the oil at least.


I think PP can handle 250 degrees without issue. In fact so could dino for the few moiiniur=tes it ws overheated.

 

[womcat]

Well my thought was the truck would warm up faster because there wouldn't be as much cold air flowing. Even with the fan clutch, there is always some air movement. Maybe the clutch isn't working as good as it should? During the winter I usually block part of it with cardboard anyway, so I thought I would try this as an experiment. It's worked great so far, until this lol. So now I see why it is a bad idea, and yes the fan is definitely back on now! I was just kinda worried because the factory gauge seems to error on the cooler side, so the 250 could be even warmer. Lesson learned I guess.

Topo, I have a KTM 525 also, and they will for sure boil over in the slow going stuff. It definitely like to puke coolant in the summer. I don't think I've boiled the gas though, impressive!

 

[eljefino]

So was it peppy without the fan?

 

[Drew99GT]

250 idling I doubt did any damage, especially if the cooling system was full. Like some others said, the fan doesn't control engine temperature, the thermostat does. Well, except when the thermostat is open and ambient temperatures are very hot and you're idling (as you found out!).

Put it all back together like it came from the factory.

 

[440Magnum]

I wouldn't worry. Damage only really begins when enough coolant is gone so that bare metal is exposed inside the cooling system. As long as coolant was there to push into the recovery tank there was probably little or no harm.

 

[Chris142]

250F while pretty warm is no real cause for concern with your iron 4.3. The Aluminum Caddy Northstar doesn't turn on the high speed fan until 240F.

I'd definatly put the fan back on as it's still needed to cool the Condenser when the defroster is on Assuming that you have AC.

 

[Planb]

250 is not that hot. Don't worry about it!

 

[tpattgeek]

I think the more important question is... what were you doing in the driveway with the truck running and the lights off????

 

[spackard]

Also, interior fan on max speed, fresh air, and heat on full, roll windows down.
Helps keep temp down, but in the long run the interior blower motor is usually more of a pain to replace than the exterior fan.

 

[zorobabel]

So how can you tell for sure the engine overheated (apart from seizing)? Check engine light? Head gasket? How long would it take for the HG failure to become obvious?

 

[Tegger]

Originally Posted By: womcat
Well my thought was the truck would warm up faster because there wouldn't be as much cold air flowing. Even with the fan clutch, there is always some air movement.

True, but that's AIR through the rad. With the thermostat closed, there is no WATER flow through the rad, and that's what counts. It does not matter what happens to the water that's stuck in the rad, or how cold you make it, so long as it doesn't freeze.

The thermostat's job is to keep the block up to temperature. It does this by refusing to allow water flow through the rad unless coolant temperatures warrant.

In very cold weather, as long as the vehicle is in motion, it's even common for the thermostat NEVER to open, and the rad NEVER to get used, even during long drives. In very cold weather, it's often sufficient for heat to be removed by radiation into the surrounding air, and from the heater core.

But when the vehicle is stationary, there's no air moving through the engine bay, and heat-transfer slows down dramatically. That's when the thermostat might open, and you'll need the rad and fan to kick in and prevent overheating.

As for the gauge reading, I don't know about your truck, but many vehicles have separate sensors for the computer and for the gauge. The only way of telling how hot an engine is getting is with an infrared thermometer, commonly and cheaply available.

 

[womcat]

Originally Posted By: Tegger
Originally Posted By: womcat
Well my thought was the truck would warm up faster because there wouldn't be as much cold air flowing. Even with the fan clutch, there is always some air movement.

True, but that's AIR through the rad. With the thermostat closed, there is no WATER flow through the rad, and that's what counts. It does not matter what happens to the water that's stuck in the rad, or how cold you make it, so long as it doesn't freeze.

The thermostat's job is to keep the block up to temperature. It does this by refusing to allow water flow through the rad unless coolant temperatures warrant.

In very cold weather, as long as the vehicle is in motion, it's even common for the thermostat NEVER to open, and the rad NEVER to get used, even during long drives. In very cold weather, it's often sufficient for heat to be removed by radiation into the surrounding air, and from the heater core.

But when the vehicle is stationary, there's no air moving through the engine bay, and heat-transfer slows down dramatically. That's when the thermostat might open, and you'll need the rad and fan to kick in and prevent overheating.

As for the gauge reading, I don't know about your truck, but many vehicles have separate sensors for the computer and for the gauge. The only way of telling how hot an engine is getting is with an infrared thermometer, commonly and cheaply available.


I know how all that works, but I was thinking in the winter the fan isn't really needed very much. When it's cold, it doesn't take hardly any vehicle speed to provide enough air through the radiator to cool it down. Obviously it means you can't sit for long periods not moving though, which I completely forgot. I know some of the newer trucks have an electric fan, which is nice. No need to be spinning a fan all the time when it's only needed once in a while. I know mine has a clutch, but it still spins quite a bit.

I was also thinking it might make a mpg difference on a smaller motor. I did return my best highway mileage on a long trip right after I left it off. Too many variables though to completely attribute it to the lack of the fan.

Also, no comment as to why I was stopped with the truck running and no lights on

 

[Bluestream]

Your truck has a viscous fan that does not spin in cold weather anyway