overheating while idle

[mushupork5]

what would cause my 76 280z to overheat hile idleing? The radiator overflow is filled to the fill line and the radiator hoses are not clogged, but still if i leave the car at idle it will start to heat up i just push on the gas while idle to pull that heat off the motor and eventually the temp goes down. Thanks

[twinturbopower]

maybe a bad fan clutch or a lean running engine, or maybe even the timings off. gotta be more specific

[2ManyZs]

So many things....

Clogged radiator, whole system needs to be flushed, thermostat not operating at 100%, water pump not operating at 100%, plus, the before mentioned timing possibility, and definately the fan clutch.

First thing I'd do is a good cooling system flush, then check and/or repair the fan clutch. If that isn't the problem, then go to the water pump, thermostat. If all that doesn't correct it, a trip to the radiator shop might be in order.

Just start with the basics that don't cost too much, then go to the higher priced fixes last so you don't waste money on what didn't need to be fixed. Of course, it could be a combination of things as well.

[Tiburon]

if you don't have a fan shroud your car can also heat up like this

[mdbrandy]

Did you ever track it down to a single source? I am currently having the exact same problem. While running down the road, the car's temp is rock steady just under the half-way mark. I sat at a ATM for 3 or 4 minutes this morning, and the temp started creeping up to somewhat over the halfway mark (this is at an ambient air temperature of about 35 degress F). As soon as I started driving again, the temp dropped back down and settled into it's normal place. I figured inadequate thermostat opening or fan clutch (coolant level is fine). A good flush couldn't hurt either, since it probably hasn't been done in 10+ years (the car sat most of the past 10 years - only 2000 miles, and most of that before 1997). So, for the experts:

Are there any obvious ways to check the fan clutch? Never had one fail before.

What is the best way to flush the coolant system? Been a while since I did that too.

Thanks.

[Bambikiller240]

Originally posted by mdbrandy

A good flush couldn't hurt either, since it probably hasn't been done in 10+ years (the car sat most of the past 10 years - only 2000 miles, and most of that before 1997).

I'd have the radiator backflushed and probably Rodded out. Lots of sediment could be packed into the core blocking flow through some of the tubes

Originally posted by mdbrandy

Are there any obvious ways to check the fan clutch? Never had one fail before.

can't help with this one, sorry

Originally posted by mdbrandy

What is the best way to flush the coolant system? Been a while since I did that too.

The way I've done it is with a garden hose with a high pressure nozzle. Filling from the bottom hose until it pours out the thermo housing, then releasing the garden hos so the block drians in a rush. I do that until no more sediment comes out of the block.

I never use chemicals, as I fear they will do damage to the aluminum head. Just my opinion.

****Look for a Cooling System Flush and Anti-Freeze Tech Article to be posted later today.

Carl

[mdbrandy]

Originally posted by Bambikiller240

****Look for a Cooling System Flush and Anti-Freeze Tech Article to be posted later today.

Carl

Thanks Carl. I'll be lookin' for that article ...

[Bambikiller240]

Originally posted by mdbrandy

Thanks Carl. I'll be lookin' for that article ...

It's already posted under Tech Articles >Cooling System Flush and Anti-Freeze

[mdbrandy]

Just finished reading it. Thanks! :classic:

[2ManyZs]

The "low-tech" way to check the fan clutch, would be to shut off the engine while it is at operating temp or above, open the hood, and try to turn the fan blades(at the base of the blades so you don't break one) by hand. If you can turn the fan by hand, then the clutch isn't locking up completely like it should.

The fan clutch can be dissasembled and re-filled with oil...I think there was an article in SportZ that told what viscosity to use that works best.... have to go back and look......

I used to flush the system using an old piece of garden hose, cut off at one end, and attached to the L at the back of the head.

[mdbrandy]

Originally posted by 2ManyZs

The "low-tech" way to check the fan clutch, would be to shut off the engine while it is at operating temp or above, open the hood, and try to turn the fan blades(at the base of the blades so you don't break one) by hand. If you can turn the fan by hand, then the clutch isn't locking up completely like it should.

The fan clutch can be dissasembled and re-filled with oil...I think there was an article in SportZ that told what viscosity to use that works best.... have to go back and look......

I used to flush the system using an old piece of garden hose, cut off at one end, and attached to the L at the back of the head.

I'll try to turn the fan when I get home from work tonight. If anyone knows what SportZ issue the fan clutch article is in, I'd appreciate it. I have all but 3 or 4 issues - it'll probably be in one of those!

If I remember, I used to buy little prestone "kits" that had a "T" that you inserted into the middle of a heater hose (permanently), and that had a garden-hose attachment on. A screw-on cap sealed it off when you were done. I wonder if I still have one of those....

It's amazing the odds and ends that I've carted around the country for 15 years during my "Z-less" period. I guess I always knew I'd have one again. :classic:

[2ManyZs]

Oh, I forgot to mention, that when the engine is cold, the fan clutch should spin quite freely. The warmer the engine gets, it should get progressively harder to spin it by hand, and when at or above optimimum temp, it should be nearly impossible to spin by hand.

So, if you can't spin it without too much trouble when the engine is cold, you know you have a problem.

I'm still searching for the article... I didn't find it in any of my SportZ mags, so it's either on the net, or in an old ZCar magazine...:stupid: One of these days I'm gonna be able to remember where everything is. Yeah, right.:disappoin

I never trusted those Prestone kits... give you 3 more possible places for a leak... and like I said somewhere, if the heater hoses spring a leak while you are driving, you won't know it until it's probably too late as the water will go under the car and down the tunnel. I know, I cooked one head like that....:stupid: