# Help-Running hot at idle - I'm stumped



## dastoria (Nov 24, 2007)

Hi,

Hoping someone had this issue and can help me. My 74 Ventura, GTO option runs hot only at idle/standing still. Its the stock 350/4B. Only changes are edelbrock intake, holley 600 and HEI ignition. The car runs great when its moving - even if only 15/20 miles per hour or 65 mph it stays right on 190 temp where my 400 firebird is always at. Every other Pontiac I have ever owned has never gotten above low 200. This car will creep up and up when in idle - I shut it off when it reaches 230, but it would keep going. Only occurs when standing still - tried everything, stumped.

I put in a new water pump with new divider plate close fitted to the impeller. Jetted up the carb to make it richer. Put timing down 2 and up 2 from its base sweet spot (10.5). Flushed system using flush (surprisingly clean) and flushed with garden hose. By-passed heater core. Put on a new 6 blade flex fan to replace the factory 5 blade flex fan. Swapped the radiator for the aluminum one from the firebird. Changed radiator cap, tried different thermostats - 160, 2 different 180s and no thermostat. (No evidence of a leaking head gasket - which doesn't surprise me because then it would be hot at times other than idle.)

No difference whatsoever - runs great unless its in idle parked. Can some help or recommend a Pontiac specialist in the Albuquerque/Santa Fe NM area, as I am stumped Local mechanics would be clueless with this car. Thanks in advance.:confused


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## geeteeohguy (Feb 2, 2008)

Being that it cools even at 15-20mph and doesn't run hot going down the road, your problem is pretty simple: you are not moving enough air through the radiator core at idle to allow the radiator to give up its heat. Things to try: fan shroud (required) with the fan half in, half out of the shroud, deeper pitched flex fan (I'm using a 7 blade, 18 inch GM flex fan off of a '69 Caddy on my '67, and it works very well and is silent), and water pump pulley diameter. You could go with a slightly smaller pulley for an AC car to spin the pump faster at idle. See if a dollar bill or a piece of paper will stick to the grille side of the radiator with it idling....it should if the fan is pulling air. Last resort, electric fans, but that should not be needed with a warmed over 350V8.


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## dastoria (Nov 24, 2007)

It does pull paper into the radiator and I have fan shroud. But I think your right its an airflow or water circulation issue because if i increase the idle speed it will start to cool off. At this point I am just stumped.


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## Eric Animal (Oct 28, 2007)

Bad fan clutch?


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## jetstang (Nov 5, 2008)

GTO is all over it, good advice.
Maybe put an electric fan in front of the mechanical, see if that helps. I put one on mine and have it on an adjustable regulator so it doesn't kick on til 200 degrees or so, that should help with idle heating.


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## dastoria (Nov 24, 2007)

Its a flex fan, so this one doesn't have a clutch. Might try the electric fans. any recommendations - keeping in mind its a 74 gto, so while loved by me, doesn't justify to much in terms of money into it. 
I hate trying 10 different things and not getting anywhere -so thanks for the help so far its getting me re motivated.


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## jetstang (Nov 5, 2008)

There are really good fans out there, I don't know the diference beyond CFM rating. The Mustang 4.6 ones are really good. Maybe put a stock 7 blade fan on and see if it fixes it. For the electric fan, measure the space between your stock fan and the radiator, and make sure it fits. I put mine as a pusher in front of the radiator, not on my Lemans, but 90 454 SS truck.
If you have a big shop fan, stick it in front of the radiator when it is hot and see if the temps come down, if it doesn't, then that's not the problem..


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## dastoria (Nov 24, 2007)

OK, quick question - disclaimer might be a dumb question. 

But could I hook up a push electric fan on the front of the radiator (non engine side) to augment my factory fan setup? 

I believe the factory set-up is a puller - pulling air thru the radiator. The electric could be a push on the other side. I theory it seems like it would work and would allow me to use a small amp draw electric fan, pretty easy to set up and plenty of room on the non engine side to set up an electric fan to augment with a on-off thermostat control. 

Would the one fan conflict or impede the other? Thanks.


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## BearGFR (Aug 25, 2008)

That's an interesting idea and something you might try if it's "easy" and not expensive.

You do have to be careful about the fan becoming an obstruction. At highway speeds most of the air flow is caused by the car moving. The fan(s) at that point are really just "in the way". In fact it's possible for a non-clutched fan at rpm to act more like a block-off plate than a fan and actually impede air flow, to the point of over heating.

Bear


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## geeteeohguy (Feb 2, 2008)

What Bear says is correct. In addition, I've heard of folks running a pusher fan in front and a regular puller fan in back of the rad have turbulence issues and dead air issues and it causes overheating going down the road. I think it's generally a no-no, but have never done it or used it.


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## dastoria (Nov 24, 2007)

That could be a snag if the one fan will conflict with the other. 

Maybe the other suggestion is the way to go. I measured my top pulley on the car and it appears to be 8 inches. That pulley turns the water pump and power steering. This car has no AC from the factory.

What would be the next size smaller of pulley and is it Pontiac specific or GM? Thanks.


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