1992 Z28 350 auto car. G92 car. It has vortec heads, SD intake, ported plenum and ported slp runners.
I have both fans wired to come on all the time. the Rad is flowing fine, new t stat(replaced 3 times!)

what the hell is causing it to overheat?

 

water pump turning right direction?

 

blockage in a hose or radiator? water pump not pumping, low coolant, bad timing.

 

When does it overheat? Idle or driving?

 

Yes
coolant is fine, timing should be fine
mainly when sitting in traffic or a light, a few times it has flutulated will driving but it's almost always at idle.

 

Are you using the dash gauge as a reference for overheating? The gauge in the dash is often not that accurate. If you can, retrieve the cool temp from the ALDL stream instead. The CTS gives a more accurate indication of the cool temp.

Also, wiring the fans to run ALL the time is a bad idea. The commutators and bushings in the motors are not made for 100% duty service. I did that a long time ago before I knew any better, and the commutator wiped out, causing a fire and lots of crispy wiring. Wire it back up like it was stock.

 

that rules out the air dam

 

yes I'm using the gauge but it is getting that hot. It will run like crap and has cut itself off before it got so hot. That was once a long time ago though. I only wired them up like that to see if the fans weren't pushing enough.
Yea air dam is fine. Not broke or anything

 

Are u shure the fans are running full speed and in the right direction ( PULLING THRU ) ??

just say'n ....mmhhhh

 

Yes, I believe they are going as fast as they can and yes they are in the right direction

 

If so , then realy is no reason for it to overheat .... unless u have something major wrong with the engine itself !!!

i would check the temp with a laser thermometer in the driveway ....

http://cgi.ebay.com/ebaymotors/NON-C...item588b5e6f59

 

Yea I might have to try that but it honestly acts like it is running hot. I've been fighting this awhile. The motor is gonna get tore down in a few months for a rebuild but I wanted to figure this out so the new setup doesn't have issues.

 

Maybe the pump is on It's way out an you're not getting the flow you need at low engine RPM, assuming you have a belt driven pump.

 

This, or like i said internal engine problems...that u will find if u tear it down anyways ...

But if the FAN(s), WP, Thermost, Radiator, Airdam....and everything else is working..then there is no reason for overheating on the cooling system side what so ever !!!!!!!

 

I might replace the pump with a new higher flowing one and see what it does
yea but I can't see what would do that. It still runs great. Pulls hard. Stock ran a 14.5 quarter with the issue.

 

Bearings, rings, sparkplugs...headgasket..valves...can be a lot ?!

not saying it is...and not saying u would realy feel a differents in running up to a point ..

 

Wouldn't something fail before 7 Years of driving?

 

pump ,belt,rad cap,head gasket

 

Too much timing?, not using or mysterious loss of coolant? (head gasket)

 

No doesn't loose coolant,I'll check the timing again. What Is a good high flow water pump?

 

A high flow water pump presents the opportunity for the coolant to get moving too fast through the radiator, thus not allowing it adequate time to cool off before it flows into the engine. I would say with your set-up a standard flow water pump would work just fine.

 

^^^^^^^^^^^^ WHAT HE SAID !!!!!!!!!!

 

Really? If the water is moving too fast through the radiator to cool off wouldn't it also be moving too fast through the engine to HEAT UP?

No. Ignore that. The problem with high volume water pumps and removing the t-stat and the like is the possibility of cavitation. As the water is forced to move too fast, pockets of air and water vapor are created which don't have the cooling properties of water.


Rule No. 1. If the radiator is NOT boiling over the engine is NOT over heating.

Rule No. 2. If the radiator IS boiling over the most likely cause (and easiest to check) is a bad radiator cap. As the cap gets old it fails to hold adequate system pressure and....it boils over into the overflow container.

Replace the cap (like $3 last I bought one) and if it continues to boil over, pressure test the system. Temps above 220 and up to 240 are normal and the coolant must be kept under pressure to keep from boiling. If the cooling system checks out proceed to your next steps: air flow, coolant flow and engine tune. A poor running motor, especially a rich condition with retarded timing, will create more heat for the same amount of power output of a properly tuned motor.

If your car is not boiling over, see Rule No. 1.

 

Ok thanks for the info, I'll check it out some more.

 

[quote=naf;4757620]Really? If the water is moving too fast through the radiator to cool off wouldn't it also be moving too fast through the engine to HEAT UP?

Absolutely NOT, only cold water can cool and prevent from overheating....if the water runs to fast it will not cool !!!!!!

BTW, its not the water that heats up...ITS THE ENGINE !!!!!! The water is used to cool it not the other way around, hope that makes sense ???

 

Well I drove it today and it still gets hot in the cold weather got up to like 240 ish range at a light.. Crap.. Plus found a intake leak at the back by the distrubutor..

 

[QUOTE=DAREDEVIL 1;4757781]Nah, you're over thinking this. The coolant is simply used as a medium to transfer heat energy from the motor to the air. The temp of the coolant rises as it passes through the block then is cooled as it passes through the radiator. It absorbs heat energy from the engine and transfers it to the air passing through the fins of the radiator. Simple.

The problem with coolant moving too fast is not that it will not effectively transfer it's heat energy to the air at the radiator (by that reasoning the inverse would also be true-it would travel through the block too fast to absorb the engine heat). High flow at the pump can push water through the motor before cooler water from the rad can reach the return side of the pump. This can lead to cavitation and vapor pockets and even collapse the return hose and retard flow.


A common source of leaks at the rear by the dist is the Oil Pressure Sending Unit (OPSU). If you haven't swapped intake gaskets any time soon I'd check there first.

How do you know that it's getting to 240? I hope you're not relying on that wavy, pointy thing in the dash that may, or may not, be an indication of the actual, TRUE state of nature at the end of its sensor? You're using an alternate means of determining engine temp? Got a scanner hooked up to read it from the CTS?

 

[quote=naf;4758351][quote=DAREDEVIL 1;4757781]

Nah, you're over thinking this.
(by that reasoning the inverse would also be true-it would travel through the block too fast to absorb the engine heat).

Sorry, but this is kind of what i ment / said !!!

 

Item 2 rad cap...........mine was boiling over ended up being my rad cap .......problem solved

 

irocs are always prone to running hot. been through running hot with both irocs going through town. i took out all my ac and condensor and carbed it finally, my car runs 180 degrees all the time everytime