New GDI radiator, Milodon water pump, known working thermostat (180), new hoses (not collapsing), air dam is present and in good condition, dual fans, second fan on manual switch, car has A/C. It overheats at very low speeds or at idle otherwise stays nice and cool. Like stopping at a light it will rise to ~220 in maybe 45 seconds. If i throw the second fan on at 180, which is the temp while cruising, it climbs slower but still rises. If i also turn the heat on it will stay steady.

L98 bored .030", 10:1, stock heads, stock exhaust, zz4 cam, upgraded TPI, stock prom, 8 deg base timing

So what do you think the problem is?
thanks guys
John

 

The fact that it overheats only at low speed or when stopped could suggest an airflow problem. Since there seem to be so many "known goods" in the equation, the first things I would check would be for a restricted a/c condenser, that both fans are turning the same direction and pulling air through the radiator rather than pushing (I only mention the latter because it's a mistake I made several years ago, and it drove me nuts trying to figure it out), and that the fan shrouds have a good tight fit to both the fans and radiator

-Bob

 

Well i thought about the A/C condensor thing but how would i go about checking it?, AC is nice and cold. I will check the fans, but they are stock so i thought the connectors could only go one way, def something to check out though.
thanks

 

I am having the same problem. But mine also overheats after I turn it off. It will go from 190 to 215 when its off, even with the fan still running. Why?

 

Are you sure your primary fan(motor/relay) is working? Also, have you checked your coolant level?

A leaking gasket might be just slight enough to make the engine heat up, but not necessarily bad enough to blow any noticeable smoke--yet. So make sure nothing needs tightening down and keep an eye on your coolant level for the next few days to make sure it's holding steady. It might be going down very slightly.

When my car was about 3 years old, something similar happened, and it was a combination of two things: 1) manifold was warped, so coolant was leaking into the block causing the car to heat-up when not moving; and 2) the fans burned-out because they were running so much.

In either case, the car would hold steady if you could keep moving, which meant waiting for rush hour to subside to get home, lol.

 

Like stated previously both fans are functioning properly. Coolant level is steady.

 

Try bumpig your timing to 12* and if it doesn't help then I would say that your fans are the culprit if you made sure that there isn't anything resticting your airflow like stated above.

 

The problem with 12 deg is i get pre ignition at anything over 8 deg. It may be worth a shot just to check eng temp at idle though.

 

You should be able to eyeball the condenser to see if the fins are clogged. A few bugs don't mean anything, you're looking for a LOT of bugs, paper, dirt/mud, bent fins, etc. There's always the possibility of crap being stuck between the radiator and condenser as well, but you probably would have seen that when you had the radiator out. Anyway, if it looks dirty, go ahead and hose it out.

If you have the stock fans and they both come on, are they as close to the GDI radiator as they were to the stock one?

I'm also curious if the onset of the overheating problem coincided with any work that was done to the car, or if it just started happening out of the blue?

-Bob

 

Overheating started after the rebuild. I cleaned out the leaves and such while putting the original radiator in after the rebuild along with the installation of the new one recently. You mean just hose off the exterior of the condesor like on the fins right? Thats not a bad idea. I remember the condesor didn't look the greates but i figured it would be ok. I will have to check it out. Maybe i can hose it from the front so i don't have to remove the radiator again.

Oh yea, the fans are just as close as before, about 3/4" away.

 

You sure your gauge is right?

 

A couple of reasons i think it is correct. First the secondary fan comes on right at 220, which is what the fan switch is supposed to turn on at. Second when it reads over 220, i start hearing pinging at higher rpm. Plus its not reading high all the time, just at idle.

I'm going to check the fans and ac condensor tonight or tommrow.

 

I think it may be time for higher CFM fans.....Remember when you are cruising and it starts to heat up (CULPRIT) radiator and at idle (CULPRIT) fan.... My .02

 

Ok both fans turn counter clock wise, if looking at them from the drivers seat. I believe that is the correct direction. Also the A/C condensor appeared to be pretty clean. So i don't know what is next. Fans are possible but i believe i've seen several cases where stock dual fans were used for highly modified engines with success. Unless of course the motors are starting to die. But the car only has 60k miles on it.

 

I know the stock dual fans did nothing to help keep my engine temps down when I bought them for my modded 305 because my single fan was taxed when I installed a cam and headers...So, at that point I went to the salvage yard and picked up a mechanical clutch fan and shroud because I went to a carb and it worked great! So, really I don't know what to tell ya except maybe trial and error....Also does it start to cool down at cruising speeds? If it does to what temp?

 

Yup, it goes right back down to ~180 while moving at around 30mph or faster. Well maybe i'll try some new fans if i stumble across some money.

 

anything wrong with your water pump, or pullies? did you put on an underdrive kit or anything like that?

 

Assuming nothing is broken, airflow through the radiator is the key to removing the heat. It is beyond me why GM didn't design and install a proper shroud around the F-Body fans to move air through the whole radiator, instead of just the small area covered by the fans.

Plus the design of the fans is not nearly as efficient as some of the aftermarket electric fan and shroud combinations. Has anyone experience with replacing the Camaro fans with something more recent, such as the Flexalite? www.flex-a-lite.com

 

Stock pullies in good condition. The WP is new but i don't know if it is any good. Also, what effect would a serpentine WP have on a regular rotation pully system engine. I don't have any reason to believe i was sent the wrong part but it is worth a shot. I'm really starting to believe i just need better fans.

 

A water pump turning in the wrong direction won't work well.

A cooling system won't overheat so quickly, unless the coolent isn't moving. Even a total air blockage takes a few minutes to overheat. On my '87 5.7 I noted an increase in cooling by flushing the system and replacing the old coolent with a high grade 5-year coolent. Previously I also changed the v belt system to a single serpentine, upgraded to an Edlebrock water pump, and installed a Hyperchip 160-degree mod. So far, the temperature has not gone above 180-degrees idling in traffic with the AC on with a cheap brass replacement radiator. If problems arise when I move to the desert, I'm prepared to upgrade to a aluminum radiator such as a Griffin and change the fans to Spals.

http://www.spal-usa.com/pdfs/11Fans.pdf

 

I would imagine it turning in the wrong direction would work much worse than mine. But i don't know. Any way of telling w/o removing the pullies. I looked around and found some numbers on the WP a while ago but couldn't match any with Milodon numbers. Those are the fans i'm getting when i have $250 burning a hole in my wallet.

BTW the coolant is new and all passages are clean. The engine was just hot tanked.