Hi Guys
So i experience High coolant temps especially when on the freeway driving above 60mph up to 255 degrees
it cools down at city street speeds and doesnt overheat in stop and go traffic!

Car is a 99, cammed 6.0 LQ9 Auto
Codes are
B2723H, B2262H B2264H
U1096H U1064H U1016H
C2120HC

i recently changed the Surge tank resorvoir due to a bad Coolant level sensor, after that i experienced the higher temps the 1st time...
Then i changed the Thermostat as well
So i am thinking there must be Air in the coolant system?!
I tried the common methods to burb the air with no success
i also tried to blow compressed air through the Surge tank and bleed out of the Steam valve T hose (through throttlebody) that goes to the radiator top
I feel like i got some Air out there. But i just drove it while it was mainky @ 230ish, but when getting on it a bit the temp went up to 250 again. And then again when getting of the Freeway the temp goes down.

The fans kick on, i dont know when driving because the vette is loud .lol
But in P the fans are definitly on and cool down the car to its operating temps for sure.

BTW i tried to go to Jiffy lube and firestone to get a machine flush/bleeding ... LOL this fools denied my Vette and said i have to go to the dealership ahaha...
So i am a bit frustrated right now
Any help

 

You did not say just what methods you have tried to get air out. Did you try the Factory Service Manual method?

"Cycle the engine RPMs from idle to 3,000 in 30 second intervals until the coolant temperature reaches 210 degrees F"

A '99 normally has both front and rear coolant air bleed ports, the rear ones piped under the intake manifold to connect to the front ones just before the throttle body connection.

A very effective way to get air out of the heads is to first make sure the surge tank is full, then disconnect the coolant air bleed line which goes from the throttle body to the radiator, capping the radiator outlet with a piece of hose bent over and clamped and clamped on the radiator outlet. Extend the hose which is attached to the throttle body to a gallon container on the floor by the passenger side fender.

Start up and watch what comes out of the hose from the throttle body as the cooling system attempts to come up to pressure during warm up. Do not let the surge tank get low.

I do this every time I open the cooling system for any reason. Usually more than a quart of coolant along with air bubbles is ejected into the container on the floor before bubbles stop.

Reconnect the air bleed hose to the radiator and refill the surge tank.

 

I did the factory option.
And I did the radiator/air bleed option.
Only I have not started the engine. I blew air through the filled surge tank and I had a bucket to catch the flutheir the radiator hose.

 

i just couldnt let my hands of it.
and did the Factory option AGAIN
and the Steam vent to radiator hose removal method AS WELL

then i talked to the shop that recently did my AC troubleshooting (Vacuum lines + bad Compressor clutch)
They said they also had to take of the Thermostat to get to the AC Compressor , so they did a Flush as well..

At this point i think it is the radiator itself! might be bad and need a replacement ? At high speed the fans are off (freeway) and the Air will cool the radiator ( theoreticly) and thats when i get the highest readings (250+)
But 230 on city streets also dont seem normal to me.

 

Have you checked for debris accumulation in the space between the a/c condenser and the radiator?

Air flow through the free-wheeling fans should be enough to keep temperatures within parameters, as long as the radiator fins are not plugged up. If they are plugged up, then the coolant temperature will rise and the fans will NOT come ON unless the car goes below 35MPH.

 

I checked for debris. There was a little but I washed it if with a water hose on low pressure.
if the fins are clocked I might need a new rad. It is a old radiator

 

Did you remove any of the lower air dam?

 

yes it was removed when I got the car. I thought about that too but I was driving it at least 80 miles after the cam install with no air dam and had no overheating

 

-check your engine air filter- a dirty enough air intake filter can cause higher temps.
-undo the last thing you swapped- no issue before that right?
-has the coolant flushed to ensure no air in it.

 

I actually installed a cold air intake dual filer setup relatively last.
I just dont see how the airfilter could effect the coolant temp.
Flush was done.

 

What was ambient temp when you drove without the center air dam?

The center air dam does a TON to help cooling at highway speeds. 255 isn't exactly crazy overheating, I would bet it's probably a combination of rising ambient temps and the lack of that center air dam. I know it sounds crazy but the whole bottom feeder thing doesn't really work without that big piece of plastic.

 

so I have a new ambient sensor since I had AC issues before ( solved! It was vacuum hose and a locked up clutch)
As I said I drove the car without the air dam before and didn't have a issue... I might take it apart today to see the radiators shape.
+ this airdams are fairly expensive for a **** piece of plastic..100+$ while I get a new radiator for 85 @ rock auto lol

 

I was thinking you wouldn't have an overheating problem if outside temp was in the 50's vs 70's. Radiator might be clogged internally, definitely a possibility. Bit more work then simpler stuff though. Another thing to consider is the coolant temp sensor. It's located in the driver side head. Pretty easy swap, not sure how you'd test that though. Cheap to replace.

Zip Corvette has center air dams for about $70.

 

You may want to take advantage of this at $58.99 with free shipping.

 

jop
Saw it earlier thus a.m and ordered it regardless.
we will see I hope it helps

 

I just looked at my radiator again.. the rad itself looked relatively clean. But the AC condenser was very dirty. So I cleaned it by brushing the dirt out of it.. i used my wife's household tools lol.. i also brushed the radiator again..
Then sprayed degreaser and simple green on both and rinsed it with the garden hose... ( no pressure washe!)

I can see somehow that with no airdam the air might get directed to the condenser 1st and then hit the rad. But if the condenser is plugged with stuff it might get less cooling air..

well the airdam is ordered.. as well as a new rad. Just in case. Rockauto makes it easy to ship stuff back if not needed and still in the package..


After cleaning

Before cleaning

 

A quick and simple thing to do is turn your heater on with the temp setting and fan the highest it will go. If your temps normalize, it is likely your radiator. If the heater doesn't get hot, you have air in the system or low coolant.

 

I have to turn it on while at high temp i didnt do that yet.
but the heater blows hot when i crank it up.
I couldn't test drive it today but i go step by step.
replacing the rad. Seems fairly easy.

 

SOOO... i did a couple tests today...
After really cleaning the radiator and also the condenser i took her for a drive today... it felt like she took longer to go into high temps. (225+) then before...
But i still got up to 245 on the freeway.
At least my fans kick on accordingly when im bellow 35mph. so i can rely on that to cool down.

I also turned on the heater to full blast when at 245.No movement down or up (at least not significant) i tried the AC as well and also no movement.

Then i took the CAI off since this was my last mod. and i felt like the CAI assembly got kinda hot, but thats relativly normal for CAI made out of steel or alu piping.

Then i saw that my Ext. temp was basicly 20 degrees HIGHER than it is really , i have recently replaced the sensor so it should be a good sensor.
BUT i saw when cooling the car down in P, that the fans that try to cool down the rad. blow hot air all the way to the front in the area of the Ambient sensor. So it reads this extra heat i assume.
Which brings me to the point that this Fan/hot air would not reach the ambient sensor IF i would have the Center AIRDAM on there.. since the air comes from the bottom of and would hit the backside of the Airdam i assume.
So i ordered the Airdam anyways. and will check that out. i know there is the discussion if the airdam is for aerodynamics or cooling... i think it is for both... And the radiator possition definitly needs help to direct the cold air to it...otherwise the air just goes the way of least resistant which is straight out of the bottom ( or at least most of the driving air).
btw i also have a front splitter installed and the high temps accured after this install.. there is also the possibility that this restricts air to the rad.?

lets see

 

Ding ding, we have a winner. I can almost guarantee you that splitter is preventing air from flowing through your radiator. There are a bunch of threads of people realizing that. Certain splitter designs are better, others worse. I think the air dam will help but you'll still probably be running a bit hot. There are a couple tricks you can do to minimize the effect the splitter is having on your temps. Stuff like programming your fans, lower temp thermostat, cutting out your front plate and adding mesh.