Might Need a new Radiator - Overheating!

[BigFrog]

Last summer my 2002 SS started running hot, it was fine through the winter. First thing this spring I had a new thermostat (chev stock) put in and the cooling system flushed. The mechanic said it looked nice and clean inside even before the flush. I took the car and noticed that as soon as it got to be 80 or more outside the temp would creep up past 210 to about 230 on the freeway. If I turn the heater on the temp drops right back down.

I took the radiator OUT of the car and cleaned the outside, it had a bunch of feathers and gunk on it (like I had scooped up a bird 2 years ago or something) and a lot of tiny rocks stuck in the fins. I noticed if I ran a garden hose through the radiator it flowed right through without backing up. I thought the gunk on the outside must have been the problem, put it back together and filled it up - but - it still creeps up to around 230 or more on the freeway before I get spooked and crank the heater up to draw off the heat.

Do I need a new radiator? Is there a good dual core I should go for or just go stock again? Is there anything else I am missing?

The car leaks no fluid and I have made sure the fluid level is up in the radiator and the reservoir, after a couple of top offs it has stayed up and is not burning or going into the oil.

Any help is much appreciated!

[2001NBMZ28]

Before condemning the radiator I'd be absolutely sure the high speed fans are coming on, there's no air in the system and the radiator cap is good. A shop should be able to pressure test the radiator with it on the car.

[DeputyLaird]

Also, see if you have the air deflector on the car, it's the plastic piece under the front of the car that is kinda like a front spoiler that directs air through the radiator at high speeds.

[SeVeReDiStOrTiOn]

I don't think it's the fans if you're at highway speeds....don't they shut off at 65mph? Get the system pressure checked like 2001nbmz28 said, also rebleed the piss out of it with the heater on....sounds like you have air in the system.

Putting on a new radiator cap wouldn't hurt either...but get it from the dealer. SLP sells a high cap radiator but it's like $400 bucks...

[2001NBMZ28]

True, it should be getting enough air at highway speeds. They don't turn off by MPH though, I watch my high speed fans cycle on/off on the highway, even with my low settings. Just reread your post about topping it off a couple times - sure sounds like air. Take the cap off, cold start, let it ldle and keep adding fluid as necessary after the thermostat opens. Don't know exactly what's going on, but don't want to see you spend money on a new radiator unless it's bad.

[BigFrog]

Thanks for the input.

The air dam is in fine shape and the fans are coming on when they should.

Are there bleader valves someplace to get air out of the system?

[dougcw]

I agree with 2001, sounds like air to me. You need to leave your cap off of the radiator until the water temp gets high enough for the thermostat to open. Once it opens the water will start coming out of the radiator at a good rate, check your water temp gauge so you'll have a good idea when it's about to happen. Shut your car off when this happens and quickly fill the radiator till it's full then check your reservoir and make sure it's filled to the hot mark. 50/50 is the recommended blend. You can have it ready standing by in a utility bucket. Hope this helps...

[JIMMY3SS]

big frog, let me know how you made out, im having the same problem even after adding a 160 thermostat

[sunsetorangess]

160* thermostat will not lower your temps without lettin the comp know its there, could be air in the system. LIke said above i doubt it's the radiator. I would look at the rad. cap. Take it over too local parts store or chinazone and see if they will pressure test your cap. If its not overheating while you are at a stop then i dont think it would be the fans but you can test them by lettin your car get too op. temps around 210 ish and see if they come on. too check your high temp fans turn the ac on and they should come on.
J

[JIMMY3SS]

ok , im a lil when it comes to my ls1, what do i need to tell the car the thermostat is there?? programmer or somthing?
thanks for your patienc3e but im learning

[sunsetorangess]

Yepp, either get it tunned or get a handheld tunner. I mean the thermostat will open up at a lower temp but the fans wont kick on until the factory tunned setting, So its not really worth the cash unless you fix the fan issue.
J

[BigFrog]

I have ran it from cold to hot with the cap off and watched it start to circulate, then shut the car off and filled it up. I can't add any more and the overflow is staying right where it should be, I am not losing any fluid for sure.

I took a trip the other day and it got a bit hot climbing an 8% grade up a canyon for a few miles but was otherwise fine. On the return trip I was on the freeway in 100 degree weather and cruising at about 70 it got hot enough to turn on the CHECK GAGES light, running the heater for about 2 minutes had it right back down to 210.

I am getting a new cap right away, seems like the next step.

Thanks again to everyone lending a hand on this.

[2001NBMZ28]

I have ran it from cold to hot with the cap off and watched it start to circulate, then shut the car off and filled it up.

When I did mine I didn't shut the car off once the thermostat opened, kept adding fluid to the radiator til it wouldn't take anymore.

[sunsetorangess]

Check your cap, cheap too replace and will most likely fix your issue
J

[BigFrog]

Replaced the cap with a genuine GM part, made no difference.

Went about 70 miles on mostly level freeway holding steady speeds around 70-75 MPH, temperature outside was 95, it got real hot after about 10 minutes (230 or so) and I had to turn the heater on to draw heat off of the engine.

I ended up leaving the heater on the last 20 minutes of the trip. The temp fluctuated between 210 and 215 with the heater on full blast (the windows down and the driver sweating and swearing up a storm).

One other thing I checked was the belt and belt tension to make sure it was not slipping, it's in fine shape.

My next step, bar any better suggestions, is to get a new radiator installed, and I was thinking I might as well go for a new water pump as well, just get it all done so I know it's done.

[sunsetorangess]

ok so you have replaced the thermostat, and the issue is still there, You have made sure your fans are coming on, I'v never seen a rad. just go bad but i hope that fixes your issue, You have done everything i can think of. Have you ever had the fluid flushed? I dont wana see you just start replaceing expensive parts for nuttin.
hmm
Any signs of overheating? Could the guage just be messed up?
J

[JIMMY3SS]

i dont think its the guage either, im having the exact problem that big frog is having, so no good on the cap huh?

[BigFrog]

It was flushed when they did the thermostat this spring, I doubt it's the gage as it is cooling back off when I run the heat. The mechanic also checked the area around the sending unit and said the gage was reading pretty accurate.

I have an extended warranty on the car (bought it used) and I am going to call the adjuster and see what they will pay for (diagnostics, repair) with this.

[2002Blackz]

Are you checking the temp with something other than the stock guage in the dash? Those are not very accurate. I had to change out my radiator, but that was because I put in a 403ci LS2. The stock radiator was fine with the HP I was making with H/C and most bolt-on's.
Good luck. Let us know what you figure out.

[Victor Rodriguez]

I was having the same problem with my trans am. I was missing two plastics. I would run it at 110mph and it would slowly start to rise. air dam was one and the one under the windshield wiper fluid bottle.