I just bought my 3rd gen and when I got it the previous owner told me it knock at cold start up. Oh by the way it is a 1989 camaro RS 305. So I brought it home and drove it the next day and it knock at start up for about 2 mins, then went away. next day no knocking I was happy. third day no knocking and just yesterday I started it up in the morning around 4:30 AM and no knocking and went to work and around 2:30 PM (103 Temp outside) started up the car with no knock and car Idle high like normal with a cold car but I didn't want to sit around and wait for I put it into drive and took off. can up to the first light and car Temp started to rise. Went to the next light and it was all the way up. Can was running fine. Had it towed and the next day checked the rad fluid and it was fine started it up with the cap off and brown rad fluid with little bubbles were coming out. checked the gauge and it was fine. Put on the rad cap and it started to get hott! Help. evertime I put on my rad cap it gets hot.

Thanks

 

OK the first thing you need to do is FLUSH that brown water out of your cooling system. Drain all the water out of the radiator then fill it up with water and run the car so it can cycle through. Drain again while you are doing this turn your heat on so it can run through tthe heater core to. This should take a few times of draining and filling but it will work once you have clear fluid drain it then add water and antifreeze. Since your doing all this go ahead and change your thermostat out to a 160 or 180 which ever you prefer. Try this before you take it to a radiator shop and spend alot of money on stuff you can do before taking it to a shop.

 

...what he said....And, while you're at it go ahead and get a new radiator cap.

 

Ok will do tomorrow morning. Thank you very much.

 

Ok I flushed the radiator three times and no I am running a prestone cleaner, but it's kinda hard because the car overheats in 6 to 10 mins from a dead cold (overnight) sit and in less then 5 mins when driving. I replaced the thermostat with a 180 and radiator cap. Now it say run the car for 7 hours but with me running the car for 10 mins every 4 hours it's going to take years! lol What do you recommend next? as I was doing all of this I noticed that the radiator was replaced. Wonder in the previous owner had problems and just passed them on to me.

Thanks,Jason

 

Make sure...
your fan is turning on at the correct time
your air dam is in place
the radiator has enough fluid
the fluid is circulating through the engine
water pump is working