97 z28 SS.

Not sure what could be wrong....I was working on my car this morning and had the car on. All the sudden I see water starting to come out of the resevoir then I hear knocking comming from either the radiator or waterpump. I'm not sure what because as soon as i saw that I immediately turned off the car. It was in the red.

I noticed the other day my car was starting to overheat as soon as i started it but then the guage went back to normal. There's no way it could get that hot that fast like 30 seconds after I start it so I figured it was just the sensor that was fubar.

Any ideas what it might be? I had my radiator changed last year so i doubt it's that.

 

If your fans are working you might just have a bad radiator cap. I would replace the cap, bleed the system and see what the temp does.

 

i'll try that. How do i bleed it?

 

Check the water pump. When mine was going out, this was one of the symptoms, along with air that managed to get into system somehow. Look for the 2 bleeder valves that are made of brass. One is near thermostat housing, and the other is located in close proximity.

Also look under water pump weep hole for leaking water to see if pump is going out. Also check system pressure to see if there is a leak causing air to get into system.

 

My 1995 z28 started doing that at 111,000 miles. Over a period of two years, I replaced the thermostat twice, flushed the radiator and block, put in new, brown anti freeze, water pump and a new radiator cap. The real problem turned out to be a radiator that got gradually stopped up and had to be replaced and the planned short life of the waterpump itself ~ approx 100,000 miles. It is running fine now but I have 147,000 miles and in a few years I expect more problems.

 

damn, that's gonna suck if it's my radiator again. I just changed the ****! Is there a way to test it?

 

You can test it with a pressure test. Fwiw I had mine cleaned and r/r at a radiator shop. (60 bucks) You have to pull it for deep cleaning of the channels or cores however. Make sure your flushing everthing when changing the rad including block.

I don't think it's your radiator causing the overflow, though.

 

Another thing i forgot to mention....after the overflow happened I looked at my hoses and they were all squished like something was sucking them. After I released the radiator cap they went back to normal.

 

i tried to flush out the block but the block screw shown on shbox.com looks all warped, like someone used the wrong wrench. Damn! I'm afraid to touch it....anyonw know what size to use to release it?