MeanWS6

Ok, using coolant like crazy. Car is fine, then after 20mins of REGULAR DRIVING she starts to get hot and I can hear the coolant boiling over, and I lose about a pint or so. No leaks, pressure tests are fine, no smoke, oil analysis was clean, compression test was fine, no smell - NOTHING

Any ideas?

joecar

Replace the radiator cap.

JohnnyC

From easiest to hardest:

Radiator Cap, Tstat, Fan, water pump

MeanWS6

checked checked and rechecked
everything is flowing smooth...

JohnnyC

Just because it is "flowing smooth" doesn't necessarily mean that the proper volume of fluid is flowing over a given period of time. If the system needs flushed, or a bad component is affecting the flow then you will not have enough flow to provide adequate cooling. I would do the following (which really is just routine maintenance, so you are not out anything if it doesn't fix the problem):

1) remove the Tstat and radiator cap.

2) buy some good radiator flush and do a complete flush of the system.

3) replace the tstat and radiator cap with new ones.

This will probably fix the problem. If not, I would then shift my attention to the operation of the fans and water pump. Have you done anything to change your fuel mixture and lean it out? I have seen this cause heating problems as well.

Good luck

ShevrolayZ28

iTrader: (4)

We often forget the most basic. Make sure there is nothing blocking the radiator and that all those plastic baffles are in their proper positions.

SpaZMaN

iTrader: (5)

how about this, are you mixing Dex-cool properly? i normally give it a 60/40 (Dexcool/H2o) mix to give it a little xtra.

JohnnyC

actually, water cools better than anti-freeze. This is why most race cars run just water. If we could just keep it from freezing and from causing corrosion we could run water only. I doubt the mix is the problem, but a flush and re-fill would allow you to get back to the perfect mix before winter.

Pro Stock John

iTrader: (34)

-change cap
-make sure both fans are coming on
-make sure you still have air dam and fan shroud

-or you have a bad headgasket or something

blackws6ta

iTrader: (1)

i would check the head gasket. get a block tester and some fluid and follow the instructions and check the head gasket. it could be blown but you wouldnt notice it in the oil.

300bhp/ton

If you are loosing water it is:

a) burning it
b) leaking it

I guess the car overheats because of lack of water, rather than overheating then venting water out of the over flow in the header tank.

So this means the water has to be going somewhere. Sadly to me it sounds like a cylinder head gasket. These can go and be very hard to detect, as the won't always contaminate the oil. I had a car last year that had a cylinder head gasket issue, very similar. You could drive for 30 mins or so before the water level got too low and it started to over heat. The oil was 100%. I ran the car for 3000 miles in this condition though before flogging it.

Lastly just check for leaks in the water system, a few months back my DD developed a leak in the radiator, however it would only leak if the car was left ticking over for 15 mins (like in a traffic jam). In normal use you would never have known it was leaking, this took me 2 months to locate and then only by accident as I was helping recover another car and left my ticking over.

slow trap

iTrader: (22)

just a few weeks ago one of my friend's blew a geaket on a firebird v-6. no water in oil but with the cap off you could see bubbles.put the cap on and try to drive it and it would overheat.it would also pressurize the coolant so when we tried to remove the cap it would overflow no mater if it was hot and overheating or not.