how to tell - head gasket

[rbs13]

hey guys, just got a question regarding head gaskets, i have a rb20det in a s13, iv gone through two water pumps (one from autobarn and a std one) and just put on a n1 waterpump, replaced the thermostat, bled the cooling system.. thats about it. i cant seem to stop the car from over heating. i have a 12 inch thermo and the std fan for aircon which i just replaced with another 12inchthermo - havent had the proper chance to test that out tho. anyway, on the way home from work the car will over heat sitting in traffic, even looking for a parking space it will over heat.. i try to turn the car off asap and let it cool but sometimes its impossible but i havent let it get to the H yet.. just one or two bars below it.. the other day when i put the other thermo on i had to take my radiator out to get to the mounts etc and when i put new water/coolant in i had a lot of white foamy shit.. i put water in first cause the servo i went to didnt have coolant. iv been told when you get white foam the head gasket could be gone. the car has overheated a fair amount of times cause the water pump broke, thermostat stoped working and cause i was in traffic.. at one stage it overheated at nite while looking in the refidex for 3-5 minutes with the bonnet up. there was a fair bit of white foam but not really any bubbles there doesnt seem to be any water in the oil last time i checked but im still worried that the gasket is ****ed. is there any SURE way to tell without taking it to a mechanic and getting charged a shit load to do so? would a compression test show it.. i know the car had 150psi when i bought it. also would there be water leaking down the side of the block? any help would be great. im about to fit intercooler/tdo6 so i want to know that the motor is in good condition before i put these on. also would the headgasket cause shitty idling? when it idles at round 1000rpm it breaks down and idles like a pig. but when i put the idling up to round 1300-1500 its fine. please help sorry for the long post. thanks guys. :wavey:

[SATO GTS]

if you have oil in the water that usually means that you have cracked the head, and if you have water in the oil then it can be a head gasket ..

you can try and take out each spark plug and have a look at the tops of the pistons to see if any of them have a shiny brownish surface or a rich blackish surface . if they are blackish then that cylinder is ok but if the piston is shinny then that is the piston the water is leaking in to . the water will turn to steam with the heat produced and then the steam burns of all the carbon in the cylinder and on top of the piston..

you say that you are having rough idle problems which does indicate head gasket..

get some one to thoroughly check it out as you dont want to install the cooler and turbs and have more problems

hope this helps

L8R